Caustics

[nicola_barbano]

Hi!
Please improve the Caustics (as in Corona)! Since the water is often present (especially in archviz field) it would be great to have it more "real", fast and easy to calculate.
Pleaseeeeee
Thank you!
Nico

[seandunderdale]

Have you got an image of what you think its the goal for caustics in Corona? Ive seen some pretty decent results done in Vray.

[nicola_barbano]

No, I don't have any image rightnow. But you can see on YT a lot of example. And yes of course, I've also seen some nice results in VRay. I mean...they quality is good, but I'm talking more about the workflow.
In Corona they are much faster, and the setup is zero. After you created a water you need just turn them ON and thats it, perfect. Some of my friends (professionals of course) they switch to Corona when they need Caustics for example.
In VRay instead I have often problems with them, since the Photon Map is an old system and Progressive is still WIP and it give to me not nice results (often just random white spots, you can see the attachment) even in basic scene and displacement.
I think Caustics (at the moment) do not give the right value to VRay5 and there's space to improve them as in Corona.

[fixeighted]

I'm not quite sure what you did to get that result but it is clearly not right, so if you zip up the scene someone can check it and correct it and mention what was
incorrectly set up
This is a similar simple scene and shows the result you will get with just the default settings.
This is using the photon map but the progressive option will produce identical results in this case.

[nicola_barbano]

For sure there was something wrong in that scene. Even if I don't know what...but anyway, later I will try a basic scene like yours or similar again...
In any case I'm not saying that the Caustics are bad...I'm saying to improve the workflow as in Corona, where the caustics they always work perfectly.
In VRay, after putting a displacement for water, in Reflection > Affect Channel in All channels, in Refraction UNtick Affect shadows...and Caustics in Progressive...Start render and I have often the white spot...

[fixeighted]

What I forgot to mention is that my example used the IPR, which for a reason I
can't remember always looks better than when you do a full render.
So in fact you will need to go to the sun light's Vray Properties dialogue and increase the 'caustics subdivisions'
until the result is to your liking. That'll clear the white spots.
Maybe this setting needs to be moved to the caustics tab to make it more apparent

[nicola_barbano]

In my previous "screen shot" I had a wrong displacement, my bad. Now it works fine...but Yes, in IPR the results is a bit different, the only way to me it's to render in Progressive with progressive caustics.
At the moment it's a limitation, as in Doc they said the same thing. Even that you can leave progressivce caustics but render in Bucket, it works.
I still thinking that there is space to improve it as in Corona...so this is why this is a "wish list" and Progressive Caustics are in WIP. eheheheheh
Thank you for the advices!
Nico

[fixeighted]

Honestly, change that setting and you will see the improvement you are looking for.
In this example the top image uses the default 1500 subdivs and the bottom one uses 12000.
These are reflective caustics but the same applies to refractives.

[nicola_barbano]

yes!Thank you!

[fixeighted]

You're welcome. I rarely have to do caustics and so forgot about this until you brought it up.

[nicola_barbano]

More or less it's the same for me. I work in archviz (and mostly are med/big size projects) and when I render the water I don't put caustics in render, or in post. So I was trying to improve the workflow and I saw that in Corona are faster and reliable (no mistakes).
But well...thank you again!
Nico

[fixeighted]

I think it's just that Corona has a slightly different methodology, but the results are based on exactly the same R&D as far as I'm aware.
Vray offers a much better implementation arguably, in that it allows for some crucial optimisations when it comes to more complex scenes,
for example the ability to specify exactly which objects can send and/or receive caustics, which is invaluable for speed reasons.
Like everything, once you know the workflow it quickly becomes simple to set up

[nicola_barbano]

Yes true! I did not think about the possibility to specify which objects can receive caustics.
Good...
Thank you!

[^Lele^]

Not only the selective receival of caustics: you will need to ensure your caustic radiuses match what you need (f.e., ensure the sun photon emit radius -in the sampling rollout- encompasses the pool, and as tightly as you can manage.).
Also, you may want to NOT cast caustics for secondary lights, like the dome, if it's clear they won't add much to the final result (that too, should it cast caustics, has a photon radius that needs to be dealt with.).

[nicola_barbano]

Hi Lele, yes yes I know all of these.
Thank you for the explanation.
Advise: If I have more than one pool (even in different position and not close to each other) or I would like caustics in some "sea/beach" area...can I just increase the emit radius as I want without any problems?