Creating an underwater scene (english)

Question

I've been trying for the last week without much success to create an underwater enviroment. I know what look I'm trying to create but I find that SoftImages depthfade is very poor. I have tried all kinds of things. The main problem I'm facing is that the Depth fade creates a uniform colour of blue once it reaches it's end distance. This makes the scene look flat and un-realistic. If the depthfade could somehow have two colours say from a lightblue ending to a dark blue the effect would be better.

I have also tried cheating the illusion of atmospheric water by using mainly blue lights and blue-green materials but the rendered image lacks a certain atmosphere. I've even tried creating "lenses" out of geometry and using texture maps to cheat a depth look but of course this does not work due to objects intersecting the "lens".

Jeremy Birn

You could do one rendered pass with depth fade going to pure black, and all the objects given a contant white shader. This makes your rendering itself into a psuedo-depthmap. Then also do a "normal" render. In compositing, use the depthmap as a mask to control any color shifts or other under-water effects, or to combine it with a full-screen water effect plate. This also lets you make a cheaper DOF effect by blurring the area it masks out as being more distant.

Besides the depthfading stuff, people love the "caustics" look you could get by putting an animated texture on a transparency mapped surface, and shining a shadow-casting light through it. This will project water patterns onto the characters. Jason Bright's Captian Nemo shader is made to be used this way, too, you apply it to a surface that you shine a light through (NOT to the subject itself.)

Go ahead and let everything that moves fast, or every important action, create bubble trails, even if it's really too deep for them to be plausible. (See The Little Mermaid for Reference ;) If you're rendering in Mental Ray, the new FXDirector volumetric fogs on spotlights can add a lot to the depth of your water.

Building an underwater shot will usually involve bringing several different layers and elements into your compositing program, and doing a lot of distortion and blurs and color shifts to them in the build.

If you want to (or have to) develop most of the look in 3D, a cool way to distort and ripple an entire shot, is to finish the rendering undistorted, and then map the whole shot as an image sequence onto a 12 x 9 b-spline grid. Then run waves or shape animation through the surface, and render a shot of the surface. This will also give a little extra softness to the scene, but that isn't a bad thing for underwater looks. You could use the alpha of the rendered animation to make the top rippling surface transparency mapped, and do a "multi-plane" look with this approach, as well. Not many people do this, because its easier to accomplish similar effects in post, but it's possible if your assignment is to do the shot in Soft.