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Approximate Ray-Approximate Ray-Tracing on the GPU with Tracing on the GPU with
Distance ImpostorsDistance Impostors
László Szirmay-KalosLászló Szirmay-KalosBarnabás AszódiBarnabás AszódiIstván LazányiIstván LazányiMátyás PremeczMátyás Premecz
TU Budapest, Hungary
GPU rendering versus GPU rendering versus Ray-TracingRay-Tracing
Inremental rendering on the GPU
Non-coherent Ray tracing
Previous workPrevious work
Ray-tracing on the GPURay-tracing on the GPU– Ray-engine (Carr et. al): Ray-engine (Carr et. al):
Bad complexity: time Bad complexity: time rays rays triangles triangles
– Regular grid (Purcell et. al): Regular grid (Purcell et. al): Problematic for dynamic objectsProblematic for dynamic objects
Environment mapping (Blinn)Environment mapping (Blinn)– Environment is at infinityEnvironment is at infinity– Localization with simple proxy Localization with simple proxy
geometrygeometry (Bjorke) (Bjorke)
Contribution of this Contribution of this paperpaper GPU friendly approximate ray GPU friendly approximate ray
tracing algorithm for casting tracing algorithm for casting incoherent rays needed, for incoherent rays needed, for example, example, when computingwhen computing– ReflectionReflectionss– RefractionRefractionss– CausticsCaustics– ……
distanceradiance
Distance ImpostorsDistance Impostors
Ray-Tracing withRay-Tracing with
Distance ImpostorsDistance Impostors
ApproximationApproximation
Approximation ErrorApproximation Error
1 iteration 4 iterations 8 iterations
ReflectionsReflections
radiance
Problems of Problems of environment map environment map based reflectionsbased reflections
Environment map Reference
Localized ReflectionsLocalized Reflections
distanceradiance
Comparison of Comparison of Localized RefrectionsLocalized Refrections
RefractionsRefractions
radiance
environment
Multiple Localized Multiple Localized RefractionsRefractions
distancenormals
environment
Comparison of Comparison of Multiple RefractionsMultiple Refractions
Multiple refraction Multiple refraction resultsresults109 FPS109 FPS
CausticsCaustics
distancetexture u, v
texture uv, power
32 x 32
Texture modulationTexture modulation
Texture uv of photon positions
Vertexshader
Billboardpositions
filter
Pixelshader
Lit texture orLight map256 x 256
Caustics Results: 180 Caustics Results: 180 FPSFPS
Application: Ray-Application: Ray-tracing effects in tracing effects in gamesgames
ConclusionsConclusions
Distance impostors to represent Distance impostors to represent geometry in ray tracinggeometry in ray tracing
Iterative ray tracing algorithmIterative ray tracing algorithm Applications (100+ FPS):Applications (100+ FPS):
– Localized reflectionsLocalized reflections– Single and multiple localized Single and multiple localized
refractionsrefractions– CausticsCaustics