Given an index, reads a tile if the data is organized in tiles (for LDM).

Given an index, reads a tile if the data is organized in tiles (for LDM). In the default LDM architecture, the LDM data is based on an octree topology (see SoVRLdmFileReader). The index passed is 0 for the tile of lowest resolution representing the entire volume (octree root node). The index increments linearly going down through the octree.