Hi i''m just working on a rain effect. I am currently using a particle system based approach and the falling rain looks quite nice. My probelm is when the rain hits the static world (ground or a wall). I want to beable to have an effect where the rain drops make a splash on the ground. Currently, at each tick i have the rain drops that collide with the ground location; i also have the normal and the polygon that the the drops collide with. I have tried using a particle system to "bounce" the rain off the surface it hits. (Similar to a spark effect using particle systems) the slpashes end up looking like sparks. An alternitive would be to create some sort of splash animation on a squence of textures and render quads on at the rain drop collision point. I''m just wondering if there are other ways to implement these rain drop splashes efficiently. Also any one know of any demos out there that have good rain effects (i seen metal gear 2 briefly, but anything for pc? jk2 and mohaa don''t have the best rain effects red faction 2''s rain looks really good from the videos...) Thanks

I don''t know if any of this can help you but:

I have been working on 3D rain myself. I was thinking of a way for rain to to fall onto a water surface and make the circular waves around the drop that you would see in that situation.

I was comtemplating a few ideas:

1) Vertex shading for which I write my own vertex shader. The ring would expand around the vertex which was hit by the drop.

2) Vertex transformation. I was thinking of running a sinwave out from the hit point on the verticies to give it dimension and simulate the ring away from the drop. This would also give to god lighting effects.

3) Texture manipulation. If I could calculate where on the texture the drop hit, then I could manually alter the texture to produce the ring.

4) Independent polygon. I was considering drawing the ring not as a part of the water surface but a sperate polygon on the water surface. This would simplify alot of tasks like calulating where the drop hit. The ring would be drawn accoring to the collision of a simple if not flat height map.

Guy

I would just set an alphablended-textured billboard at the collision point for a couple frames, if you are going for the MGS2 effect. It looks so sweet in that game, but all it is a billboard flashed quick enough for you not to realize that its not animated. But it all depends on the level of detail you want: if you want like a Thompson''s water sealer commercial effect (lol) or something to that degree, then Arion''s solutions would be good.

I would stick to your particle spark effect. Just tweak the code and settings until it looks nice. One tip would be to make it really really small because that''s what it would look like in the real world. They need lots more gravity than sparks and ofcource a different texture.

When you collide the raindrops with the world first check what surface it lands on. A lot of surfaces don''t splash at all. If you''d splash there it would kill the effect (no splash on sand, grass, etc. basically anything that''s relatively soft/fluffy/bumpy).

Don''t do the rings. I did it once in my project. It really only looks good in water. Not on other surfaces (well... maybe an aphalt road flooded with rain).

Sander Maréchal
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