The triangle record's padding word (word 11): the source instance index
of a triangle in a merged mesh (the record's instance has
INSTANCE_FLAG.merged), which the walk returns as BvhHit.instance
and BvhCandidate.instance. 0 in every other mesh; builders always write 0,
and assembleTraceScene writes the index after the build.
The triangle record's
paddingword (word 11): the source instance index of a triangle in a merged mesh (the record's instance has INSTANCE_FLAG.merged), which the walk returns asBvhHit.instanceandBvhCandidate.instance. 0 in every other mesh; builders always write 0, andassembleTraceScenewrites the index after the build.