Issue: No settings in the caustic has an effect.

[Uhlhorn]

I am trying to use caustics, but when changing any value of the caustics, it has absolute no effect to the render result. Do I have a problem with understanding, or is it a bug?

And in the RT render the caustics will not appear. How can I get caustics into the RT render?

[vladimir.nedev]

What kind of lights are you using in your scene ? You might need to increase their Caustics Subdivs found in the V-Ray Light tab, when the light is selected.

And in the RT render the caustics will not appear. How can I get caustics into the RT render?

RT rendering doesn't support caustics, as computing the caustics can take a significant amout of time each time something is changed (besides the camera view).

Greetings,
Vladimir Nedev

[Uhlhorn]

What kind of lights are you using in your scene ? You might need to increase their Caustics Subdivs found in the V-Ray Light tab, when the light is selected.

The „Caustics subdivs“ is the only value that is working. If I increase this value the number of light dots will increase too. But it is not possible to get these tiny dots larger as described in the documentation: http://docs.chaosgroup.com/display/V...tanceParameter

RT rendering doesn't support caustics, as computing the caustics can take a significant amout of time each time something is changed (besides the camera view).

Ah, okay, that makes sense. (In Modo You can use the preview rendering to get final results too. Often the quality is better as the quality of the bucket render. Sometimes it is faster too.)

[vladimir.nedev]

The „Caustics subdivs“ is the only value that is working. If I increase this value the number of light dots will increase too. But it is not possible to get these tiny dots larger as described in the documentation: http://docs.chaosgroup.com/display/V...tanceParameter

That example doesn't look like something from a real scene, not sure if I can reproduce it. It was probably achieved with some very specific parameters and light position.
Here is a quick 5-step example of the parameters. I did it, just to make sure they work:

First step, everything at default values:


Second step, decreased the Photon size parameter of the directional light to 1.0 meter (from the default of 2.0 meters).
This focuses the caustic photons on the cone object, so more of them will go through it, instead of being wasted on the diffuse plane ( where they don't do anything, just disappear).


With the previous change, the caustics get very sharp, because of the Max Photons being only 30 in the global caustics settings.
So the next change is to increase them to 100. This makes the caustics smoother.


After that I increased Max Density to 4mm , this makes V-Ray disregard photons that are too close to each other.
So the number of caustic photons in the caustics map gets down to 28 K ( from 229K ) and the caustics get blurrier again.


Finally to make them a bit sharper again, and to fix the light leaks visible at the base of the cone, I decreased the Search Distance to 30mm.


This is not a work-flow or anything, but the final image does look better than the first image.
I did experiment with each parameter until I got it relatively right.

Ah, okay, that makes sense. (In Modo You can use the preview rendering to get final results too. Often the quality is better as the quality of the bucket render. Sometimes it is faster too.)

Can you enable caustics in MODO's preview though ? I can't find an option for this.

Greetings,
Vladimir Nedev

[Uhlhorn]

Can you enable caustics in MODO's preview though ? I can't find an option for this.

You can not enable it in preview separately, it’s enabled if caustics itself is enabled.
In other words: If You enable caustics in the Global illumination settings, it will render in the preview render and in the bucket render.

The other things You wrote about I have to try. I will reply to it later.

[vladimir.nedev]

You can not enable it in preview separately, it’s enabled if caustics itself is enabled.
In other words: If You enable caustics in the Global illumination settings, it will render in the preview render and in the bucket render.

Strange, I get caustics in MODO's final render, but no caustics in Preview. Might have messed something up.

Greetings,
Vladimir Nedev

[1funk]

Modo's preview does not support Direct caustics

[Uhlhorn]

Hmm, I’m not sure. If I switch caustics on, Modo is not rendering any caustics. But if I switch on „Volumetrics“ the caustics appear. :-/
Indirect caustics are shown in Preview. Mostly I work with indirect light. Nearly no of my scene has any other kind of light.

Here is the scene file of my caustics test: https://dl.dropboxusercontent.com/u/...usticsTest.zip

[vladimir.nedev]

Hmm, I’m not sure. If I switch caustics on, Modo is not rendering any caustics. But if I switch on „Volumetrics“ the caustics appear. :-/
Indirect caustics are shown in Preview. Mostly I work with indirect light. Nearly no of my scene has any other kind of light.

Here is the scene file of my caustics test: https://dl.dropboxusercontent.com/u/...usticsTest.zip

Reflective caustics like the one in this scene are disabled by default in V-Ray, since they can introduce a lot of hard to clear noise.
Vlado made improvements to handling these though, and I am not completely sure, but we might enable them by default in the near future.

See attached image. You also have to disable the caustics map, as in this case it gives a worse result than directly tracing the reflections.
This is because there is no light in the scene (the IES file wasn't in the bundle).
With environment importance sampling, the environment gets turned into a Dome light, but I haven't exposed any parameters to control its caustics generation.
So you can't fine tune it for a good result.



Greetings,
Vladimir Nedev

[Uhlhorn]

(the IES file wasn't in the bundle).

I have updated the scene file. This IES is part of the Modo distribution too.

Ah, there is an additional caustic setting in the „Gobal Illumination Advanced“. I didn’t know it. Thank You.

[Barba10]

I m using this post to ask a question.
Does Vray next has caustics in RT GPU?
Tks

[vladimir.nedev]

I m using this post to ask a question.
Does Vray next has caustics in RT GPU?
Tks

Calculating a caustics map on the GPU is not supported.
However, area lights will generate some reflective/refractive caustics even with only path tracing without a caustics map.
Certainly you won't get caustics from point light sources.

Greetings,
Vladimir Nedev