feat: add s_hook() module to hooks.scad

hooks.scad

@@ -1,7 +1,6 @@
 //////////////////////////////////////////////////////////////////////
 // LibFile: hooks.scad
 //   Functions and modules for creating hooks and hook like parts.
-//   At the moment only one part is supported, a ring hook.  
 // Includes:
 //   include <BOSL2/std.scad>
 //   include <BOSL2/hooks.scad>
@@ -298,3 +297,110 @@ module ring_hook(base_size, hole_z, or, ir, od, id, wall, hole="circle",
 }
 
 
+// Module: s_hook()
+// Synopsis: Creates an S-shaped hook
+// SynTags: Geom
+// Topics: Parts, Hooks
+// See Also: ring_hook()
+// Usage:
+//   s_hook(or, [sides], [l_shaft=], [r_loop1=], [angle1=], [r_loop2=], [angle2=], ...) [ATTACHMENTS];
+// Description:
+//   Creates an S-shaped hook by sweeping a cross-section profile along a turtle-graphics path.
+//   The hook consists of a central shaft with configurable loops on each end.  Each loop can
+//   have an optional straight stem extension and a reverse curl.  The cross-section can be a
+//   regular polygon (controlled by `sides`) or a circle (when `sides` < 3).
+//   .
+//   The hook is oriented along the Y axis, centered at the origin.  The +Y end has loop1 and
+//   the -Y end has loop2.  By default both loops curve 180 degrees creating a classic S shape.
+//   .
+//   End caps are generated using rotate_sweep to close the ends of the swept shape cleanly.
+// Arguments:
+//   or = outside radius of the cross-section shape.  Default: 2
+//   sides = number of sides for the cross-section polygon.  Values less than 3 produce a circle.  Default: 6
+//   ---
+//   l_shaft = length of the straight central shaft.  Default: 25
+//   r_loop1 = radius of the loop at the +Y end.  Default: 5
+//   angle1 = arc angle in degrees for loop1.  Default: 180
+//   l_stem1 = length of straight segment after loop1.  Default: 0
+//   r_curl1 = radius of the reverse curl at the +Y end.  Default: 0
+//   angle_curl1 = arc angle in degrees for curl1.  Default: 0
+//   r_loop2 = radius of the loop at the -Y end.  Default: 5
+//   angle2 = arc angle in degrees for loop2.  Default: 180
+//   l_stem2 = length of straight segment after loop2.  Default: 0
+//   r_curl2 = radius of the reverse curl at the -Y end.  Default: 0
+//   angle_curl2 = arc angle in degrees for curl2.  Default: 0
+//   anchor = Translate so anchor point is at origin (0,0,0).  See [anchor](attachments.scad#subsection-anchor).  Default: CENTER
+//   spin = Rotate this many degrees around the Z axis.  See [spin](attachments.scad#subsection-spin).  Default: 0
+//   orient = Vector to rotate top towards.  See [orient](attachments.scad#subsection-orient).  Default: UP
+// Example(3D): Default S-hook with hexagonal cross-section
+//   s_hook();
+// Example(3D): Circular cross-section
+//   s_hook(sides=0);
+// Example(3D): Longer shaft
+//   s_hook(l_shaft=50);
+// Example(3D): Larger loop on +Y end
+//   s_hook(r_loop1=12);
+// Example(3D): Added stem on +Y end
+//   s_hook(l_stem1=5);
+// Example(3D): Stem and curl on -Y end
+//   s_hook(l_stem2=4, r_curl2=5, angle_curl2=70);
+// Example(3D): Extended arc with curl
+//   s_hook(sides=0, angle1=230, l_stem1=3, r_curl1=3, angle_curl1=90);
+// Example(3D): Asymmetric hook
+//   s_hook(or=3, r_loop1=10, angle1=220, r_loop2=6, angle2=160, l_shaft=30);
+
+function s_hook(or=2, sides=6, l_shaft=25,
+    r_loop1=5, angle1=180, l_stem1=0, r_curl1=0, angle_curl1=0,
+    r_loop2=5, angle2=180, l_stem2=0, r_curl2=0, angle_curl2=0,
+    anchor=CENTER, spin=0, orient=UP) = no_function("s_hook");
+module s_hook(or=2, sides=6, l_shaft=25,
+    r_loop1=5, angle1=180, l_stem1=0, r_curl1=0, angle_curl1=0,
+    r_loop2=5, angle2=180, l_stem2=0, r_curl2=0, angle_curl2=0,
+    anchor=CENTER, spin=0, orient=UP)
+{
+    dummy = assert(is_finite(l_shaft) && l_shaft > 0, "l_shaft must be positive")
+            assert(is_int(sides), "sides must be an integer")
+            assert(is_finite(or) && or > 0, "or must be positive")
+            assert(is_finite(r_loop1) && r_loop1 >= 0, "r_loop1 must be non-negative")
+            assert(is_finite(r_loop2) && r_loop2 >= 0, "r_loop2 must be non-negative")
+            assert(is_finite(angle1) && angle1 >= 0, "angle1 must be non-negative")
+            assert(is_finite(angle2) && angle2 >= 0, "angle2 must be non-negative");
+    _stem1 = max(l_stem1, 1e-10);
+    _stem2 = max(l_stem2, 1e-10);
+    shape = sides > 2 ? regular_ngon(sides, or, align_side=FWD) : circle(or);
+    path1 = turtle(["setdir", 90, "ymove", l_shaft/2,
+                     "arcleft", r_loop1, angle1,
+                     "move", _stem1,
+                     "arcright", r_curl1, angle_curl1]);
+    path2 = turtle(["setdir", -90, "ymove", -l_shaft/2,
+                     "arcleft", r_loop2, angle2,
+                     "move", _stem2,
+                     "arcright", r_curl2, angle_curl2]);
+    all_pts = concat(path1, path2);
+    bnds = pointlist_bounds(all_pts);
+    sz = [bnds[1].x - bnds[0].x + 2*or,
+          bnds[1].y - bnds[0].y + 2*or,
+          2*or];
+    off = [(bnds[0].x + bnds[1].x)/2,
+           (bnds[0].y + bnds[1].y)/2,
+           0];
+    endcap = right_half(shape);
+    anchors = [
+        named_anchor("loop1", point3d(last(path1)), UP),
+        named_anchor("loop2", point3d(last(path2)), DOWN),
+        named_anchor("shaft_top", [0, l_shaft/2, 0], BACK),
+        named_anchor("shaft_bot", [0, -l_shaft/2, 0], FWD),
+    ];
+    attachable(anchor, spin, orient, size=sz, offset=off, anchors=anchors) {
+        union() {
+            path_sweep(shape, path1);
+            path_sweep(shape, path2);
+            move(last(path1)) rotate_sweep(endcap);
+            move(last(path2)) rotate_sweep(endcap);
+        }
+        children();
+    }
+}
+
+
+// vim: expandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap