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          Institute: MPI für Informatik     Collection: Computer Graphics Group     Display Documents



ID: 231308.0, MPI für Informatik / Computer Graphics Group
Spherical Harmonic Gradients for Mid-Range Illumination
Authors:Annen, Thomas; Kautz, Jan; Durand, Frédo; Seidel, Hans-Peter
Editors:Keller, Alexander; Jensen, Henrik Wann
Language:English
Publisher:Eurographics
Place of Publication:Aire-la-Ville, Switzerland
Date of Publication (YYYY-MM-DD):2004
Title of Proceedings:Rendering Techniques 2004 : Eurographics Symposium on Rendering
Start Page:331
End Page:336
Place of Conference/Meeting:Norrköping, Sweden
(Start) Date of Conference/Meeting
 (YYYY-MM-DD):
2004-06-21
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:Spherical harmonics are often used for compact description of
incident radiance in low-frequency but distant lighting
environments. For interaction with nearby emitters, computing
the incident radiance at the center of an object only is
not sufficient. Previous techniques then require expensive
sampling of the incident radiance field at many points
distributed over the object. Our technique alleviates this
costly requirement using a first-order Taylor expansion of the
spherical-harmonic lighting coefficients around a point. We
propose an interpolation scheme based on these gradients
requiring far fewer samples (one is often sufficient). We show
that the gradient of the incident-radiance spherical harmonics
can be computed for little additional cost compared to the
coefficients alone. We introduce a semi-analytical formula to
calculate this gradient at run-time and describe how a simple vertex shader can
interpolate the shading. The interpolated
representation of the incident radiance can be used with any
low-frequency light-transfer technique.
Last Change of the Resource (YYYY-MM-DD):2005-05-24
External Publication Status:published
Document Type:Conference-Paper
Communicated by:Hans-Peter Seidel
Affiliations:MPI für Informatik/Computer Graphics Group
Identifiers:LOCALID:C125675300671F7B-8DECFDE55BFA3E80C1256EBE0030D372-...
ISBN:3-905673-12-6
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