How to project an image from a Cycle's Sun light I'm trying to project a caustics texture from a light in Cycles. It works with Point or Spot lights, but I'm trying to emulate the sun projecting caustics underwater, so I need the shadows and light rays to be parallel. Here is an image from the test scene, note that the shadows are not parallel.



And here's the light's material setup:



The question is if there's a way to project from a Sun light. I know that an option is to take the light far, far away (that's why the Light Falloff Node is there, for controlling the strength).
Short answer: 

No.

Long answer:


  Their position is not taken into account; they are always located outside of the scene, infinitely far away, and will not result in any distance falloff. 


Which leads me to believe that it would not be possible, as there would be no way to map the texture to a source set up like that. The exact reasons you want to use it makes it an impossibility I am afraid.

Alternative answer:

You can project an image from a plane with a simple Transparent BSDF setup between any light and your subject.




And it also works with volumetrics: