add key bitting cutting code, add picture, and update README

README.md

@@ -1,2 +1,15 @@
 # keygen
-OpenSCAD tools for generating physical keys
+Tools for generating physical keys.
+
+![152698](doc/key.png "Key in OpenSCAD")
+
+## How it Works
+1. Get some nice pictures of the side and tip of your key.
+I recommend a flatbed scanner.
+2. Trace the key outline, warding, and embossing in Inkscape
+3. Use the provided Inkscape plugin to convert the paths to OpenSCAD polygons.
+4. Look up online the various parameters of your key, such as plug diameter,
+cut depths and locations.
+5. Use the provided OpenSCAD functions `key_code_to_heights`,
+`key_blank` and `key_bitting` to generate a 3D model of your key.
+6. Send the key to be 3D printed.

keygen.scad

@@ -129,4 +129,33 @@ module key_blank(outline_points,
         key_emboss(emboss_right_adj, emboss_depth, false, thickness, emboss_right_paths);
         key_emboss(emboss_left_adj, emboss_depth, true, thickness, emboss_left_paths);
     }
+}
+
+function key_code_to_heights(code, depth_table) = [for(i=[0:len(code)-1]) depth_table[search(code[i], "0123456789")[0]]];
+
+module key_bitting_cutter(flat, angle, tool_height) {
+    polygon([[-0.5 * flat, 0],
+            [0.5 * flat, 0],
+            [0.5 * flat + tan(0.5 * angle) * tool_height, tool_height],
+            [0.5 * flat - tan(0.5 * angle) * tool_height, tool_height]]);
+}
+
+module key_bitting(heights,
+                   locations,
+                   flat,
+                   angle=100,
+                   cutter_width=5,
+                   cutter_height=5) {
+    // Rotate the cutting tool to the proper orientation
+    rotate(-90, [0, 0, 1]) rotate(90, [1, 0, 0])
+        // Union together a handful of trapezoids
+        // that comprise the cuts
+        union() {
+            for(i=[0:len(heights)-1]) {
+                // Move to the proper location and height
+                translate([locations[i], heights[i]])
+                    linear_extrude(height=cutter_width, center=true)
+                        key_bitting_cutter(flat, angle, cutter_height);
+            }
+        }
 }

sc4.scad

@@ -1,11 +1,22 @@
 use <keygen.scad>
 include <sc4.gen.scad>
 
-key_blank(outline_points,
-          warding_points,
-          outline_paths=outline_paths,
-          emboss_right_points=emboss_points,
-          emboss_right_paths=emboss_paths,
-          emboss_left_points=emboss_points,
-          emboss_left_paths=emboss_paths,
-          offset=-outline_points[187]);
+bitting_code = "024689";
+
+cut_locations = [for(i=[.231, .3872, .5434, .6996, .8558, 1.012]) i*25.4];
+depth_table = [for(i=[0.335:-0.015:0.199]) i*25.4];
+
+heights = key_code_to_heights(bitting_code, depth_table);
+
+difference() {
+    key_blank(outline_points,
+              warding_points,
+              outline_paths=outline_paths,
+              emboss_right_points=emboss_points,
+              emboss_right_paths=emboss_paths,
+              emboss_left_points=emboss_points,
+              emboss_left_paths=emboss_paths,
+              offset=-outline_points[187],
+              plug_diameter=12.7);
+    key_bitting(heights, cut_locations, .7874);
+}