Preserving Realism in real-time Rendering of Bidirectional Texture Functions

Preserving Realism in real-time Rendering of

Bidirectional Texture Functions

Preserving Realism in real-time Rendering of

Bidirectional Texture Functions

Jan Meseth, Gero Müller, Jan Meseth, Gero Müller,

Reinhard KleinReinhard Klein

Bonn UniversityBonn University

Computer Graphics GroupComputer Graphics Group

University of Bonn University of Bonn Computer Graphics Group Computer Graphics GroupJan Meseth, Gero Müller, Reinhard KleinJan Meseth, Gero Müller, Reinhard Klein

MotivationMotivationMotivationMotivation

Hiqh-quality rendering in real-timeHiqh-quality rendering in real-time



Current real-time applications:Current real-time applications: triangular modelstriangular models simple materials simple materials

TexturesTextures Bump MappingBump Mapping Displacement Displacement

MappingMapping



Our approachOur approach more accurate material representationmore accurate material representation Real-time renderingReal-time rendering


Problem DescriptionProblem DescriptionProblem DescriptionProblem Description

Real-world materials:Real-world materials: complex reflectance behavior (pointwise BRDF)complex reflectance behavior (pointwise BRDF) mesostructure with highly complicated self-mesostructure with highly complicated self-

occlusion, interreflection and self-shadowingocclusion, interreflection and self-shadowing changing perceived normalchanging perceived normal


Previous WorkPrevious WorkPrevious WorkPrevious Work

BTF representation by DanaBTF representation by Dana

( , , ) ( , , , , , )l l v vBTF x l v BTF x y



Efficient Rendering of Spatial Bi-directional Efficient Rendering of Spatial Bi-directional Reflectance Distribution FunctionsReflectance Distribution FunctionsMcAllister, Lastra, Heidrich, Graphics Hardware 2002McAllister, Lastra, Heidrich, Graphics Hardware 2002

, , , ,( , , ) ,d x s x i x ii

BTF x l v L l v

0 0

, , , 0 0

0 0

i

i

i

N

x x

i x y z y y

zz

C l

L l v v v v C l

lC



Efficient Rendering of Spatial Bi-directional Efficient Rendering of Spatial Bi-directional Reflectance Distribution FunctionsReflectance Distribution FunctionsMcAllister, Lastra, Heidrich, Graphics Hardware 2002McAllister, Lastra, Heidrich, Graphics Hardware 2002

Rendering in real-time Rendering in real-time Good results for simple Good results for simple materialsmaterialsView-dependent effects View-dependent effects require many lobesrequire many lobesInsufficient for materials Insufficient for materials with high depth variationwith high depth variation



Efficient Cloth Modeling and RenderingEfficient Cloth Modeling and RenderingDaubert, Lensch, Heidrich, Seidel, Rendering Workshop 2001Daubert, Lensch, Heidrich, Seidel, Rendering Workshop 2001

,( , , ) , ,z i xi

BTF x l v T x v l L l v

view-dependentshadowing andmasking term

area fore-shortening



Efficient Cloth Modeling and RenderingEfficient Cloth Modeling and RenderingDaubert, Lensch, Heidrich, Seidel, Rendering Workshop 2001Daubert, Lensch, Heidrich, Seidel, Rendering Workshop 2001

view-dependent occlusion factorview-dependent occlusion factor evaluated per color channelevaluated per color channel change of perceived normal restrictedchange of perceived normal restricted based on synthesized materialsbased on synthesized materials



Towards Interactive Bump Mapping with Towards Interactive Bump Mapping with Anisotropic Shift-Variant BRDFsAnisotropic Shift-Variant BRDFsKautz, Seidel, Graphics Hardware 2000Kautz, Seidel, Graphics Hardware 2000

Fast, Arbitrary BRDF Shading for Low-Fast, Arbitrary BRDF Shading for Low-Frequency Lighting Using Spherical Frequency Lighting Using Spherical HarmonicsHarmonicsKautz, Sloan, Snyder, Rendering Workshop 2002Kautz, Sloan, Snyder, Rendering Workshop 2002


Our ApproachOur ApproachOur ApproachOur Approach

truly view-dependent truly view-dependent perceived normalperceived normal reflectance propertiesreflectance properties

minimize approximation errorminimize approximation errorsuitable for real-time renderingsuitable for real-time rendering


Data AnalysisData AnalysisData AnalysisData Analysis

Fitting Lafortune lobes to the entire BTF data for one Texel

Fitting a Reflectance Field to the BTF data for one pixel

Energy plot for one Texel of the Corduroy Data Set


Reflectance FieldReflectance FieldReflectance FieldReflectance Field

describes intensity of surface point for describes intensity of surface point for varying light and fixed view directionvarying light and fixed view direction

good approximation by lobe-like modelgood approximation by lobe-like model

,

, , ,, , ,

v iN x

v v i v i v ii

RF x l a x b x c x l


BTF RenderingBTF RenderingBTF RenderingBTF Rendering

Preprocessing:Preprocessing:1.1. fit Reflectance Fields fit Reflectance Fields RFRFvivi for various view for various view

directions directions vvii

Runtime:Runtime:1.1. determine current view direction determine current view direction vv

2.2. select closest view directions from select closest view directions from {v{vii}}

3.3. compute color according to compute color according to RFRFvivi

4.4. interpolate between individual resultsinterpolate between individual results


BTF RenderingBTF RenderingBTF RenderingBTF Rendering

Storage requirements:Storage requirements: stack of floating point texturesstack of floating point textures about 400 MB per materialabout 400 MB per material

employ BTF synthesis algorithmemploy BTF synthesis algorithmstore indices instead of color valuesstore indices instead of color valuesreduces storage to about 25 MB per materialreduces storage to about 25 MB per material


ResultsResultsResultsResults

Textures andBump-Mapping

Reflectance Field BTF Rendering


ResultsResultsResultsResults


Conclusions and Conclusions and Future WorkFuture Work

Conclusions and Conclusions and Future WorkFuture Work

in-depth analysis of measured BTF datain-depth analysis of measured BTF datanew approach to BTF renderingnew approach to BTF rendering

high-qualityhigh-quality real-timereal-time

moderate storage requirements for high-moderate storage requirements for high-frequency detail materialsfrequency detail materials

combine with Image Based Lightingcombine with Image Based Lighting


AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements

Funded by European Union under the Funded by European Union under the project RealReflect (IST-2001-34744)project RealReflect (IST-2001-34744)

www.realreflect.orgwww.realreflect.org

Documents

Preserving Realism in real-time Rendering of Bidirectional Texture Functions