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Lithic

Is it possible to relief map a fractal surface

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I'm fairly pleased with my terrain LOD and shading now overall, but I think the surface looks kind of flat; all I'm doing now is some simple normal mapping. I've been considering applying the relief mapping algorithm I use elsewhere, but it seems that would require huge numbers of texture fetches.

 

With the high-detail fractal surface I'm currently using, I'm already doing 33 texture fetches per pixel with the fractal algorithm alone (11 bands with a anti-repetition algorithm that requires 3 lookups per band), and I'm worried that multiplying this by a large number of search iterations (10 or so) for relief mapping it might choke the GPU.

 

At what point will I be texture-fetch limited? Do I have better options than simple normal mapping with a high-texture-fetch fractal noise-based surface?

 

 

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Decent GPU has memory bandwidth of 100 GB/s;

 

bandwidth = 100,000,000,000 bytes

resolution = 1980 x 1080 pixels

fetches_per_pixel = 33 fetches

bytes_per_fetch = 4 bytes

bandwidth / resolution / fetches_per_pixel / bytes_per_fetch = 360 FPS.

 

Of course cache would improve that, but I'd say you're too close to the limit.

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Thanks for confirming my suspicions. I was able to get some pretty decent surface detail out of the normal mapping by making it stronger, setting a -1 mipmap bias, adding more color variation, which has the nice effect of creating a good surface albedo as well, and otherwise tweaking what I had. Guess I'll just have to make the normal mapping work.

 

 

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