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# Matte question

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 Matte question on Dec 12, 2010 at 7:13:58 pm

I have 2 pieces of footage:
-one containing an "energy ball", with a short "particle trail" going around in circles in the horizontal plane (aka orbiting). It was made in a 3D application and then rendered.
-the other is the footage of a real person (not created in a 3D application), with a background. (I know how to eliminate the background).

My goal is to combine the 2 so that the "energy ball" rotates around the person. The difficulty lies in the fact that the "energy ball" must, in its orbiting, go alternately in front and then _behind_ the person.
I know the basics of matting, but how do I make a footage behave, alternately, normally (when the ball is in front of the person) and like a matte (when the ball is behind the person)?

 Re: Matte questionon Dec 13, 2010 at 4:22:32 am

If the particles don't trail beyond 180 degrees behind the energy ball, you can use the Split Layer operation to alternately put the person in front of and behind the ball & particles layer, simulating the orbiting you want.

Actually, you might be able to get away with more than 180 degrees. It all depends on how far this orbit occurs from the subject.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

 Re: Matte questionon Dec 13, 2010 at 10:19:42 am

I have a follow-up question to the first one.

If, instead of the ball with a trail, the ball would, in its revolving motion, "draw" a solid trail (that would NOT disappear after a time) _around_ the person... so in the end the person would be encircled by a solid "torus"...
Would _that_ be possible in AE?

And many thanks for the previous answer.

 Re: Matte questionon Dec 13, 2010 at 6:45:42 pm

You'd have to build it in AE using 3D layers.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

 Re: Matte questionon Dec 13, 2010 at 9:27:24 pm

How exactly should I use 3D layers in this case? I am new at this.

 Re: Matte questionon Dec 14, 2010 at 8:06:48 pm

I don't know that you'd have to use 3d layers. Again, this depends on the path which it takes, but you could use whatever method you want to make the trail (stroke on a mask, etc.). Then split the layer for the parts where it's "behind" the guy and the parts where it's "in front".

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

 Re: Matte questionon Dec 16, 2010 at 6:08:18 pm

[Michael Szalapski] "I don't know that you'd have to use 3d layers"

[Michael Szalapski] "Again, this depends on the path which it takes"

I detail this matter in a previous post.

What I really want to know is if the trail can actually encircle the character, like a torus around this person's waist.

 Re: Matte questionon Dec 16, 2010 at 7:00:09 pm

[Michael Szalapski] "I don't know that you'd have to use 3d layers"

I did. I was just saying that the layer didn't need to be a 3d AE layer. I've been working with After Effects since before the 3d layers were a big thing and this sort of effect would be achieved all the time with 2d layers.

[Michael Szalapski] "Again, this depends on the path which it takes"
[Richard Smith] "I detail this matter in a previous post."

Sorry; I didn't make myself clear. I understand that it's circling the guy. I meant the ease of achieving the effect would depend on how wide of a space there was between the top and bottom portion (in the viewer's field of view) of the circle, how far from him it traveled on the x-axis, how thick the looping thing was, etc.

[Richard Smith] "What I really want to know is if the trail can actually encircle the character, like a torus around this person's waist."

Yes.
I don't have AE on this computer and my AE machine is in the middle of a render at the moment, but here's an example with Photoshop.

Pink layer above person layer.
Person layer above blue layer.
All in 2d.
Blue layer and pink layer are, essentially the same thing, just duplicated and masked.
Photoshop file.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

 Re: Matte questionon Dec 16, 2010 at 7:44:23 pm

Oh, I see now...
And the images are much appreciated.

 Re: Matte questionon Dec 17, 2010 at 3:11:00 am

Sure, and you can do it in 2D.

Obviously, putting the render behind the talent is easy. Duplicate and mask the rendered layer to put it in 'front' of the talent. Basically, it's a 3 layer sandwich.

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"Putting the HARM in 'harmonica' since 2005."
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