PDA

View Full Version : size of normalization cube map



yakuza
02-29-2004, 08:56 AM
I've got tangent space bumpmapping working, thanks primarily to Paul's excellent tutorial, as well as numerous other tutorials and examples.
http://www.paulsprojects.net/tutorials/simplebump/simplebump.html

I've got a question about the normalization cubemap. Most examples I've seen use a cube map with dimensions of 32. I've used Mark Kilgards "A Practical and Robust Bump-mapping Technique for Today’s GPUs" document to create the normalization cube map, and have experimented with various sizes of cube maps.

I've seen that when values below 32 (16 and 8) are used, artifacts are visible on the surface, however no discernable visual difference is apparent with cubemap sizes above 32 (64 and 128). So I'm guessing that the examples I've seen use 32 for the size, as that consumes the minimal texture memory with good visual results.

Is that about right, or am I missing some critical detail?


[This message has been edited by yakuza (edited 02-29-2004).]

mikael_aronsson
02-29-2004, 10:53 PM
I am not sure the beginners forum is a good place for stuff like this.

Mikael

Jan
03-01-2004, 02:54 AM
nVidia has just recently put up a new paper on their site ( developer.nvidia.com ), which talks about normalization.

THEY use a cubemap sized 256*256. And still they say, that it gives some artifacts in certain situations.

Using 32*32 sounds to me VERY bad, the changes between two normals should be quite big.

Certainly there are a lot of cases where you won´t notice the low resolution, especially on very bumpy surfaces. Try out a completely flat surface and make screenshots of it using different cubemap resolutions. Then compare them. It should help you to decide, which is the best resolution.

Jan.

PS: When using Specular Lighting, it should get much more noticable.

dorbie
03-01-2004, 03:51 AM
Moving to the advanced forum.