Rendering engineer Angelo Pesce has posted an interesting two-part piece on the importance of rendering with correct math and physics instead of hacks. He argues that when when rendering engineers don't know what they're doing, they're giving artists models that can't achieve the result they're aiming for or that are too complicated.

According to Pesce, two problems can arise when artists take whatever models they're given and tweak them in unpredictable ways to make them fit the idea they want to express: "The first one is that such tweaking could end up with suboptimal use of our precious, scarce, computing resources. The second, somewhat related to the other, is that bad models could be too complicated to fit [and] to find parameters that achieve the desired look."

In order to avoid these problems, he suggests working together with artists to see what they're trying to do and ask them to make prototypes with their DCC tools. That way, you can see if it's possible to express their art in a more procedural way.

Pesce also advises that you find out what your artists need and the physics, basing models on their needs and good math: "Good math does not mean correct physics, we are far from that in real-time rendering, but reasonable physics, models that are based on solid ideas."

Posted by Eric Caoili at 11:35 AM | Permalink | Comments (2)

3D graphics programmer Jeremy Shopf has written up an interesting post documenting techniques for "performing shading calculations at a frequency lower than per-pixel." Depending on lighting effect frequency and surface orientation relative to camera, developers can compute values at a lower resolution or at an adaptive sampling.

On the likely most used technique, Off-screen Particles, Shopf explains, "The basic idea is that you blend your particles into a lower than screen resolution texture to save on fill rate. Particles, like smoke, are notorious fill rate hogs due to massive amounts of overdraw and potentially expensive per-pixel lighting computations. In order to get correct particle occlusion, a manually downsampled depth buffer has to be used for depth testing the lower resolution particle buffer." He goes on to mention a problem that can develop with particle-scene intersections, offering a solution and suggestions for optimizations.

Shopf also summarizes Bilateral Upsampling: "The concept is to bilinearly interpolate lower resolution illumination results while applying a weighting function to interpolants so that values aren't interpolated across boundaries. In some situations it is required to perform additional computation near boundaries. This situation is handled similarly to the off-screen particle method: edge detection and selective higher resolution calculation in edge regions."

The third and final method Shopf examines is Adaptive Soft Shadows with Push-Pull Reconstruction, a technique introduced by Gaël Guennebaud: "This trick computes soft shadow amounts at adaptive resolution rather than simply at a lower resolution as in the previously discussed methods. While not as simple to upsample, computing values adaptively based on surface orientation and shadow frequency allocates more fidelity in regions that need it. The other methods simply pick some lower resolution and forgo any higher frequency information."

Posted by Eric Caoili at 02:23 PM | Permalink | Comments (1)

Many games, even on current "next-gen" hardware, render particles using camera facing quads. In his Intel-supported Visual Computing piece, veteran coder Mike Krazanowski (Tomb Raider: Anniversary) suggests a neat alternative solution using pixel shaders and a little bit of math.

Though rendering particles using camera facing quads has been a practice employed in games for many years, Krazanowski's method uses shader technology to "give a more accurate visual representation of the simulated volumes as well as potentially decrease the necessary number of particles, which in turn will help to improve render performance."

According to Krazanowski, shaders have served as a significant advancement for the software developer's ability to define the functions used to render a scene in the hardware: "Even on cheap consumer graphics hardware, the software developer can define almost any function imaginable (usually only limited by available registers and functions made available to the shading language)."

He continues: "Using pixel shaders, render-to-texture technology and a little bit of math, I claim that we can more correctly simulate the volumes that the particles were intended to represent."

Posted by Eric Caoili at 02:00 PM | Permalink | Comments (158)

Organizers behind annual computer graphics conference SIGGRAPH have announced several highlights for the 2008 event, including an expanded format for the Computer Animation Festival and featured speaker presentations.

The expanded Computer Animation Festival will feature a variety of variety of competition screenings at Los Angeles' Nokia Theatre, on-site awards presentations, talks, discussions, panels, and more. In addition, SIGGRAPH 2008 will host the return of FJORG!, the 32-hour international computer graphics "iron-animator" competition.

Walt Disney and Pixar Animation Studios President (and Pixar co-founder) Ed Catmull has been scheduled as a featured speaker, as has artist and U2 3D film director Catherine Owens. Also, new tech demos for innovative technologies and applications, such as Origami Optics, Rome Reborn, and ZCam, will be available for attendees to interact with.

SIGGRAPH 2008 will take place on August 11 to August 15 in Los Angeles, California and is expected to draw an estimated 30,000 industry professionals from around the globe.

Posted by Eric Caoili at 06:32 PM | Permalink | Comments (25)