   Static Sparse Mask Textures
  Hi,I'm rendering my terrain using a very similar approach as described in this paper Click (Just read Section 5.4. Terrain Rendering)For terrain texturing I'm using traditional approach: using detailmaps, colormaps and blendmaps. However this texturing approach is sometimes inflexible and memory consuming. I'm trying to understand how "Static Sparse Mask Textures" works. This is described at section "5.2.4 Static Sparse Mask Textures". I'm not native english speaker, I don't understand the idea.  They say empty areas in the quadtree texture don't take up any memory. How do I store mask textures in a quadtree texture representation? And What exactly is an indirection texture?   
  The atlas stores small (eg 32x32) UNIQUE tiles of your mask texture. Another textures, mapping to your terrain_coordinates, points into this texture for the actual mask values. This one is called the indirection texture.The atlas only stores unique tiles, so empty (32x32 of black) will only show up once, hence the memory saving. This will have a big impact on the amount of texture sampling you need to do though (2x for a naive implementation, 5x in my worst case).I found that a low resolution for my blend map, together with linear interpolation, works in my case.