For Shadow Volumes With Intersecting Polygons
Use a stencil enter/leave counting approach
- Draw shadow volume twice using face culling
- 1st pass: render front faces and increment when depth test passes
- 2nd pass: render back faces and decrement when depth test passes
- This two-pass way is more expensive than invert
- And burns more fill rate drawing shadow volumes
- Inverting is better if no polygon intersections