implementing Manifold Next Event Estimation

[Bigguns]

Renderman has this , and it's great to add fast and sharp caustics into the eyes. Right now, it's impossible in vray and limitating the eyes realism a lot. Also, I found that in Vray next the caustic from raytraced surface like glass are worst then before .

https://renderman.pixar.com/louise

This would greatly help if you can implement this. Let me know


Here's a video where we can clearly see real eye caustics in action.
https://drive.google.com/file/d/1F0XAZVBWhJsxBf9ZJYJOnWo7VNraeJj1/view

[vlado]

How are the Corona caustics working out for you? I'd much rather implement their method as it's way more general than just for eyes.

Best regards,
Vlado

[kosso_olli]

How are the Corona caustics working out for you?

We tested it on some car shots, and so far it is the most advanced caustic solver. Of course the render is still slower with caustics, but the whole setup is much simpler. You basically get caustics with a click. And they looked great on the cars, we got really nice patterns on the floor from the body and the wheels.

[Bigguns]

Vlado, I have to test them, gonna do it today, What I'm wondering is, is it going to affect hairs and everything ? If it's the case, it may make the hairs look less good and render times MUCH slower just to get little caustics in the eyes. The advantage of the the renderman method is to save on render time when you need just caustics on a small object. So implementing both would be good to me. If one need general caustics it could use corona overall caustics and if it need it just for some small specific object it can use the renderman method.

[Bigguns]

here's my test. So my feedback is, WAY better then before, that's the good news, BUT haha it needs to denoise completely to be usefull for eyes and that I don't see it happening, most of the renders, even if I let them render, they just won't denoise.. and noise in the iris break the realism .

so as you can see, some scene just won't denoise.. and I have almost nothing in the scene, an eey and 1 or 2 lights.. so imagine on a whole character it would take foerver to denoise

caustics in eyes for character is vital, otherwise look's fake dead CG .. and having what renderman has for these situation is the best I have seen. It render's fast and create precise noise free caustics in small area like eyes like in this tutorial again : https://renderman.pixar.com/louise

if you can make it work perfectly in corona and then in vray with the caustics that corona has it would be great, but I don't think it's possible and at a fast render time like in renderman. rendring character is already super long, having the renders 10 times longer just to get these caustics in the eyes don't make sens to me, so having that manifold thing integrated is what makes the most sens.

The other caustics, it's good for cars, pool water etc.But for small thing like eyes, it needs something specifics to not kill the rendertime.

[Bigguns]

some more with some that won't denoise anytime soon.. and there is nothing else in the scene and it takes forever so imagine with a whole character..

[Bigguns]

here's some that were VERY noisy ... and impossible to denoise

[Bigguns]

and here's some test in Vray, doing an old trick for fast and sharp caustics.. but it's not super accurate though.. since the std light have to not cast shadow and it only work's for crips casutics so with soft light you would still get sharp caustics wich don't make sens..
I found that the vray soft caustics ( like the one you get with a refracted object and without activating the caustics in the render tab ) less good then before, in vray 3,6 at least I was getting some soft caustics for the eye it was helping, now there is not much.. I opened old scene and it was not looking the same..way more flat now.. I don't know what has changed in that regard, but it was better before.

[Bigguns]

BTW, I found that Alsurface don't receive caustics, but it worked with sss2, so there is something to check there.. alsurface should receive caustics too

[kosso_olli]

The Corona examples with the shaders and maps look highly convincing!

[andy51]

When you say the standard lights must not cast shadows, are these max standard lights or V-Ray lights. I remember that to get caustics working properly, the material (if transparent) must have affect shadows turned off, I never use max standard lights myself

[Bigguns]

Andy51, it's with std light ( and vray light, but the vray light need to have the generate caustic set to 0 since the caustics will come from the std max light) and in the max light, you have to make the cone just big enought to cover the are you want caustics so that maximum photons are in the zone, plus you have to put that light in inverse square and boost the strengh a lot, like 500 or more. But it's a great tips for REALLY fast crips caustics in a pool or for cars etc.

[demonslayer]

Are there updates on this? I struggle to get caustics looking right on a Iris with the the VrayAlsurface shader. Like Bigguns posted it seems not to work with Alsurface at all.

[^Lele^]

Any value of sss mix below 1.0 works as intended here.
You or Luc should share a scene if you have an issue, and we'll look into it, be it for bug fixing, or for workarounds.

[Bigguns]

I mean, it should work at a value of one too... why not ?? When I use SSS alsurface, I don't need ANY diffuse ..it's for skin, so why you I add diffuse component to try to work around something that should work by default?