linear_sweep() fixes and tweaks to xrgn geometries.

attachments.scad

@@ -1567,7 +1567,7 @@ function named_anchor(name, pos, orient=UP, spin=0) = [name, pos, orient, spin];
 // Usage: Spheroid/Ovoid Geometry
 //   geom = attach_geom(r=|d=, ...);
 // Usage: Extruded 2D Path/Polygon/Region Geometry
-//   geom = attach_geom(region=, l=|h=, [extent=], ...);
+//   geom = attach_geom(region=, l=|h=, [extent=], [shift=], [scale=], [twist=], ...);
 // Usage: VNF Geometry
 //   geom = attach_geom(vnf=, [extent=], ...);
 //
@@ -1583,6 +1583,8 @@ function named_anchor(name, pos, orient=UP, spin=0) = [name, pos, orient, spin];
 //   size = If given as a 3D vector, contains the XY size of the bottom of the cuboidal/prismoidal volume, and the Z height.  If given as a 2D vector, contains the front X width of the rectangular/trapezoidal shape, and the Y length.
 //   size2 = If given as a 2D vector, contains the XY size of the top of the prismoidal volume.  If given as a number, contains the back width of the trapezoidal shape.
 //   shift = If given as a 2D vector, shifts the top of the prismoidal or conical shape by the given amount.  If given as a number, shifts the back of the trapezoidal shape right by that amount.  Default: No shift.
+//   scale = If given as number or a 2D vector, scales the top of the shape, relative to the bottom.  Default: `[1,1]`
+//   twist = If given as number, rotates the top of the shape by the given number of degrees clockwise, relative to the bottom.  Default: `0`
 //   r = Radius of the cylindrical/conical volume.  Can be a scalar, or a list of sizes per axis.
 //   d = Diameter of the cylindrical/conical volume.  Can be a scalar, or a list of sizes per axis.
 //   r1 = Radius of the bottom of the conical volume.  Can be a scalar, or a list of sizes per axis.
@@ -1663,7 +1665,8 @@ function named_anchor(name, pos, orient=UP, spin=0) = [name, pos, orient, spin];
 //   geom = attach_geom(region=region, l=length, extent=false);
 //
 function attach_geom(
-    size, size2, shift,
+    size, size2,
+    shift, scale, twist,
     r,r1,r2, d,d1,d2, l,h,
     vnf, region,
     extent=true,
@@ -1713,9 +1716,17 @@ function attach_geom(
               ? ["rgn_extent", region, cp, offset, anchors]
               : ["rgn_isect",  region, cp, offset, anchors]
           : assert(is_finite(l))
+            let(
+                shift = default(shift, [0,0]),
+                scale = is_num(scale)? [scale,scale] : default(scale, [1,1]),
+                twist = default(twist, 0)
+            )
+            assert(is_vector(shift,2))
+            assert(is_vector(scale,2))
+            assert(is_num(twist))
             extent==true
-              ? ["xrgn_extent", region, l, cp, offset, anchors]
+              ? ["xrgn_extent", region, l, twist, scale, shift, cp, offset, anchors]
-              : ["xrgn_isect",  region, l, cp, offset, anchors]
+              : ["xrgn_isect",  region, l, twist, scale, shift, cp, offset, anchors]
     ) :
     let(
         r1 = get_radius(r1=r1,d1=d1,r=r,d=d,dflt=undef)
@@ -1922,7 +1933,7 @@ function _get_cp(geom) =
     assert(type!="other", "Invalid cp value")
     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]
+       [each centroid(geom[1]), if (type=="xpath") 0]
     )
   : let(points = type=="vnf"?geom[1][0]:flatten(force_region(geom[1])))
     cp=="mean" ? [each mean(points), if (type=="xpath") geom[2]/2]
@@ -2160,11 +2171,21 @@ function _find_anchor(anchor, geom) =
         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]
+            rgn = geom[1],
+            L = geom[2],
+            twist = geom[3],
+            scale = geom[4],
+            shift = geom[5],
+            u = (anchor.z + 1) / 2,
+            shmat = move(lerp([0,0], shift, u)),
+            scmat = scale(lerp([1,1], scale, u)),
+            twmat = zrot(lerp(0, -twist, u)),
+            mat = shmat * scmat * twmat
         )
-        approx(anchor_xy,[0,0]) ? [anchor, up(anchor.z*L/2,cp), anchor, oang] :
+        approx(anchor_xy,[0,0]) ? [anchor, apply(mat, up(anchor.z*L/2,cp)), anchor, oang] :
         let(
-            newgeom = list_set(geom, [0,len(geom)-3], [substr(geom[0],1), point2d(cp)]),
+            newrgn = apply(mat, rgn),
+            newgeom = attach_geom(two_d=true, region=newrgn, extent=type=="xrgn_extent", cp=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),

skin.scad

@@ -523,15 +523,14 @@ function skin(profiles, slices, refine=1, method="direct", sampling, caps, close
 //   maxseg = If given, then any long segments of the region will be subdivided to be shorter than this length.  This can refine twisting flat faces a lot.  Default: `undef` (no subsampling)
 //   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.
-//   cp = Centerpoint for determining intersection anchors or centering the shape.  Determines the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: `[0,0,0]`
+//   cp = Centerpoint for determining intersection anchors or centering the shape.  Determines the base of the anchor vector.  Can be "centroid", "mean", "box" or a 3D point.  Default: `"centroid"`
 //   atype = Set to "hull" or "intersect" to select anchor type.  Default: "hull"
 //   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#subsection-anchor).  Default: `"origin"`
 //   spin = Rotate this many degrees around the Z axis after anchor.  See [spin](attachments.scad#subsection-spin).  Default: `0`
 //   orient = Vector to rotate top towards, after spin.  See [orient](attachments.scad#subsection-orient).  Default: `UP`
 // Extra Anchors:
-//   centroid_top = The centroid of the top of the shape, oriented UP.
+//   "origin" = Centers the extruded shape vertically only, but keeps the original path positions in the X and Y.  Oriented UP.
-//   centroid = The centroid of the center of the shape, oriented UP.
+//   "original_base" = Keeps the original path positions in the X and Y, but at the bottom of the extrusion.  Oriented UP.
-//   centroid_bot = The centroid of the bottom of the shape, oriented DOWN.
 // Example: Extruding a Compound Region.
 //   rgn1 = [for (d=[10:10:60]) circle(d=d,$fn=8)];
 //   rgn2 = [square(30,center=false)];
@@ -574,27 +573,27 @@ module linear_sweep(
     region, height, center,
     twist=0, scale=1, shift=[0,0],
     slices, maxseg, style="default", convexity,
-    cp=[0,0,0], atype="hull", h,
+    cp, atype="hull", h,
     anchor, spin=0, orient=UP
 ) {
     h = first_defined([h, height, 1]);
     region = force_region(region);
     check = assert(is_region(region),"Input is not a region");
-    anchor = get_anchor(anchor, center, BOT, BOT);
+    anchor = center==true? "origin" :
+        center == false? "original_base" :
+        default(anchor, "original_base");
     vnf = linear_sweep(
         region, height=h, style=style,
         twist=twist, scale=scale, shift=shift,
         slices=slices, maxseg=maxseg,
-        anchor=CTR
+        anchor="origin"
     );
-    cent = centroid(region);
     anchors = [
-        named_anchor("centroid_top", point3d(cent, h/2), UP),
+        named_anchor("original_base", [0,0,-h/2], UP)
-        named_anchor("centroid",     point3d(cent),      UP),
-        named_anchor("centroid_bot", point3d(cent,-h/2), DOWN)
     ];
-    geom = atype=="hull"? attach_geom(cp=cp, region=region, h=h, extent=true, anchors=anchors) :
+    cp = default(cp, "centroid");
-        atype=="intersect"? attach_geom(cp=cp, region=region, h=h, extent=false, anchors=anchors) :
+    geom = atype=="hull"? attach_geom(cp=cp, region=region, h=h, extent=true, shift=shift, scale=scale, twist=twist, anchors=anchors) :
+        atype=="intersect"? attach_geom(cp=cp, region=region, h=h, extent=false, shift=shift, scale=scale, twist=twist, anchors=anchors) :
         assert(in_list(atype, ["hull", "intersect"]));
     attachable(anchor,spin,orient, geom=geom) {
         vnf_polyhedron(vnf, convexity=convexity);
@@ -607,7 +606,7 @@ function linear_sweep(
     region, height, center,
     twist=0, scale=1, shift=[0,0],
     slices, maxseg, style="default",
-    cp=[0,0,0], atype="hull", h,
+    cp, atype="hull", h,
     anchor, spin=0, orient=UP
 ) =
     let( region = force_region(region) )
@@ -616,7 +615,9 @@ function linear_sweep(
     assert(is_vector(shift, 2), str(shift))
     let(
         h = first_defined([h, height, 1]),
-        anchor = get_anchor(anchor, center, BOT, BOT),
+        anchor = center==true? "origin" :
+            center == false? "original_base" :
+            default(anchor, "original_base"),
         regions = region_parts(region),
         slices = default(slices, max(1,ceil(abs(twist)/5))),
         scale = is_num(scale)? [scale,scale] : point2d(scale),
@@ -655,14 +656,12 @@ function linear_sweep(
             for (rgn = regions) vnf_from_region(rgn, down(h/2), reverse=true),
             for (rgn = trgns) vnf_from_region(rgn, up(h/2), reverse=false)
         ]),
-        cent = centroid(region),
         anchors = [
-            named_anchor("centroid_top", point3d(cent, h/2), UP),
+            named_anchor("original_base", [0,0,-h/2], UP)
-            named_anchor("centroid",     point3d(cent),      UP),
-            named_anchor("centroid_bot", point3d(cent,-h/2), DOWN)
         ],
-        geom = atype=="hull"? attach_geom(cp=cp, region=region, h=h, extent=true, anchors=anchors) :
+        cp = default(cp, "centroid"),
-            atype=="intersect"? attach_geom(cp=cp, region=region, h=h, extent=false, anchors=anchors) :
+        geom = atype=="hull"? attach_geom(cp=cp, region=region, h=h, extent=true, shift=shift, scale=scale, twist=twist, anchors=anchors) :
+            atype=="intersect"? attach_geom(cp=cp, region=region, h=h, extent=false, shift=shift, scale=scale, twist=twist, anchors=anchors) :
             assert(in_list(atype, ["hull", "intersect"]))
     ) reorient(anchor,spin,orient, geom=geom, p=vnf);