declutter catear_v3

catear_headband.scad

@@ -13,33 +13,36 @@ EAR_ANGLE = 42;
 WITH_RAKE = true;
 DETAILS = true;
 
+catear_v3_control_points = function (S, sf, bf, mn, a) let (s=S/2, R=rotation_matrix(a)) [
+  [ s   ,       0, 0],
+  [ S*bf, S*sf*mn, 0] * R,
+  [-S*bf, S*sf*mn, 0] * R,
+  [-s   ,       0, 0],
+];
+
 /**
  * unsupported parameters: chamfer, chamfer_shape, details, end_caps
  */
-module catear_v3(height, thickness, fractal=0, side_len=30, bend_factor=0.15, stretch_factor=1.2, debug=false, chamfer=CHAMFER, chamfer_shape=CHAMFER_SHAPE, details=true, end_caps=true, skew=2.0) {
-  S = side_len;
-  s = S/2;
-  sf = stretch_factor;
-  bf = bend_factor*2;
-  mn = 1.16; // magic number
-  f=skew*S*0.2;
-
-  a = skew*10;
-  R = [[cos(a), -sin(a), 0],
-       [sin(a),  cos(a), 0],
-       [     0,       0, 1]];
-
-  A = [ s   ,       0, 0];
-  B = [ S*bf, S*sf*mn, 0] * R;
-  C = [-S*bf, S*sf*mn, 0] * R;
-  D = [-s   ,       0, 0];
-
-  curve_vertices = bezier_curve_vertices([A, B, C, D], $fn);
+module catear_v3(height, thickness, fractal=0, side_len=30, bend_factor=0.15, stretch_factor=1.2, debug=false, chamfer=CHAMFER, chamfer_shape=CHAMFER_SHAPE, details=true, end_caps=true, skew=2.0, $fn=$fn) {
+  control_points = catear_v3_control_points(
+    S=side_len,
+    sf=stretch_factor,
+    bf=bend_factor,
+    mn=1.16,
+    a=skew*10
+  );
+  curve_vertices = bezier_curve_vertices(control_points, $fn);
   if (debug) {
-    translate([0, 0, 2*height]) rotate(90) bezier_curve_debug([A, B, C, D]);
+    translate([0, 0, 2*height]) rotate(90) bezier_curve_debug(control_points);
     echo("curve_vertices: ", curve_vertices);
   }
-  rotate(90) render_curve(curve_vertices, width=thickness, height=height, chamfer=chamfer, debug=debug);
+  rotate(90) render_curve(
+    curve_vertices,
+    width=thickness,
+    height=height,
+    chamfer=chamfer,
+    debug=debug
+  );
 }
 
 /**

primitives.scad

@@ -14,6 +14,12 @@ mat_T = function (mat) [
   ]
 ];
 
+rotation_matrix = function(a) [
+  [cos(a), -sin(a), 0],
+  [sin(a),  cos(a), 0],
+  [     0,       0, 1]
+];
+
 bezier_matrix = [[1, -3,  3, -1],
                  [0,  3, -6,  3],
                  [0,  0,  3, -3],