There is no automatic way. Reflections and refractions are only calculated for rays of light which tracked backward from the camera through explicit bending due to direct reflection and refraction. Poser doesn't do those focused bits of light transmitted through curved transparent surfaces that are then diffusely reflected by other surfaces, i.e. caustics. However, you can fake them.

Many people don't know there are some crazy things you can do with the material room on a light. Here I've created a spotlight and attached an image to it in the material room. You can point this light anywhere you want to simulate caustics. You can draw any pattern in an image and attach it (like a light gel) to the light. The light behaves as if the image is being held in front of the bulb - whatever is in the image colors or darkens the light coming from the bulb and is projected onto other surfaces.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)