A Practical Analytic Model for the Radiosity of Translucent Scenes
Two translucent horses
The translucency inter-reflection
Light propagation in scenes with translucent objects is hard to
model efficiently for interactive applications. The inter-reflections
between objects and their environments and the subsurface scattering
through the materials intertwine to produce visual effects like
color bleeding, light glows and soft shading. Monte-Carlo based
approaches have demonstrated impressive results but are computationally
expensive, and faster approaches model either only interreflections
or only subsurface scattering. In this paper, we present
a simple analytic model that combines diffuse inter-reflections and
isotropic subsurface scattering. Our approach extends the classical
work in radiosity by including a subsurface scattering matrix
that operates in conjunction with the traditional form-factor matrix.
This subsurface scattering matrix can be constructed using analytic,
measurement-based or simulation-based models and can capture
both homogeneous and heterogeneous translucencies. Using a fast
iterative solution to radiosity, we demonstrate scene relighting and
dynamically varying object translucencies at near interactive rates.
Publications
"A Practical Analytic Model for the Radiosity of Translucent Scenes"
Yu Sheng, Yulong Shi, Lili Wang, Srinivasa G. Narasimhan
ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games (I3D),
March 2013. [PDF]
[Presentation slides]
Pictures
[left] Two translucent horses (63k
polygons) illumina ted by a point light source. The three
zoomed-in regions show that our method can capture both
global illumination effects. [middle] The missing light
transport component if only subsurface scattering is
simulated. [right] The same mesh rendered with a different
lighting and viewing position. Our model supports
interactive rendering of moving camera, scene relighting,
and changing translucencies.
Renderings of the "bowls and bunny"
scene under different lighting conditions. [left] Light scattered through three
colored bowls illuminates different parts of the bunny. The scene is illuminated
by three spot light sources, with one located inside each bowl. [middle] The
same scene is illuminated by three point light sources, one above the green bowl
and two inside the other two bowls. [right] The same scene illuminated by
environment lighting.
[left] A rose model (72k polygons)
rendered with the lighting from St. Peter's Basilica
environment map and a point light source between the petals.
[middle] The missing light transport component if only
subsurface scattering is simulated. [right] The global
illumination if the rose was opaque and only diffuse
inter-reflections (classical radiosity) is simulated.
Our model
also supports heterogeneous translucent materials. Note
the color bleeding effects on both sides of the marble
block and the orange color on the right part of the
ceiling to the reflection from the translucent block.
Videos
I3D 2013 Video:
This video shows all our examples of interactive rendering of
translucent scenes using our analytic models.
A diffuse bowl illuminated by a moving point light
A translucent bowl illuminated by the same light
The bunny scene under the St. Peter's Basilica environment map
The missing light transport if only subsurface scattering is simulated
The bunny scene illuminated by a moving point light
The same scene at a different viewpoint
A rose illuminated by a moving point light and the St. Perter's Basilica environment map
The same scene at a different viewpoint
A scene with 10 translucent chess and a diffuse board
The missing light transport if only subsurface scattering is simulated