resizing normal map

Gizmo

Has anyone found the most integral resampling method when resizing a normal map to half its original resolution? Is the ordinary 'bicubic' the best at resizing a sensative normal map, or another.

MoP

i'd just use bicubic, and then run the NVidia filter set to "normalize" to make sure it's all ok.

motives

same here. But there's no techy smart explanation behind it.. i just do it that way. Eric Chadwick to the tech-rescue maybe?

oXYnary

Was enough edge bleed (yes, yes I forget the proper term) left around the original to allow a reduction?

Eric Chadwick

Heh. No expert, just learning like everyone else. From what I've heard, resizing normal maps is mostly OK if you follow MoP's lead.

The only problem is when you create the mips for a normal map. You get odd interpolations from 2D rescaling, instead of "proper" interpolation by recasting from the geometry for each lower mip. So with 2d rescaling the mipped curvature isn't as pretty when you view the mapped surface from a distance (or edge-on). If you want to read up on it, find the Nvidia paper "Let’s Get Small" by Kevin Bjorke.

Bottom line though, no one really cares about it in a real game, the difference is just too subtle. Resizing is a nice quick way to avoid the long rendertime of multisampling at actual-res.

I love this shit.

malcolm

I would recommend reexporting the normal map at the smaller size, if you scale it bluring will occur and the normals will change.