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# particle emitter and falling leaves

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 particle emitter and falling leaves on Dec 10, 2008 at 5:58:30 pm

Hi. I posted this earlier and no one answered. I'm hoping someone out there can help me. Thanks.

I have used the particle emitter to reproduce a bunch of leaves that I want to have randomly fall from the sky. Then, I'd like each one to stop falling when it hits the ground. After each one hits the ground I'd like it to just lie on the ground for the rest of the animation. The problem that I'm having is making each one stop movement when it hits the ground. Can anyone advise me on how to do this? Thanks. Ellen

 Re: particle emitter and falling leaveson Dec 10, 2008 at 7:54:33 pm

What have you tried so far?
The conceptual problem is telling the emitter's spawn where the ground is. If the emitter is moving, that distance is different for every particle.

bogiesan

 Re: particle emitter and falling leaveson Dec 11, 2008 at 2:57:35 am

Well the way I've avoided it so far is to dolly in above the ground before they hit, but this isn't really what I want to do. So I guess the question is how to tell particles where the ground is? Any ideas? Or maybe it's not possible. Maybe I should use the replicator and figure out the stop position in the replicated layer.

 Re: particle emitter and falling leaveson Dec 11, 2008 at 6:09:02 pm

Changing the speed of a Particle is not as easy as it should be. Peter Wiggins wrote a tutorial on this:
http://idustrialrevolution.com/content/view/24/47/1/0/

Your problem is that you wave a lot of leafs at different locations so you can't slow down all of them at once.

For you I think it would be easier to animate 5 or so your self. Duplicate them and move them so they start and stop at different points in the time line. Make sure the record button is off and you can change the scale as well to create depth. Hope this helps. And yes, I understand that that would be a pain in the...

Stephen Smith
Salt Lake Video

Check out my DVD Money Making Graphics & Effects for Final Cut Studio 2

 Re: particle emitter and falling leaveson Dec 11, 2008 at 11:47:55 pm

these guys used to offer something to get you started but, the rat bastards have gone ultrcommercial, even insulting:

http://machouse.mhvt.net/?p=648

> MacHouse no longer offers video tutorials to guests or freeloaders.<

Luckily, there's guys like Stephen. Buy his Cow DVD. (I receive no compensation whatsoever for saying this, they're good products, he's engaging, knows his stuff.)

bogiesan

 Re: particle emitter and falling leaveson Dec 12, 2008 at 6:27:40 am

What you need is the behavior called edge collision.

Apply Edge Collision to the Emitter.

Turn off all the active edges except for Bottom Face.

Turn the Bounce Strength to 0.

Adjust the Height to the point where you want the leaves to stop.

Hope this helps.

 Re: particle emitter and falling leaveson Dec 12, 2008 at 6:18:00 pm

Cool, Andy, thanks man, figured there must be something in the app to make this work.
Just tried it.
Difficult to get it to work in 3D space, seems artificial, and I can't get the dang leaves to stop spinning once they hit the ground.
Suggest the OP use at least two emitter players. one further back, and use different leaf system settings and edge settings.

thansk again, Andy.

bogiesan

 Re: particle emitter and falling leaveson Dec 12, 2008 at 9:34:37 pm

I've got a nice st of falling leaves coming from a line off the top of the screen.
1. Can't get them to appear in different z-space, they're all at the same plane.
2. Can't get the leaves to stop moving or turning once they hit the ground level.
3. They march toward the camera.

Very frustrating. I hate Motion, but, hey, that's just me.

bogiesn

 Re: particle emitter and falling leaveson Dec 13, 2008 at 12:07:35 am

Adjust the Shape in the Emitter to Rectangle, the arrangement to Random Fill and activate the 3D button to get the leaves to fall in 3D space. You also need to adjust the X Rotation in Properties to 90 so that the rectangle shape is oriented correctly (that should address the "marching toward camera" issue as well). You also likely want to introduce some randomness in the Birth Rate as well for a more natural appearance.

To get them to stop spinning is tricker because any behavior that you use to arrest the spin, will do so on all the leaves, not just the ones on the ground. To accomplish this required 2 identical emitters.

Make sure the emitter is in a group. Duplicate the emitter and turn the bottom one off. Go to the point in the timeline where all or most of the leaves are on the ground. You can't make a 3D mask, but if your camera move isn't too great, you can fake it with an image mask.

In the top group, using the Shape tool, draw a rectangle from the top of the frame until just above the "ground" where the leaves are. Make sure it covers the whole frame left to right. Give it a small feather to soften the edge.

Hit CMD+SHIFT+M to add an image mask to the top group and drag the rectangle you just made onto the image mask. Turn the top group off and the bottom group on.

For this emitter apply the Rotational Drag behavior. Increase drag until the leaves stop turning.

Build another rectangle in this group only this time you are covering up the "ground" area, but nothing else. Apply the same feather to that rectangle as the one above. Create an image mask for the bottom group and drag the new rectangle onto it.

What you should have now is one emitter that rotates the leaves and disappears before it hits the ground and a second emitter that doesn't rotate the leaves, but you don't see the leaves fall.

Turn on both layers and watch. When I did this the first time, there was a thin gray line where the feathering of my image masks didn't quite overlap. All I had to do was select the rectangle that was serving as the image mask in the top layer and nudge it down by holding down CMD and tapping the down arrow until the gray line disappears.

Let me know if this works for you. If you're still having problems, I'll send you my test project and you can dissect it.

Andy

 Re: particle emitter and falling leaveson Dec 13, 2008 at 4:59:42 pm

Sure hope the OP comes back to find this! I'm on vacation, won't get to try this for a few weeks.

You rule, man. Could make a delightful tutorial for Motion. Think about tweaking it up and submitting it.

But, I gotta say, your very helpful explanation only points out how Motion's process is hopelessly complex and defies the logical approach most people would attempt to use to problem solving. (This is where i say how much I loathe Motion's behavior paradigm).

bogiesan

 Re: particle emitter and falling leaveson Dec 13, 2008 at 6:13:24 pm

It's funny you mentioned making this a tutorial because I was thinking about that when I finally figured it out.

I have to disagree with you about Motion being horribly complex, although I might have agreed with you as little ago as 6 months.

I came from an AE background initially though I would only consider myself an intermediate user. When I got Motion 3 I decided that Motion was finally worth some attention (I couldn't stand Motion 2 for the most part).

For about 6-8 months, I was using Motion AND After Effects. Whenever I got to a place where I was stuck in Motion, I'd go finish or redo the project in AE cuz I knew how it worked.

Finally, I realized I wasn't getting any better at Motion. I was still using keyframes more often than not. I was working in the Timeline (and being frustrated with the shortcuts). I made a conscious decision to put down AE (mainly due to seeing the things that Patrick Sheffield and Mark Spencer were putting together using Motion). I put down AE and ONLY used Motion.

For a while things were tough, but since I'm a lazy man at heart, I was always looking for the easier way to do something and it finally lead to a kind of epiphany. That moment when someone comes to you asking for a particular kind of motion graphic, and I began to visualize it first in Motion and not AE. That's when I knew I had turned a corner.

Behaviors, emitters, and replicators used to mystify me completely because it wasn't the paradigm I was used to. But I wouldn't call it illogical. In fact, compared to AE expressions, it's like a 2 piece jigsaw puzzle.

I know you hate Motion compared to AE, but I applaud the fact that continue to try and work with it and get better. Just understand that I've been in your position, and it DOES get better.

Besides Motion's only in version 3. Wait until it gets to 7 or 8.

Andy

PS: I have no idea how I would have done this project in AE. How would you have approached the leaves turning problem?

 Re: particle emitter and falling leaveson Dec 16, 2008 at 5:19:13 pm

If you can do it, I can do it.

bogiesan