CSE 167 Lecture Notes - Lecture 17: Path Tracing, Global Illumination, Trilinear Filtering
7 Mar 2019
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Idea: use map shape - 2 stage idea. First, map (square) texture to basic map shape. Or vice versa, object to map shape, map shape to square. Cylinder: r, theta, z with (s,t) = (theta/(2*pi), z) Note: seams when wrapping around (theta = 0 or 2*pi) No singularities in any of the 6 faces! (i. e. no distortions!) Texture map each of the 6 faces. Uniform steps in screen space != uniform steps in world space! Perspective foreshortening is not getting applied to our interpolated parameters. Parameters should not be compressed with distance! Rather than interpolating u and v directly, interpolate u/z and v/z. Also need to interpolate z and multiply per-pixel. Solution: we do know w ~ 1/z. So, interpolate uw and vw and w, and compute. U = uw/w and v = vw/w for each pixel. Actually, each pixel maps to a region in texture. For each pixel, linearly interpolate between 2 closest levels (e. g. trilinear filtering)
