Subsurface scattering in point-based rendering
The point-based graphics method of surface rendering has been
touted as an alternative to polygon-based graphic methods because of its simplicity
and flexibility. But point-based techniques have not offered sufficient rendering
quality when it comes to translucent materials such as human skin – until
now.
A new framework from the department of computer engineering at
Sejong University and ETH Zurich in Switzerland enables realistic rendering of
subsurface scattering in such materials.
A novel approach to point-based rendering allows the method to be used for translucent
materials such as human skin.
Point-based rendering is typically a three-pass process, so to
simulate subsurface scattering in multilayered materials, the engineers added two
new computation passes: shadow map generation and splat-based diffusion. The latter
uses splats to approximate the light diffusion phenomenon inside a material; the
assumption is that the diffusion of light is isotropic, so its effect can be expressed
as a Gaussian distribution applied to the radius of the splat. The overall diffusion
effect across the surface is determined by combining the contribution of all the
splats.
As the splat’s radius increases in the surface splatting,
the process slows down because of an increase in the number of fragments projected
on the screen space. Although the number of splats with large radii decreases, the
large overlapping area between splats means that the outcome does not change very
much, enabling a reduction of the number of splats when the amplitude of the radius
is large.
“Although in this paper we apply the surface splatting with
subsurface scattering to human facial skin, our method can be used for various translucent
objects such as marble, leaves and milk by analyzing the scattering of laser or
structured light patterns,” said Soo-Mi Choi, a co-author of the paper. “In
the future, we plan to optimize the number of splats required to produce each diffuse
color image and to adjust the resolution using perception-based metrics.”
Choi and colleagues published their results in the November 2010
article “Subsurface scattering using splat-based diffusion in point-based
rendering,” Vol. 53, No. 5, of
Science China Information Sciences.
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