View Full Version : Underwater Caustics

06 June 2007, 09:06 AM
Hi everyone, I have trouble setting up underwater caustics. I am currently using Maya 8.5, I am rendering in Mental Ray with raytrace shadows casted by a spot light, obviously with caustics and gi turned on in the light attribute. I have the photon intensity on 2000, and exponent on 3.6. But I can't grasp the rest of the settings I'm suppose to use for the shaders. I'd appreciate anyone who possese knowledge of the proper settings to enlighten me. Thanks in advance.

06 June 2007, 09:25 AM
Anyone? I just want some settings.

06 June 2007, 06:24 PM
This is not the easiest thing to do. There will be a lot of testing and tweaking. Within in the light attributes > mental ray tab the Photon intensity should be quite high i believe,try 8000 to start. The main attribute that will affect the caustics you are looking for is the Caustic Photons #. Crank this way up 300,000 to start and increase by 100,000 when testing. The higher it is = the crisper and more focused the caustics will be. Only downside is render time. Oh yes the exponent should be okay around 3.

Try this and let me know what happens :)

06 June 2007, 10:02 AM
Is there anything I have to do to the surface of the water or the sea floor at all? I tried to study the ocean example from the visor, but they were using Nurbs, and I only know polygons =P

06 June 2007, 04:59 PM
If you mean more than modeling it the way you want, No you shouldn't have to. Caustics is the calculation of how light bends when travelling through a certain material. if you have just a flat plane I don't believe you'll getany. If the ocean is wavy you should definately see some. Try it out. You shouldn't need GI either. just a low final gather setting should work for testing.

If you haven't yet tried the Maya Help its very "helpful" do a search for caustics and run with it. the only thing you have to be careful with is the number they use. many times your values will be much differnt (depending on scene size etc.). Just notice the ratios and procedures they use.

06 June 2007, 12:48 AM
Alright, I'll definetly try that. I used an ocean shader, so right away I expect it to cast caustics, but I guess I'll sculpt the geo a bit and add a bump on it and see what happens.

06 June 2007, 03:18 PM
Depending on how accurate your need the caustics to be, I would strongly suggest using a light with a noise texture attached to it to create the effect. It would save you loads of tiem rendering and making changes would be alot easier if you rendered it out on a seperate pass and multiplied the results onto it in post.

06 June 2007, 05:06 PM
Oh right, I heard my teacher talking about that once, but that's just emulating caustics right? You have to animate the texture if are doing a video sequece?

06 June 2007, 08:24 PM
If you have Maya Fluid just open up the Visor and find there a scene called under the Ocean Examples. Works great for most under water scenes.

06 June 2007, 02:34 AM
@lazzhar : wow long time no see man ! Those fluid examples are great, but my machine cries every time I even think about using them.... :(

@thunderbreak : yeah its just emulation. you can get those sequences with a little work, right out of maya. Heres how :

1. Take a noise/fractal/water texture from hypershade, tweak the hell out of it to look like caustics (you can get loadsa references online). RMB>test texture to check for sure.
2. Just animate the time with a small expression on the time (eg: noise1.time = time/20; //depending on how fast/slow you want it) .
3. Then set up in your render globals how much footage you need.
4. Then right click on the texture in hypershade and render texture range.
5. When fcheck opens up, you can view what you've just created.
6. If it works for you, just save the animation somewhere.
7. Then hook up the new texture to your light.

Easy, managable caustics..... it all boils down to how much depth and accuracy you need.

06 June 2007, 10:40 AM
Hi razorback, always hanging here but busy life makes us coming less.

I think the file I was refering to is very light and should render quickly. The use of fluid here is just for the Ocean texture you plug into the light. It's basiclly the same as you described.

CGTalk Moderation
06 June 2007, 10:40 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.