Join David Mattingly for an in-depth discussion in this video Stereoscopic 3D basics, part of Stereoscopic 3D Environments in Maya.
Before we open up Maya, let's take a look at some stereoscopic 3D basics. There are three terms you need to be familiar with. The first is intraocular distance. Second, zero parallax plane. And the third is stereo type. The reason we have the perception of depth in our vision is that our right and left eye record a slightly different version of the scene in front of us. How different the scene your eyes record is profoundly influenced by the interocular distance, or the distance between your two eyes.
On most humans, the interocular distance is around 63 millimeters, or 2.5 inches. When you're inside of Maya, you're not dealing with human eyes, but with cameras, and Maya calls that the interaxial distance. But whether you're dealing with cameras or human eyeballs, that interaxial distance is generally based on the distance between two human eyes. Inside of Maya, you can change that interaxial distance to whatever you want. However, if you have the interaxial distance too far apart, you run the risk of your viewer not being able to resolve the image and also giving them headaches.
If you have too little interaxial distance, you won't get much 3D effect. So you'll have to adjust it to get just the right amount. When you look into the distance, for instance, at the sky, your eyes are basically parallel to each other. But if you focus on something closer, for instance, holding a finger up in front of your face, your eyes rotate in to focus on that object. The point where your two eyes meet when they rotate in is the called the zero parallax plane. That zero parallax plane will move back and forth to match the point where your eyes converge on each other as they rotate in and out.
When viewing stereoscopic content on a screen, whether on your computer monitor or the screen of your local cinema, the zero parallax plane can be thought of as the surface of the screen. And any object behind the zero parallax plane will appear to the viewer to be behind the screen and any object in front of the zero parallax plane will appear to be in front of the screen. The final thing you need to consider when setting up your 3D stereoscopic scene is the type of stereo you'll be using.
There are four types to choose from in Maya, off, converged, off-axis and parallel. Off is no stereo at all, so you're not going to use that one. The second is converged. When using converged, Maya automatically rotates the camera in so that their focus meets at the zero parallax plane. The third is off-axis. In this type, you won't see the cameras physically rotate in, but they are. Maya handles the convergence of the cameras internally so the process is somewhat invisible.
This is the recommended stereo type when working in Maya. Finally, there's parallel. Parallel keeps the cameras pointed straight ahead, effectively placing the zero parallax plane far back at the horizon. Remember that everything in front of the zero parallax plane will appear to be in front of the screen, so this technique doesn't place anything behind the screen. If you use this type of stereo, you'll need to fix that in post so that some of the objects in the scene appear to be behind the screen.
Pixar uses the parallel type of stereo for all of its movies since it allows you to control where the zero parallax plane occurs after you're done rendering. Since off-axis is the simplest type of stereo to use in Maya, that's what we'll be using in this tutorial. So let's jump into Maya.