One-vertex, no-index geometry for a new or demoted mesh node. The optional
attribute set comes from metadata so a later commit can fill its buffers
without changing the layout after WebGPU has seen the node.
One vertex keeps every attribute's count nonzero and gives a real bounding
sphere. Three r184 handles zero-position buffers with radius 0 and absent
positions with radius -1 (not NaN); the single vertex is conservative, not
a workaround for NaN bounds. Optional attributes need stubs from birth
because WebGPU caches the vertex layout on first draw.
One-vertex, no-index geometry for a new or demoted mesh node. The optional attribute set comes from metadata so a later commit can fill its buffers without changing the layout after WebGPU has seen the node. One vertex keeps every attribute's count nonzero and gives a real bounding sphere. Three r184 handles zero-position buffers with radius 0 and absent positions with radius -1 (not NaN); the single vertex is conservative, not a workaround for NaN bounds. Optional attributes need stubs from birth because WebGPU caches the vertex layout on first draw.