are there any _realistic_ looking methods for drawing rain?
i've tried all kinds of different things, including particles:
* 100 2d billboards in a 20x20 area around the camera. looks great til you look up or down.
* a "rain cone" around the camera (like a skybox). works great, til you look down.
* a "rain box" consisting of two cones pointing up and down, with a circular section between them. works great, until the ground clips the bottom cone.
* a "tall rain box " 10x10x1000 tall, made from 10x10 quads. similar to the cone, with just a small gap whne you look up, but again, clipped by the ground. mapmaps had to be tuned off to get the correct effect, without a noticeable change where mip levels changed.
* a particle system - looks great, you can see rain falling past you when you look down. but it looks like i'd need something like 10,000 to 100,000 particles visible onscreen at once. i kicked the render queque up to as high as 5000 entries for testing, using 4000 for rain, and reserving 1000 for normal uses. but for a true implementation, i'd need to reserve 3000 entries for normal uses. granted, i can draw whatever is in the queue, clear it, draw the rain, clear it again, then continue as normal, but the large number of particles is a concern. even if i bypass the queue.
i'm thinking that a combo of "rain skybox" and particle system may be the way to go.