3D texturing artifact problem

[paintor]

Hi, im doing a simple texture based volume renderer using 3D textures, i'm having trouble with the first slice drawn aparently not using the correct texture co-ords and generating artefacts in my images. all the other slices work correctly, but the first one drawn (in many cases, not just if the slice number is 0) gets a plane though the 3D texture, I dont think i've done anything horribly wrong, and thought that maybe someone would know what it was, or has had a similar problem,

any ideas ??

[dorbie]

Not from that description. There's a chance it's a texture filtering issue if the slice is at the edge and aligned with the volume, but apart from that no explanation.

[martinho_]

do you use CLAMP_TO_EDGE wrap mode for the 3 dimensions?, borders use to cause problems with other wrap modes

[paintor]

hi, i tried all the different clamping modes and the same effect happens. Basically for volume rendering im generating a list of polygons as slices. (i've reduced my code to just rendering the polygons for now with the texturing to try and eliminate problems) i've found that producing a poligon before the list and texturing that polygon first with the same texture co-ordinates (tehn hiding it) solves the problem, this is odviously a bit of a hack, but kind of proves that my tex co-ord generation is correct. its as if any first texturing operation incurs an error. could this be driver related ??