Motion trails

[Mylenium]

Hey guys,

I'm trying to find a way create motion trails behind fast moving particles rendered from Maya in AE. You can see a full description of the situation here. (http://forums.cgsociety.org/showthread.php?f=87&t=509841) As you can see someone suggested doing this in compositing rather then in MR so I was hoping someone here might have some ideas. Thanks!

Not sure. It all hinges on the size of your particles, how fast they really move and what you actually want (and hence which limitations you are willing to accept). Do you mean mortionblur or really trails? In case of motionblur, you need to render a motion vector pass and then use ReelSmart Motionblur to stretch out your particles using the vector info. A brute-force approach to the matter would be to simply use CC Motionblur. If you're more looking for a trail-like look, the Echo effect might give you what you need. Be aware though, that neither of this will give 100% physically correct results and that things like shadows and reflections may not be affected by them. In case the particles are too small, results will be incorrect either way as these post effects will not be able to make sense of the motion direction and overlap behaviors.

Mylenium

[vtcgman]

Hey thanks for the thoughs. I'm playing around with you suggestions right now butI'm having a few problems. First off, the particles are moving really fast, so when I try to use CC Force Motion Blur and Echo I get gaps between the particles and the echoed particles. I haven't really found a way to get ride of that. And as for the Reel Smart Motion Blur, I've actually tried that but the vector shader for maya doesn't work on the blobby particles, you actually have to instance geometry to the particles which is not really an option for me as I have too many particles and it crashes when I try to instance.

As for what I'm looking for, more a motion blur effect but the echo tails looked ok too. :)

[trancor]

In maya, mental ray takes a long time to render, if you could, try rendering out the particles in software render with a rather large 3d motion blur set on it, a few frames worth. If you need to, add the particles to their own render layer, that is if you have other objects in the scene you don't want to add these motion trails to in after effects. I realize the software motion blur can only give you so long of trails depending on how fast the particles are moving. So here is what you could try in after effects below.


In the past I've wanted to do this, but ended up using up my two week trial of the saphire plugins to do it. After reading the post I wanted to try doing it without several thousand dollar plugins. Below is an image of the plugins I used and then the trail to the right, to the right of the trail is a little block, this is what I started with.

Normaly I overlay and overlay filters till I achieve the look I want, the image below has a few filters that may drag down your computer, I don't know your spects though.

http://upload.metal-asylum.net/cgtalk/ae/trails.jpg



The echo is the length of the trail, the gausian blue is to allow room for the vector blur to work. The vector blur will meld the obish blurred blocks together to create a beam and the levels is to bring the alpha up becayse the blur from the guas and vector leaves the clip rather transparent.

Below is the ammount of room between frames and the blocks (this is with just echo on so you can see.)

http://upload.metal-asylum.net/cgtalk/ae/trailsEcho.jpg


Sure it doesn't look great, but you can play with the levels to make it more of a concrete trail and the gausian blur for how fat the trail is.

As a last step I would just put either the edited clip on top of a duplicate of the original clip with no effects and do an overlay or a screen, perhaps a pin light, depending how things look.

Now the only problem with what I showed you is that the frames don't have much space between them. In your case if you have faster moving particles and more space, I'd jack up the gausian blur, perhaps add a levels to bring up the alpha before adding the vector blur.


Hopefully this helps, good luck.


edit- The vector map I used is the clip I'm effecting.

[b9999]

I think it would be lot easier if you use Trapcode Particular with a custom particle shape. If you can afford to buy this plugin of course. If not, maybe this could be done in CC Particle World, but I'm not sure.

Here is my example: trail made with Trapcode Particular

http://youtube.com/watch?v=ebbPYXFIBKk

[Shinjipierre]

First off, the particles are moving really fast, so when I try to use CC Force Motion Blur and Echo I get gaps between the particles and the echoed particles. I haven't really found a way to get ride of that.


Then, increase the framerate of your rendering, you'll have more interpolation, less gaps. But well, it depends on how long it is to render.

[vtcgman]

Hey guys, thanks for the replies, I guess I have some work to do now!

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