You already guessed what I'm up to.. reflective water :-) I also read
the ShaderX article, I just don't get the perspective part quite right.
The matrix you show below doesn't quite seem to fix my problem. Looking
at it, I think it just translates the projected vertex coordinates
([-1,1],[-1,1],[-1,1]) into texture coord space ([0,1],[0,1],[0,1]). I
got that right, too.. The problem just seems to be that the space
between the vertices gets distorted by perspective-correct texture
mapping. If I increase the tesselation level enough, or move the camera
far away, so the polygons become smaller, the problem isn't visible any
longer. Also changing the vertex program output of the texture w value
doesn't seem to have any effect on coordinate interpolation.
Does your fragment shader do anything more then looking up the texel at
the interpolated texture coordinates? Also at what point in your
program do you project the texture (calculate x/z,y/z)? The vertex
program code snippet you sent me doesn't seem to do that..
Cheers,
jonas
On Mar 30, 2005, at 2:03 PM, Nicholas Francis wrote:
Hi Jonas...
You want to take a look at texture w coordinate to undo the effects of
the perspective correction. You use the texture matrix together with
eye-space texgen to set it up.
For GooBall, we couldn't get their stuff to work, so we rolled our
own (the paper was still well worth the read). The matrix we used
ended up looking like this:
.5 0 0 .5
0 -.5 0 .5
0 0 .5 .5
0 0 0 1
If you're using a rectangle texture, you wat to multiply the two upper
rows with the texture dimensions.
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