DISTRIBUTED RAY TRACING – Some Implementation Notes Multiple Distributed Sampling Jitter - to Break up Patterns

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DISTRIBUTED RAY TRACING – some implementation notes multiple distributed sampling jitter - to break up patterns DRT - theory v. practice brute force - generate multiple rays at every sampling opportunity alternative: for each subsample, randomize at each opportunity DRT COMPONENTS anti-aliasing and motion blur supersampling - in time and space: anti-aliasing jitter sample in time and space: motion blur depth of field - sample lens: blurs shadows – sample light source: soft shadows reflection – sample reflection direction: rough surface transparency – sample transmission direction: translucent surface REPLACE CAMERA MODEL shift from pinhole camera model to lens camera model picture plane at -w, not +w camera position becomes lens center picture plane is behind 'pinhole' negate u, v, w, trace ray from pixel to camera ANTI-ALIASING: ORGANIZING subpixel samples Options 1. Do each subsample in raster order 2. do each pixel in raster order, do each subsample in raster order 3. do each pixel in raster order, do all subsamples in temporal order 4. keep framebuffer, do all subsamples in temporal order SPATIAL JITTERING for each pixel 200x200, i,j for each subpixel sample 4x4 s,t JITTERED SAMPLE jitter s,t MOTION BLUR – TEMPORAL JITTERING for subsample get delta time from table jitter delta +/- 1/2 time division move objects to that instant in time DEPTH OF FIELD generate ray from subsample through lens center to focal plane generate random sample on lens disk - random in 2D u,v generate ray from this point to focal plane point VISIBILITY - as usual intersect ray with environment find first intersection at point p on object o with normal n SHADOWS generate random vector on surface of light - random on sphere REFLECTIONS computer reflection vector generate random sample in sphere at end of R TRANSPARENCY compute transmission vector generate random sample in sphere at end of T SIDE NOTE randomize n instead of ramdomize R and T .

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