Creating a
realistic computer simulation of how light suffuses a room is crucial not just
for animated movies. Special computing methods should ensure this, but they
require great effort. Computer scientists from Saarbrücken have now developed a
novel approach that turned out to be so promising, that it was adopted by
companies in record time—among others by Pixar, well-known in the movie
industry for its computer animation, and now a subsidiary of the Walt Disney
Company. The realistic depiction of light transport in a room is important
within the production of computer-generated movies. If it does not work, the 3D
impression is rapidly lost. Hence, the movie industry's digital light experts
use special computing methods, requiring enormous computational power and therefore
raising production costs. Not only in the film industry, but also in the
automobile industry, the companies invest to make lighting conditions for a
computer generated image as realistic as possible. Already during the
development process, entire computing centers are used to compute and display
realistic pictures of the complex car models in real time. Only in this way,
designers and engineers can evaluate the design and the product features in an
early stage and optimize it during the planning phase.
With current
computing methods, it has not been possible to compute all illumination effects
in an efficient way. The so-called Monte Carlo Path Tracing could depict very
well the direct light incidence on surfaces and the indirect illumination by
reflecting light from surfaces in a room. But it does not work well for
illumination around transparent objects, like semi-transparent shadows from
glass objects, or illumination by specular surfaces. This, on the other hand,
was the advantage of photon mapping. But this method again led to disappointing
results for direct lighting of surfaces. But since these two approaches were
mathematically incompatible, it was not possible to merge them, and therefore
it was necessary to compute them separately from each other for the particular
images. This raised the computation costs for computer-animated movies. Researchers
developed a mathematical approach in 2012 that combines both methods with each
other in a clever way. They reformulated photon mapping as a Monte Carlo
process. Hence, they could integrate it directly into the Monte Carlo Path
Tracing method. For every pixel of the image the new algorithm decides
automatically, via so-called multiple importance sampling, which of both strategies
is suited best to compute the illumination at that spot.
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