spherical harmonic lighting of wavelength-dependent phenomena

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Spherical Harmonic Lighting of Wavelength-dependent Phenomena. Clifford Lindsay, Emmanuel Agu Worcester Polytechnic Institute (USA). Introduction. Modeling of Light Interference As A BRDF. - PowerPoint PPT Presentation

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  • Spherical Harmonic Lighting of Wavelength-dependent Phenomena

    Clifford Lindsay, Emmanuel AguWorcester Polytechnic Institute (USA)

  • IntroductionModeling of Light Interference As A BRDFCompactly Store Surface Response and Hemispheric Light Contribution In Terms Of Spherical Harmonic CoefficientsEvaluation of Light And Reflection Is Done on GPUWorking With Spectral Color Space Instead of RGB

  • Spherical HarmonicsWe can then use these coefficients to reconstruct an approximation to the original signalWe can use spherical harmonics to approximate the original, where ci is a vector of SH coefficientSpherical harmonics is a set of basis functions defined in spherical coordinates

  • InterferenceFactors that Affect Light Interference:Refractive index and thickness of the thin filmRefractive indices of the media 1 & 2Incident Angle and incident SPD (Spectral Power Distribution)

  • Spectral BRDFJust Like Regular BRDFs (but different)Rendering equationFunction of 4 angles (incident, reflection)Conservative

    Whats Different?Different Color InteractionDifferent Material InteractionDifferent Viewer Interaction (non-reciprocal)

  • Previous Work in S.H.Diffuse Reflection Maps, Hanrahan, Ramamoorthi, 2001Physically Based BRDFs, Westin 1992Isotropic BRDFs with SH Maps, Hanrahan, Ramamoorthi, 2002Arbitrary BRDFs, Kautz et al, 2002Radiance Transfer, Glossy Surfaces, Self-shadow, and Interreflection, Sloan et al, 2002

  • Our ApproachTwo Stage Approach:1. Pre-computation2. Render

  • Pre-computationTotal Light Contribution:BRDF Response: Texture map based all possible view vectors Set of coefficients approximating total light contribution

  • GPURendering:Index Texture Map Based on view VSumming the coefficients for final contributionAdd ambient, diffuse, Fresnel for additional realism

  • ConclusionReal-time rendering of complex materials previously available to offline renderers (ray tracers)Data and Data structures that are GPU friendlyEvaluation of Spherical Harmonics is a linear operationIncreased realism with Image Based Lighting and accurate BRDFs with GPU acceleration

  • Results

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