You need to enable caustics as a render effect as well. Surface caustics work (i.e. a reflected light spot appears on the floor in front of the mirror), but the volume caustics don’t work (probably because C4D’s standard volumetric lights are not a true volumetric effect).
Does this work on other renderers? [SOLVED]
NWoolridge
#7
I imagine Srek will say the same thing. I tried this in Arnold, but Arnold can only do soft, imprecise caustics, and it didn’t track the reflected beam through an environmental fog.
A true light simulation render engine, like Maxwell, would probably do it. Also Corona, which has excellent reflective and refractive caustics:
sirio
#8
Vray can do that too, here is an example I’ve made a few years ago: https://www.facebook.com/3drenderandbeyond/photos/2629419427082660
The physical result was very close to the reference photo.
xdennisx
#9
If you want to have a laser effect, why not use a spline, sweep nurbs and a pure Luminace material with glow effect on? Would be easier to pull it off, right? The deflection could also be easily faked with 3 nulls and a tracer for example.
demis
#10
@xdennisx for static renders yes that can be easy. But making an animation with many bounces is impossible this way.
IceCaveMan
#11
Don’t think Octane could do this currently, but they are soon releasing PPM Hybrid kernel render option. PPM = Progressive Photon Mapping w/advanced caustics.
Currently Octane gives you caustics, but not w/this math. model.
This type of modeling is historically VERY heavy computationally.
This image is from academic paper on PPM:
3dfluff
#12
It works, just keep in mind it is entirely crap. Volumetric caustics only work within the confines of the volumetric light. Which means as soon as the ray of light hits the mirror it immediately leaves. The system was really 99% designed for making nice patterns through refractive surfaces, not shoot pewpew lazers at mirrors (fun fact, I once broke a digital camera by shooting a laser at the sensor. The photo came out great though but it fried the camera) You can work around this with a second larger weaker volumetric caustic light to define an area:
IceCaveMan
#13
This makes me laugh out loud. I can imagine 3 reactions to such a moment:
Visceral - I blew something up!
Financial - Damn…Mu$t replace!
Academic - This merits further inquiry
verysame
#14
LuxRender seems to be quite good at this kind of stuff, not sure there’s a bridge for C4D though (haven’t tried LuxCore, perhaps that works)
https://forums.luxcorerender.org/viewtopic.php?f=2&t=2784
IceCaveMan
#15
Yes.
In fact LuxRender was the explicit inspiration for Octane’s upcoming PPM. An Octane user was persistent in asking for it repeatedly based on what he’d seen with LuxRender.
Finally Jules decided: “this is a good idea and we can do it.” Coming this next year.
xdennisx
#16
Ok, you’re right. What about XParticles? I guess you could also pull this off with Thinking particles but it’s been a while… https://f.io/8cg4nJ_G
demis
#18
@xdennisx There’s also this but I was looking for a more general solution. The laser beam was just an example.
https://nitro4d.com/product/magic-laser/
demis
#20
LuxRender looks so dope ! That wavelength dispersion effect …
Does Redshift support light dispersion ?
3dfluff
#21
It was more a slow realisation the following day that every photo I had taken immediately after the laser incident had this etched line running through it. You could actually see the same mark burnt into the sensor from the outside. I think I feigned ignorance and Panasonic replaced it under warranty 
verysame
#23
Not sure how accurate is Redshift in that regard. I regularly use material dispersion but from a technical standpoint, I don’t know how much that relates to the effect you’re after.
Luxcore delivers some of the most beautiful caustic/volumetric IMHO, but of course, it’s time-consuming.
I don’t follow it much though from what I’ve seen it seems they’re improving rendering times quite a bit.
These are from another thread on their forum:
https://forums.luxcorerender.org/download/file.php?id=2305&mode=view
https://forums.luxcorerender.org/download/file.php?id=4883&mode=view
__dropbox.com/s/qky4gg2suayb8x4/softbodyslomo.mov
Srek
#24
Nothing to add here, except that when i wanted reflecting lasers a couple of years ago i created an Xpresso setup thet would place and adjust parallel lights according to angle of reflection.