View Full Version : How to make 2 collision test?

10 October 2007, 02:21 AM
Ok, so I'm creating a snowglobe and getting my feet wet with particle flow for the first time. Besides reading the manual (so so) and watchied the movies on, I am planning to purchase a DVD of some sort about particles. Until then...

In case you don't know what a snowglobe is (just to be on the safe side, image here ( Not mine, just a photo.)

So what I do is, when the particles are falling, I have an SDeflector that is just a tad smaller then the glass. If the particles hit that, they will bounce back. So far so good. Playing the preview in the viewport is just dandy.

But I also want the particles to disappear when they hit the ground (bottom of the globe). So I added another collision test at the bottom of the event (UDeflector - see attached screenshot) which has the ground attached to it, and that will delete the particles that hits the ground.

Well, it kinda works, but the prollem is that when I do this, and play it back in the viewport, the preview virtually comes to a crawl. I only preview about 100 particles in the viewport, but still.

If I take the ground collision test out, and preview even 1000 particles, it has no affect on the playback. The ground object is a patch, made of splines. Would this be a reason that the preview comes to a crawl, or my event setup has some issues? Such as, I can only have 1 collision test per event or something...?


Is this the way to do 2 collision tests, right after another?

10 October 2007, 02:42 AM
I guess I've just found out. It was the ground indeed. Seems like the patch surface was too complex (although it's just a little bumpy surface). When I replaced the UDeflector with just a simple deflector plane and used that, the playback speed regained consciousness! Woo-hoo!

10 October 2007, 05:27 PM

The reason that you were getting slow response times are because you were using a patch which has a really high resolution. When Pflow is calculating the collisions it is looking at each vert/face and asking if its touching or not. In the future, if you need to make a colision with an object i always try and create a Low res mesh proxy with an optimize modifier and run the calculations on that. It can speed things up and create the same effect.

Keep on noodling particles are fun!


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10 October 2007, 05:27 PM
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