Question: Are texture samples specified to be taken at a corner or center?

[trbabb]

When calling, e.g., textureSampleGrad(tex, sampler, st, dst_dx, dst_dy), is the effective sampled area of the texture a patch with "origin" at st, e.g. st + J * xy, with xy in [0,1]^2 and J the Jacobian to sample? Or is st the center of the sampled patch, with st in [-0.5, 0.5]`? Or something else?

What does the spec say? I couldn't find anything explicit, but I might not be searching for the right keywords.

[almarklein]

Maybe this helps: https://docs.pygfx.org/stable/_gallery/validation/validate_image1.html (the texture coords of a plane geometry are [0..1]).

When you sample from a texture, the st represents the "center" of the sample. E.g. with linear interpolation you'd get the exact pixel value when st is exactly on top of a pixel, but if it's in between two pixels, you get the mean.

Does this make sense? Or are you asking for a specific detail for the Grad-variant of texture sampling? I'm not 100% sure I understand the question.