Pool caustics

[MixDesign]

I have had a surprisingly difficult time getting caustics to work for a swimming pool.

I'm using:
- basic Water material provided by V-Ray with the material Fog Multiplier reduced to 0.01. It is applied to a plane. I tried a volume, too.
- GI Caustics Reflective and Refractive Caustics are checked.
- Photon Mapped Caustics is enabled w/ defaults.
- Sunlight is only light in scene with Caustic Photons Caustic Subdivisions increased to 6000 and Emit Radius increased to 500.

I added the Caustics Render Element to see if anything was happening. It is black.
I've changed the Photon Mapped Caustics settings way up and way down.
I've changed the Sunlight Caustic Photons settings way up and way down.
I'd be happy to upload images/screenshots/files if somebody is willing to help.

[caecarvalho]

You have to uncheck ‘affect shadows’ in your v-ray water material in the refraction tab. Besides this, set refraction ior to 1,33 and add a noise map in the bump or displacement slot. I’m out of the office now, but, if you still can’t get caustics to work, I’ll attach a scene with the configuration in my next post.

best regards,

Caetano

[MixDesign]

Caetano, thank you so much for your response. Unfortunately, the "affect shadows" was already checked, so this did not solve the problem. Refraction was 1.3 and there was indeed a noise map in both the bump and displacement slots. The "Affect Channels" in the water refraction was set to "Color + Alpha" so I set it to "All Channels" to experiment, but no luck. If you are willing to share that scene, that would be greatly appreciated.

[caecarvalho]

Hello, first, I have to correct something I wrote in the previous post: "affect shadows" should be off for caustics to work, not on as I stated in my previous post (sorry about that). But I think there's a bug in VFS 4.00.02: When trying to render caustics with interactive render, caustics will not show up and the photon caustics tab in the UI, will desapear. So I'm attaching a file, with a simple pool scene with working caustics made with SU2018 and VFS 4.00.02, but you should not try to render with interactive, because it will not render caustics correctly, and will bug the UI (at least that's what's happening in my machine). If you have the same problem, please report it in this thread, so someone from chaos can see, or if not, I'll PM Peter or Konstantin with the link for this thread.

Best regards,

Caetano

[MixDesign]

Caetano, this was extremely helpful. Based on your directions, I was able to get caustics to show up. Then I opened your file and rendered and it was WAY better than what I had. I've been trying to duplicate it. I've replicated all the settings as far as I can tell. However, no matter what I do, I get little bitty ripples. Your file is in centimeters, mine is in inches. No matter what I do, I can't get my the noise map in my Displacement layer to scale. I saved out your material and loaded into my file and get a very similar result to my water material. If you are willing to help a bit more, I'd appreciate it. Attached is my file.

[caecarvalho]

Hey mixdesign (sorry, don't know your name),

unfortunatelly I've only seen your post today, I've played with your file scene and found what's wrong, but I'm leaving the office now a bit in a hurry, and won't be able to write you properly. Tomorow I'll write what I've found in your file that's preventing you to achieve the same results as in mine. Anyway, I'm uploading your file with the corrections and nice caustics.

Best regards,

Caetano

[MixDesign]

Caetano,

Thank you for your continued help. I downloaded the file and as-is, it renders the pool caustics beautifully. I looked through the settings--render, sun, material--and couldn't find anything different.

So I looked at the model setup. After experimentation, I found two things that seem to affect it: applying the material to the group and the combination of sizes in the noise map and the texture (in the SketchUp material editor, but it requires setting the material's binding property to be set to VRay's Texture Helper so the SketchUp texture sizes can be used).

When I applied the material to the surface directly, not the group, it never worked, no matter what the noise map and texture sizes were set to.

Leaving it applied to the group, I played with the scales.
- Noise Map Size = 1, texture sizes 4"x4" to 15"x15" worked well. Personally, liked the look of about 10" x 10".
- Noise Map Size = 0.5, texture sizes needed to double, which was not surprising.
Finally, I created another water material and didn't set it to use VRay's Texture Helper (and therefore, I couldn't change the texture size).
- Noise Map Sizes = 4 to 15 gave the same results as leaving the noise map size at 1 and changing the texture map size.

Two questions:
1. Why does the material have to be applied to the group?
2. How does the noise map size and the texture size relate? Am I correct in remembering that VRay's native units are meters? Does a noise map size of 1 mean 1 meter?

Thank you for all your help. I feel like I finally have a way to recreate this effect reliably on future projects and I'm starting to learn how the procedural map scaling works in real-world units.

Best,
Damon

[caecarvalho]

Hello Damon,

You figured most of the things. Now, answering your questions:

1- For displacement to work in any surface, first, this surface must be a group, second, the material has to be applyied to both front and back faces, as well as to the group. That's the procedure for displacement to work.
2- I binded the material to a v-ray texture helper, so I could control the noise map size/ tiling throught the sketchup material, but you don't need that. You can achieve the same results leaving the biding in auto mode and messing with the noise map only. There's a tiling option inside the noise map under the 'texture placement' tab. I did this way just because I think it's more convenient.
3- V-Ray internal units are in inches, no matter what are your sketchup units (as far as I remember).
4- About the noise map size, I think the size parameter is probably the size of the noise pattern that will be placed randomly in your surface, and not the size of the texture, because noise is a procedural texture in v-ray. The size is probably in inches.

If you want to go deeper into this you can PM Peter, or Konstantin (from chaos), asking some more questions and linking this thread.

Good to know that you got it to work!

Best,

Caetano

[MixDesign]

Caetano,

Excellent! I think I understand all the elements now, and I was able to implement it from scratch in another file. I appreciate the thorough responses!

Best,
Damon

[GD3DESIGN]

Looks like you already have this sorted out....but just in case, check out the following thread and Shiyan lin's excellent tutorial:

https://forums.chaosgroup.com/forum/...563-pool-water

https://www.youtube.com/watch?v=elaHI1doJVY