Nivida Quadro2 and lighting prob

Hi all

I've written a grass placement routine that uses mesh manipulation to place simple grass meshes on a landscape. The grass is lit by several DX lights.

I recently updated the drivers for my card (Nvidia Quadro2) as it was occasionally crashing when I went to full screen, and I was losing work.

Now many of the grass blades are not lit correctly - they show bright white on their tips. If I use updatenormals or use a looped manual update of the normals, it only worsens the issue! The mesh's brushes have no shininess, the vertex colors are at 255,255,255, all surfaces are set brushfx 0.

My other machine (RadeonPro9800) does not display this problem.

Obviously it's a driver issue, but has anyone else come across this or have any suggestions?

If you fix all the normals to 1,0,0 does the problem go away?

If yes try dumping the value of the normals and look for Nans as the geometry itself may be causing normal calulations to go astray. If back and front facing triangles of a flat mesh share verts the normal may be mathematically problematic and a doublesided surface may be the way to go.

skid

Yep, it's having the back to back tris that's the problem.

Setting the vertex normals seems to have no effect on this issue - removing the backing polys and setting the surface to double-sided solves the issue.

Newer cards seem to handle back to back polys better - so something to watch out for when writing code for older machines I guess.

The newer 70 series nVidia drivers have known issues like you describe above. You should try the latest 60 series, I think 66.92 or 66.93 and see if it goes away.