Using arb_fragment_program, how can I access pixels adjacent to the current fragment to build up an interpolation kernel? I want to be sure I am accessing a single pixel value at particular offsets from the current pixel that is being rasterized. Thanks.

Quote:Original post by Krohm
You must render to a texture and use texture lookups, in other words, perform a post-processing effect.

Oh sorry. I should have mentioned that I have already rendered to texture the thing that I want to "blur". Then I re-render that texture to a screen alligned quad.

Quote:Original post by Krohm
You can do that by having a uniform containing 1.0/TEXTURE_DIMENSION, which is a texel width/height. I have tried doing this with NEAREST and it worked just ok to index a large LUT dynamically. Last-gen graphics cards allows you to access the texels indexed as integers directly, but I'm not sure it already makes sense to use this functionality.

Infact this is what I did. I actually first created another pbuffer exactly the same size as the texture and enabled GL_NEAREST filtering to be absolutely sure that I was accessing a single pixel at a time from the texture map when I offset from my current texture coords.

I just wanted to be absolutely sure that this was the "right" method. As I dont want to be working harder than I have to. There donesnt seem to be a particularly "clean" way in arb_fragment_program to fetch more than one texel without several lines of +1 and -1 increments from the current texture coords.