CGTalk - Using rigid bodies to "paint" emission texture on colliding surface? Or other solutio

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NEO^AMiGA

04-08-2007, 12:11 AM

..n?

Kinda tricky one, eeey? =) Let's see if i can describe this one in detail. I have like 400 coins flying over a hill. The coins are rigid bodies that I create and set of with a neat lil script. What will happen is that the coins takes of, with the help of initial velocity and some other attributes, they fly over the hill and land on the other side. Since they have some random attributes some might never get airborne but instead just roll over the hill.

A little pic to illustrate this: click me (http://www.irry.com/neo/bilder/temp/3d/coinsOverHill.jpg)

The thing is that i must add some general dust and some larger debris to this scene. The debris mainly where the coins hit the gound with a huge velocity. And then some dust trail after each coin.

My first thought was that I could maybe make the rigid bodies to create an "emission map" for the ground? What I mean is that at each frame the posision of each individual coin and the pressure the coin creates on the ground are "sampled/saved/stored" and saved as an animated texture for the ground. A black and white texture in the range 0 to 1 (or 0 to 255 if you prefer). Then this texture could be used as an emission texture for the ground. But would this even be possible? =) Does not sound like the easiest thing to do.

But on the other hand, creating 400 emitters and parenting them to the coins ain't all that realistic either. Sure, I can script that but I bet it will be both slow and painfull and involve more then one crash. =/

Am I atacking this problem from the wrong angle? Any other ideas?

Als

04-09-2007, 12:58 AM

Well, it's very tricky suggesting what is best aproach...

Have you baked your rigid bodies? This is what I would do, if you are happy with your animation, then even more so.
You don't need 400 emitter to emit from coins. Combine mesh on all your coins. If they are nurbs, even better you can control how many polygons you need for it. Then you can emit from this mesh. Just you will need to keep history on.
You can also make your coins soft bodies with make copy soft, and make weigth to one.
Now you will have particles which are following your rigid bodies. Then you can make new particles by coliding event with soft body particles, or you can set passive rigid body which collides with particles (in a different layer then other coins) which would colide with your sof t body particles and generate new ones.
In bonus tools you have tool paint emitters if this is what you want to do.
If you want to make nice smoke and dust you might maybe try emitting fluids with very high transparency. They will be noticed because of the movement).
You can also emit 2D fluids by coins. By emitting from coins to fluid, you can also generate 2D fluid texture which you can use for mixing in hypershade with other materials of effects.

Als

_stev_

04-09-2007, 01:20 AM

Using instanced geometry on a particle system is another option. Then you could easily emit from the coin particles. Also, you could setup collision events to emit more particles (dust) when the coin particles collide with the ground.

Stev

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