The SciTech Award Goes to... Side Effects' Andrew Clinton and Mark Elendt
COW Library : Cinematography : Debra Kaufman : The SciTech Award Goes to... Side Effects' Andrew Clinton and Mark Elendt
At the 84th Annual Academy Awards for Technical Achievements, Side Effects senior mathematician Mark Elendt and 3D graphics programmer Andrew Clinton will pick up a Technical Achievement Award (an Academy Certificate) for the invention and integration of micro-voxels in the Mantra software. "This work allowed, for the first time, unified and efficient rendering of volumetric effects such as smoke and clouds, together with other computer graphics objects, in a micro-polygon imaging pipeline," says the Academy's citation.
The integration of micro-voxels in Mantra is a leap forward in rendering volumes. Placing this achievement in context highlights its significance. The 3D animation/visual effects software company Side Effects is celebrating its 25th year, and Elendt -- employee #3 -- has been along for most of the ride. He recalls the early days of rendering. "In the early 1990s when I started, a single frame of film or video took 20 minutes to an hour to render," he says. Today? It takes about the same amount of time; although the compute power has exploded exponentially so has the detail and artistry in each much more complicated visual effect. Elendt reports that one frame -- rendering Aslan's fur -- in The Chronicles of Narnia: The Lion, the Witch and the Wardrobe took over 24 hours to render across eight different machines.
"The software is being pushed further and further," he says. "The quality of the animation today is just astounding. We have to try to make sure that customers are able to do things quickly and efficiently without hitting hardware limits."
From The A-Team. Rhythm & Hues relied on Mantra's micro-voxel rendering solution for Golden Compass and The A-Team
From the beginning, Side Effects' philosophy was to build software that was both open and flexible. That included Mantra, the company's renderer, which is built into its flagship software Houdini. When he joined Side Effects six years ago, Clinton began working exclusively on Mantra. "Even then, one key thing about Mantra was that it had its own programming language built into it," he says. "Studios create a library of shaders, all of them customizable with different colors and textures. One of the great things about Mantra is the full control over what you can do with it through the shading language."
The technology for rendering volumes, however, wasn't ideal. "There were two techniques for rendering volumes," says Elendt. "Ray-marching and sprite rendering were used not just by Mantra but almost every other renderer in the marketplace." Neither solution was very good, however, when it came to handling the complexities and depth of volumes. "If you had two clouds that overlapped and tried to render it, it was hard to figure out the right transparency and color of the overlapping part," says Clinton. "When you render sprites, you're trying to approximate 3D volumes and project it into 2D space. It's not really 3D, so the shadows can be wrong and it can look not entirely correct."
"We wanted something purely 3D that was programmable so users wouldn't run into limitations with parameters such as overlapping volumes," he adds.
The need was acute. Clinton recalls being asked to put together an example for properly shaded volumes to show to clients...and not being satisfied with the results. "We worked hard to put examples together with what we had," he says. "It took quite a bit of work but it wasn't well integrated with the renderer and didn't do motion blur, so it wasn't very useable." At the same time, Side Effects' dynamics team was working on fluid simulations (puffs of smoke, explosions, and so on) and wanted to find the best way to render them.
Clinton and Elendt took a closer look at another rendering technique, REYES (an acronym for Render Everything You Ever Saw), which was published by Pixar Animation Studios in 1987. This is an algorithm used by many rendering systems that worked by taking a very complicated 3D object -- a sub-division or NURBS surface -- and split it into micro-polygons that would shape and render into pixels.
"Many rendering algorithms rely on a refinement process to render complex surfaces," says Elendt. "A sub-division surface might be split into simpler patches when then get refined to Bezier patches and eventually get converted to polygons for rendering. The most popular of these algorithms -- the REYES algorithm -- refines all surfaces into micro-polygons, which are polygons roughly the size of a pixel."
Amelia from Fox Searchlight Pictures. Toronto-based Mr. X used the micro-voxel rendering solution on Amelia, Resident Evil: Afterlife and Hot Tub Time Machine.
The two took this algorithm, which worked only on surfaces, and found a way to apply it to volumes. "We found a parallel for all the different things you'd do with surfaces in the REYES architecture, and found a way to do it with volumes," says Clinton. "In simplest terms, micro-voxels are a divide and conquer strategy to render volumetric objects for computer graphics. We take all these different types of volumes and break them up into micro-voxels, just like surfaces would be broken down into micro-polygons. That way, you can have two different volumes overlapping and it's handled all in the same architecture."
"Micro-voxels are very similar in spirit to micro-polygons," he adds. "A complicated volume primitive such as a cloud or burst of flame is sliced and diced to form simpler volume primitives, which are then turned into micro-voxels. In their final form, micro-voxels run through the same shading pipeline as micro-polygons, which allow them to be displacement shaded and lit like other surfaces."
Several studios have done just that. Rhythm & Hues relied on Mantra's micro-voxel rendering solution for Golden Compass and The A-Team, and Toronto-based Mr. X used it on Amelia, Resident Evil: Afterlife and Hot Tub Time Machine.
The micro-voxel rendering solution for volumes was shipped in beta version in 2006 and launched as a release in 2007. The need was so gaping that some studios began to use it in production when the algorithm was still in beta form.
"The big advantage of micro-voxels is that they allow volume primitives to be integrated into the rendering processes," concludes Clinton. "With micro-voxels, the renderer can apply motion blur, occlusion culling and other techniques and still end up with properly lit and composited volumes."
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