Perpixel lit terrain artifacts

I am having trouble with an ugly “fishnet” type of artifact on my terrain. It is a heightfield, the pervertex normals are sent from VP into a TEX0 normalization cubemap. L and H goes to TEX3 and TEX4. In the registercombiners I do the usual calculations. I’ve rendered the normals on top and they seem fine. I did water a while ago and had the exact same problems. I belive this issue was up here, about this type of artifact, but I could not find it again searching the archives.

Here’s a screenshot: —[REMOVED]—

The per-vertex normals are shown in green.
I realize its linearly interpolated, but the verts are shared (GL_TRIANGLE_STRIP) and, well, shouldn’t the lighting appear so much smoother!?

Thanks for you help.

[This message has been edited by fritzlang (edited 12-18-2002).]

[This message has been edited by fritzlang (edited 12-19-2002).]

The artifacts on the “slope” to the right looks like mach banding. This is common
problem when gouraud shading a low polygon surface, per-vertex that is.

In front to the left looks ok though, which is weird. How does it look if you just use diffuse lighting?

When I used normalization cube maps the first time I normalized the normals passed
in, this resulted in some strange results.

[This message has been edited by roffe (edited 12-18-2002).]