Lateral Thinking Needed

Adobe After Effects

Lateral Thinking Needed

Posted by Dan Lachevre on August 15, 2008 at 12:49 am

We have a confusing problem trying to precisely position the ends of a 3d Stroke. We are using 3d stroke but there may be a better way around this

Overview:
We have a 3d scene featuring a girl holding a bunch of lightbulbs attached to cables. The lightbulbs float in the air above her in a cluster and behave like balloons. The Lightbulbs and the girl are shot on a turntable on green screen and rotate. We have these oriented to camera and everything looks convincing as the camera rotates around her.

The problem is now we need to attached cables from the bulbs to the girl’s hand and have decided to use 3d stoke which can’t be parented to the 2d bulb layer.

Is there anyway to link one end of the stroke to the 2d bulbs and the other end to the 2d girl? The x and y are linked but is there is a way to override with scripting?

We would also like the bulbs to ebb and bob in the air like balloons so it would be great if there was a way of parenting the mask verticees to the 3d position of the bulbs.

There may be a way via this Post below but I’m not quite sure how it would work:
Re: attach track to mask
by yikesmikes on Sep 22, 2007 at 2:58:13 am

Some lateral thinking is need here I think!

Thanks in advance

Danny

Dan Lachevre replied 17 years, 8 months ago 4 Members · 4 Replies
4 Replies

Darby Edelen
August 15, 2008 at 2:14 am

I’m not familiar with the details of 3D Stroke, but here is an expression that will convert a layer’s anchor point from a 3D world position to a 2D layer position. Hopefully this will help.

l = thisComp.layer("MyController");
fromComp(l.toComp(l.anchorPoint));

So if you point the ‘l’ variable to a 3D null this expression will return a 2D coordinate on the layer it is applied to that corresponds precisely to the location of the 3D point.

Darby Edelen

NVIDIA
Santa Clara, CA
Roland R. kahlenberg
August 15, 2008 at 1:38 pm

Darby, 3D Stroke works with mask(s). Perhaps Write-on or even Beam (if a straight line works) may be able to do the trick?

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Jack Leto
August 17, 2008 at 4:11 pm

Is there anyway to link one end of the stroke to the 2d bulbs and the other end to the 2d girl

Roland’s Beam suggestion is a good way to go. You could motion track her hand and each bulb (target the tracking data to seperate Nulls), then parent the ‘ends’ of the Beam to the Null objects.

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MOTIONOLOGIST
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Dan Lachevre
August 19, 2008 at 4:41 am

Hi Guys

Thanks for this. We couldn’t get 3d stroke to work in the end [though I’m sure there is a way – we’re just a bit under the hammer]. What we’ve decided to do is a 2d stoke instead using the regular Stoke filter. As the camera zooms quite fast and is close in the shear number combined with motion blur kinda fools the eye.

However….

Our problem is now that because the bulbs are oriented to camera [Y only] we can’t parent them to the cables or the entire thing will move. What we want to do is have the bulbs bob up and down like balloons and automatically bend the stoke using the mask vertice.

IS there a way to easily do this?

Any help appreciated

Cheers

Danny

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