Weather

[Sygata]

Do any games make use of accumalative rain or snow? Is it possible to use UDK to create interactive rain as in it actually forms puddles and causes wetness. All tutorials just show how to use shaders to create the illusion of rain.
For example, if I to create a real world recreation in UDK could I make so that my level starts dry, then it rains which creates puddles and makes everything wet and then it stops and everything dries up.

Would such a system just be too costly because it requires having each rain drop as a particle ?

[TorQueMoD]

That would require fluid dynamics which typically use a large series of blob meshes instead of particles. Nvidia is working on it using PhysX

http://www.youtube.com/watch?v=o07KjfBx8GE

But its not gonna be easy to render on most people's machines as they are today... another 3 years and sure.

I know in the source engine you could animate a water plane to give it the illusion of filling an area.... you could do this in some spots to increase the illusion but short answer, no.

Even with the Nvidia system, you'll notice that they try to get the fluid off scene as soon as possible as its very costly.

[TheAgent]

Real time filling up of water very costly, a material shader that changes to wetness in matinee not very costly at all.

Just use Material Instance Constants and control them via matinee.

[ambershee]

You could fake it using heavy scripting. As for accumulation of something like snow, this is usually handled by a shader style effect. I'm not sure how viable that would be in UDK. Interactive snow is not viable at all.

[Sygata]

Thank you for the feedback, so things such as water splashing interactions are accomplished through matinee? and to leave player foot prints would you use shaders?