Terrain LOD: Runtime Regular-Grid Approaches

Miscellaneous Notes...

Elevation Paging

• it is desirable to support terrain larger than memory
• however, there are very few papers or implementations which address the paging in-and-out of terrain detail
• perhaps one possible solution, for regular-grid terrain, would be to do an analogous thing with elevation that Clipmapping does with textures.
• there are 2 types of paging:
  1. blocks are paged in on demand, at full resolution
  2. blocks can be paged in at low-detail, then higher levels of detail incrementally
• the second capability is far more useful and potentially more difficult

Streaming

• if you can page terrain data, it follows that with a little more effort you can stream it from sources such as the internet

Resources

• the Game Developer's Algorithms Mailing List (GDAlgo) at 3DGameDev.com hosts a lively discussion of terrain algorithms
• reducing memory requirements for regular heightfields
  • storing delta values by Steve Baker
  • "wavelet compression" might have some application to terrain LOD - it can bring in successive amounts of detail into an image in a way that seems to be directly analogous to height fields
    • the book Texturing and Modelling: A Procedural Approach, pp 248-255, describes "Surflets", wavelets applied to surfaces
    • it does hint at an application to heightfields and LOD, but only barely - mostly it talks about volumetric stuff and non-realtime rendering approaches