Function build_bindings 

pub fn build_bindings(
    atlas_2d: &Atlas2D,
    atlas_cube: &AtlasCube,
    sampler: SamplerId,
) -> Option<ShadowGpuBindings>

Builds a [ShadowGpuBindings] from the lane’s atlas resources, if every required handle is present.

Returns None only when the lane hasn’t finished initialising yet (rare — only the very first frame between on_initialize and execute).