Underwater scene (caustic, vol lights...)

[janpec]

Hello!

I am developing underwater game with UDK and have some few questions. I have been searching for this on different forums and tutorials but i havent found any detailed information. I would like to implement caustics in my game however i have no idea what way should i pick to create that effect and if it is even possible to create it with UDK. Is there a way to do with with shader (some sort of moving decal texture on each model) and how costly would be that to performance or is there a way to add caustic to lights which would be most realistic way.

Also how are volumetric lights and godrays expensive to performance?

[FlynT]

Caustics could be realized with decals, in that way the perfomance hit will be as small as possible. Afaik a form of caustics are in the GDC Demo map.

Godrays are actual cheaper than SSAO so all in all they shouldn't hit the perfomance that much.
Volumetric Lights are a combination of a mesh and a emissive material so the perfomance hit would be also not that much.

[Nawrot]

Whizzle can have kind of caustics you want: http://www.udk.com/showcase-whizzle
I am not sure but it could have some kind of tutorial on this forum.

For caustic like that, you need postprocess shader to make wavy deformation, then some transparent material applied to flat surfaces that emulates sunlight rays.

[Wyldhunt]

You can add material effects to lights also. Make the material that acts the way you want it to and plug that material in to the Function slot in the lights properties. The light will project the emissive of the material as an overlay over everything that the light shines on. So, don't use diffuse in the material. plug it in to emissive instead. It supports panning, rotating, etc. So, you can make some really advanced light effects with it.

It will not create the underwater light rays though. That would need to be flat planes with an emissive material that looked like light rays, or meshes like they use for god lights above water level.

[janpec]

Thank you guys for all your interesting input. I have been looking for shader effect something like Wizzle has, but material applied to light sounds good too. I am just maybe laying backwards with decal texture as caustic since it doesnt look that realistic and i saw how that looks in Call of duty Black Ops and there it looked very very bad. But afcourse thats another piece of engine...

[Nawrot]

I found that FRACTALIUS PLUGIN for photoshop is easy and fast way to make nice caustic alpha masks.

For great example of water and underwater look how "Just Cause 2" did it.

[janpec]

Where can i found how Just Cause 2 did it? Is there behind scenes development video or something?