I continue to try and figure out caustics from time to time and still have problems with one thing in particular. see the image below:
My usual problem is trying to get sweat droplets/condensation to have nice caustics and it always fails. In the image I tested a sphere, a cube, and a torus knot. On the left the geo is free-floating. On the right it is penetrating the grey block. Notice the very big change in the square and sphere. I get the same thing with the sphere if I change the shape to a 1/2 dome that penetrates as well.
I can’t see how this is correct, but I am not really sure what is going on. Can anyone at Chaos clarify what is happening with internal reflections and caustics - is something odd going on?
Here are my caustic settings, more or less default, and the relevant material settings. Caustics generated by a Max spotlight only, set to only generate caustics.
Normals and trace depth are not the problem. Not sure what the progressive method is either - do you mean the directly visible option you can access with that line of code? If so, I have tried it but AFAIK it just makes the process visible, it doesn’t do anything differently.
Maybe this is totally normal behaviour? I’m looking at the reference I pulled and looking at the render and now I’m thinking it doesn’t look as odd as I originally thought .
I know I’ve never been very happy with the caustics and droplets I’ve done in the past, but maybe it’s more about my expectations being off?
Anyway, I just want to verify (if possible) that Vray is doing the correct thing with penetrating caustic generators like this, then I can figure out what I might be doing wrong.
Well if you look at the references, there are no (or only weak) caustics in the shadows outside of the droplets - most of the caustics effect only appears inside the droplets themselves - which is what I’m seeing my tests here as well.
What about what’s happening inside the droplet? I can’t seem to get any of the more clear or perhaps more subtle, concentration of light in the drops. They just go milky white in this case. Could it be caustic settings? The directly visible method doesn’t help in order to experiment/refine, because you can’t see caustics inside the drops, and the caustics render element has the same issue (last time I tried it anyway)
I think ur sphere is too perfect to give you what you want to see… try modeling it 1st setting it up proper model with layers then see if you like it more…
Remember u need 2 side material since ur object just go into wall where it should bend and touch like it happens in reality…
The shape here is just a primitive to remove variables. I’ve done more than the odd bit of modeled sweat and I’ve seen much the same sort of thing. It’s not about the geo particularly. The material is two sided and reflect on backside is on etc.
You can’t have co-planar faces, and an air-gap creates totally different effects. The correct way to get the refraction to work is interpenetrating like it is now. The issue (if there is one) is only with caustics.
I’ve been playing around with trying to get a decent droplet system (for animation) today and thought I’d give caustics a whirl while I was at it.
Here’s where I got with it, nothing too fancy in the settings and as you can see that the interior of the droplets looks generally brighter (as per your tests) but I thought I’d post it anyway and see if this is the sort of thing you’re after (or not!)
Hi AJ -
That’s pretty much exactly what I am looking for. You are getting the brighter interior, but it is getting concentrated away from the light source and projecting some caustics outside of the droplets. Looks great.
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