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How to make a dome master? <3>
-Snell's Window-

Fisheye Refractor, or Fisheye Lens

Snell's Window

A fish in still water can see the world above the water through a circlular window overhead.
This is an optical phenomenon known as "Snell's Window," and it happens to not only fish eyes.
If you lie in water and look up the water surface, you will see just the same thing:
By the action of the refraction of light, a 180-degree view of the world above the water
condensed into a cone angle of about 97.2 degrees in water with refractive index 1.33.

fish's view & equidistant projection


So you can take circular fisheye photos without a fisheye lens under water.
But a flat water surface does not produce the equidistant projection.
Put the cursor over the image to compare them.

To get genuine dome masters, you need to dent the water surface slightly.
It is difficult in the real world but relatively easy in 3D CG software.
You need to use raytracing in this method as well as in the reflectiong mirror method
and will lose the alphe channel.

fisheye refractor


FOR 3DS MAX USERS: You can download a max scene file containing
a reflecting mirror and camera from PineappleWare Download Page.

Other Methods

There are other ways to make dome masters.
Some people generate their dome masters using their own program from scratch.
Or you may use a plug-in on your favorite 3D CG software,
which can render dome masters directly from a scene.

image rendered by FisheyeRender plug-in

The above image was rendered by 3ds max plus FisheyeRender plug-in.

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