real-time, all-frequency shadows in dynamic scenes
DESCRIPTION
Some materials are get from the author and this paper is presented by CG, Huang. Real-Time, All-Frequency Shadows in Dynamic Scenes. Outline. Introduction Relate work Convolution Generation of Area Lights for Environment Maps Limitations Result. Outline. Introduction Relate work - PowerPoint PPT PresentationTRANSCRIPT
Real-Time, All-Frequency Shadows in Dynamic Scenes
Thomas Annen* Zhao Dong* Tom Mertens†
Philippe Bekaert† Hans-Peter Seidel* Jan Kautz‡
*MPI InformatikGermany
†Hasselt UniversitytUL - IBBT, EDM, Belgium
‡University College LondonUK
Some materials are get from the author and this paper is presented by CG, Huang
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result
Introduction• Enable real-time, all-frequency shadows in
dynamic scenes.• Support area light as well as wnviroment
lighting.• The key contribution is renderng plausible soft
shadow.• Enviroment-lit scenes can be rendered.
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result
1. Soft Shadows2. Convolution3. Precomputation and Simplification4. Environment map sampling
Soft shadows• Early work on shadow mapping extensions
image-based rendering to average hard shadow.[Chen and Williams 93; Agrawala et al. 00]
• Classic shadow volumn method was extended to soft shadows.[Assarsson and Akenine-Moller 03]
Convolution• Soler and Sillion[98] propose an image-based
shadow algorithm based on convolution.• Don’t support self-shadowing.
• Variance shadow maps[Donnelly and Lauritzen 06]
• Convolution shadow maps[Annen et al. 07]
Precomputation and simplification• PRT [Sloan et al. 02] calculate and stroes an
illumination-invariant transport solution off-line and uses it for real-time relighting.• Challenging to support fully dynamic scenes with
arbitrary illumination.
Environment map sampling• Agarwal et al.[03] proposed an efficient point
sampling strategy for environment maps.• Arbree et al. Use disk-shaped light sources to
approximation.• This paper approximate an environment with
a collection of square light sources.
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result
c
L
Convolution shadow map• x R3
• p R2 • P = T(x)• Shadow function:s(x):=f(d(x),z(p))
• Binary result:– 1 if d(x)<=z(p)– 0 else
x
p
d(x)
z(p)
Shadow test function: s(x)• What kind of
function is s(x)?
• Heaviside Step Function: H(t)
Sha
dow
term
for x’c
L
x
p d(x’)z(p)
x’
• Approximate shadow test with Fourier series
Convolution shadow map
)(tH c1 +c2 +..+c4 +..+c8 +..+c16
Convolution shadow map
• Step function becomes sum of weighted sin()
• Series is separable!
)sin()cos()cos()sin()sin( zdzdzd
)(tH c1 +c2 +..+c4 +..+c8 +..+c16
Convolution• Bulid on convolution-based methods.• Simulate penumbrae by filtering shadows
depending on the configuration of blocker, receiver, and light source.
CSM order reduction• Annen et al[07] using a Fourier series to
construct the f, but it’s prone to some artifacts and shadows at contact points may too bright.
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result
Generation of Area Lights for Environment Maps
Outline• Introduction• Relate work• Convolution• Illumination with Soft Shadows• Limitations• Result
1. Ringing Suppression2. Textured light sources
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment
Maps• Limitations• Result• Conclusions and Future work
1. DirectX 102. Dual-Core AMD 2.2GHz3. NVIDIA GeForce 8800 GTX graphics card
Result
• Buddha scene with 70k face
MM: MipmapsSAT: Summed area table
Result
Result
• Performance of this paper and image quality depend on:– choice of prefilter– Number of area lights– Shadow map size
Result
• Demonstrate the effect of the sharpening function G().
Result
• Shows the influence of the number of light sources used for approximating the environment map.
Outline• Introduction• Relate work• Convolution• Generation of Area Lights for Environment Maps
• Limitations• Result• Conclusions and Future work
1. Based on convolution.2. Fast enough to render many area light sources simul- taneously.3. Provide plausible results, even though they are not
entirely physically correct.4. At future work, intend to explore the use area lights for
indirect illumination.