Update README.md

Basic documentation

README.md

@@ -1 +1,21 @@
-# blender-rigidbody-exporter
+# Blender Rigidbody Exporter
+This plugin exports the rigidbody world from a Blender project.
+It exports to a json-based format that closely resembles the structure of the bpy API.
+
+## Collision shapes
+### Mesh
+The mesh is the most flexible collision shape and allows several face loops.
+
+### Convex Hull
+
+
+### Cone, Cylinder, Capsule, Sphere
+These all map to a circle shape in 2D.
+
+### Box
+Corresponds to a rectangle/box shape in 2D.
+
+### More complex shapes
+Some models have a very complex shape.
+The requirement for a polygon shape is that it should be convex.
+For a more complex concave shape this can be solved by using "Mesh > Clean up > Split Concave Faces"