Porting tiny_bvh_minimal_gpu to Gigi.
BVHs in BVH_GPU format can be saved from the viewer.
This uses the traverse.cl logic to trace the rays.
tinybvh is at: https://github.com/jbikker/tinybvh/
RenderSize
ViewMode
TMax The maximum length ray allowed
CostDivider Cost View Mode: divides by this number to help show the range.
DistanceDivider Distance View Mode: divides by this number to help show the range.
LightDirection The direction the light is shining.