From 6b20232f9954318f8a023a0835fe453d77af50cd Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Mon, 15 Nov 2021 23:55:57 -0500
Subject: [PATCH 1/9] remove nil and noop

---
 attachments.scad | 16 +++++++++-------
 shapes3d.scad    | 21 ---------------------
 threading.scad   |  1 -
 3 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/attachments.scad b/attachments.scad
index c95c460..f3dde57 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -1885,7 +1885,8 @@ module show_anchors(s=10, std=true, custom=true) {
                     anchor_arrow(s, color="cyan");
                 }
                 color("black")
-                noop($tags="anchor-arrow") {
+//                tags("anchor-arrow")
+                {
                     xrot(two_d? 0 : 90) {
                         back(s/3) {
                             yrot_copies(n=2)
@@ -1897,13 +1898,14 @@ module show_anchors(s=10, std=true, custom=true) {
                         }
                     }
                 }
-                color([1, 1, 1, 0.4])
-                noop($tags="anchor-arrow") {
+                color([1, 1, 1, 1])
+                tags("anchor-arrow")
+                {
                     xrot(two_d? 0 : 90) {
                         back(s/3) {
-                            zcopies(s/21) cube([s/4.5*len(anchor[0]), s/3, 0.01], center=true);
+                             cube([s/4.5*len(anchor[0]), s/3, 0.01], center=true);
                         }
-                    }
+                   }
                 }
             }
         }
@@ -1953,7 +1955,7 @@ module anchor_arrow(s=10, color=[0.333,0.333,1], flag=true, $tags="anchor-arrow"
 // Example:
 //   anchor_arrow2d(s=20);
 module anchor_arrow2d(s=15, color=[0.333,0.333,1], $tags="anchor-arrow") {
-    noop() color(color) stroke([[0,0],[0,s]], width=s/10, endcap1="butt", endcap2="arrow2");
+    color(color) stroke([[0,0],[0,s]], width=s/10, endcap1="butt", endcap2="arrow2");
 }
 
 
@@ -1971,7 +1973,7 @@ module anchor_arrow2d(s=15, color=[0.333,0.333,1], $tags="anchor-arrow") {
 //   expose_anchors() cube(50, center=true) show_anchors();
 module expose_anchors(opacity=0.2) {
     show("anchor-arrow")
-        children();
+       children();
     hide("anchor-arrow")
         color(is_undef($color)? [0,0,0] :
               is_string($color)? $color :
diff --git a/shapes3d.scad b/shapes3d.scad
index 422b3f8..9c5b5c1 100644
--- a/shapes3d.scad
+++ b/shapes3d.scad
@@ -2304,27 +2304,6 @@ module path_text(path, text, font, size, thickness, lettersize, offset=0, revers
 // Section: Miscellaneous
 
 
-// Module: nil()
-//
-// Description:
-//   Useful when you MUST pass a child to a module, but you want it to be nothing.
-module nil() union(){}
-
-
-// Module: noop()
-//
-// Description:
-//   Passes through the children passed to it, with no action at all.  Useful while debugging when
-//   you want to replace a command.  This is an attachable non-object.
-//
-// Arguments:
-//   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
-//   orient = Vector to rotate top towards, after spin.  See [orient](attachments.scad#orient).  Default: `UP`
-module noop(spin=0, orient=UP) attachable(CENTER,spin,orient, d=0.01) {nil(); children();}
-
-
-
-
 // Module: interior_fillet()
 //
 // Description:
diff --git a/threading.scad b/threading.scad
index ff40aba..61cbbf5 100644
--- a/threading.scad
+++ b/threading.scad
@@ -535,7 +535,6 @@ module npt_threaded_rod(
                 higbee=r1*PI/2
             );
             if (hollow) cylinder(l=l+1, d=size*INCH, center=true);
-            else nil();
         }
         children();
     }

From 7dfb99c5bb83403af9b0f9a64813a36c491adb0c Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 06:15:56 -0500
Subject: [PATCH 2/9] fix test

---
 tests/test_transforms.scad | 50 +++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/tests/test_transforms.scad b/tests/test_transforms.scad
index ec338a1..6a4d14b 100644
--- a/tests/test_transforms.scad
+++ b/tests/test_transforms.scad
@@ -8,7 +8,7 @@ module test_translate() {
         assert_equal(translate(val, p=[1,2,3]), [1,2,3]+val);
     }
     // Verify that module at least doesn't crash.
-    translate([-5,-5,-5]) translate([0,0,0]) translate([5,5,5]) nil();
+    translate([-5,-5,-5]) translate([0,0,0]) translate([5,5,5]) union(){};
 }
 test_translate();
 
@@ -21,8 +21,8 @@ module test_move() {
         assert_equal(move(x=val.x, y=val.y, z=val.z, p=[1,2,3]), [1,2,3]+val);
     }
     // Verify that module at least doesn't crash.
-    move(x=-5) move(y=-5) move(z=-5) move([-5,-5,-5]) nil();
-    move(x=5) move(y=5) move(z=5) move([5,5,5]) nil();
+    move(x=-5) move(y=-5) move(z=-5) move([-5,-5,-5]) union(){};
+    move(x=5) move(y=5) move(z=5) move([5,5,5]) union(){};
 }
 test_move();
 
@@ -35,7 +35,7 @@ module test_left() {
     assert_equal(left(0,p=[1,2,3]),[1,2,3]);
     assert_equal(left(-5,p=[1,2,3]),[6,2,3]);
     // Verify that module at least doesn't crash.
-    left(-5) left(0) left(5) nil();
+    left(-5) left(0) left(5) union(){};
 }
 test_left();
 
@@ -48,7 +48,7 @@ module test_right() {
     assert_equal(right(0,p=[1,2,3]),[1,2,3]);
     assert_equal(right(5,p=[1,2,3]),[6,2,3]);
     // Verify that module at least doesn't crash.
-    right(-5) right(0) right(5) nil();
+    right(-5) right(0) right(5) union(){};
 }
 test_right();
 
@@ -61,7 +61,7 @@ module test_back() {
     assert_equal(back(0,p=[1,2,3]),[1,2,3]);
     assert_equal(back(5,p=[1,2,3]),[1,7,3]);
     // Verify that module at least doesn't crash.
-    back(-5) back(0) back(5) nil();
+    back(-5) back(0) back(5) union(){};
 }
 test_back();
 
@@ -74,7 +74,7 @@ module test_fwd() {
     assert_equal(fwd(0,p=[1,2,3]),[1,2,3]);
     assert_equal(fwd(-5,p=[1,2,3]),[1,7,3]);
     // Verify that module at least doesn't crash.
-    fwd(-5) fwd(0) fwd(5) nil();
+    fwd(-5) fwd(0) fwd(5) union(){};
 }
 test_fwd();
 
@@ -87,7 +87,7 @@ module test_down() {
     assert_equal(down(0,p=[1,2,3]),[1,2,3]);
     assert_equal(down(-5,p=[1,2,3]),[1,2,8]);
     // Verify that module at least doesn't crash.
-    down(-5) down(0) down(5) nil();
+    down(-5) down(0) down(5) union(){};
 }
 test_down();
 
@@ -100,7 +100,7 @@ module test_up() {
     assert_equal(up(0,p=[1,2,3]),[1,2,3]);
     assert_equal(up(5,p=[1,2,3]),[1,2,8]);
     // Verify that module at least doesn't crash.
-    up(-5) up(0) up(5) nil();
+    up(-5) up(0) up(5) union(){};
 }
 test_up();
 
@@ -112,7 +112,7 @@ module test_scale() {
         assert_equal(scale(point2d(val)), [[val.x,0,0],[0,val.y,0],[0,0,1]]);
         assert_equal(scale(val), [[val.x,0,0,0],[0,val.y,0,0],[0,0,val.z,0],[0,0,0,1]]);
         assert_equal(scale(val, p=[1,2,3]), v_mul([1,2,3], val));
-        scale(val) nil();
+        scale(val) union(){};
     }
     assert_equal(scale(3), [[3,0,0,0],[0,3,0,0],[0,0,3,0],[0,0,0,1]]);
     assert_equal(scale(3, p=[1,2,3]), 3*[1,2,3]);
@@ -124,7 +124,7 @@ module test_scale() {
     assert_equal(scale([2,3,4], p=cb), cube([2,3,4]));
     assert_equal(scale([-2,-3,-4], p=cb), [[for (p=cb[0]) v_mul(p,[-2,-3,-4])], [for (f=cb[1]) reverse(f)]]);
     // Verify that module at least doesn't crash.
-    scale(-5) scale(5) nil();
+    scale(-5) scale(5) union(){};
 }
 test_scale();
 
@@ -134,10 +134,10 @@ module test_xscale() {
     for (val=vals) {
         assert_equal(xscale(val), [[val,0,0,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]]);
         assert_equal(xscale(val, p=[1,2,3]), [val*1,2,3]);
-        xscale(val) nil();
+        xscale(val) union(){};
     }
     // Verify that module at least doesn't crash.
-    xscale(-5) xscale(5) nil();
+    xscale(-5) xscale(5) union(){};
 }
 test_xscale();
 
@@ -147,10 +147,10 @@ module test_yscale() {
     for (val=vals) {
         assert_equal(yscale(val), [[1,0,0,0],[0,val,0,0],[0,0,1,0],[0,0,0,1]]);
         assert_equal(yscale(val, p=[1,2,3]), [1,val*2,3]);
-        yscale(val) nil();
+        yscale(val) union(){};
     }
     // Verify that module at least doesn't crash.
-    yscale(-5) yscale(5) nil();
+    yscale(-5) yscale(5) union(){};
 }
 test_yscale();
 
@@ -160,10 +160,10 @@ module test_zscale() {
     for (val=vals) {
         assert_equal(zscale(val), [[1,0,0,0],[0,1,0,0],[0,0,val,0],[0,0,0,1]]);
         assert_equal(zscale(val, p=[1,2,3]), [1,2,val*3]);
-        zscale(val) nil();
+        zscale(val) union(){};
     }
     // Verify that module at least doesn't crash.
-    zscale(-5) zscale(5) nil();
+    zscale(-5) zscale(5) union(){};
 }
 test_zscale();
 
@@ -184,7 +184,7 @@ module test_mirror() {
         assert_approx(mirror(val), m, str("mirror(",val,")"));
         assert_approx(mirror(val, p=[1,2,3]), apply(m, [1,2,3]), str("mirror(",val,",p=...)"));
         // Verify that module at least doesn't crash.
-        mirror(val) nil();
+        mirror(val) union(){};
     }
 }
 test_mirror();
@@ -194,7 +194,7 @@ module test_xflip() {
     assert_approx(xflip(), [[-1,0,0,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]]);
     assert_approx(xflip(p=[1,2,3]), [-1,2,3]);
     // Verify that module at least doesn't crash.
-    xflip() nil();
+    xflip() union(){};
 }
 test_xflip();
 
@@ -203,7 +203,7 @@ module test_yflip() {
     assert_approx(yflip(), [[1,0,0,0],[0,-1,0,0],[0,0,1,0],[0,0,0,1]]);
     assert_approx(yflip(p=[1,2,3]), [1,-2,3]);
     // Verify that module at least doesn't crash.
-    yflip() nil();
+    yflip() union(){};
 }
 test_yflip();
 
@@ -212,7 +212,7 @@ module test_zflip() {
     assert_approx(zflip(), [[1,0,0,0],[0,1,0,0],[0,0,-1,0],[0,0,0,1]]);
     assert_approx(zflip(p=[1,2,3]), [1,2,-3]);
     // Verify that module at least doesn't crash.
-    zflip() nil();
+    zflip() union(){};
 }
 test_zflip();
 
@@ -341,7 +341,7 @@ module test_xrot() {
         assert_approx(xrot(a, p=path[0]), apply(m, path[0]));
         assert_approx(xrot(a, p=path), apply(m, path));
         // Verify that module at least doesn't crash.
-        xrot(a) nil();
+        xrot(a) union(){};
     }
 }
 test_xrot();
@@ -356,7 +356,7 @@ module test_yrot() {
         assert_approx(yrot(a, p=path[0]), apply(m, path[0]));
         assert_approx(yrot(a, p=path), apply(m, path));
         // Verify that module at least doesn't crash.
-        yrot(a) nil();
+        yrot(a) union(){};
     }
 }
 test_yrot();
@@ -371,7 +371,7 @@ module test_zrot() {
         assert_approx(zrot(a, p=path[0]), apply(m, path[0]));
         assert_approx(zrot(a, p=path), apply(m, path));
         // Verify that module at least doesn't crash.
-        zrot(a) nil();
+        zrot(a) union(){};
     }
 }
 test_zrot();
@@ -390,7 +390,7 @@ module test_skew() {
     assert_approx(skew(sxy=2, sxz=3, syx=4, syz=5, szx=6, szy=7), m);
     assert_approx(skew(sxy=2, sxz=3, syx=4, syz=5, szx=6, szy=7, p=[1,2,3]), apply(m,[1,2,3]));
     // Verify that module at least doesn't crash.
-    skew(undef,2,3,4,5,6,7) nil();
+    skew(undef,2,3,4,5,6,7) union(){};
 }
 test_skew();
 

From d576526b60a72a3fac8e9e895e3b4ee2653ab249 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 18:49:37 -0500
Subject: [PATCH 3/9] VNF interface update skin.scad and shapes2d.scad

---
 attachments.scad |   4 +-
 shapes2d.scad    |  90 ++++++++++++++++++++++++++-----------
 skin.scad        | 115 +++++++++++++++++++++++------------------------
 vnf.scad         |   7 +--
 4 files changed, 128 insertions(+), 88 deletions(-)

diff --git a/attachments.scad b/attachments.scad
index f3dde57..7991ff2 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -29,6 +29,8 @@ $parent_geom = undef;
 $tags_shown = [];
 $tags_hidden = [];
 
+_ANCHOR_TYPES = ["intersect","hull"];
+
 
 // Section: Anchors, Spin, and Orientation
 //   This library adds the concept of anchoring, spin and orientation to the `cube()`, `cylinder()`
@@ -1885,7 +1887,7 @@ module show_anchors(s=10, std=true, custom=true) {
                     anchor_arrow(s, color="cyan");
                 }
                 color("black")
-//                tags("anchor-arrow")
+                tags("anchor-arrow")
                 {
                     xrot(two_d? 0 : 90) {
                         back(s/3) {
diff --git a/shapes2d.scad b/shapes2d.scad
index cfd6c18..08fc969 100644
--- a/shapes2d.scad
+++ b/shapes2d.scad
@@ -244,15 +244,20 @@ module circle(r, d, anchor=CENTER, spin=0) {
 //   ellipse(d=50, anchor=FRONT, spin=45);
 // Example(NORENDER): Called as Function
 //   path = ellipse(d=50, anchor=FRONT, spin=45);
-module ellipse(r, d, realign=false, circum=false, anchor=CENTER, spin=0) {
-    r = get_radius(r=r, d=d, dflt=1);
-    dummy = assert((is_finite(r) || is_vector(r,2)) && all_positive(r), "Invalid radius or diameter for ellipse");
+module ellipse(r, d, realign=false, circum=false, uniform=false, anchor=CENTER, spin=0)
+{
+    r = force_list(get_radius(r=r, d=d, dflt=1),2);
+    dummy = assert(is_vector(r,2) && all_positive(r), "Invalid radius or diameter for ellipse");
     sides = segs(max(r));
     sc = circum? (1 / cos(180/sides)) : 1;
-    rx = default(r[0],r) * sc;
-    ry = default(r[1],r) * sc;
+    rx = r.x * sc;
+    ry = r.y * sc;
     attachable(anchor,spin, two_d=true, r=[rx,ry]) {
-        if (rx < ry) {
+        if (uniform) {
+            assert(!circum, "Circum option not allowed when \"uniform\" is true");
+            polygon(ellipse(r,realign=realign, circum=circum, uniform=true));
+        }
+        else if (rx < ry) {
             xscale(rx/ry) {
                 zrot(realign? 180/sides : 0) {
                     circle(r=ry, $fn=sides);
@@ -270,14 +275,42 @@ module ellipse(r, d, realign=false, circum=false, anchor=CENTER, spin=0) {
 }
 
 
-function ellipse(r, d, realign=false, circum=false, anchor=CENTER, spin=0) =
+// Iterative refinement to produce an inscribed polygon
+// in an ellipse whose side lengths are all equal
+function _ellipse_refine(a,b,N, _theta=[]) =
+   len(_theta)==0? _ellipse_refine(a,b,N,lerpn(0,360,N,endpoint=false))
+   :
+   let(
+       pts = [for(t=_theta) [a*cos(t),b*sin(t)]],
+       lenlist= path_segment_lengths(pts,closed=true),
+       meanlen = mean(lenlist),
+       error = lenlist/meanlen
+   )
+   all_equal(error,EPSILON) ? pts
+   :
+   let(
+        dtheta = [each deltas(_theta),
+                  360-last(_theta)],
+        newdtheta = [for(i=idx(dtheta)) dtheta[i]/error[i]],
+        adjusted = [0,each cumsum(list_head(newdtheta / sum(newdtheta) * 360))]
+   )
+   _ellipse_refine(a,b,N,adjusted);
+
+
+
+function ellipse(r, d, realign=false, circum=false, uniform=false, anchor=CENTER, spin=0) =
+    let(
+        r = force_list(get_radius(r=r, d=d, dflt=1),2),
+        sides = segs(max(r))
+    )
+    uniform ? assert(!circum, "Circum option not allowed when \"uniform\" is true")
+              reorient(anchor,spin,two_d=true,r=[r.x,r.y],p=_ellipse_refine(r.x,r.y,sides))
+    :
     let(
-        r = get_radius(r=r, d=d, dflt=1),
-        sides = segs(max(r)),
         offset = realign? 180/sides : 0,
         sc = circum? (1 / cos(180/sides)) : 1,
-        rx = default(r[0],r) * sc,
-        ry = default(r[1],r) * sc,
+        rx = r.x * sc,
+        ry = r.y * sc,
         pts = [for (i=[0:1:sides-1]) let(a=360-offset-i*360/sides) [rx*cos(a), ry*sin(a)]]
     ) reorient(anchor,spin, two_d=true, r=[rx,ry], p=pts);
 
@@ -780,6 +813,7 @@ module trapezoid(h, w1, w2, angle, shift=0, chamfer=0, rounding=0, anchor=CENTER
 //   align_pit = If given as a 2D vector, rotates the whole shape so that the first inner corner is pointed towards that direction.  This occurs before spin.
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `CENTER`
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
+//   atype = Choose "hull" or "intersect" anchor methods.  Default: "hull"
 // Extra Anchors:
 //   "tip0" ... "tip4" = Each tip has an anchor, pointing outwards.
 //   "pit0" ... "pit4" = The inside corner between each tip has an anchor, pointing outwards.
@@ -801,7 +835,8 @@ module trapezoid(h, w1, w2, angle, shift=0, chamfer=0, rounding=0, anchor=CENTER
 //           stroke([[0,0],[0,7]], endcap2="arrow2");
 // Example(2D): Called as Function
 //   stroke(closed=true, star(n=5, r=50, ir=25));
-function star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit, anchor=CENTER, spin=0, _mat, _anchs) =
+function star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit, anchor=CENTER, spin=0, atype="hull", _mat, _anchs) =
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"")  
     assert(is_undef(align_tip) || is_vector(align_tip))
     assert(is_undef(align_pit) || is_vector(align_pit))
     assert(is_undef(align_tip) || is_undef(align_pit), "Can only specify one of align_tip and align_pit")
@@ -843,10 +878,11 @@ function star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit
                 named_anchor(str("midpt",i), pos, unit(pos,BACK), 0),
             ]
         ]
-    ) reorient(anchor,spin, two_d=true, path=path, p=path, anchors=anchors);
+    ) reorient(anchor,spin, two_d=true, path=path, p=path, extent=atype=="hull", anchors=anchors);
 
 
-module star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit, anchor=CENTER, spin=0) {
+module star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit, anchor=CENTER, spin=0, atype="hull") {
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
     assert(is_undef(align_tip) || is_vector(align_tip));
     assert(is_undef(align_pit) || is_vector(align_pit));
     assert(is_undef(align_tip) || is_undef(align_pit), "Can only specify one of align_tip and align_pit");
@@ -874,7 +910,7 @@ module star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit,
         ]
     ];
     path = star(n=n, r=r, ir=ir, realign=realign, _mat=mat, _anchs=anchors);
-    attachable(anchor,spin, two_d=true, path=path, anchors=anchors) {
+    attachable(anchor,spin, two_d=true, path=path, extent=atype=="hull", anchors=anchors) {
         polygon(path);
         children();
     }
@@ -948,7 +984,7 @@ module jittered_poly(path, dist=1/512) {
 // Function&Module: teardrop2d()
 //
 // Description:
-//   Makes a 2D teardrop shape. Useful for extruding into 3D printable holes.
+//   Makes a 2D teardrop shape. Useful for extruding into 3D printable holes.  Uses "intersect" style anchoring.  
 //
 // Usage: As Module
 //   teardrop2d(r/d=, [ang], [cap_h]);
@@ -979,7 +1015,7 @@ module jittered_poly(path, dist=1/512) {
 module teardrop2d(r, ang=45, cap_h, d, anchor=CENTER, spin=0)
 {
     path = teardrop2d(r=r, d=d, ang=ang, cap_h=cap_h);
-    attachable(anchor,spin, two_d=true, path=path) {
+    attachable(anchor,spin, two_d=true, path=path, extent=false) {
         polygon(path);
         children();
     }
@@ -1008,7 +1044,7 @@ function teardrop2d(r, ang=45, cap_h, d, anchor=CENTER, spin=0) =
         ),
         maxx_idx = max_index(column(path,0)),
         path2 = list_rotate(path,maxx_idx)
-    ) reorient(anchor,spin, two_d=true, path=path2, p=path2);
+    ) reorient(anchor,spin, two_d=true, path=path2, p=path2, extent=false);
 
 
 
@@ -1023,7 +1059,7 @@ function teardrop2d(r, ang=45, cap_h, d, anchor=CENTER, spin=0) =
 // See Also: circle(), ellipse()
 // Description:
 //   When called as a function, returns a 2D path forming a shape of two circles joined by curved waist.
-//   When called as a module, creates a 2D shape of two circles joined by curved waist.
+//   When called as a module, creates a 2D shape of two circles joined by curved waist.  Uses "hull" style anchoring.  
 // Arguments:
 //   r = The radius of the end circles.
 //   spread = The distance between the centers of the end circles.  Default: 10
@@ -1094,6 +1130,8 @@ function _superformula(theta,m1,m2,n1,n2=1,n3=1,a=1,b=1) =
 // Description:
 //   When called as a function, returns a 2D path for the outline of the [Superformula](https://en.wikipedia.org/wiki/Superformula) shape.
 //   When called as a module, creates a 2D [Superformula](https://en.wikipedia.org/wiki/Superformula) shape.
+//   Note that the "hull" type anchoring (the default) is more intuitive for concave star-like shapes, but the anchor points do not
+//   necesarily lie on the line of the anchor vector, which can be confusing, especially for simpler, ellipse-like shapes.  
 // Arguments:
 //   step = The angle step size for sampling the superformula shape.  Smaller steps are slower but more accurate.
 //   m1 = The m1 argument for the superformula. Default: 4.
@@ -1108,6 +1146,7 @@ function _superformula(theta,m1,m2,n1,n2=1,n3=1,a=1,b=1) =
 //   d = Diameter of the shape.  Scale shape to fit in a circle of diameter d.
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `CENTER`
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
+//   atype = Select "hull" or "intersect" style anchoring.  Default: "hull". 
 // Example(2D):
 //   supershape(step=0.5,m1=16,m2=16,n1=0.5,n2=0.5,n3=16,r=50);
 // Example(2D): Called as Function
@@ -1133,8 +1172,9 @@ function _superformula(theta,m1,m2,n1,n2=1,n3=1,a=1,b=1) =
 // Examples:
 //   linear_extrude(height=0.3, scale=0) supershape(step=1, m1=6, n1=0.4, n2=0, n3=6);
 //   linear_extrude(height=5, scale=0) supershape(step=1, b=3, m1=6, n1=3.8, n2=16, n3=10);
-function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER, spin=0) =
+function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER, spin=0, atype="hull") =
     let(
+        assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\""),
         r = get_radius(r=r, d=d, dflt=undef),
         m2 = is_def(m2) ? m2 : m1,
         n2 = is_def(n2) ? n2 : n1,
@@ -1146,11 +1186,11 @@ function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER
         rads = [for (theta = angs) _superformula(theta=theta,m1=m1,m2=m2,n1=n1,n2=n2,n3=n3,a=a,b=b)],
         scale = is_def(r) ? r/max(rads) : 1,
         path = [for (i = [steps:-1:1]) let(a=angs[i]) scale*rads[i]*[cos(a), sin(a)]]
-    ) reorient(anchor,spin, two_d=true, path=path, p=path);
+    ) reorient(anchor,spin, two_d=true, path=path, p=path, extent=atype=="hull");
 
 module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=undef, d=undef, anchor=CENTER, spin=0) {
     path = supershape(step=step,m1=m1,m2=m2,n1=n1,n2=n2,n3=n3,a=a,b=b,r=r,d=d);
-    attachable(anchor,spin, two_d=true, path=path) {
+    attachable(anchor,spin,extent=atype=="hull", two_d=true, path=path) {
         polygon(path);
         children();
     }
@@ -1165,7 +1205,7 @@ module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=und
 // Topics: Shapes (2D), Paths (2D), Path Generators, Attachable
 // See Also: regular_ngon(), pentagon(), hexagon(), octagon()
 // Description:
-//   Creates a 2D Reuleaux Polygon; a constant width shape that is not circular.
+//   Creates a 2D Reuleaux Polygon; a constant width shape that is not circular.  Uses "intersect" type anchoring.  
 // Arguments:
 //   N = Number of "sides" to the Reuleaux Polygon.  Must be an odd positive number.  Default: 3
 //   r = Radius of the shape.  Scale shape to fit in a circle of radius r.
@@ -1192,7 +1232,7 @@ module reuleaux_polygon(N=3, r, d, anchor=CENTER, spin=0) {
             cp = polar_to_xy(r, ca)
         ) named_anchor(str("tip",i), cp, unit(cp,BACK), 0),
     ];
-    attachable(anchor,spin, two_d=true, path=path, anchors=anchors) {
+    attachable(anchor,spin, two_d=true, path=path, extent=false, anchors=anchors) {
         polygon(path);
         children();
     }
@@ -1219,7 +1259,7 @@ function reuleaux_polygon(N=3, r, d, anchor=CENTER, spin=0) =
                 cp = polar_to_xy(r, ca)
             ) named_anchor(str("tip",i), cp, unit(cp,BACK), 0),
         ]
-    ) reorient(anchor,spin, two_d=true, path=path, anchors=anchors, p=path);
+    ) reorient(anchor,spin, two_d=true, path=path, extent=false, anchors=anchors, p=path);
 
 
 // vim: expandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap
diff --git a/skin.scad b/skin.scad
index 61e74a2..c7c8996 100644
--- a/skin.scad
+++ b/skin.scad
@@ -150,11 +150,11 @@
 //   method = method for connecting profiles, one of "distance", "fast_distance", "tangent", "direct" or "reindex".  Default: "direct".
 //   z = array of height values for each profile if the profiles are 2d
 //   convexity = convexity setting for use with polyhedron.  (module only) Default: 10
-//   anchor = Translate so anchor point is at the origin.  (module only) Default: "origin"
-//   spin = Rotate this many degrees around Z axis after anchor.  (module only) Default: 0
-//   orient = Vector to rotate top towards after spin  (module only)
-//   extent = use extent method for computing anchors. (module only)  Default: false
-//   cp = set centerpoint for anchor computation.  (module only) Default: object centroid
+//   anchor = Translate so anchor point is at the origin.  Default: "origin"
+//   spin = Rotate this many degrees around Z axis after anchor.  Default: 0
+//   orient = Vector to rotate top towards after spin 
+//   atype = Select "hull" or "intersect anchor types. Default: "hull"
+//   cp = set centerpoint for anchor computation.  Default: "centroid"
 //   style = vnf_vertex_array style.  Default: "min_edge"
 // Example:
 //   skin([octagon(4), circle($fn=70,r=2)], z=[0,3], slices=10);
@@ -383,18 +383,17 @@
 //          }
 //      }
 module skin(profiles, slices, refine=1, method="direct", sampling, caps, closed=false, z, style="min_edge", convexity=10,
-            anchor="origin",cp,spin=0, orient=UP, extent=false)
+            anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull")
 {   
     vnf = skin(profiles, slices, refine, method, sampling, caps, closed, z, style=style);
-    attachable(anchor=anchor, spin=spin, orient=orient, vnf=vnf, extent=extent, cp=is_def(cp) ? cp : centroid(vnf))
-    {      
-        vnf_polyhedron(vnf,convexity=convexity);
+    vnf_polyhedron(vnf,convexity=convexity,spin=spin,anchor=anchor,orient=orient,atype=atype,cp=cp)
         children();
-    }
 }        
 
 
-function skin(profiles, slices, refine=1, method="direct", sampling, caps, closed=false, z, style="min_edge") =
+function skin(profiles, slices, refine=1, method="direct", sampling, caps, closed=false, z, style="min_edge",
+              anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull") =
+  assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"")
   assert(is_def(slices),"The slices argument must be specified.")
   assert(is_list(profiles) && len(profiles)>1, "Must provide at least two profiles")
   let(
@@ -490,13 +489,13 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
                                                         ".  Method ",method[i]," requires equal values"))
                refine[i] * len(pair[0])
           )
-          subdivide_and_slice(pair,slices[i], nsamples, method=sampling)]
+          subdivide_and_slice(pair,slices[i], nsamples, method=sampling)],
+      vnf=vnf_join(
+          [for(i=idx(full_list))
+              vnf_vertex_array(full_list[i], cap1=i==0 && fullcaps[0], cap2=i==len(full_list)-1 && fullcaps[1],
+                               col_wrap=true, style=style)])
   )
-  vnf_join(
-      [for(i=idx(full_list))
-          vnf_vertex_array(full_list[i], cap1=i==0 && fullcaps[0], cap2=i==len(full_list)-1 && fullcaps[1],
-                           col_wrap=true, style=style)]);
-
+  reorient(anchor,spin,orient,vnf=vnf,p=vnf,extent=atype=="hull",cp=cp);
 
 
 // Function&Module: path_sweep()
@@ -566,13 +565,12 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
 //   caps = Can be a boolean or vector of two booleans.  Set to false to disable caps at the two ends.  Default: true
 //   style = vnf_vertex_array style.  Default: "min_edge"
 //   transforms = set to true to return transforms instead of a VNF.  These transforms can be manipulated and passed to sweep().  Default: false.
-//   convexity = convexity parameter for polyhedron().  Only accepted by the module version.  Default: 10
-//   anchor = Translate so anchor point is at the origin.  (module only) Default: "origin"
-//   spin = Rotate this many degrees around Z axis after anchor.  (module only) Default: 0
-//   orient = Vector to rotate top towards after spin  (module only)
-//   extent = use extent method for computing anchors. (module only)  Default: false
-//   cp = set centerpoint for anchor computation.  (module only) Default: object centroid
-//
+//   convexity = convexity parameter for polyhedron().  (module only)  Default: 10
+//   anchor = Translate so anchor point is at the origin. Default: "origin"
+//   spin = Rotate this many degrees around Z axis after anchor. Default: 0
+//   orient = Vector to rotate top towards after spin  
+//   atype  = Select "hull" or "intersect" anchor types.  Default: "hull"
+//   cp = set centerpoint for anchor computation.  Default: "centroid"
 // Example(2D): We'll use this shape in several examples
 //   ushape = [[-10, 0],[-10, 10],[ -7, 10],[ -7, 2],[  7, 2],[  7, 7],[ 10, 7],[ 10, 0]];
 //   polygon(ushape);
@@ -812,20 +810,19 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
 //   }
 module path_sweep(shape, path, method="incremental", normal, closed=false, twist=0, twist_by_length=true,
                     symmetry=1, last_normal, tangent, relaxed=false, caps, style="min_edge", convexity=10,
-                    anchor="origin",cp,spin=0, orient=UP, extent=false)
+                    anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull")
 {
     vnf = path_sweep(shape, path, method, normal, closed, twist, twist_by_length,
                     symmetry, last_normal, tangent, relaxed, caps, style);
-    attachable(anchor=anchor, spin=spin, orient=orient, vnf=vnf, extent=extent, cp=is_def(cp) ? cp : centroid(vnf))
-    {      
-        vnf_polyhedron(vnf,convexity=convexity);
+    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
         children();
-    }
 }        
 
 
 function path_sweep(shape, path, method="incremental", normal, closed=false, twist=0, twist_by_length=true,
-                    symmetry=1, last_normal, tangent, relaxed=false, caps, style="min_edge", transforms=false) = 
+                    symmetry=1, last_normal, tangent, relaxed=false, caps, style="min_edge", transforms=false,
+                    anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull") = 
+  assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"")
   assert(!closed || twist % (360/symmetry)==0, str("For a closed sweep, twist must be a multiple of 360/symmetry = ",360/symmetry))
   assert(closed || symmetry==1, "symmetry must be 1 when closed is false")
   assert(is_integer(symmetry) && symmetry>0, "symmetry must be a positive integer")
@@ -919,7 +916,9 @@ function path_sweep(shape, path, method="incremental", normal, closed=false, twi
                                      apply(transform_list[L], rshape)),
       dummy = ends_match ? 0 : echo("WARNING: ***** The points do not match when closing the model *****")
     )
-    transforms ? transform_list : sweep(is_path(shape)?clockwise_polygon(shape):shape, transform_list, closed=false, caps=fullcaps,style=style);
+    transforms ? transform_list
+               : sweep(is_path(shape)?clockwise_polygon(shape):shape, transform_list, closed=false, caps=fullcaps,style=style,
+                       anchor=anchor,cp=cp,spin=spin,orient=orient,atype=atype);
 
 
 // Function&Module: path_sweep2d()
@@ -946,11 +945,11 @@ function path_sweep(shape, path, method="incremental", normal, closed=false, twi
 //   style = vnf_vertex_array style.  Default: "min_edge"
 //   ---
 //   convexity = convexity parameter for polyhedron (module only)  Default: 10
-//   anchor = Translate so anchor point is at the origin.  (module only)  Default: "origin"
-//   spin = Rotate this many degrees around Z axis after anchor.  (module only) Default: 0
-//   orient = Vector to rotate top towards after spin  (module only)
-//   extent = use extent method for computing anchors. (module only)  Default: false
-//   cp = set centerpoint for anchor computation.  (module only) Default: object centroid
+//   anchor = Translate so anchor point is at the origin.  Default: "origin"
+//   spin = Rotate this many degrees around Z axis after anchor.  Default: 0
+//   orient = Vector to rotate top towards after spin 
+//   atype = Select "hull" or "intersect" anchor types.  Default: "hull"
+//   cp = set centerpoint for anchor computation.  Default: "centroid"
 // Example: Sine wave example with self-intersections at each peak.  This would fail with path_sweep(). 
 //   sinewave = [for(i=[-30:10:360*2+30]) [i/40,3*sin(i)]];
 //   path_sweep2d(circle(r=3,$fn=15), sinewave);
@@ -967,7 +966,8 @@ function path_sweep(shape, path, method="incremental", normal, closed=false, twi
 //   path_sweep2d(circle(r=3.25, $fn=32), select(ellipse,floor(L*.2),ceil(L*.8)),closed=false);
 //   path_sweep2d(circle(r=3.25, $fn=32), select(ellipse,floor(L*.7),ceil(L*.3)),closed=false);
 
-function path_sweep2d(shape, path, closed=false, caps, quality=1, style="min_edge") =
+function path_sweep2d(shape, path, closed=false, caps, quality=1, style="min_edge",
+                      anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull") = 
    let(
         caps = is_def(caps) ? caps
              : closed ? false : true,
@@ -992,23 +992,21 @@ function path_sweep2d(shape, path, closed=false, caps, quality=1, style="min_edg
                         ) 
                         select(path3d(ofs[0],pt.y),map)
                       ]
-                  )
+                  ),
+        vnf = vnf_vertex_array([
+                         each proflist,
+                         if (closed) proflist[0]
+                        ],cap1=fullcaps[0],cap2=fullcaps[1],col_wrap=true,style=style)
    )
-   vnf_vertex_array([
-                     each proflist,
-                     if (closed) proflist[0]
-                    ],cap1=fullcaps[0],cap2=fullcaps[1],col_wrap=true,style=style);
+   reorient(anchor,spin,orient,vnf=vnf,p=vnf,extent=atype=="hull",cp=cp);
 
 
 module path_sweep2d(profile, path, closed=false, caps, quality=1, style="min_edge", convexity=10,
-                    anchor="origin", cp, spin=0, orient=UP, extent=false)
+                    anchor="origin", cp="centroid", spin=0, orient=UP, atype="hull")
 {
    vnf = path_sweep2d(profile, path, closed, caps, quality, style);
-   attachable(anchor=anchor, spin=spin, orient=orient, vnf=vnf, extent=extent, cp=is_def(cp) ? cp : centroid(vnf))
-    {      
-        vnf_polyhedron(vnf,convexity=convexity);
+   vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
         children();
-    }
 }
 
 // Extract vertex mapping from offset face list.  The output of this function
@@ -1071,11 +1069,11 @@ function _ofs_face_edge(face,firstlen,second=false) =
 //   style = vnf_vertex_array style.  Default: "min_edge"
 //   ---
 //   convexity = convexity setting for use with polyhedron.  (module only) Default: 10
-//   anchor = Translate so anchor point is at the origin.  (module only) Default: "origin"
-//   spin = Rotate this many degrees around Z axis after anchor.  (module only) Default: 0
+//   anchor = Translate so anchor point is at the origin. Default: "origin"
+//   spin = Rotate this many degrees around Z axis after anchor. Default: 0
 //   orient = Vector to rotate top towards after spin  (module only)
-//   extent = use extent method for computing anchors. (module only)  Default: false
-//   cp = set centerpoint for anchor computation.  (module only) Default: object centroid
+//   atype = Select "hull" or "intersect" anchor types.  Default: "hull"
+//   cp = set centerpoint for anchor computation. Default: "centroid"
 // Example: This is the "sweep-drop" example from list-comprehension-demos.
 //   function drop(t) = 100 * 0.5 * (1 - cos(180 * t)) * sin(180 * t) + 1;
 //   function path(t) = [0, 0, 80 + 80 * cos(180 * t)];
@@ -1097,7 +1095,8 @@ function _ofs_face_edge(face,firstlen,second=false) =
 //   inside = [for(i=[24:-1:2]) up(i)*rot(i)*scale(1.2*i/24+1)];
 //   sweep(shape, concat(outside,inside));
 
-function sweep(shape, transforms, closed=false, caps, style="min_edge") =
+function sweep(shape, transforms, closed=false, caps, style="min_edge",
+               anchor="origin", cp="centroid", spin=0, orient=UP, atype="hull") = 
     assert(is_consistent(transforms, ident(4)), "Input transforms must be a list of numeric 4x4 matrices in sweep")
     assert(is_path(shape,2) || is_region(shape), "Input shape must be a 2d path or a region.")
     let(
@@ -1128,15 +1127,13 @@ function sweep(shape, transforms, closed=false, caps, style="min_edge") =
 
 
 module sweep(shape, transforms, closed=false, caps, style="min_edge", convexity=10,
-             anchor="origin",cp,spin=0, orient=UP, extent=false)
+             anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull")
 {
     vnf = sweep(shape, transforms, closed, caps, style);
-    attachable(anchor=anchor, spin=spin, orient=orient, vnf=vnf, extent=extent, cp=is_def(cp) ? cp : centroid(vnf))
-    {      
-        vnf_polyhedron(vnf,convexity=convexity);
-        children();
-    }
-}        
+    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
+         children();
+}    
+         
 
 
 // Section: Functions for resampling and slicing profile lists
diff --git a/vnf.scad b/vnf.scad
index 5e44e2d..815534f 100644
--- a/vnf.scad
+++ b/vnf.scad
@@ -787,10 +787,11 @@ function _slice_3dpolygons(polys, dir, cuts) =
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `"origin"`
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
 //   orient = Vector to rotate top towards, after spin.  See [orient](attachments.scad#orient).  Default: `UP`
-module vnf_polyhedron(vnf, convexity=2, extent=true, cp=[0,0,0], anchor="origin", spin=0, orient=UP) {
+//   atype = Select "hull" or "intersect" anchor type.  Default: "hull"
+module vnf_polyhedron(vnf, convexity=2, extent=true, cp="centroid", anchor="origin", spin=0, orient=UP, atype="hull") {
     vnf = is_vnf_list(vnf)? vnf_join(vnf) : vnf;
-    cp = is_def(cp) ? cp : centroid(vnf);
-    attachable(anchor,spin,orient, vnf=vnf, extent=extent, cp=cp) {
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
+    attachable(anchor,spin,orient, vnf=vnf, extent=atype=="hull", cp=cp) {
         polyhedron(vnf[0], vnf[1], convexity=convexity);
         children();
     }

From 45e64f309c08c0f100d112a62f037afb317239ff Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 20:33:51 -0500
Subject: [PATCH 4/9] bug fixes

---
 shapes2d.scad | 3 ++-
 skin.scad     | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/shapes2d.scad b/shapes2d.scad
index 08fc969..977e942 100644
--- a/shapes2d.scad
+++ b/shapes2d.scad
@@ -1173,8 +1173,9 @@ function _superformula(theta,m1,m2,n1,n2=1,n3=1,a=1,b=1) =
 //   linear_extrude(height=0.3, scale=0) supershape(step=1, m1=6, n1=0.4, n2=0, n3=6);
 //   linear_extrude(height=5, scale=0) supershape(step=1, b=3, m1=6, n1=3.8, n2=16, n3=10);
 function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER, spin=0, atype="hull") =
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"")
     let(
-        assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\""),
+
         r = get_radius(r=r, d=d, dflt=undef),
         m2 = is_def(m2) ? m2 : m1,
         n2 = is_def(n2) ? n2 : n1,
diff --git a/skin.scad b/skin.scad
index c7c8996..585e781 100644
--- a/skin.scad
+++ b/skin.scad
@@ -814,7 +814,7 @@ module path_sweep(shape, path, method="incremental", normal, closed=false, twist
 {
     vnf = path_sweep(shape, path, method, normal, closed, twist, twist_by_length,
                     symmetry, last_normal, tangent, relaxed, caps, style);
-    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
+    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, atype=atype, cp=cp)
         children();
 }        
 
@@ -1005,7 +1005,7 @@ module path_sweep2d(profile, path, closed=false, caps, quality=1, style="min_edg
                     anchor="origin", cp="centroid", spin=0, orient=UP, atype="hull")
 {
    vnf = path_sweep2d(profile, path, closed, caps, quality, style);
-   vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
+   vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, atype=atype, cp=cp)
         children();
 }
 

From 47bf93e6cb3ebfbc744848334732a9e64dcf3f34 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 20:46:37 -0500
Subject: [PATCH 5/9] more anchoring fixes

---
 drawing.scad |  4 +++-
 regions.scad |  6 ++++--
 skin.scad    | 18 +++++++++---------
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/drawing.scad b/drawing.scad
index 85b686e..dea89a6 100644
--- a/drawing.scad
+++ b/drawing.scad
@@ -598,6 +598,8 @@ module dashed_stroke(path, dashpat=[3,3], width=1, closed=false) {
 //   start = Start angle of arc.
 //   wedge = If true, include centerpoint `cp` in output to form pie slice shape.
 //   endpoint = If false exclude the last point (function only).  Default: true
+//   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  (Module only) Default: `CENTER`
+//   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  (Module only) Default: `0`
 // Examples(2D):
 //   arc(N=4, r=30, angle=30, wedge=true);
 //   arc(r=30, angle=30, wedge=true);
@@ -703,7 +705,7 @@ function arc(N, r, angle, d, cp, points, width, thickness, start, wedge=false, l
 module arc(N, r, angle, d, cp, points, width, thickness, start, wedge=false, anchor=CENTER, spin=0)
 {
     path = arc(N=N, r=r, angle=angle, d=d, cp=cp, points=points, width=width, thickness=thickness, start=start, wedge=wedge);
-    attachable(anchor,spin, two_d=true, path=path, extent=true) {
+    attachable(anchor,spin, two_d=true, path=path, extent=false) {
         polygon(path);
         children();
     }
diff --git a/regions.scad b/regions.scad
index d5a2b28..1e453f5 100644
--- a/regions.scad
+++ b/regions.scad
@@ -288,6 +288,7 @@ function force_region(poly) = is_path(poly) ? [poly] : poly;
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `"origin"`
 //   spin = Rotate this many degrees after anchor.  See [spin](attachments.scad#spin).  Default: `0`
 //   cp = Centerpoint for determining intersection anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 2D point.  Default: "centroid"
+//   atype = Set to "hull" or "intersect to select anchor type.  Default: "hull"
 // Example(2D): Displaying a region
 //   region([circle(d=50), square(25,center=true)]);
 // Example(2D): Displaying a list of polygons that intersect each other, which is not a region
@@ -298,13 +299,14 @@ function force_region(poly) = is_path(poly) ? [poly] : poly;
 //   region(rgn);
 module region(r, anchor="origin", spin=0, cp="centroid")
 {
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
     r = force_region(r);
     dummy=assert(is_region(r), "Input is not a region");
     points = flatten(r);
     lengths = [for(path=r) len(path)];
     starts = [0,each cumsum(lengths)];
     paths = [for(i=idx(r)) count(s=starts[i], n=lengths[i])];
-    attachable(anchor, spin, two_d=true, region=r, extent=false, cp=cp){
+    attachable(anchor, spin, two_d=true, region=r, extent=atype=="hull", cp=cp){
       polygon(points=points, paths=paths);
       children();
     }
@@ -646,7 +648,7 @@ module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg,
         slices=slices, maxseg=maxseg,
         style=style
     );
-    attachable(anchor,spin,orient, cp=cp, vnf=vnf, extent=!anchor_isect, anchors=anchors) {
+    attachable(anchor,spin,orient, cp=cp, region=region, h=height, extent=atype=="hull", anchors=anchors) {
         vnf_polyhedron(vnf, convexity=convexity);
         children();
     }
diff --git a/skin.scad b/skin.scad
index 585e781..3880f08 100644
--- a/skin.scad
+++ b/skin.scad
@@ -16,9 +16,9 @@
 
 // Function&Module: skin()
 // Usage: As module:
-//   skin(profiles, slices, [z=], [refine=], [method=], [sampling=], [caps=], [closed=], [style=], [convexity=], [anchor=],[cp=],[spin=],[orient=],[extent=]) [attachments];
+//   skin(profiles, slices, [z=], [refine=], [method=], [sampling=], [caps=], [closed=], [style=], [convexity=], [anchor=],[cp=],[spin=],[orient=],[atype=]) {attachments};
 // Usage: As function:
-//   vnf = skin(profiles, slices, [z=], [refine=], [method=], [sampling=], [caps=], [closed=], [style=]);
+//   vnf = skin(profiles, slices, [z=], [refine=], [method=], [sampling=], [caps=], [closed=], [style=], [anchor=],[cp=],[spin=],[orient=],[atype=]);
 // Description:
 //   Given a list of two or more path `profiles` in 3d space, produces faces to skin a surface between
 //   the profiles.  Optionally the first and last profiles can have endcaps, or the first and last profiles
@@ -500,9 +500,9 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
 
 // Function&Module: path_sweep()
 // Usage: As module
-//   path_sweep(shape, path, [method], [normal=], [closed=], [twist=], [twist_by_length=], [symmetry=], [last_normal=], [tangent=], [relaxed=], [caps=], [style=], [convexity=], [transforms=], [anchor=], [cp=], [spin=], [orient=], [extent=]) [attachments];
-// Usage: As function   
-//   vnf = path_sweep(shape, path, [method], [normal=], [closed=], [twist=], [twist_by_length=], [symmetry=], [last_normal=], [tangent=], [relaxed=], [caps=], [style=], [convexity=], [transforms=]);
+//   path_sweep(shape, path, [method], [normal=], [closed=], [twist=], [twist_by_length=], [symmetry=], [last_normal=], [tangent=], [relaxed=], [caps=], [style=], [convexity=], [anchor=], [cp=], [spin=], [orient=], [atype=]) {attachments};
+// Usage: As function
+//   vnf = path_sweep(shape, path, [method], [normal=], [closed=], [twist=], [twist_by_length=], [symmetry=], [last_normal=], [tangent=], [relaxed=], [caps=], [style=], [transforms=], [anchor=], [cp=], [spin=], [orient=], [atype=]) {attachments};
 // Description:
 //   Takes as input a 2D polygon path, and a 2d or 3d path and constructs a polyhedron by sweeping the shape along the path.
 //   When run as a module returns the polyhedron geometry.  When run as a function returns a VNF by default or if you set `transforms=true`
@@ -923,9 +923,9 @@ function path_sweep(shape, path, method="incremental", normal, closed=false, twi
 
 // Function&Module: path_sweep2d()
 // Usage: as module
-//   path_sweep2d(shape, path, [closed], [caps], [quality], [style], [convexity=], [anchor=], [spin=], [orient=], [extent=], [cp=]) [attachments];
+//   path_sweep2d(shape, path, [closed], [caps], [quality], [style], [convexity=], [anchor=], [spin=], [orient=], [atype=], [cp=]) {attachments};
 // Usage: as function
-//   vnf = path_sweep2d(shape, path, [closed], [caps], [quality], [style]);
+//   vnf = path_sweep2d(shape, path, [closed], [caps], [quality], [style], [anchor=], [spin=], [orient=], [atype=], [cp=]);
 // Description:
 //   Takes an input 2D polygon (the shape) and a 2d path and constructs a polyhedron by sweeping the shape along the path.
 //   When run as a module returns the polyhedron geometry.  When run as a function returns a VNF.
@@ -1044,9 +1044,9 @@ function _ofs_face_edge(face,firstlen,second=false) =
 
 // Function&Module: sweep()
 // Usage: As Module
-//   sweep(shape, transforms, [closed], [caps], [style], [convexity=], [anchor=], [spin=], [orient=], [extent=]) [attachments];
+//   sweep(shape, transforms, [closed], [caps], [style], [convexity=], [anchor=], [spin=], [orient=], [atype=]) [attachments];
 // Usage: As Function
-//   vnf = sweep(shape, transforms, [closed], [caps], [style]);
+//   vnf = sweep(shape, transforms, [closed], [caps], [style], [anchor=], [spin=], [orient=], [atype=]);
 // Description:
 //   The input `shape` must be a non-self-intersecting 2D polygon or region, and `transforms`
 //   is a list of 4x4 transformation matrices.  The sweep algorithm applies each transformation in sequence

From cd664f830c1a8c9bd8aabce0c6d6229d10099d24 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 22:13:00 -0500
Subject: [PATCH 6/9] attachment bugfixes

---
 regions.scad  | 2 +-
 shapes2d.scad | 3 ++-
 skin.scad     | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/regions.scad b/regions.scad
index 1e453f5..253d91b 100644
--- a/regions.scad
+++ b/regions.scad
@@ -297,7 +297,7 @@ function force_region(poly) = is_path(poly) ? [poly] : poly;
 //       [square([60,10], center=true)]
 //   );
 //   region(rgn);
-module region(r, anchor="origin", spin=0, cp="centroid")
+module region(r, anchor="origin", spin=0, cp="centroid", atype="hull")
 {
     assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
     r = force_region(r);
diff --git a/shapes2d.scad b/shapes2d.scad
index 977e942..ad93b84 100644
--- a/shapes2d.scad
+++ b/shapes2d.scad
@@ -1189,7 +1189,8 @@ function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER
         path = [for (i = [steps:-1:1]) let(a=angs[i]) scale*rads[i]*[cos(a), sin(a)]]
     ) reorient(anchor,spin, two_d=true, path=path, p=path, extent=atype=="hull");
 
-module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=undef, d=undef, anchor=CENTER, spin=0) {
+module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=undef, d=undef, anchor=CENTER, spin=0, atype="hull") {
+    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
     path = supershape(step=step,m1=m1,m2=m2,n1=n1,n2=n2,n3=n3,a=a,b=b,r=r,d=d);
     attachable(anchor,spin,extent=atype=="hull", two_d=true, path=path) {
         polygon(path);
diff --git a/skin.scad b/skin.scad
index 3880f08..cf60b33 100644
--- a/skin.scad
+++ b/skin.scad
@@ -1130,7 +1130,7 @@ module sweep(shape, transforms, closed=false, caps, style="min_edge", convexity=
              anchor="origin",cp="centroid",spin=0, orient=UP, atype="hull")
 {
     vnf = sweep(shape, transforms, closed, caps, style);
-    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, vnf=vnf, atype=atype, cp=cp)
+    vnf_polyhedron(vnf,convexity=convexity,anchor=anchor, spin=spin, orient=orient, atype=atype, cp=cp)
          children();
 }    
          

From 2bfb4e39e7af0d0445a34daae9f6d7d3eb83e461 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Tue, 16 Nov 2021 23:12:03 -0500
Subject: [PATCH 7/9] more fixes

---
 attachments.scad | 19 ++++++++++++-------
 regions.scad     |  2 +-
 vnf.scad         |  2 +-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/attachments.scad b/attachments.scad
index 7991ff2..057a5f4 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -1518,15 +1518,20 @@ function _get_cp(geom) =
     let(cp=select(geom,-3))
     is_vector(cp) ? cp
   : let(
+       f=echo(type=geom[0]),
         type = in_list(geom[0],["vnf_extent","vnf_isect"]) ? "vnf"
              : in_list(geom[0],["rgn_extent","rgn_isect"]) ? "path"
+             : in_list(geom[0],["xrgn_extent","xrgn_isect"]) ? "xpath"
              : "other"
     )
     assert(type!="other", "Invalid cp value")
-    cp=="centroid" ? centroid(geom[1])
+    cp=="centroid" ? (
+       type=="vnf" && (len(geom[1][0])==0 || len(geom[1][1])==0) ? [0,0,0] :
+       [each centroid(geom[1]), if (type=="xpath") geom[2]/2]
+    )
   : let(points = type=="vnf"?geom[1][0]:flatten(force_region(geom[1])))
-    cp=="mean" ? mean(points)
-  : cp=="box" ? mean(pointlist_bounds(points))
+    cp=="mean" ? [each mean(points), if (type=="xpath") geom[2]/2]
+  : cp=="box" ?[each  mean(pointlist_bounds(points)), if (type=="xpath") geom[2]/2]
   : assert(false,"Invalid cp specification");
 
 
@@ -1758,7 +1763,7 @@ function _find_anchor(anchor, geom) =
             pos = point2d(cp) + rot(from=RIGHT, to=anchor, p=[maxx,midy])
         ) [anchor, pos, anchor, 0]
     ) : type == "xrgn_isect"? ( //region
-        assert(anchor.z==0, "The Z component of an anchor for a 2D shape must be 0.")
+        assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
         let(
             rgn_raw = move(-point2d(cp), p=geom[1]),
             l = geom[2],
@@ -1788,10 +1793,10 @@ function _find_anchor(anchor, geom) =
             oang = approx(xyvec, [0,0])? 0 : atan2(xyvec.y, xyvec.x) + 90
         ) [anchor, pos, vec, oang]
     ) : type == "xrgn_extent"? ( //region
-        assert(anchor.z==0, "The Z component of an anchor for a 2D shape must be 0.")
+        assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
         let(
-            rgn_raw = geom[1], l = geom[2],
-            rgn = is_region(rgn_raw)? rgn_raw : [rgn_raw],
+            rgn = force_region(geom[1]),
+            l = geom[2],
             anchor = point3d(anchor),
             xyanch = point2d(anchor),
             m = (
diff --git a/regions.scad b/regions.scad
index 253d91b..c75dfae 100644
--- a/regions.scad
+++ b/regions.scad
@@ -637,7 +637,7 @@ function region_parts(region) =
 //   mrgn = union(rgn1,rgn2);
 //   orgn = difference(mrgn,rgn3);
 //   linear_sweep(orgn,height=20,convexity=16) show_anchors();
-module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg, style="default", convexity, anchor_isect=false, spin=0, orient=UP, cp="centroid", anchor="origin") {
+module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg, style="default", convexity, anchor_isect=false, spin=0, orient=UP, cp="centroid", anchor="origin", atype="hull") {
     region = force_region(region);
     dummy=assert(is_region(region),"Input is not a region");
     anchor = center ? "zcenter" : anchor;
diff --git a/vnf.scad b/vnf.scad
index 815534f..3efcf20 100644
--- a/vnf.scad
+++ b/vnf.scad
@@ -877,7 +877,7 @@ function vnf_area(vnf) =
 /// The centroid of a tetrahedron is the average of its vertices.
 /// The centroid of the total is the volume weighted average.
 function _vnf_centroid(vnf,eps=EPSILON) =
-    assert(is_vnf(vnf) && len(vnf[0])!=0 ) 
+    assert(is_vnf(vnf) && len(vnf[0])!=0 && len(vnf[1])!=0,"Invalid or empty VNF given to centroid") 
     let(
         verts = vnf[0],
         pos = sum([

From 475129fd95821a48423561730ed77a44d1d4fc53 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Wed, 17 Nov 2021 13:38:07 -0500
Subject: [PATCH 8/9] revamp extruded region attachables and apply to
 linear_sweep.

---
 attachments.scad | 102 ++++++++++++++---------------------------------
 regions.scad     |   5 ++-
 skin.scad        |   8 ++--
 strings.scad     |   2 +-
 vnf.scad         |   2 +-
 5 files changed, 40 insertions(+), 79 deletions(-)

diff --git a/attachments.scad b/attachments.scad
index 057a5f4..daf0cbd 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -1515,10 +1515,10 @@ function _attach_transform(anchor, spin, orient, geom, p) =
 
 
 function _get_cp(geom) =
+    
     let(cp=select(geom,-3))
     is_vector(cp) ? cp
   : let(
-       f=echo(type=geom[0]),
         type = in_list(geom[0],["vnf_extent","vnf_isect"]) ? "vnf"
              : in_list(geom[0],["rgn_extent","rgn_isect"]) ? "path"
              : in_list(geom[0],["xrgn_extent","xrgn_isect"]) ? "xpath"
@@ -1549,20 +1549,22 @@ function _get_cp(geom) =
 //   anchor = Vector or named anchor string.
 //   geom = The geometry description of the shape.
 function _find_anchor(anchor, geom) =
+    is_string(anchor)? (  
+          anchor=="origin"? [anchor, CENTER, UP, 0]
+        : let(
+              anchors = last(geom),
+              found = search([anchor], anchors, num_returns_per_match=1)[0]
+          )
+          assert(found!=[], str("Unknown anchor: ",anchor))
+          anchors[found]
+    ) :
     let( 
         cp = _get_cp(geom),
         offset_raw = select(geom,-2),
         offset = [for (i=[0:2]) anchor[i]==0? 0 : offset_raw[i]],  // prevents bad centering.
-        anchors = last(geom),
         type = geom[0]
     )
-    is_string(anchor)? (  
-          anchor=="origin"? [anchor, CENTER, UP, 0]
-        : let(found = search([anchor], anchors, num_returns_per_match=1)[0])
-          assert(found!=[], str("Unknown anchor: ",anchor))
-          anchors[found]
-    ) : 
-    assert(is_vector(anchor),str("anchor=",anchor))
+    assert(is_vector(anchor),str("Invalid anchor: anchor=",anchor))
     let(anchor = point3d(anchor))
     anchor==CENTER? [anchor, cp, UP, 0] :
     let(
@@ -1725,8 +1727,7 @@ function _find_anchor(anchor, geom) =
     ) : type == "rgn_isect"? ( //region
         assert(anchor.z==0, "The Z component of an anchor for a 2D shape must be 0.")
         let(
-            rgn_raw = move(-point2d(cp), p=geom[1]),
-            rgn = is_region(rgn_raw)? rgn_raw : [rgn_raw],
+            rgn = force_region(move(-point2d(cp), p=geom[1])),
             anchor = point2d(anchor),
             isects = [
                 for (path=rgn, t=triplet(path,true)) let(
@@ -1753,68 +1754,27 @@ function _find_anchor(anchor, geom) =
         let(
             rgn = force_region(geom[1]),
             anchor = point2d(anchor),
-            m = rot(from=anchor, to=RIGHT) * move(-[cp.x, cp.y, 0]),
-            rpts = apply(m, flatten(rgn)),
+            rpts = rot(from=anchor, to=RIGHT, p=flatten(rgn)),
             maxx = max(column(rpts,0)),
-            idxs = [for (i = idx(rpts)) if (approx(rpts[i].x, maxx)) i],
-            miny = min([for (i=idxs) rpts[i].y]),
-            maxy = max([for (i=idxs) rpts[i].y]),
-            midy = (miny+maxy)/2,
-            pos = point2d(cp) + rot(from=RIGHT, to=anchor, p=[maxx,midy])
-        ) [anchor, pos, anchor, 0]
-    ) : type == "xrgn_isect"? ( //region
-        assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
-        let(
-            rgn_raw = move(-point2d(cp), p=geom[1]),
-            l = geom[2],
-            rgn = is_region(rgn_raw)? rgn_raw : [rgn_raw],
-            anchor = point3d(anchor),
-            xyanch = point2d(anchor)
-        ) approx(xyanch,[0,0])? [anchor, [0,0,anchor.z*l/2], unit(anchor,UP), 0] :
-        let(
-            isects = [
-                for (path=rgn, t=triplet(path,true)) let(
-                    seg1 = [t[0],t[1]],
-                    seg2 = [t[1],t[2]],
-                    isect = line_intersection([[0,0],xyanch], seg1, RAY, SEGMENT),
-                    n = is_undef(isect)? [0,1] :
-                        !approx(isect, t[1])? line_normal(seg1) :
-                        unit((line_normal(seg1)+line_normal(seg2))/2,[0,1]),
-                    n2 = vector_angle(xyanch,n)>90? -n : n
-                )
-                if(!is_undef(isect) && !approx(isect,t[0]))
-                [norm(isect), isect, n2]
-            ],
-            maxidx = max_index(column(isects,0)),
-            isect = isects[maxidx],
-            pos = point3d(cp) + point3d(isect[1]) + unit([0,0,anchor.z],CENTER)*l/2,
-            xyvec = unit(isect[2],[0,1]),
-            vec = unit((point3d(xyvec)+UP*anchor.z)/2,UP),
-            oang = approx(xyvec, [0,0])? 0 : atan2(xyvec.y, xyvec.x) + 90
-        ) [anchor, pos, vec, oang]
-    ) : type == "xrgn_extent"? ( //region
-        assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
-        let(
-            rgn = force_region(geom[1]),
-            l = geom[2],
-            anchor = point3d(anchor),
-            xyanch = point2d(anchor),
-            m = (
-                approx(xyanch,[0,0])? [[1,0,0],[0,1,0],[0,0,1]] :
-                rot(from=xyanch, to=RIGHT, planar=true)
-            ) * move(-[cp.x, cp.y]),
-            rpts = apply(m, flatten(rgn)),
-            maxx = max(column(rpts,0)),
-            idxs = [for (i = idx(rpts)) if (approx(rpts[i].x, maxx)) i],
-            ys = [for (i=idxs) rpts[i].y],
+            ys = [for (pt=rpts) if (approx(pt.x, maxx)) pt.y],            
             midy = (min(ys)+max(ys))/2,
-            xypos = point2d(cp) + (
-                approx(xyanch,[0,0])? [0,0] :
-                rot(from=RIGHT, to=xyanch, p=[maxx,midy])
-            ),
-            pos = point3d(xypos) + unit([0,0,anchor.z],CENTER)*l/2,
-            vec = unit((point3d(xyanch)+UP*anchor.z)/2,UP)
-        ) [anchor, pos, vec, oang]
+            pos = rot(from=RIGHT, to=anchor, p=[maxx,midy])
+        ) [anchor, pos, unit(anchor), 0]
+    ) : type=="xrgn_extent" || type=="xrgn_isect" ? (  // extruded region
+        assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
+        let(
+            anchor_xy = point2d(anchor),
+            L = geom[2]
+        )
+        approx(anchor_xy,[0,0]) ? [anchor, up(anchor.z*L/2,cp), anchor, oang] :
+        let(
+            newgeom = list_set(geom, [0,len(geom)-3], [substr(geom[0],1), point2d(cp)]),
+            result2d = _find_anchor(anchor_xy, newgeom),
+            pos = point3d(result2d[1], cp.z+anchor.z*L/2),
+            vec = unit(point3d(result2d[2], anchor.z),UP),
+            oang = atan2(vec.y,vec.x) + 90
+        )
+        [anchor, pos, vec, oang]
     ) :
     assert(false, "Unknown attachment geometry type.");
 
diff --git a/regions.scad b/regions.scad
index c75dfae..6097494 100644
--- a/regions.scad
+++ b/regions.scad
@@ -612,7 +612,7 @@ function region_parts(region) =
 //   style = The style to use when triangulating the surface of the object.  Valid values are `"default"`, `"alt"`, or `"quincunx"`.
 //   convexity = Max number of surfaces any single ray could pass through.  Module use only.
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `"origin"`
-//   anchor_isect = If true, anchoring it performed by finding where the anchor vector intersects the swept shape.  Default: false
+//   atype = Set to "hull" or "intersect" to select anchor type.  Default: "hull"
 //   cp = Centerpoint for determining intersection anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
 //   orient = Vector to rotate top towards, after spin.  See [orient](attachments.scad#orient).  Default: `UP`
@@ -637,7 +637,8 @@ function region_parts(region) =
 //   mrgn = union(rgn1,rgn2);
 //   orgn = difference(mrgn,rgn3);
 //   linear_sweep(orgn,height=20,convexity=16) show_anchors();
-module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg, style="default", convexity, anchor_isect=false, spin=0, orient=UP, cp="centroid", anchor="origin", atype="hull") {
+module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg, style="default", convexity,
+                    spin=0, orient=UP, cp="centroid", anchor="origin", atype="hull") {
     region = force_region(region);
     dummy=assert(is_region(region),"Input is not a region");
     anchor = center ? "zcenter" : anchor;
diff --git a/skin.scad b/skin.scad
index cf60b33..467dba0 100644
--- a/skin.scad
+++ b/skin.scad
@@ -154,7 +154,7 @@
 //   spin = Rotate this many degrees around Z axis after anchor.  Default: 0
 //   orient = Vector to rotate top towards after spin 
 //   atype = Select "hull" or "intersect anchor types. Default: "hull"
-//   cp = set centerpoint for anchor computation.  Default: "centroid"
+//   cp = Centerpoint for determining "intersect" anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 //   style = vnf_vertex_array style.  Default: "min_edge"
 // Example:
 //   skin([octagon(4), circle($fn=70,r=2)], z=[0,3], slices=10);
@@ -570,7 +570,7 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
 //   spin = Rotate this many degrees around Z axis after anchor. Default: 0
 //   orient = Vector to rotate top towards after spin  
 //   atype  = Select "hull" or "intersect" anchor types.  Default: "hull"
-//   cp = set centerpoint for anchor computation.  Default: "centroid"
+//   cp = Centerpoint for determining "intersect" anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 // Example(2D): We'll use this shape in several examples
 //   ushape = [[-10, 0],[-10, 10],[ -7, 10],[ -7, 2],[  7, 2],[  7, 7],[ 10, 7],[ 10, 0]];
 //   polygon(ushape);
@@ -949,7 +949,7 @@ function path_sweep(shape, path, method="incremental", normal, closed=false, twi
 //   spin = Rotate this many degrees around Z axis after anchor.  Default: 0
 //   orient = Vector to rotate top towards after spin 
 //   atype = Select "hull" or "intersect" anchor types.  Default: "hull"
-//   cp = set centerpoint for anchor computation.  Default: "centroid"
+//   cp = Centerpoint for determining "intersect" anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 // Example: Sine wave example with self-intersections at each peak.  This would fail with path_sweep(). 
 //   sinewave = [for(i=[-30:10:360*2+30]) [i/40,3*sin(i)]];
 //   path_sweep2d(circle(r=3,$fn=15), sinewave);
@@ -1073,7 +1073,7 @@ function _ofs_face_edge(face,firstlen,second=false) =
 //   spin = Rotate this many degrees around Z axis after anchor. Default: 0
 //   orient = Vector to rotate top towards after spin  (module only)
 //   atype = Select "hull" or "intersect" anchor types.  Default: "hull"
-//   cp = set centerpoint for anchor computation. Default: "centroid"
+//   cp = Centerpoint for determining "intersect" anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 // Example: This is the "sweep-drop" example from list-comprehension-demos.
 //   function drop(t) = 100 * 0.5 * (1 - cos(180 * t)) * sin(180 * t) + 1;
 //   function path(t) = [0, 0, 80 + 80 * cos(180 * t)];
diff --git a/strings.scad b/strings.scad
index 962ea30..57f92ef 100644
--- a/strings.scad
+++ b/strings.scad
@@ -17,7 +17,7 @@
 // Arguments:
 //   str = string to operate on
 //   pos = starting index of substring, or vector of first and last position.  Default: 0
-//   len = length of substring, or omit it to get the rest of the string.  If len is less than zero the emptry string is returned.  
+//   len = length of substring, or omit it to get the rest of the string.  If len is zero or less then the emptry string is returned.  
 // Example:
 //   substr("abcdefg",3,3);     // Returns "def"
 //   substr("abcdefg",2);       // Returns "cdefg"
diff --git a/vnf.scad b/vnf.scad
index 3efcf20..92b7ce5 100644
--- a/vnf.scad
+++ b/vnf.scad
@@ -783,7 +783,7 @@ function _slice_3dpolygons(polys, dir, cuts) =
 //   vnf = A VNF structure, or list of VNF structures.
 //   convexity = Max number of times a line could intersect a wall of the shape.
 //   extent = If true, calculate anchors by extents, rather than intersection.  Default: true.
-//   cp = Centerpoint of VNF to use for anchoring when `extent` is false.  Default: `[0, 0, 0]`
+//   cp = Centerpoint for determining intersection anchors or centering the shape.  Determintes the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: "centroid"
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#anchor).  Default: `"origin"`
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#spin).  Default: `0`
 //   orient = Vector to rotate top towards, after spin.  See [orient](attachments.scad#orient).  Default: `UP`

From ba2e1d45f17724de652c90aeca15e794b6d50e77 Mon Sep 17 00:00:00 2001
From: Adrian Mariano <avm4@cornell.edu>
Date: Wed, 17 Nov 2021 14:16:22 -0500
Subject: [PATCH 9/9] remove anchor_isect reference

---
 regions.scad | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/regions.scad b/regions.scad
index 6097494..059235d 100644
--- a/regions.scad
+++ b/regions.scad
@@ -657,7 +657,7 @@ module linear_sweep(region, height=1, center, twist=0, scale=1, slices, maxseg,
 
 
 function linear_sweep(region, height=1, center, twist=0, scale=1, slices,
-                      maxseg, style="default", cp="centroid", anchor_isect=false, anchor, spin=0, orient=UP) =
+                      maxseg, style="default", cp="centroid", atype="hull", anchor, spin=0, orient=UP) =
     let(
         region = force_region(region)
     )
@@ -702,7 +702,7 @@ function linear_sweep(region, height=1, center, twist=0, scale=1, slices,
             for (rgn = regions) vnf_from_region(rgn, ident(4), reverse=true),
             for (rgn = trgns) vnf_from_region(rgn, up(height), reverse=false)
         ])
-    ) reorient(anchor,spin,orient, cp=cp, vnf=vnf, extent=!anchor_isect, p=vnf, anchors=anchors);
+    ) reorient(anchor,spin,orient, cp=cp, vnf=vnf, extent=atype=="hull", p=vnf, anchors=anchors);