Paging terrain data - Longbow Digital Arts Discussion

Author	Topic: Paging terrain data
Lithium Member	posted January 19, 2001 03:01 AM Is anybody working with very large terrain (> 2k x 2k)? I was thinking along the lines on how I would handle texture and heightmaps. Heightmaps, power of two: 1k x 1k = 1MB 2k x 2k = 4MB 4k x 4k = 16MB 8k x 8k = 64MB For large heightmaps, I could probably use Windows file mapping. This way, instead of copying the heightmap into an allocated buffer, I could simply access the data directly as a file mapping. This sounds like it could work very well. For textures, since there is only a limited amount of video memory in hardware, I would have to page in terrain texture when it is needed. If I synthesize a single texture for the terrain, I could save it to file first. Then I can access it with file mapping. If each heightmap cell is exactly one texture pixel, the required storage for a single 32-bit texture would be huge: 1k x 1k x 3 = 3MB 2k x 2k x 3 = 12MB 4k x 4k x 3 = 48MB 8k x 8k x 3 = 192MB Any thoughts? IP:
MooZ New Member	posted June 12, 2001 11:18 AM Hy, I think that if you want to perform window file mapping, you'd better store your heightmap as a set of patchs instead of a linear buffer. As if, your patch class will have a member pointing to the corresponding file position. Only visible patches will be loaded in memory. And if your camera don't perform teleportation, you will only have a small set of patches to load from file every frame. IP:
Dreamer Member	posted June 12, 2001 11:30 AM Texturing - TM's terrain texturing works with Vertex-based textures - that way you could calculate your texture layout on the fly (although I don't believe TM does that from what I've seen, no matter what other people say) based on height/angle ranges. Since each texture only has to be large enough to cover one Triangle in your Heightmap, you could save lots of memory that way. IP:
Lithium Member	posted June 15, 2001 11:52 PM I haven't looked at my terrain code in months. What I was doing at the time was synthesizing a unique landscape texture with lighting baked in, and then load it at runtime. Then all I had to do was specify the right texture coordinates for the terrain, instead of slowing down the frame rate with real-time multi-texturing. But I think this is only good for small terrain, 1024x1024 and smaller. I would definitely go with Dreamer's suggestion and use real-time Ecosystems like LDA does. IP: