Water Caustics

[Ibontxu]

Hi everyone. I've been trying to make a swimming pool with water caustics and i can't get it. That's what i would like to do:



I've made millions of trials and everything i can do is thing like this:



I like this water, but i can't get caustics. I make a surface, aply bump map on it, check caustics on like tha manual says... but it doesn't work .I hope you could help me.

So, my questions are:

- has the water need to be modeled in sketchup (sandbox) or it can be a flat surface with bump (or noise) aplied?

- it has to be a light pointing to the water or we can get caustics effect only with sketchup sun (physical camera enabled)? what light is the best for that (rectangular, omni, sun...?

- Has the physical camera need to be enabled or we can get caustics effect only with skydome?

- Have the swimming pool tiles to be reflective?

Many thanks to everyone

[dalomar_cg]

Re: Water Caustics

I like this water, but i can't get caustics. I make a surface, aply bump map on it, check caustics on like tha manual says... but it doesn't work

Ahh I wish it were just that easy....

Anyway, there are a number of things going on, but I'm going to try to only get into the ones that matter. Using bump for this is not going to work. Why?? Bump is actually a fake. All it does is adjust the normal for shading/reflection purposes, not actually change any of the geometry. For caustics calculations, this just won't do, as all those calculations will see is the original flat surface. Displacement is actually the best way to go with this, but considering how flakey displacement is I would suggest modeling it somehow if you can.

Other major thing...It doesn't look like there's a light in the scene (ie you're only using GI), and in order to achieve sharper caustics you will need more than just GI lighting. The best things for caustics is a nonphysical light of some kind. In laymans terms that means a light that is a point in some aspect. So for SU this means an omni light would probably be the best way to go.

As far as the physical camera goes, that doesn't matter as long as the light has enough intensity to actually affect the illumination within the scene. One of the things I do is typically try to have "caustics only" lights, where there intensity is barely enough to see in the scene, but by using the caustics multiplier, your able to see their effect only with the caustics (the other side of this is that regular lights need their caustics subds @1). Chances are that you're not going to be able to get a good result without increasing the caustics multiplier some what, so why not make it work for you.

the swimming pool tiles don't really matter.

You've got two challenges with this one...first is simply getting the caustic affect in this situation, and second is to tweek the caustics so they look how you want it. Tackle the first challenge then worry about the second. Most of the caustics work I've done takes a lot of tweeking, so just make sure you know how to get them first. Leave all of the values (except the multiplier) at their defaults until you get them down.

hth and I'll see if I can come up with anything else

[Ibontxu]

Re: Water Caustics

Thanks for your quick response, Dalomar, and for taking time to write all that text! well, i havent been able to get caustics yet, but i'm going to explain what i've done until now because i may have done a lot of things bad.

- I've modeled water with the sandbox tool, applied white color, made it completely transparent, created vray linked material and give to it those settings:



- I create an omnilight, render with the render presets (irmap+qmc), with caustics option enabled in general options rollout.



The problem is that if i set the light multiplier low it can't be seen it's effect on water, and if i set it high swimming pool tiles get burned.



So I decided to make the render not only woth GI but Physical camera enabled. I set the light multiplier much higer for generating caustics and render.

It doesn't matter how high i set the caustics multiplier, i cant see them.



Ive tried with only an omnilight (with sky and environment black)...



I have one final question too: I have seen a lot of underwater renders, with light coming tgrough water... but if i put a light under the water and the camera it will be no caustics, isnt it? because the water is only a surface not a solid, and unless we dont make light pass through it there cant be any caustic effect, i think. It's a bit confusing.

Thanks again for your help

[dalomar_cg]

Re: Water Caustics

Do you mind just sending me the model?...I got in working in vfRhino, but want to make sure that the setup will work in SU as well.

If its under 4 mb then email will work. dalomar@asgvis.com
If not, then send me an email, and I can tell you where to put it.

[dalomar_cg]

Re: Water Caustics

This is as far as I got without messing with things too much

[kgoku]

Re: Water Caustics

Do you guys mind send me that model with that caustics? I can´t manage to get right on that too! I always get the same problem with too much light or too few and no caustics...

hommersimpson@hotmail.com

Thanks a lot!

[luchangliang_cg]

Re: Water Caustics

I'm waiting for the answer too. It's seems very intresting.

[Ibontxu]

Re: Water Caustics

I don't know how to do it, i sent my model to dalomar but i had no answer. Surely he has been very busy, but as soon as he send me his reply i will tell you what's his procedure to achieve good caustics.

[dalomar_cg]

Re: Water Caustics

Yea I have been busy...I'm still in grad school, so I've been preparing my final thesis presentations... I started to work things out, but want to refine it a little more...I'll try to send it off (or maybe post it here) sometime this weekend maybe

[Free Agent_cg]

Re: Water Caustics

Hi Dalomar
it seems you never got back to this (understandable) but could you explain this further water gives me nightmares, no matter what i try i cant get caustics on water, reflected or refracted, got both reflect and refract caustics on, caustics on, mesh water, displacement water.... please help

[dalomar_cg]

Re: Water Caustics

I did get the scene back to ibontxu, but never heard back from him. Caustics are notoriously tricky, and in this case its even more of a curve ball. The sun itself won't generate the caustics that are needed (too complicated...not going to get into it), so you actually have to add another light to generate the caustics. This means balancing the intensity of the light with the scene and getting the intensity of the caustics to match. IOW its a big circus. I'll send you the scene via email and you can see for yourself

[Free Agent_cg]

Re: Water Caustics

thank you i would appreciate it

[dalomar_cg]

Re: Water Caustics

Already sent...Nomer I'll get you too

[nomeradona_cg]

Re: Water Caustics

thanks damien

[peterko10ko]

Re: Water Caustics

this is only a guess i cant test this right now but i think if you want to add lights in the water with caustics you should make the water a box instead of just the top layer. and group it all together. make sure you add displacement to the sides of the water too. let me know if it works if someone tries this...