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punks
10-15-2010, 04:35 AM
I'm planning to start an underwater scene, can anybody give me tips how to do it? I tried once but the the env fog is hindering the light streaks and even the rest of the lights... how to deal with it? pls help me...

gerardo
11-08-2010, 01:56 AM
I made this type of lighting sometime ago...

http://imagic.ddgenvivo.tv/forums/SGCCTools/dolphinsmall.jpg


and although solutions depend on each take, I've found that usually the more flexible way to solve the effects for underwater lighting is in post. Simulating the light absorption according to the density of the water, the light scattered by water particles/dust, volumetric lighting effects and vertical polarization is easily approached by passes. A fog effect might be insufficient depending on the depth of the underwater photography you are trying to simulate, because the light absorption is apparent not only according to the distance from the observer but also depending on the depth (starting from the water surface). The first aspect may be solved with a fog or a thickness gradient, faster passes may be obtained with a distance-to-camera gradient or an RGB depth pass (which will work also for better control of the foreground, midground and background elements). The second aspect might be solved with a pass from a distance-to-object gradient (in the Y axis). With these passes you could have more control in post to simulate the light absorbed at different depths, from the longest wavelength to the shortest (reds disappear at 3m-5m, orange and violet at 5m-10m, yellows at 10m-20m, greens at 20m-30m and blues at 40m-60m). Color adjustments are easily performed in an uniform color model. farthest the distance, lowest the saturation, luminance and contrast. General scattered lighting might be achieved with area lights or dome lights and a glow filter may help to sell the effect as well. Patterns of concentrated light due to refracted rays (caustics) can be a sequence of textures frontprojected in a light (a different light pass). Volumetric lighting, bubbles and floating particles can be other passes. For the polarized light, may use low values for glossiness (or any solution you use for blurred reflections) and very very low reflection/specular values for all materials below the water surface.



Gerardo

InfernalDarkness
11-15-2010, 07:14 AM
Env Fog in Maya is insufficient for these types of scenes (volumetric lighting). Or are you using Max?

You will need to use ray-marching (mental ray parti_volume or equivalent in Vray) or better yet, work on learning the technique that Gerardo shared!

If you're looking for easy volumetric lighting "out of the box", then Maya will not be a friendly package for you. Most other packages do this far, far better, although at much higher render times.

punks
11-15-2010, 07:19 AM
@InfernalDarkness:
Ya i'm using maya... I tried with both the possibilities like by using Volume primitives and Env.fog from the render settings... But both are not working according to my need...

InfernalDarkness
11-15-2010, 07:32 AM
Ya i'm using maya... I tried with both the possibilities like by using Volume primitives and Env.fog from the render settings... But both are not working according to my need...

Like I said, neither of these methods, nor Maya's Software renderer, will work properly for what you want to do.

You need to use mental ray and the parti_volume shaders. Google parti_volume and search for it here. And be prepared for a lot of work, and lots of trial and error alongside long test renders.

That said, here's a recent WIP scene using this shader so that you know it's workable:

http://img7.imageshack.us/img7/8075/wildtwistymr15foggyproj.jpg

This is not a standalone render. It will be used in conjunction with many other passes to create a final scene. So while it appears very low-quality, I hope this example helps.

punks
11-15-2010, 07:38 AM
ya i got the idea... well when it comes to trial and error, long test renders i'm always ready.. I learnt the word 'patience' by working on this scene.!!:)
BTW thanks a lot for considering my post....

CHRiTTeR
11-15-2010, 03:37 PM
blue/greenish tinted fog with some dirt floatin around will give you a good start

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