punctualIndexTexture property
The per-frame light-index texture: each item's
[lightListOffset, +lightListCount) slice indexes into
punctualParamsTexture. Null when no item is reached by any light.
In froxel mode (froxels non-null) callers set this to the froxel data
texture instead, which the shader reads through the same sampler.
Implementation
final gpu.Texture? punctualIndexTexture;