PDA

View Full Version : Oh yes, an underwater scene without caustics


Pancho
09-07-2006, 01:18 AM
Just to make a small difference I want to create one without nice beams shining through the water nor with caustics running across the white sand.

I just wonder how do I create the environment? I just created a node setup which colors my objects according to their distance to the camera and their position beneath the water. But for the environment I wanted to get rid of the ugly fog version and create something more realistic. Its should make a difference in which direction you are looking, with the light or into the light. There's this kind of SSS effect going on The light gets blurred, colored and there is some falloff going on. Although there are tiny objects in the water, which give you a foggy feeling. Also I need to look through the water from beyond. Refraction and total reflection within the water are essential.

Is Omega a solution? But how, if I'm already in the water itself? I really want to go a step in a more realistic direction, so just plain simple fog won't do it, at least that's what I think.

Cheers
Pancho

Panikos
09-07-2006, 05:48 AM
I would follow the classic way. A raytracing Point light with Specular only, no diffuse casting shadows on the seabottom surface only, excluding all other objects. Add a child object to this light, a small ball with a texture of your choice on the Transparency map, render away.
Texture size should be proportional to the ball size.
You can use Clipmap instead of Transparency for faster (but sharper) results.

Pancho
09-07-2006, 08:49 AM
Hi, Panikos,

didn't see you around for a while. Thanks for the reply, but there won't be any ground. At least not visible. So it's very deep water and I don't know how to create the environment (the background). Actually there will be a water plane which can be seen from beyond, but otherwise I don't know how to create the color of the sea. It shouldn't be acurate in a physical way, but at least it should look like it. It should include the light falloff from the surface and the correct coloring. I set up my nodes with gradients for my object color. So each meter the light will travels beneath the sea 40% red, 5% green and 2% blue light get absorbed. Usually folks use fog to simulate the light scattering and falloff beneath the sea, but I guess it won't work that simple. Also the fog will be above the water and that is not appreciated. The sky needs to be clear. I thought about spheres around the camera with transparency settings and so on, but it will mess up my ray recursion. I guess more than 16 spheres would be necessary, but this screws up the rest of the rendertimes.

My point is: If i look parallel to the water surface into the sea, actually after 100m the light is pretty much absorbed. But what I see isn't black, but blue. This is due to the raleigh () scattering in the water. How do I simulate this effect which also depends on the incidence angle from the sun in relation to the viewers sight.

Thanks in advance
THomas

vonbon
09-07-2006, 02:57 PM
Havn't tried it but maybe you can parent a point light(w/falloff) to the camera. Then use a gradient Bkgrnd and add some dust particles and bubbles. Then animate the camera and I'm
thinking that it'll look like going thru water. Maybe even animate the Bkgrnd.

Not sure if you can use gradients with light falloff.

CGTalk Moderation
09-07-2006, 02:57 PM
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.