1) If I sample a texture with texture2DRect( diffuseTex , gl_TexCoord[0].xy ) ;
where xy are non-normalized coordinates (i.e. from (0,0) to (800,600),
where does a coordinate of (0,0) sample? Is this the bottom left cornor of a texel or the center or...?
2) What offsets do I need if I want to sample the right and left neighbor of the current texel in the fragment shader.
Well, thanks. But actually that did not answer my questions.
First of all I am using texture2DRect(), which uses NON normalized coordiantes (I wrote it in my posting). Second I want to know where the sampling point in the texels is.
For regular textures, (0,0) is the lower left corner of the lower left texel, so I would imagine that it is the same for rectangular textures as well.
If each texel is already lined up with a pixel boundary, then gl_TexCoord[0].xy should already be selecting the center of a texel, so you'll just want to add 1.0 in each direction that you want to get the neighbor texel.
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