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Published byElaine Poole Modified over 2 years ago

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computer graphics & visualization

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Raytracing … or where did my performance go? M.G. Chajdas

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Ray-tracing Name says it all: Trace rays – Lots of rays – And some more Hardware vendors love it!

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Ray-tracing

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Goal

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The rendering equation 5D: BRDF 5D: BRDF 4D: Light Result

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Rendering equation If you think it‘s complex … It doesn‘t capture: – Phosphoresence – Flurorescence – Intereference – Subsurface scattering

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Solving the equation Maple? Matlab?

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Rendering equation What makes it complicated to evaluate? Outgoing light depends on incoming light I.e. it‘s recursive

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Direct illumination

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Global illumination … Loss of energy with more bounces!

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Global illumination Mirror-BRDF:

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Global illumination Diffuse-BRDF:

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How to get it fast? Clever sampling Clever intersections

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Sampling

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Intersections

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Classic search problem Trees to the rescue – Space partitioning: Subdivide the space – Object partitioning: Group objects

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BSP

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struct Plane { float normal [3]; float dist; }; struct Node { int plane; int children [2]; int boundingBoxMin [3]; int boundingBoxMax [3]; }; struct Leaf { int cluster; int area; int boundingBoxMin [3]; int boundingBoxMax [3]; int firstFaceIndex; int faceCount; int firstBrushIndex; int brushCount; }; Use the source, Luke!

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BVH

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Raytracing, recap Raytracing can solve the rendering equation – It can simulate all light transport paths Requires lots of rays – Sample the important directions only, so less rays are wasted – Build acceleration structures so each individual ray is cheap

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Raytracing, limitations

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