Allow more subtle side sculpting of SA/DSA to make the tops less square.

To enable this, you need to set

$enable_more_side_sculpting = true

(as well as ensuring that the existing enable_side_sculpting is set).

There is also an additional method for doing the extra sculpting that
can be enabled via:

  $enable_more_side_sculpting = "slow"

This was actually my first attempt which looks nice at 1u but doesn't
scale nicely to wider/taller keys.

src/settings.scad

@@ -75,6 +75,8 @@ $dish_overdraw_height = 0;
 $height_slices = 1;
 // this enables some fancy and currently hardcoded logic to bow the sides and corners of SA keycaps
 $enable_side_sculpting = false;
+// this enables even more fancy and hardcoded logic for corner bowing of SA keycaps. (Also needs enable_side_sculpting to be true)
+$enable_more_side_sculpting = false;
 
 //minkowski radius. radius of sphere used in minkowski sum for minkowski_key function. 1.75 for G20
 $minkowski_radius = .33;

src/shapes/rounded_square.scad

@@ -20,13 +20,60 @@ module rounded_square_shape(size, delta, progress, center = true) {
 		extra_height_this_slice = (height_difference - extra_side_size) * progress;
 		extra_corner_radius_this_slice = ($corner_radius + extra_corner_size);
 
-		offset(r=extra_corner_radius_this_slice){
+                square_size = [width - extra_width_this_slice, height - extra_height_this_slice];
-			square(
+		offset(r = extra_corner_radius_this_slice) offset(r = -extra_corner_radius_this_slice) {
-				[
+                    if ($enable_more_side_sculpting != false && progress > 0) {
-					width - extra_width_this_slice - extra_corner_radius_this_slice * 2,
+                        side_rounded_square(square_size, r = 0.4 * progress);
-					height - extra_height_this_slice - extra_corner_radius_this_slice * 2
+                    } else {
-				],
+			square(square_size, center=center);
-				center=center
+                    }
-			);
+		}
+}
+
+// Brings in a square at each corner by r, applied over the length of each side.
+module side_rounded_square(size, r) {
+    if ($enable_more_side_sculpting == "slow") {
+        side_rounded_square_slow(size, r);
+    } else {
+        side_rounded_square_fast(size, r);
+    }
+}
+module side_rounded_square_fast(size, r) {
+    iw = size.x - 2 * r;
+    ih = size.y - 2 * r;
+    resolution = 100;
+    sr = r / resolution * 2;
+    sh = ih / resolution;
+    sw = iw / resolution;
+    union() {
+        translate([-iw/2, 0]) scale([sr, sh]) circle(d = resolution);
+        translate([iw/2, 0]) scale([sr, sh]) circle(d = resolution);
+        translate([0, -ih/2]) scale([sw, sr]) circle(d = resolution);
+        translate([0, ih/2]) scale([sw, sr]) circle(d = resolution);
+        square([iw, ih], center=true);
+    }
+}
+module side_rounded_square_slow(size, r) {
+    // These two from: https://openscadsnippetpad.blogspot.co.nz/2017/05/circle-defined-by-three-points.html
+    function len3(v) = sqrt(pow(v.x, 2) + pow(v.y, 2));
+    function circle_by_three_points(A, B, C) = let (
+        yD_b = C.y - B.y,  xD_b = C.x - B.x,  yD_a = B.y - A.y,
+        xD_a = B.x - A.x,  aS = yD_a / xD_a,  bS = yD_b / xD_b,
+        cex = (aS * bS * (A.y - C.y) + bS * (A.x + B.x) - aS * (B.x + C.x)) / (2 * (bS - aS)),
+        cey = -1 * (cex - (A.x + B.x) / 2) / aS + (A.y + B.y) / 2
+        )
+        [cex, cey];
+
+    w = size.x - r * 2;
+    h = size.y - r * 2;
+    cw = circle_by_three_points([-w / 2, 0], [0, r], [w / 2, 0]);
+    rw = len3([w / 2, 0] - cw);
+    ch = circle_by_three_points([0, -h / 2], [r, 0], [0, h / 2]);
+    rh = len3([0, h / 2] - ch);
+    intersection() {
+        translate(cw + [0, h / 2]) circle(r = rw, $fa=1);
+        translate(cw * -1 + [0, -h / 2]) circle(r = rw, $fa=1);
+        translate(ch + [w / 2, 0]) circle(r = rh, $fa=1);
+        translate(ch * -1 + [-w / 2, 0]) circle(r = rh, $fa=1);
     }
 }