Spatio-Temporal Photon Density Estimation
Using Bilateral Filtering
Markus
Weber, Marco Milch, Karol Myszkowski,
Kirill Dmitriev, Przemyslaw Rokita,
and Hans-Peter Seidel
MPI Informatik
Motivation
For HDR images and videos captured in the real-world information
corresponding to luminance levels for each pixel is only available
(camera calibration may be required to recover absolute luminance
levels). Given such limited information the most general image and
video processing algorithms rely only on pixel values taking into
account their local neighborhood in space and time (camera and object
motion compensation may be required in the latter case). Recovering
lightness in such an input material as might be required for luminance
compression (tone mapping) or object appearance prediction is an
under-constrained problem whose solution may lead to some errors. For
computer generated images information about lighting (direct, indirect,
caustic paths, and so on), reflectance is explicitly available but its
quality might be poor. For example stochastic noise in lighting (which
is a HDR signal) is common in the global illumination computation.
Also, BRDFs describing surface reflectance can be poorly sampled and
some high frequency information may be poorly reconstructed. Then
different strategies applied to filtering each of those information
layers might be desirable.
Abstract
We present a method for efficient filtering of noise in indirect
lighting distribution inherent for Monte Carlo methods used for the
global illumination computation. For this purpose we use
spatio-temporal bilateral filtering of photon density over the meshed
scene surfaces. Bilateral fileting enables control over the
level-of-details in reconstructed lighting. All changes of lighting
below this level are treated as stochastic noise and are suppressed.
Bilateral filtering proves to be efficient in preserving sharp features
in lighting which is in particular important for high-quality caustic
reconstruction. Also, flickering between subsequent animation frames is
substantially reduced due to extending bilateral filtering into
temporal domain.
This work (PDF, 730
kB) has been presented at Computer Graphics International 2004
(BibTeX Entry).
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