wip pins

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/genscad b/genscad
index b2b83bfc4981d86c69e0ca0d0013464d4f0570e5..26814fe974e86beda03e6095ab89c4f1d6fe737f 100755 (executable)
--- a/genscad
+++ b/genscad
@@ -10,6 +10,8 @@ from moebius import *
 nomsize = 20
 thick = 1.0
 
+sliceat = 1.675;
+
 nv = 80
 nw = 80
 
@@ -74,6 +76,46 @@ def make_moebius(objname):
           for b in (-1, +1) ])
   so.writeout(objname, nomsize)
 
-make_moebius('MoebiusCore')
+def make_pinlocations():
+  bests = [ None, None ] # bests[ y>=0 ] = (locn, normal)
 
+  def goodness(info):
+    # we find the one with biggest Z (actually, the least -ve)
+    return (
+      0 * np.linalg.norm(info[0][0:2])
+      -abs(info[1][2])
+    )
+    return abs(info[1][1])
+
+  for v in range(0, nv):
+    for w in range(0, nw):
+      core_quad = [ m.point(v+a, w+b)
+                    for a in (1, 0)
+                    for b in (1, 0) ]
+      for p,q in [ (core_quad[i], core_quad[(i+1) % 4])
+                   for i in range(0,4) ]:
+        normal = (m.point_offset(v,  w,   0.5) - core_quad[0] +
+                  m.point_offset(v+1,w+1, 0.5) - core_quad[3]);
+        if normal[2] > 0: # inwards, make outwards
+          normal = -normal
+
+        #print(repr((p,q)), file=sys.stderr)
+        if (p[2] > -sliceat) == (q[2] > -sliceat): continue
+
+        lincomb = (-sliceat - p[2]) / (q[2] - p[2])
+        here = p * (1-lincomb) + q * lincomb;
+        best_key = here[1] >= 0
+        prospective = (here,normal)
+        if (bests[best_key] is None or
+            goodness(prospective) > goodness(bests[best_key])):
+          bests[best_key] = prospective
+  def print_bests(name, info_index):
+    print('moebius_pin_%s=[' % name)
+    for b in bests: print(repr(list(b[info_index])),',')
+    print('];')
+  print_bests('locns', 0)
+  print_bests('normals', 1)
+
+make_moebius('MoebiusCore')
+make_pinlocations()
 print('moebiuscore_nomsize=%s;' % repr(nomsize))

diff --git a/moebius-demo.scad b/moebius-demo.scad
index 9d99c56c01343c3254b11d51255995124f683c4d..1b2c6ff019c1a414b12799a85e196e7c109de7a7 100644 (file)
--- a/moebius-demo.scad
+++ b/moebius-demo.scad
@@ -9,3 +9,13 @@ intersection(){
   translate([0,0, 200-sliceat])
     cube(center=true, 400);
 }
+
+%for (i=[0,1]) {
+  hull(){
+    translate( moebius_pin_locns[i] * moebiuscore_nomsize )
+      sphere(2 + i);
+    translate( moebius_pin_locns[i] * moebiuscore_nomsize +
+              moebius_pin_normals[i] * moebiuscore_nomsize*0.5 )
+      sphere(2 + i);
+  }
+}