Papers

A Frequency Analysis of Light Transport
Frédo Durand, Nicolas Holzschuch, Cyril Soler, Eric Chan, and François Sillion
ACM Transactions on Graphics, Proceedings of SIGGRAPH 2005
Quick links: abstract, paper [pdf], video [mp4], bibtex
We present a signalprocessing framework for light transport. We study
the frequency content of radiance and how it is affected by phenomena
such as shading, occlusion, and travel in free space. This extends
previous work that considered either spatial or angular dimensions,
and offers a comprehensive treatment of both space and angle.
We characterize how the radiance signal is modified as light
propagates and interacts with objects. In particular, we show that
occlusion (a multiplication in the primal space) amounts in the
Fourier domain to a convolution by the frequency content of the
blocker. Propagation in free space corresponds to a shear in the
spaceangle frequency domain, while reflection on curved objects
performs a different shear along the angular frequency axis. As
described by previous work, reflection is a convolution in the primal
space, and therefore amounts to a multiplication in the Fourier
domain. Our extension shows how the spatial components of lighting are
affected by this angular convolution.
We show that our signalprocessing framework predicts the
characteristics of interactions such as caustics, and the
disappearance of the shadows of small features. Predictions on the
frequency spectrum of the radiance function can then be used to
control sampling rates or the choice of reconstruction kernels for
rendering. Other potential applications include precomputed radiance
transfer and inverse rendering.
  
An Efficient Hybrid Shadow Rendering Algorithm
Eric Chan and Frédo Durand
Proceedings of the Eurographics Symposium on Rendering 2004
Quick links: abstract, paper [pdf], submission video [mpg], bibtex, slides
We present a hybrid algorithm for rendering hard shadows accurately
and efficiently. Our method combines the strengths of shadow maps
and shadow volumes. We first use a
shadow map to identify the pixels in the image that lie near shadow
discontinuities. Then, we perform the shadow volume algorithm only at
these pixels to ensure accurate shadow edges. This approach
simultaneously avoids the edge aliasing artifacts of standard shadow
maps and avoids the high fillrate consumption of standard shadow
volumes. The algorithm relies on a hardware mechanism for
rapidly rejecting nonsilhouette pixels during rasterization. Since
current graphics hardware does not directly provide this mechanism, we
simulate it using available features related to occlusion culling and
show that dedicated hardware support requires minimal changes to
existing technology.
  
Rendering Fake Soft Shadows with Smoothies
Eric Chan and Frédo Durand
Proceedings of the Eurographics Symposium on Rendering 2003
Quick links: abstract, paper [pdf], submission video (DivX 5.0.3) [avi], comparison video (DivX 5.0.3) [avi], demo video (DivX 5.0.3) [avi], bibtex, slides
We present a new method for realtime rendering of shadows in dynamic
scenes. Our approach builds on the shadow map algorithm by attaching
geometric primitives that we call "smoothies" to the objects'
silhouettes. The smoothies give rise to fake shadows that appear
qualitatively like soft shadows, without the cost of densely sampling
an area light source. The soft shadow edges hide objectionable
aliasing artifacts that are noticeable with ordinary shadow maps. Our
algorithm computes shadows efficiently in image space and maps well to
programmable graphics hardware. We present results from several
example scenes rendered in realtime.
  
Efficient Partitioning of Fragment Shaders for Multipass
Rendering on Programmable Graphics Hardware
Eric Chan, Ren Ng, Pradeep Sen, Kekoa Proudfoot, and Pat Hanrahan
Proceedings of the SIGGRAPH / Eurographics Workshop on Graphics
Hardware 2002
Quick links: abstract, paper [pdf], video [mov], video [avi], bibtex, slides
Realtime programmable graphics hardware has resource constraints that
prevent complex shaders from rendering in a single pass. One way to
virtualize these resources is to partition shading computations into
multiple passes, each of which satisfies the given constraints. Many
such partitions exist for a shader, but it is important to find one
that renders efficiently. We present Recursive Dominator Split (RDS),
a polynomialtime algorithm that uses a cost model to find
nearoptimal partitions of arbitrarily complex shaders. Using a
simulator, we analyze partitions for architectures with different
resource constraints and show that RDS performs well on different
graphics architectures. We also demonstrate that shader partitions
computed by RDS can run efficiently on programmable graphics hardware
available today.
 
Back to home page

Page last updated on August 9 2005.
