laser beam through smoke

Hi, everyone
I’m searching a tutorial for laser beam through the smoke.
As usually laser beam is invisible until reached an obstacle.
It can be visible only through smoke or powder.
Do you know a trick for blender cycles?
Thank you very much.

Not exactly sure why you would need trickery to do that - what you describe here is pretty much Cycles’ default behaviour…:wink:

Dust/smoke = volume material. See this quick and dirty example:
Laser light at the top and a simple cube with volume scatter shader (made irregular with a noise texture connected to the density input). The “laser” is only visible when crossing the cube’s volume and where it hits the ground.