Nodes grouped by depth, deepest level first, for a refit that goes level by
level (the GPU refit's repair pass): every node comes after all its
descendants. levelStarts[level] to levelStarts[level + 1] index into
levelNodes; there are levelStarts.length - 1 levels.
Nodes grouped by depth, deepest level first, for a refit that goes level by level (the GPU refit's repair pass): every node comes after all its descendants.
levelStarts[level]tolevelStarts[level + 1]index intolevelNodes; there arelevelStarts.length - 1levels.