Shadow Systems

Use a single shadow map only when its receiver region is genuinely bounded. For large moving views, make shadow coverage an explicit spatial hierarchy.

Cached clipmap workflow

1. Define concentric light-space square levels.
2. Snap each level center to its own texel grid.
3. Cross-fade adjacent levels in shader space.
4. Refresh near levels continuously.
5. Cache coarse levels and update them under a frame budget.
6. Invalidate intersecting levels when important casters or streamed terrain change.
7. Scale normal bias by world-space texel width.

Read references/cached-clipmap-shadows.md before implementing a large-world directional light.