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lighting rain effect

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Anyone knows how to light 2D overlay rain effect? ATI demo (toyshop) has an example of doing this, but i juat can't figure out how they've done it. It looks like some parts of rain effects are affected by scene lighting while other parts aren't.

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She (the head of that demo) did a presentation on the demo, and explained step by step how they did all the effects in the demo.

You'd be well off to search for the .ppt file :) shouldn't be too hard to find

hth,
-Michael g.

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i've read the presentation. One thing i'm not sure is how they light certain region of 2D overlay effects by scene lighting. In one scene, a small parts of rain was lighted by spotlighting (or maybe, it's just my eyes playing trick on me) i just don't understand how a lighting source in 3D world is interpreted in 2D overlay. and there was no explanation about this.

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A 2-D overlay can just be thought of as drawing on a plane in 3-D space where the normal is oriented in the opposite direction as the camera's direction vector. If you think of it like this, you're now drawing a plane in 3-D space and there's no reason the verts cannot be lit by the scene.

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if you mean the rain in the street lamp light cone, then this is explained reall well in the .ppt:

They just insert a plane into the light cone which has a scrolling rain texture on it and use an alpha texture that gets tranparent where the plane leaves the light cone.

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Quote:
Original post by Matt Aufderheide
Does the ATI toyshop demo run on Nvidia cards? I have a GeForece 6800 with latest drivers and DX and it gives me some error about a backbuffer format not supported..


ATI demos are designed to not run on Nvidia hardware (it's part of their specs).

LeGreg

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Quote:
Original post by m4gnus
if you mean the rain in the street lamp light cone, then this is explained reall well in the .ppt:

They just insert a plane into the light cone which has a scrolling rain texture on it and use an alpha texture that gets tranparent where the plane leaves the light cone.


hmm ... so, i guess they have 2D overlay rain effect (which is also illuminated properly) and another rain plain (ind 3D) under light lamp?

Also, it looks like the rain effect uses refraction for lighting ... I'm guessing that you would need some kinda refraction map for this to work. However, i think refraction cube mapping might be too much for the rain effect (it's just one rain drop refracting incoming light anyway.) Is it possible to use the current frame buffer (the scene already rendered behind rain effect overlay) as refraction map somehow?

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Quote:

Also, it looks like the rain effect uses refraction for lighting ...

rly? is that even noticable?

if it is:
i'd say they have a simple refraction map, render all the raindrops with that map to a texture and apply the resulting (fullscreen)refraction map as a displacement to the scene.

regards,
m4gnus

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