   Simulating rain
  Hi,I have some questions about the simulation of rain that I hope some of you more experienced developers can help with.Searching the web these are the main categories I found: 1 - Particle system around camera (ex: http://www.gamasutra.com/features/20000623/vanderburg_03.htm, ...) 2 - Rain box/cone/cylinder/etc. around camera (possibly with several layers: ex: http://niniane.org/rainsnow/) 3 - Post processing rain effect (ex: http://www.google.co.uk/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fati.amd.com%2Fdeveloper%2Fsiggraph06%2FTatarchuk-Rain.pdf&ei=O4zmRtaQKqGyQNWb-YsL&usg=AFQjCNGNmnHw2_WTq-VMX5OTPCjmPcHfdQ&sig2=7liVJKpFyXs9GVK3I92vPA)(any others you guys can think of?)One of the requirements I have is that I have to seamlessly transition from inside to outside when raining, for example when looking trough an open door/window where you can clearly see it raining outside.This seems doable for example by using something like rain portals that render a "wall" of rain at the door/window and switch the particle system/rain box on an off when the player/camera passes trough. Or using and overhead map texture (not sure how to do this?) stating inside/outside zones to toggle the rain on and off (however I guess I would still need the portals to simulate the "wall" of rain trough the doors/windows).Using the post processing effect, looks rather hard to do the transition from inside to outside since the way the "wall" of rain and the main effect would be rendered differently and it would be noticeable when the player does the transition.Any suggestions what techniques would be better, any other suggestion or links to projects/papers that focus on simulating rain?Thanks.   
  There was a Hellgate: London demonstration not long ago that focused on their rain effect. It looked _very_ nice. Basicly they used billboarded particles for drops and fins on objects to make spray. A nice touch was that by using many different drop textures they could create a cone of light from a streetlight.[Edit] Here it is: clicky. Shows the rain along with some other effects.   ;  check out the DX10 example in NVIDIA's DirectX 10 SDK ... you can do this on DX9 cards very well and it is very fast.   ;Quote:Original post by wolfcheck out the DX10 example in NVIDIA's DirectX 10 SDK ... you can do this on DX9 cards very well and it is very fast.Yeah I second that... their sample is an implementation of a paper from SIGGRAPH a couple years ago and looks really great (and is pretty cheap). Plus you can't complain about full source code and assets :D   