VRay caustics - what type of light

[Jiri.Matys]

Hi,

I want to make some nice caustics from artificial lights, no VRay sun and sky. What type of light I should use? Small VRay Plane Light or something different like 3ds max cone light or something?
I saw some really nice caustics in corona in a pool scene. I have a scene with light under the water in a pool and a house near the pool so there should be caustics from those lights. How you will set up the lights to have nice result?

Thank you.

[fixeighted]

I just did a very quick test with a disk light and all seems to work well,
I don't have any reference but it works both underwater and on a wall nearby.
Can you link the Corona image you saw?

[Jiri.Matys]

Somethink like that. I saw even better but didnt save them.
Caustics is sharp in reflection. Probably this is lit by sun.

[fixeighted]

Yeah both those would be caused by the sun, so reflective plus refractive. My quick test has some nice ones just from a little disc...they do show on the wall but of course would be quite diffuse.
I love what they do within the water itself though...I'll see if I can find real reference to check if they are accurate

[Jiri.Matys]

Oh, sorry, this looks weird, not what I am looking for It could be nice but it is too blury.

This is my quick test. Noiser image is right after caustics shows up, second is after 15 minutes of rendering on 2990WX(almost 200 passes). It looks much better and nice caustics started to shows up but with this speed I will render only this crop for hours.

Really want to know from Lele or Vlado or somebody if there is a way of somehow speed this up or make caustics sharper.

[Jiri.Matys]

Almost forgot. My Min shading rate is 3 and Min Subdivs is 36.

[fixeighted]

Sorry, I thought you just needed the underwater ones.

With your kind of setup I get much much faster results at pretty much default settings, so maybe something specific in your scene/settings is making it
much noisier. Over to Vlado et al to sort out

[Jiri.Matys]

Yes, my scene is big one like from corona images, not just two boxes.
I did a test with standard caustics and some photoshoping.

If I change settings to be more sharp there is a lot of noise. With blur caustics noise is not so much problem but it doesnt look realistic. I am trying to find some good balance.

[Jiri.Matys]

Image of my result

[^Lele^]

You're doing *dispersive* caustics, which means triple photon counts.
A max subdivs of 36 will be woefully low to try and resolve these.
You will need a much, much higher max AA to get them cleaned.
Lowering MSR slightly is good in this case, so to give priority to the caustics, but do not go below 3.
The best you can do is to try and set up a caustic pass, and then recomp that into the base render from the generated RE.
That way you'll be able to get the render done in a decent time, with normal settings, and the caustics to cook for as long as they need to.

[Jiri.Matys]

You're doing *dispersive* caustics, which means triple photon counts.
A max subdivs of 36 will be woefully low to try and resolve these.
You will need a much, much higher max AA to get them cleaned.
Lowering MSR slightly is good in this case, so to give priority to the caustics, but do not go below 3.
The best you can do is to try and set up a caustic pass, and then recomp that into the base render from the generated RE.
That way you'll be able to get the render done in a decent time, with normal settings, and the caustics to cook for as long as they need to.

No Lele, I make dispersion in Photoshop
I am doing standard caustics without dispersion in VRay.

[Jiri.Matys]

Now I am trying to make a caustics pass look right and composite it. This is why I use PS and make disperion there
But still when I try to make caustics sharp (Photon map or progressice) there is a lot of noise.

[Jiri.Matys]

You're doing *dispersive* caustics, which means triple photon counts.
A max subdivs of 36 will be woefully low to try and resolve these.
You will need a much, much higher max AA to get them cleaned.
Lowering MSR slightly is good in this case, so to give priority to the caustics, but do not go below 3.
The best you can do is to try and set up a caustic pass, and then recomp that into the base render from the generated RE.
That way you'll be able to get the render done in a decent time, with normal settings, and the caustics to cook for as long as they need to.

I set MIN subdivs to 36 as docs said to higher this up. MAX subdivs I have at 100 as usual.

[^Lele^]

I need more coffee, you're right on all counts.
100 max could still be falling short.
Share the scene (mail will do, no need to do so publicly) and i'll try and fiddle with it so to see what could be improved.

[fixeighted]

I inadvertently made a David Hockney version
My work here is done