Added subdivide_long_segments(), path_add_jitter(), jittered_poly()

paths.scad

@@ -569,6 +569,41 @@ function _corner_roundover_path(p1, p2, p3, r, d) =
 
 
 
+// Function: path_add_jitter()
+// Topics: Paths
+// See Also: jittered_poly(), subdivide_long_segments()
+// Usage:
+//   jpath = path_add_jitter(path, <dist>, <closed=>);
+// Description:
+//   Adds tiny jitter offsets to collinear points in the given path so that they
+//   are no longer collinear.  This is useful for preserving subdivision on long
+//   straight segments, when making geometry with `polygon()`, for use with
+//   `linear_exrtrude()` with a `twist()`.
+// Arguments:
+//   path = The path to add jitter to.
+//   dist = The amount to jitter points by.  Default: 1/512 (0.00195)
+//   ---
+//   closed = If true, treat path like a closed polygon.  Default: true
+// Example:
+//   d = 100; h = 75; quadsize = 5;
+//   path = pentagon(d=d);
+//   spath = subdivide_long_segments(path, quadsize, closed=true);
+//   jpath = path_add_jitter(spath, closed=true);
+//   linear_extrude(height=h, twist=72, slices=h/quadsize)
+//      polygon(jpath);
+function path_add_jitter(path, dist=1/512, closed=true) =
+    assert(is_path(path))
+    assert(is_finite(dist))
+    assert(is_bool(closed))
+    [
+        path[0],
+        for (i=idx(path,s=1,e=closed?-1:-2)) let(
+            n = line_normal([path[i-1],path[i]])
+        ) path[i] + n * (collinear(select(path,i-1,i+1))? (dist * ((i%2)*2-1)) : 0),
+        if (!closed) last(path)
+    ];
+
+
 // Function: path3d_spiral()
 // Description:
 //   Returns a 3D spiral path.
@@ -928,6 +963,31 @@ module modulated_circle(r, sines=[[1,1]], d)
 }
 
 
+// Module: jittered_poly()
+// Topics: Extrusions
+// See Also: path_add_jitter(), subdivide_long_segments()
+// Usage:
+//   jittered_poly(path, <dist>);
+// Description:
+//   Creates a 2D polygon shape from the given path in such a way that any extra
+//   collinear points are not stripped out in the way that `polygon()` normally does.
+//   This is useful for refining the mesh of a `linear_extrude()` with twist.
+// Arguments:
+//   path = The path to add jitter to.
+//   dist = The amount to jitter points by.  Default: 1/512 (0.00195)
+// Example:
+//   d = 100; h = 75; quadsize = 5;
+//   path = pentagon(d=d);
+//   spath = subdivide_long_segments(path, quadsize, closed=true);
+//   linear_extrude(height=h, twist=72, slices=h/quadsize)
+//      jittered_poly(spath);
+module jittered_poly(path, dist=1/512) {
+    polygon(path_add_jitter(path, dist, closed=true));
+}
+
+
+
+
 // Section: 3D Modules
 
 

skin.scad

@@ -542,6 +542,7 @@ function _skin_core(profiles, caps) =
 
 
 // Function: subdivide_and_slice()
+// Topics: Paths, Path Subdivision
 // Usage:
 //   newprof = subdivide_and_slice(profiles, slices, <numpoints>, <method>, <closed>);
 // Description:
@@ -569,7 +570,39 @@ function subdivide_and_slice(profiles, slices, numpoints, method="length", close
   slice_profiles(fixpoly, slices, closed);
   
 
+// Function: subdivide_long_segments()
+// Topics: Paths, Path Subdivision
+// See Also: subdivide_path(), subdivide_and_slice(), path_add_jitter(), jittered_poly()
+// Usage:
+//   spath = subdivide_long_segments(path, maxlen, <closed=>);
+// Description:
+//   Evenly subdivides long `path` segments until they are all shorter than `maxlen`.
+// Arguments:
+//   path = The path to subdivide.
+//   maxlen = The maximum allowed path segment length.
+//   ---
+//   closed = If true, treat path like a closed polygon.  Default: true
+// Example:
+//   path = pentagon(d=100);
+//   spath = subdivide_long_segments(path, 10, closed=true);
+//   stroke(path);
+//   color("lightgreen") move_copies(path) circle(d=5,$fn=12);
+//   color("blue") move_copies(spath) circle(d=3,$fn=12);
+function subdivide_long_segments(path, maxlen, closed=false) =
+    assert(is_path(path))
+    assert(is_finite(maxlen))
+    assert(is_bool(closed))
+    [
+        for (p=pair(path,closed)) let(
+            steps = ceil(norm(p[1]-p[0])/maxlen)
+        ) each lerp(p[0],p[1],[0:1/steps:1-EPSILON]),
+        if (!closed) last(path)
+    ];
+
+
+
 // Function: slice_profiles()
+// Topics: Paths, Path Subdivision
 // Usage:
 //   profs = slice_profiles(profiles, slices, <closed>);
 // Description: