add filets

helper/filet.scad

@@ -0,0 +1,42 @@
+include <./halfspace.scad>
+include <./math.scad>
+
+// Some modules for simple subtractive filets
+
+module cylindricalFiletNegative(p0, p1, n, r) {
+  l = norm(p1-p0);
+
+  align_to(p0=p0, p1=p1, p2=p0-n)
+  rotate(a=[45,0,0])
+  rotate(a=[0,90,0])
+  zFiletNegative(length = l, r = r);
+}
+
+module zFiletNegative(length, r) {
+
+  p1 = [0,0,0];
+  p2 = [0,0,length];
+  n1 = [-1,-1,0] / norm([-1,-1,0]);
+  dr = sqrt(2*r^2);
+
+  difference() {
+
+    hull() {
+      translate(v=[0,0,0])
+      cube(size=[r,r,r]);
+
+      translate(v = p2-[0,0,0.1])
+      cube(size=[r,r,0.1]);
+
+    }
+
+    hull() {
+      translate(v = p1-n1*dr)
+      cylinder(r = r, h=0.0001, $fn = 32);
+
+
+      translate(v = p2-n1*dr)
+      cylinder(r = r, h=0.0001, $fn = 32);
+    }
+  }
+}

helper/halfspace.scad

@@ -10,16 +10,17 @@ module halfspace(vpos, p) {
         cube(size=[inf, inf, inf], center=true);
     } else {
         translate(p)
-        align(a=ref, b = vpos)
+        alignPlanar(a=ref, b = vpos)
         translate(v = [0, 0, -inf/2])
         cube(size = [inf, inf, inf], center = true);
     }
 
-    module align(a,b) {
-        rot_axis = cross(a,b);
-        angle = acos(a*b/(norm(a)*norm(b)));
+}
 
-        rotate(v=rot_axis, a=angle)
-        children(0);
-    }
+module alignPlanar(a,b) {
+    rot_axis = cross(a,b);
+    angle = acos(a*b/(norm(a)*norm(b)));
+
+    rotate(v=rot_axis, a=angle)
+    children(0);
 }

helper/math.scad

@@ -24,4 +24,28 @@ module mirror4XY(p, dx, dy) {
     children(0);
 }
 
+// Generate a 4x4 matrix that causes a change of basis
+// such that the origin is at point p0, the x axis is aligned
+// from p0 to p1 and point p2 is in the first quadrant.
+// Copied and pasted from https://trmm.net/Basis/
+module align_to(p0,p1,p2) {
+
+    x = unit(p1-p0);
+    yp = unit(p2-p0);
+    z = unit(cross(x,yp));
+    y = unit(cross(z,x));
+
+    echo(p0,p1,p2);
+    echo(x,y,z);
+
+    multmatrix([
+            [x[0], y[0], z[0], p0[0]],
+            [x[1], y[1], z[1], p0[1]],
+            [x[2], y[2], z[2], p0[2]],
+            [ 0,   0,    0,    1]
+        ])
+    children();
+}
+
+function unit(v) = v/norm(v);
 function lerp(a, b, t) = (b * t + a * (1 - t));