Added support for rounding factor k to path_to_bezier and smooth_path.

beziers.scad

@@ -318,26 +318,40 @@ function bezier_polyline(bezier, splinesteps=16, N=3) = let(
 	);
 
 
+
 // Function: path_to_bezier()
 // Usage:
-//   path_to_bezier(path,[tangent],[closed]);
+//   path_to_bezier(path,[tangent],[k],[closed]);
 // Description:
 //   Given an input path and optional path of tangent vectors, computes a cubic (degree 3) bezier path that passes
 //   through every point on the input path and matches the tangent vectors.  If you do not supply
 //   the tangent it will be computed using path_tangents.  If the path is closed specify this
-//   by setting closed=true.
+//   by setting closed=true.  If you specify the curvature parameter k it scales the tangent vectors,
+//   which will increase or decrease the curvature of the interpolated bezier.  Negative values of k create loops at the corners,
+//   so they are not allowed.  Sufficiently large k values will also produce loops.
 // Arguments:
 //   path = path of points to define the bezier
 //   tangents = optional list of tangent vectors at every point
+//   k = curvature parameter, a scalar or vector to adjust curvature at each point
 //   closed = set to true for a closed path.  Default: false
-function path_to_bezier(path, tangents, closed=false) =
+function path_to_bezier(path, tangents, k, closed=false) =
   assert(is_path(path,dim=undef),"Input path is not a valid path")
   assert(is_undef(tangents) || is_path(tangents,dim=len(path[0])),"Tangents must be a path of the same dimension as the input path")
+  assert(is_undef(tangents) || len(path)==len(tangents), "Input tangents must be the same length as the input path")
+  let(
+     k = is_undef(k) ? repeat(1, len(path)) :
+         is_list(k) ? k : repeat(k, len(path)),
+     k_bad = [for(entry=k) if (entry<0) entry]
+  )
+  assert(len(k)==len(path), "Curvature parameter k must have the same length as the path")
+  assert(k_bad==[], "Curvature parameter k must be a nonnegative number or list of nonnegative numbers")
   let(
     tangents = is_def(tangents)? tangents : deriv(path, closed=closed),
     lastpt = len(path) - (closed?0:1)
   )
-  [for(i=[0:lastpt-1]) each [path[i], path[i]+tangents[i]/3, select(path,i+1)-select(tangents,i+1)/3],
+  [for(i=[0:lastpt-1]) each [path[i],
+                             path[i]+k[i]*tangents[i]/3,
+                             select(path,i+1)-select(k,i+1)*select(tangents,i+1)/3],
    select(path,lastpt)];
 
 

rounding.scad

@@ -9,10 +9,10 @@
 //   ```
 //////////////////////////////////////////////////////////////////////
 
-include <BOSL2/beziers.scad>
-include <BOSL2/strings.scad>
-include <BOSL2/structs.scad>
-include <BOSL2/skin.scad>
+include <beziers.scad>
+include <strings.scad>
+include <structs.scad>
+include <skin.scad>
 
 
 // CommonCode:
@@ -409,16 +409,23 @@ function _rounding_offsets(edgespec,z_dir=1) =
 
 // Function: smooth_path()
 // Usage:
-//   smooth_path(path, [tangents], [splinesteps], [closed]
+//   smooth_path(path, [tangents], [k], [splinesteps], [closed]
 // Description:
 //   Smooths the input path using a cubic spline.  Every segment of the path will be replaced by a cubic curve
 //   with `splinesteps` points.  The cubic interpolation will pass through every input point on the path
 //   and will match the tangents at every point.  If you do not specify tangents they will be computed using
-//   deriv().  Note that the magnitude of the tangents affects the result.  See also path_to_bezier().  
+//   deriv().  See also path_to_bezier().
+//
+//   Note that the magnitude of the tangents affects the result.  If you increase it you will get a blunter
+//   corner with a larger radius of curvature.  Decreasing it will produce a sharp corner.  You can specify
+//   the curvature factor `k` to adjust the curvature.  It can be a scalar or a vector the same length as
+//   the path and is used to scale the tangent vectors.  Negative values of k create loops at the corners,
+//   so they are not allowed.  Sufficiently large k values will also produce loops.
 // Arguments:
 //   path = path to smooth
 //   tangents = tangent vectors of the path
 //   splinesteps = number of points to insert between the path points.  Default: 10
+//   k = curvature parameter, a scalar or vector to adjust curvature at each point
 //   closed = set to true for a closed path.  Default: false
 // Example(2D): Original path in green, smoothed path in yellow:
 //   color("green")stroke(square(4), width=0.1);
@@ -428,21 +435,30 @@ function _rounding_offsets(edgespec,z_dir=1) =
 // Example(2D): A more interesting shape:
 //   path = [[0,0], [4,0], [7,14], [-3,12]];
 //   polygon(smooth_path(path,closed=true));
-// Example(2D): Scaling the tangent data can decrease or increase the amount of smoothing:
-//   shape = square(4);
-//   polygon(smooth_path(shape, tangents=0.5*deriv(shape, closed=true),closed=true));
+// Example(2D): Scaling the tangent data using the curvature parameter k can decrease or increase the amount of smoothing.  Note this is the same
+//   as just multiplying the deriv(square(4)) by k.
+//   polygon(smooth_path(square(4), k=0.5,closed=true));
 // Example(2D): Or you can specify your own tangent values to alter the shape of the curve
 //   polygon(smooth_path(square(4),tangents=1.25*[[-2,-1], [-2,1], [1,2], [2,-1]],closed=true));
 // Example(FlatSpin):  Works on 3d paths as well
 //   path = [[0,0,0],[3,3,2],[6,0,1],[9,9,0]];
 //   trace_polyline(smooth_path(path),size=.3);
-function smooth_path(path, tangents, splinesteps=10, closed=false) =
-  let(
-     bez = path_to_bezier(path, tangents=tangents, closed=closed)
+// Example(2D): The curve passes through all the points, but features some unexpected wiggles.  These occur because the curvature is too low to change fast enough.  
+//   path = [[0,0], [0,3], [.5,2.8], [1,2.2], [1,0]];
+//   polygon(smooth_path(path));
+//   color("red") place_copies(path)circle(r=.1,$fn=16);
+// Example(2D):  Using the k parameter is one way to fix this problem.  By allowing sharper curvature (k<1) at the two points next to the problematic point we can achieve a smoother result.  The other fix is to move your points.  
+//   path = [[0,0], [0,3], [.5,2.8], [1,2.2], [1,0]];
+//   polygon(smooth_path(path,k=[1,.5,1,.5,1]));
+//   color("red") place_copies(path)circle(r=.1,$fn=16);
+function smooth_path(path, tangents, k, splinesteps=10, closed=false) =
+  let (
+     bez = path_to_bezier(path, tangents, k=k, closed=closed)
   )
   bezier_polyline(bez,splinesteps=splinesteps);
 
 
+
 // Module: offset_sweep()
 //
 // Description: