I was hoping for an opinion/guideline on something:
I’m quoting a job for which we need to create the illusion of an object projecting light and creating something like holographic type floating in the air - kinda 3D type made out of light instead of Princess Leia, but along those lines
I have some thoughts on how to do it but was thinking about using KT to create the “ghostly” quality of the type. What I’m wondering: do you think it would be workable to also create the volumetric light beams with KT, or is that just an inefficient approach? So far I’ve only had a few minutes to test and I’m getting thin lines of light but not good wide beams (more like lasers than spotlights). Clearly the right shape can be done with the right Pflow, just not sure that this is really a good way to go about it, and was hoping for some thoughts/guidance from the KT experts.
What’s making the Princess Leia? You could project that mesh (or particle system) back to the light source and be reasonably efficient (in that there would be no particles in the shadow). Of course, the particles in the shadow should scatter the light that the particles not in shadow scatter, but that’s up to you.
We used Krakatoa for the Holotable in Avatar (the big tree display in the middle of the Ops command center), but we did not have to do any beams, just the display itself. The trouble with Krakatoa is that if you want a beam of light, you would have to fill the room with particles and let the light hit them, which is obviously inefficient. Normally, in Max the volumetric lights are calculated inside the light’s cone. You could create PRTs in the shape of the Light’s cone and link the PRT Loader to the light so it would always stay put, this making the particles stick to the light. I haven’t done this before, but it sounds like a plan.
For example, create a Cone, turn to PRT Volume and you should have something to work with. When the light passes through it, it will color the particles accordingly. You can also use the Per-Pixel Camera Map to project textures onto the particles (just align and link a camera to the light and select in the Per-Pixel Camera Map - it should even show up in the viewports).
So yes, there are lots of things you could try, but you can always combine Krakatoa renderings with VRay volumetric rendering to get the best of both worlds…
What’s making the “princess” is an art directors imagination I explained already that it wouldn’t really “work” like that - as in the light won’t just stop in mid-air and make the text, it needs to bounce off of something in the air to show the shape, but they don’t really care. It just needs to look kinda like that. So the text is made of light project up from below that magically stops in mid-air to create a ghostly type shape made of ghostly sort of light.
I am not really sure I follow what you mean about the shadows etc. I’m very inexperienced with particles as well as KT (except for a small bit of realflow). What I was thinking was to emit particles from the bottom of the floating letters and have them track back to the object that is supposed to be casting the light. This would have the “beams” line up perfectly with the letters, which in turn I would make with a PRT volume and render separately. Is that what you mean by projecting the mesh back?
Just not sure I wouldn’t be better off to fake the beams of light that bridge the gap between the object and the type.
Thanks Bobo - the Holotable is what made me think of KT for this
I think the method you are describing is kinda opposite what I was thinking, but maybe would work better? My thought was to actually create beams of particles, rather than having a mist of particles that had beams of light going through it. This way I could only project particles in the patterns that I need. Does that make any better sense? I can definitely do it with Vrayenvironment fog and spotlights, but the precise alignment wouldn’t be there, so thought this could be a cool way to try it. I’d have to try and get my head around the PRT cone method you outline, but that would probably give me the effect of Vray fog but with better precision.
I meant, is it geometry that you are clipping the particles to, or is it an image projected onto some particles, or what?
No matter what it is, it’s probably possible to project it’s “density” back to the light source, which would make it fairly efficient. Especially since those particles would not even have to be “lit”, and could just have their emissive strength set by a KCM comparing positions.
Ah, now I understand. The idea I think is geometry that the particles are clipped to, but it may be possible to project it onto particles instead.
I’m not really sure what you mean by projecting its density back though. I may just have to go with volumetric lights due to my lack of experience in this area.
I explained already that it wouldn’t really “work” like that - as in the light won’t just stop in mid-air and make the text, it needs to bounce off of something in the air to show the shape, but they don’t really care. It just needs to look kinda like that. So the text is made of light project up from below that magically stops in mid-air to create a ghostly type shape made of ghostly sort of light.