update documentation

README.md

@@ -4,16 +4,39 @@ Tools for generating physical keys.
 ![Key in Inkscape](doc/inkscape.png "SC4")
 ![Key in OpenSCAD](doc/key.png "152698")
 
-## 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 engraving 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.
+## How to use it
+```
+usage: keygen.py [-h] [-b BITTING] [-u OUTLINE] [-w WARDING] [-o OUTPUT]
+                 filename
+
+Generates keys.
+
+positional arguments:
+  filename              OpenSCAD source file for the key
+
+optional arguments:
+  -h, --help            show this help message and exit
+  -b BITTING, --bitting BITTING
+                        Key bitting
+  -u OUTLINE, --outline OUTLINE
+                        Key blank outline
+  -w WARDING, --warding WARDING
+                        Key warding
+  -o OUTPUT, --output OUTPUT
+                        Output file (defaults to a.stl)
+
+All remaining arguments are passed to OpenSCAD.
+```
+
+### Examples
+
+```bin/keygen.py scad/schlage_classic.scad --bitting 25536 -o housekey.stl```
+```bin/keygen.py scad/schlage_classic.scad -u 6-pin -w L -b 999999 -o all_section_bump_key.stl```
+```bin/keygen.py scad/schlage_classic.scad -o key.png --render```
+
+## Contributing
+
+There is a very limited selection of keys right now, to help out, see the guide on [how to model keys](doc/how_to_model_keys.md).
 
 ## Music