Rain shaders

[Crispy]

Re: discussion on jdude's thread about rain

 

I found this SIGGRAPH paper about doing rain using shaders: http://ati.amd.com/developer/siggraph06/Tatarchuk-Rain.pdf

 

There's a lot of stuff there that we can probably skip; detailed puddle/ripple modelling, fancy reflections, and so on, but the pure precipitation part could be useful. I don't have time to read it closely right now, and I haven't even skimmed most of it, but I did notice a couple of highlights:

• The use of particles alone is explicitly mentioned as not being good enough; this matches our experience. It's also mentioned further down that their demo is CPU-bound, because of the particles they do use. Again, this is something we were suspecting; with the sheer quantity of particles being processed, it's the CPU and not the GPU taking most of the load for rain.
  
• The method presented for precipitation in this paper uses only a single fullscreen quad, and its performance does not depend on how heavy the rain is. Judging by Dram's experiments with the fancy shaders that he was adding (bloom and that special post-processing effect), perhaps we can work a similar method into D3 without renderer modification?
  

Some obvious drawbacks right off the bat:

• The paper covers only outdoor uses. There is no mention of being able to disable the effect while indoors and still have it raining outdoors, etc.
  
• There's no shader code presented, meaning someone would need to write the shader from scratch. I have no experience with this, and although I'd like to learn I don't have time to do so right now.
  
• They recommend lighting the rain effect with the in-scene lights. I don't know if we can do this without renderer modification.
  
• This sadly has to be considered a low priority feature. Rain is already possible using particles; it's just a bitch for performance.
  

[Tels]

Re: discussion on jdude's thread about rain

 

I found this SIGGRAPH paper about doing rain using shaders: http://ati.amd.com/developer/siggraph06/Tatarchuk-Rain.pdf

 

Quite interesting. However, they seem to have created a seperate shader/effect/code for each effect (puddles, ripples, reflections, lightning, droplets etc etc). And they also use a lightmap based engine, which D3 isn't.

 

Given all that and the apparent lack of anyone versed in shaders, I don't think we can do something right now. But maybe someone creates a D3 Wet Mod?

 

Speaking of this, are there other mods for instance for fire already for D3? I couldn't find much.

[New Horizon]

We should be checking out the ETQW SDK...there might be some good hints in there about weather effects. I know they probably have an entirely new system, but it might have some hints.