Render the transparent object bounds to a low-res frame-buffer and ray-march the
bounds volume, tagging shadow tiles along the way.
The bounds volume is inflated by half a pixel as a conservative rasterization
alternative, to ensure the tiles needed by all LOD0 pixels get tagged.
The bounds are rendered with front face culling and then the fragment shader
ray-marches against the bounds volume.
Each ray-marching step size equals the world space size of the pixel at the step
depth.
The step bounding sphere radius is also sent to the shadow usage tagging library
to ensure the whole step volume is tagged.
Pull Request: https://projects.blender.org/blender/blender/pulls/104580
25016b56ef