I'm rather new to Blender, and try to learn it to make physics animations and visualise my data. However, I have difficulties getting the refraction working. I hope I am doing something stupid wrong, but after googling and trying for a few days, I hope the community can help me.

What I want to do is shine a 'laser' (spot light) through a cube that is rotating. Depending on the angle, the spot should move. The steps I took are: - remove the default cube - change to Cycles render (although I tried it also with internal) - add a plane and scale it. - add a cube, add material, set surface to glass BSDF, set surface to 'Is Transmission Ray' - add a spotlight, increase the strength to 50000, size 1d, blend 0 - at the render preferences, set the Samples to 2000 - rotate the cube, insert some key frames, and reder it.

The result is that the majority of the light goes straight through the cube, while a minimal amount seems to be refracted (the noisy white dots??). See the figure below. The red dot is not moving when the cube is rotating, while the white dots are.

The .blend file is available here: https://www.dropbox.com/s/3g8v6bp5s7plx85/test.blend?dl=0

I hope somebody can help me. Thanks for any help!



Thanks already for all the comments. With the Luxrenderer I could make it work, so that is at least a working option.

It still would be good to get it working in Cycles and understand it. There seems to be some discrepancy in the answers whether or not this is possible. A working example might work wonders.

The 'Is Transmission Ray' was tried as I read it somewhere (not the best argument) It didn't change the result one way or the other. The same holds for different values of the IOR.

position 1

  • 2
    $\begingroup$ This has been asked before, I don't think Cycles supports this kind of light interaction, you'll have to use another render engine. See blender.stackexchange.com/questions/82848/… and blender.stackexchange.com/questions/90698/… $\endgroup$ Commented Oct 15, 2017 at 13:13
  • $\begingroup$ Maybe tweak the index of refraction (IOR) off the glass material? $\endgroup$
    – Linguini
    Commented Oct 15, 2017 at 16:30
  • 1
    $\begingroup$ Like Duarte said, you need to use an engine like Luxrender (free) to get this to work accurately and physically. $\endgroup$
    – bertmoog
    Commented Oct 15, 2017 at 18:27
  • $\begingroup$ Cycles can most certainly do this—its hallmark is the high physical fidelity of its rendering, after all. Have you tried narrowing the angle of your spotlight to more closely simulate a narrow laser beam? $\endgroup$ Commented Oct 18, 2017 at 6:05
  • $\begingroup$ Also, what are you doing with the “Is Transmission Ray” business? $\endgroup$ Commented Oct 18, 2017 at 6:06


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