Vray Caustics not working

[frantafxstc]

Hi,

is there a way to make vray caustics work? I am talking about caustics for small real size objects like eye caustics or water droplets.
I’ve spent lot of time trying to make it work, but your caustics solution seems to be useless and not working at all, the only way to get
at least some bad looking caustics is to make everything very big. Very disappointed and hoping there is a solution.

Thanks.

[pixelwerk]

It's a lot about the settings and by far not really intuitive to set up. I was struggeling with caustics a lot in the past and I'm still not able to get reproduceable results, even when using the same values between different scenes. This tutorial might help you in your case: https://www.youtube.com/watch?v=EvOsensDeU4&t=

[Ihno]

For those things "eye caustics or water droplets" its best imo to use the GPU renderer and disable or raise the max ray intense parameter as well as the Samples limit. The Samples limit by a lot.. like 10-15 times.
For setting up the photon caustics I'd highly suggest testing the settings in a very simple and fast scene to get used to them before setting it up in the production scene.

[frantafxstc]

Thanks for the tips. I did some more testing and used additional light with the directional parameter se to 1 (like in the video above) and it makes a huge difference for small objects so their caustics effect is now visible, but there are still lot of issues. I still have little control over the effect, it looks differently under various conditions so one has to tweak it for every lighting, weird behavior when is it connected with the SSS material (multiplies the SSS effects it seems), blotchy appearance/no precision. I am using versions 3.6/7 which are the most suitable for my needs and there is also the bug which causes reflections to be turned off when the caustics effect is turned on so one has to use mesh lights which bypasses this bug. This bug is pretty old yet is still there in these versions. This effect is hell of a challenge when one needs it for real sized small objects like eyes or water droplets, the developers should care more about it.

[Buck]

Also, one thing to note when working with small objects, set the shadow bias on your lights to a lower value. For instance in Maya they default to 0.02 I change them to 0.002

You'll get better definition in fine details. May or may not affect photon caustics, I don't know.

[Drawehn]

I honestly think Vray caustics are terrible. We tried a lot with pool caustics and the shadows always turned out way too dark. We even contacted support about it but that didn't get us anywhere. I think they are currently Vray's weakest points apart from the lens effects which I still can't get quick and good results with.

[kosso_olli]

I honestly think Vray caustics are terrible. We tried a lot with pool caustics and the shadows always turned out way too dark. We even contacted support about it but that didn't get us anywhere. I think they are currently Vray's weakest points apart from the lens effects which I still can't get quick and good results with.

Did you try the new lens effects in V-Ray Next? They were completely rebuilt, much faster and easier to use. I have nothing to complain about since Next.

[^Lele^]

The caustics are photon mapped (Remeber we had GI calculated with Photon Mapping too?).
It's tech which is decades old, even in V-Ray, and has limitations (although, with high enough -gulp- settings, it can do nigh anything.).
There's active research into new methods, but that research is ongoing (Although Corona's are fairly usable in a few situations.).

[Karol.Osinski]

Well..yes, they can be real pain and requires A LOT OF PATIENCE. It is always good to start with the basics of how they are generated. Few days ago Christoper Nichols has written really great article about them and I really recommend reading it, it helps one to understand why is it so difficult to calculate them.

https://www.chaosgroup.com/blog/what...-the-right-way


I approached them once or twice in the past with mixed results. For one project they took so much time to render/adjust that I literally spent 80% of time on this damn effect - should I change the size of the light? How much water surface affect the shape? How many photon map subdivs? + 3 other parameters I can't remember now. And every time you wanna test them you gotta re-launch the render and wait for the photon to build again...


After all, I don't want to complain too much, I just wish they are a bit faster to calculate + maybe one day - work in IPR. I don't mind studying different settings etc cuz I think their beauty partially lays in their difficulty.

[^Lele^]

I recall the first time i bathed in a pool of Caustics in Vancouver.
Literally, a very shaded corner of a park nearby tall (really, tall) skyscrapers was being brightly lit by reflective caustics coming apparently out of nowhere.
There was absolutely no discernible correlation with the lighting around me, i couldn't for the life of me figure out which was the source, and yet, somehow, light ended up concentrating in that precise spot, otherwise in complete shade.
That's when i realised that caustics of that kind are *highly* unlikely, and so calculating them has to be a very, very difficult task for anything which isn't using Nature's numbers (of photons. in the billions of billions per second. ~10^18 or so. Compared to some million/ten of million photons for renders. These synthetic photons had better be smarter...).

[Karol.Osinski]

Ha ha! At first I thought I am reading some imagined, surreal analogy to caustics lol. This makes me think *AGAIN* of how powerful and incredible is nature, and whenever I see something amazing such caustics or even "aerial perspective" beautiful blending with the environment in a distant, (as silly and nerdish as it might sounds) I ask myself - How powerful must be a "system" of nature itself to generate all these effects with zero effort and in real time. I love the way computer graphics can help you to appreciate the world around you.

[markus_s_cg]

Interesting thread. I recently had a case where I wanted to use caustics on a render of a beach (see attached image), but because I had to limit the area where the light emits photons, there is a sharp cutoff in the distance where the caustics stop and the sea-bottom becomes very dark.
If I increased the area, the number of photons would also need to be increased or the detail would be lost (unless I am missing something). Is there anything I could have done differently to improve this without creating too many photons?

The article regarding Corona was interesting btw. Hopefully, Vray gets this method implemented as well. I like the simplified setup they apparently have in Corona. Would Corona be able to solve my example better though? How does it deal with caustics/photons over a large area?

[^Lele^]

Is there anything I could have done differently to improve this without creating too many photons?

A second "sun", which covered the area with some lower-density solution (after all, it was far enough to not matter.
There would probably be some overlap (the edges are round for a sun), and you'd likely have to render twice (Close, high-res, far, low-res), and comp the passes because of that, but it may still work.
Corona would solve it n.p., but crucially not without work done (read: it won't be for free, for all the smarts that went into the engine.).