I believe it's not possible with just one pass.

Untested idea: you could render two images, and combine them in your
favorite image manipulation software.

One of the images would be a scene with only the sphere in solid white
(ambient 1.0), with alpha output enabled. This would help you to determine
the boundaries of the sphere, and also get your anti-aliasing right.
The other image would be the final scene, with your sphere refracting
objects in the background. Don't bother with the background showing out of
the sphere.

The combination process would be multiplying the two images. This would
discard everything that's not inside the sphere.

Post a reply to this message