Deferred Shadows Marching
D.S.M. is a rendering technique to simulate cascaded shadows directly in screen space. Born as improvement of deferred lighting, DSM tries to reconstruct the shadows in post processing by ray marching the lights trajectories in screen space.
D.S.M. can virtually simulate unlimited spot lights casting shadows without any performance hits, in a single rendering pass.
PRO:
- Geometry indipendent
- Lights number indipendent
- Does not store shadowmaps/lightmaps or other expensive memory in GPU
- Can be merged with other forward/deferred rendering techinques
- Optimal for rendering moving/appearing soft lights, particles or flashes.
- Fake shadows, sometimes DSM produces artifacts or incorrect results
- DSM can only cast shadows of geometry that fits in the screen
