Hue's Beginner's Guide to Fulldome Production
Page 1 | Page 2 | Page 3Dome masters can be created in a 2D fashion or in a 3D fashion. The first pair of images are a tree photo which has been mirrored on both the x and y axis in a 2D After Effects comp, creating a kaleidoscopic effect. This is an appropriate way to deal with material which will not suffer from a bit of distortion, and which does not need to create a sense of realistic space. (But if you were to place a video of a dancer along the edge of a 2D dome master, for instance, they would appear squished horizontally by about a third when projected onto the dome.)
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The second pair of images were created in a 3D world, and will properly create a realistic 3D space in the dome. This is done by placing objects in 3D space around a camera rig specially designed to create a dome master. (See my other tutorials on Maya and After Effects setups.) Notice how the green torus and the red cylinder in the dome master are half again wider horizontally than when they are projected onto the dome. Almost all of the distortion in the dome master occurs out near the edges and in a horizontal direction. Also notice that although the tree kaleidoscope has the same distortion, it is not especially noticeable with this sort of image.
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In the following two images, you see a hemi-sphere, and a flat disk. Basic middle school geometry will tell you that the two yellow lines in the first image are exactly the same measure, while the two lines in the second image are different by a factor of approximately 1:1.5. In other words, the line across the middle is about two-thirds the length of the line along the edge. The distortion required to make a dome master look correct when projected onto a domed surface is governed by these proportions. There is very little distortion at the center of the dome master and there is little or no vertical distortion moving out from the center to the edge. But there is a 1.5 to 1 horizontal squeeze ratio along the horizon or "springline."(And of course this grows proportionally from 1:1 at the center to 1:1.5 at the edge, according to the math governing a "polar projection." A classic full 180 degree fisheye distortion will create a proper dome master.)
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So, why can't I just put a fisheye lens on my video camera and shoot full video dome masters? Read on...