I want to create an animation where a sphere moves. This sphere is going to be textured with a PBR work flow. However, the sphere will feature a relatively complex node setup, wherein one of the main elements is refraction.

Here is the issue...

The sphere is a placeholder object for the main character of a short film (sphere like main character), and will be in almost every scene. In order to make sense in the narrative, the shader for this character has to be semi-transparent/refractive.

Since this sphere is going to be in nearly every shot in some capacity, I want to keep render times for this object to the absolute smallest amount of time possible (preferably under 1 minute per frame).

Is there a way to optimize a refractive material or the lighting in the scene, or maybe perhaps there is a way to fake refraction, in order to keep render times as low as possible?

This is the effect I am going for: fluorite sphere


This might be a little bit of a late answer, but Cycles' caustics handles large light sources very well, but small ones with difficulty. I'd recommend using the Light Path node, and two lamps for every light source. One is a lamp that shines for everything that is NOT reflective/refractive. The other one is a large lamp for ONLY reflective/refractive caustics.

To do this, I'd use the Is Reflection Ray and the Is Transmission Ray outputs of the Light Path node.

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    $\begingroup$ could you please add a description on where exactly and how to use that in the node tree? A screenshot would help a lot! $\endgroup$ – aliasguru Aug 4 '16 at 11:36

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