Hello @DNorman, I tried to replicate your method by appending your node setup to a new blend file.
For some reason it only works if I add your glass cube and the plane from your file. There must be a specific setting tied to the cube and/or the plane that makes it work but I can’t find it. Do you remember what it is ?
Sometimes I can make it work with your cube but with my new plane and not yours for some reason.
I made it work with default render settings so I assume the issue does not come from those.
test_laser.blend (149.3 KB)
Yes sorry I did not mention you need to use the shadow causics option.
My light has the “shadow caustics” box ticked. (oject data - properties -settings-shadow caustics)
My glass cuboid has the “cast shadow caustics” box ticked. (object properties-shading-caustics-cast shadow caustics)
It is also important to set the refractive object to shade smooth or shade auto smooth (in flat shade it will not work).
Finally the plane has the “receive shadow caustics” box ticked.
That is why it did not work for new your plane and glass object.
Ps
It will not work well with over lapping or consecutive glass objects.
Hello everyone,
As a conclusion for this thread, I wrote an article on my website about all of the different methods to make lasers with refraction that I learned thanks to this discussion. I also added a few methods I found for Eevee.
You can read it here : soyuzkerman.net/article/blender-lasers/0-0-introduction/
Thank you again for your help, this has been an interesting journey !