Custom Camera Example

[benjamin-heasly]

It would be nice to have an example of how RenderToolbox could be used with non-standard cameras that one of the renderers already supports. For example, a stereo camera.

(We currently create stereo image pairs by rendering twice and using the conditions file to specify two camera positions. But this loses some efficiency relative to a true stereo camera, and in general it would be nice for computational photography simulations to show how RenderToolbox may be used with custom cameras.)