demo: Store coarse LODs before fine LODs in the resulting IB
demo: Store coarse LODs before fine LODs in the resulting IB

Some GPUs, like earlier ARM Mali models, compute the range of vertices
referenced by each draw call and transform the entire range. For this to
work efficiently with index buffer ranges used by LODs each LOD has to
use a consecutive range of vertices from the original VB.

Since we optimize the vertex buffer for vertex fetch we get this
locality for free *if* coarse LODs are there before fine LODs since
vertex fetch optimization reorders for locality of forward buffer
traversal.

Before this change the vertex range of all LODs was about the total
vertex count, making vertex transform cost of coarse LODs too high; now
each LOD references the range with the size that's close to the total
number of vertices each LOD uses.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer