[PD] gem/GLSL: how to compute correct coordinates for rectangular textures

[Matteo Sisti Sette]

Hi,

I guess if I had a deep understanding of openGL I could find the answer, 
but I am obviously looking for a shortcut (at the moment) to solve the 
specific problem I'm facing which should be pretty simple.

In the attached patch I try to use a trivial shader to texture a 
rectangle with an image; the uniform variable "curtex" tells the shader 
which texture to use.

It works fine if all images have the same size; however, if the textures 
have different sizes, no matter the value of "curtex", the texture 
coords that are computed are correct for the image loaded by the 
[pix_image] that immediately follows the [glsl_program], but are not 
correct for other images.

So the question is: how should I change the vertex and/or fragment 
shader code (or the patch maybe) so that the texture coordinates are 
computed according to the dimensions of the texture that is actually 
sampled?

It is important to NOT assume that the textures come from [pix_image] 
objects, or at least, that they are loaded from image files: actually, 
in real life, textures may be the video input generated by a [pix_film] 
or an image captured by a [pix_snap].


Thanks a lot in advance

-- 
Matteo Sisti Sette
matteosistisette at gmail.com
http://www.matteosistisette.com
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