Vicon MX is a big step forward in the world of motion capture.

MoCap is part of the buzz at SIGGRAPH 2004. There's ILM's infrared capture system, which was used on Van Helsing, Sony's Imagemotion performance capture system launched for Polar Express and Vicon's new MX suite. This is the next generation of realtime optical motion capture systems that greatly improves the quality, flexibility and ease with which motion capture data can be applied to realtime and off-line applications ranging from film, television and video games to virtual prototyping, scientific visualization and biomechanical analysis.

Headlining the new Vicon MX suite is the MX40. According to Jon Damush, business development manager for Vicon, "The MX 40 is the world's highest resolution motion capture camera. It is proprietary architecture built completely in-house. Its foundation is a four-million-pixel center that runs at full resolution all the way up to…166 frames per second. It can actually run all the way up to 10,000 frames per second at lower resolutions. So, it's pretty versatile."

Just how much of an improvement is the MX40 over previous models? "Dramatic," Damusch claimed. "You could literally say on the order of magnitude in terms of the data quality that's achieved. There are actually two main improvements that come with the MX40. The most visible change is obviously that it's four-mega-pixels. But what's going on under the hood is as equally impressive. And that is the cameras now can do their own gray-scale processing."

Jon Damush, Vicon’s business development manager.

In the past, optical motion capture systems would have to pick a target threshold. They did this by sending out light via a strobe from the front of the cameras and they would record the reflections off a plastic marker. Damush explained, "What we would basically do when we engineered the camera we would pick an intensity that we would expect the reflection to come back at. And we would say, if we get a reflection below this intensity, don't pay any attention to it. And if you get a reflection above this intensity, it's probably a reflected marker. So basically we're picking a very specific line or threshold, if you will, that we expect to get a reflection back above. So what that means is, when you had reflections right around that line, they would sometimes be visible and sometimes not be visible, and that would typically show up on the edges of the reflection." That leads to what is typically referred to as pixel noise. "And that's inherent to just about every optical motion tracking system there is," said Damush. "By using a gray-scale, we get for every pixel on that sensor 256 shades of gray. Now we no longer have to guess at a value to threshold. We get the whole image, and we can process that whole image to come up with the 3D position of the data.

In layman's terms, what does that mean? "We're no longer using a light switch that's on or off. We're now using a slider. You can see value all the way along the scale. Which means that the accuracy that the camera produces is a) about three times better just from the number of pixels that are present and b) about 10 times better due to the fact that we can now use gray scale. Our previous generation systems would have data accuracies on the order of a 10th of a millimeter to a half of a millimeter. Now we're down to the sub-hundredths of a millimeter."

If you don't think that's dramatic, just ask Brian Rausch, manager of Motion Capture and Scanning at Sony Computer Ent. of America, why they purchased the MX40. "Grayscale, grayscale, grayscale. I decided to go with the MX40 system over others for the "pixel handling" rather than a pixel being only ON or OFF it now has 256 levels of gray to help control the circle of a marker. We are looking forward to the noise reduction that this promises to bring us."