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This tutorial is designed to be a no-frills beginner's guide to building and using a 5 camera hemi-cubic rig in Maya for creating fulldome content.
There are two main flavors of playback systems for fulldome presentation, "real time" and "pre-rendered." Real time systems can be compared to web pages, in that they require a script (like HTML code) which tells the system when, where and how to display images. A real time fulldome system can then take a still image, a .x file, or a small .avi file and display it with instructions to move, rotate or resize on the fly. The other flavor of fulldome projection is often called "pre-rendered playback" and can be compared to movie or video playback. This second type of playback requires a 30 frames per second sequence of large format images called "dome masters" (see our tutorial "What is a Dome Master".)
There are a variety of ways to create "dome masters." They can be made in 2D or 3D depending on the content and desired effect. There are several other methods of using 3D software to create dome content, some involving domed reflections, fisheye shaders, and fisheye refraction devices. This tutorial will cover the creation and use of a 3D "hemi-cubic" camera in Maya, but the principles will apply to any 3D animation package.
The image on the right is a "dome master" from my fulldome piece, "Wings of Memory," which won a Domie in DomeFest 2004. Note that it is a circular image within a black square. It is a true 180 degree fisheye projection made using a hemi-cubic camera in both Maya and After Effects.
Note the "stretching" of the image out around the edge of the circle. The camera you will learn to make in this tutorial will create 5 panels which must then be "stitched" together to create the dome master. This requires special stitching software that knows how to take the five panels and create a properly distorted dome master. There is a free download at Spitz for the "Glom Stitcher" and most planetariums will have that software or a similar product from Sky-Skan.
The following is a step-by-step guide to creating and using a 5 camera hemi-cubic rig in Maya.
STEP 1
Create>Cameras>Camera>Option Box
to make a new camera. Be sure you create the simple one node camera as shown.
STEP 2
The option box settings should look like this.
STEP 3
This is how the new camera will look. It is sitting at the center of the grid, facing forward. The part of the camera icon touching the center of the grid is the exact view point of the camera (this will be important to know later). Note the settings in the channel box, in particular the three settings shown in the Shapes section.
If you forgot to open the option box in step 2, you can set the three settings now in the channel box.
Horizontal Film Aperture = 1
Vertical Film Aperture = 1
Focal Length = 12.7
STEP 4
Press ctrl-A to open the attribute editor for the camera. You should see a 90 degree Angle of view. This is very important. The dome master process will not work unless all of these settings are exactly as shown. In the top grey box of the Channel box, name the camera Fcam. This will be your FRONT camera.
There are special cases in which you may want to overscan in order to use the overscan features in the stitcher, and this will require different settings. But for a simple hemi-cubic camera, these are the correct settings. (And if you know what I meant by that, you probably don't need this tutorial anyway...;-) )
© Copyright 2008 ARTS Lab / University of New Mexico