Scott McMillan wrote:
>
> I have been playing with scaling the texture matrix and I have
> come across a weird result on my Linux box running Mesa 3.0
> (that doesn't show up on my SGI at work).
>
> The attached program scales the texture matrix (2, 2, 0), and
> renders a textured triangle strip with texture coords in the
> range [0, 1] (the result looks like I have an identity texture
> matrix with texture coords in the range [0, 2] and I have set
> clamp.
>
> The resulting texturing gets messed up in area outside the normal
> texture (where the CLAMP causes the edge pixel to be "stretched"
> across the polygon), but (and this is the good part) ONLY WHEN THE
> POLYGON GETS TOO CLOSE TO THE VIEW.
>
> Can anyone else recreate this in current beta versions (I am still
> trying to set up CVS at home)? If so, is this a bug or just an
> area outside of the spec?
I still need someone to answer the last question above. If this is
not a bug, somebody please tell me and I will discontinue this traffic.
I checked out the CVS repository version last night and tried the
program there, and it behaves slightly differently than version 3.0.
Note again that this occurs in the painting (is shading the right word)
of the textured triangles ONLY in regions where the texture coordinates
exceed 1.0 and GL_CLAMP is being used.
Here's more info:
In Mesa 3.0, the texture (which is an orange and black checkerboard)
is rendered as gray and black in this region when the polygon gets
too close to the view. In MesaCVS, it is rendered all white in
GL_DECAL mode and all black in GL_MODULATE.
Scaling the texture matrix has nothing to do with it. Instead of
scaling by two, I can double the texture coordinates and get the same
affect.
How close the polygon must be to the viewer to see this affect is
affected by how large the texture coordinates get.
Using GL_REPEAT does exhibit this problem.
As this is my first look at the Mesa code I am still unfamiliar with
the layout so I am incapable of tracking this bug down any time soon.
Hope this helps,
scott
--
Scott McMillan mailto:[EMAIL PROTECTED]
Cambridge Research Associates http://www.cambridge.com
1430 Spring Hill Road, Ste. 200 Voice: (703) 790-0505 x7235
McLean, VA 22102 Fax: (703) 790-0370
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