Hi Diogo,
> - triangle T=(V1,V2,V3), in which V1, V2, V3 are vertexes that have some
> properties (world space position, normal, diffuse color, texture
> coordinates 0 (in uniform space), texture coordinates 1 (in texture space,
> [0..texture size[), etc),
>
> - texture size
>
> - position inside the triangle (absolute value in texture space)
>
>
>
> is to find out the rectangle that bounds the texel in world space (origin+2
> vectors)...
if I understand your setup correctly, you're dealing with a linear transform
(from a plane in UV-space to a plane in world space), so the partial
derivatives with respect to u and v are constants across the triangle.
If this is not too much setup overhead, you could proceed by finding the world
space directions U and V corresponding to the u/v axes for the triangle
by solving for a 3x2 matrix with the world-space-directions U and V as
columns:
matrix(U V) * (A-B) = A.worldpos - B.worldpos
matrix(U V) * (B-C) = B.worldpos - C.worldpos
where A, B are 2D u/v coordinates (in pixel units).
cheers,
Manuel
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