Question

can someone point me to a paper/algorithm/resource/whatever that tells me how to implement a texture minification filter (applies when texels are smaller than pixels) in a raytracer?

thanks!

Answer 1

thank you guys for your answers, but since I didn’t find any appropriate techinque i created something myself which turned out to work very well:

i assume my ray to be a cone with a coneradius of half a pixel on the imageplane. when the ray hits a surface, i calculate the ellipse which is projected onto the surface (the ellipse from the plane-cone intersection). Then, using the texturecoordinate derivatives at the intersection point, i project this ellipse into texturespace. now i know which part of the texture lies under my pixel and can subsample this area

I Also use RipMaps to improve the quality – and i chose the RipMap level based on the size of the ellipse in Texturespace