Interactive Rendering of Translucent Deformable Objects
Tom Mertens, Jan Kautz, Philippe
Bekaert, Hans-Peter Seidel, Frank Van Reeth
Abstract
Realistic rendering of materials such as milk, fruits, wax, marble, and so on,
requires to simulate subsurface scattering of light. We present an algorithm
for plausible reproduction of subsurface scattering effects. Unlike previously
proposed work, our algorithm allows to interactively change lighting,
viewpoint, subsurface scattering properties, and even object geometry. The key
idea behind our algorithm is two-fold. We derive an efficient and accurate form
factor for computing the amount of light scattered from a whole surface patch
to a given sample point, which greatly reduces the amount of computation
compared to sampling based schemes. Secondly, we use a hierarchical data
structure to facilitate fast integration, effectively reducing the integration
complexity from quadratic to linear. This hierarchical structure also allows
for efficient incremental updates and rendering of deformed geometry. Our
experiments show that translucent objects can be re-rendered interactively,
even if they are deformed or if the subsurface scattering properties change.
Publication
Interactive Rendering of Translucent Deformable Objects, Tom Mertens,
Jan Kautz, Philippe Bekaert, Frank Van Reeth, Hans-Peter Seidel, Proceedings of
Eurographics Symposium on Rendering, Leuven, Belgium, June 25-27, 2003 PDF
Video
DivX (14Mb)
Notes:
All scenes are rendered on a Dual Xeon 2.4Ghz, on an ATI Radeon 9700Pro, under
Windows. All scenes are rendered in on-the-fly mode, except for scene 3.
Scene 1: Material Change
The bust model constists of 10K triangles, and is lit by a point light source.
We start with changing the scale of the BSSRDF parameters, going from
moderately translucent to very translucent (material is marble). Then, we
change the scale back to before, and we iterate over a few other materials:
skim milk, whole milk, human skin 1, human skin 2, candle wax and ketchup.
Finally we return to skimmilk, and while showing the back of the bust, we make
it more translucent again.
Scene 2: Candle Twist
A butterfly subdivision model (5K tris) is lit by a flickering and moving point
light source inside. We apply a twist deformation such that the model gets
thinner and more light scatters through for the inside. The deformation
algorithm itself eats some CPU time, that's why the frame rate seems to drop
while twisting.
Scene 3: Shadow leak
A dent is added to the top of a tesselated cube of 16K triangles in incremental
mode (this explains the brief dark spot: links are invalidated to get updated).
We now light the model with a spot light, including shadows. Notice the shadow
'leaks' from the top plane to the adjacent plane. Also, we have a higher frame
rate than in on-the-fly-mode.
Scene 4: Perlin Noise Cube 1
A tesselated cube of 16K triangles is distorted with a perlin noise function,
resulting in a full deformation. The material is whole milk, and is changed to
skim milk. The model is first lit by a point light, followed by a spot light
with shadows.
Scene 5: Perlin Noise Cube 2
Same situation, but the lighting has been done with an environent map. Note the
fresnel reflection effects.
Screenshots
