Light, computer, action! New algorithm goes to Hollywood

Ask any serious movie buff and they will tell you that the key to good cinematography is lighting. This is equally as true for computer-animated movies as for their live-action counterparts. Today, the movie industry’s digital light experts use special computing methods, requiring enormous computational power, to produce realistic lighting effects.

Over recent years, there have been two main computational methods for modeling light in a scene, Monte Carlo path tracing and photon mapping. Each method has its own respective set of advantages and disadvantages. But, unfortunately, the two methods are mathematically incompatible — or at least they were until now.

A team of scientists working in Germany and the Czech Republic have developed an approach to combine the two methods. They reformulated photon mapping as a Monte Carlo process, thus enabling it to be directly integrated into the Monte Carlo path tracing method. For every pixel of the image, the team’s new algorithm — known as ‘VCM’ — automatically decides which of the two methods is best suited to computing the illumination at that spot.

“We know of four different companies that partially integrated VCM in their commercial products only a few months after the scientific publication,” says Philipp Slusallek, professor of computer graphics at Saarland University, scientific director at the German Center for Artificial Intelligence (DFKI) and director of research at the Intel Visual Computing Institute at Saarland University, Germany. “The most recent example is the new version of the software RenderMan developed by the company Pixar. For decades this has been the most important tool in the movie industry,” he explains. Pixar, a subsidiary of the Walt Disney Company, is responsible for some of the most popular animated movies of recent years, such as ‘Up’, ‘Cars’, ‘Finding Nemo’, ‘WALL-E’,  and ‘The Incredibles’.

- Andrew Purcell