How to use the overlapping area of 2 layers as a matte?

Adobe After Effects

How to use the overlapping area of 2 layers as a matte?

Posted by Aivaras Seduika on April 4, 2011 at 6:18 pm

Hi guys,
This is wrecking my brain, please help!
The brief is to have 3d layers floating around, and images reveal as 2 pre-determined layers overlap. The image is within the overlapping area of the 2 layers.
Kind of like a boolean operation in 3ds max if someone’s familiar with this, where you can set the result to be the intersecting area.

Is there any way to achieve this with what’s built in to AE?
I’ve tried playing with channel operands but not really getting anywhere.

I’ve been trying to use overlay modes to combine RGB channels of 2 layers and use the combined value as a luma matte, but not getting anywhere.

Anyone point me in the right direction?
Thanks loads.

Walter Soyka replied 15 years, 5 months ago 3 Members · 8 Replies
8 Replies

Brian Charles
April 4, 2011 at 6:32 pm

Is it possible to Precomp the 2 intersecting layers and use them as a track matte?
Aivaras Seduika
April 4, 2011 at 6:36 pm

Thanks for your reply Brian,
Yes this works, but the track matte becomes the combined alpha area of the 2 layers, not the intersecting (or overlapping) area.
Just the overlapping bit is the bit I need to be the matte.
Cheers
Aivaras Seduika
April 4, 2011 at 7:10 pm

Hi Dave,
Yes I will be, but only in the master ‘top’ comp containing these layer-overlapping pre-comps, so the camera inside the actual pre-comp will be static.
Aivaras Seduika
April 4, 2011 at 7:28 pm

Thanks dave,
How would you have done it if it was a static camera?
Thanks
Walter Soyka
April 4, 2011 at 8:40 pm

[Aivaras Seduika] “The brief is to have 3d layers floating around, and images reveal as 2 pre-determined layers overlap. The image is within the overlapping area of the 2 layers.”

Copy those two layers into a new comp. Color the top layer white, and color the bottom layer black. Add a blank adjustment layer in between the layers (to break 3D intersection). Toggle the Preserve Transparency switch [link] of the top layer.

The top white layer will only show when it intersects the bottom black layer. You can use this comp as a luma matte.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events
Aivaras Seduika
April 4, 2011 at 9:27 pm

Thanks very much guys for taking your time to reply! I’ll give these ideas a go tomorrow, will update then.
Cheers
Aivaras Seduika
April 7, 2011 at 3:45 pm

Walter, thanks very much for your advice – it worked! It’s still not very flexible as a device due to the need for duplicate pre-comps (one to use as a luma matte, the other sitting over the top as a diffuse layer), but it works well enough for what I need.
Thanks again!
Walter Soyka
April 7, 2011 at 3:48 pm

[Aivaras Seduika] “Walter, thanks very much for your advice – it worked!”

Glad to hear it, and happy to help!

[Aivaras Seduika] “It’s still not very flexible as a device due to the need for duplicate pre-comps (one to use as a luma matte, the other sitting over the top as a diffuse layer), but it works well enough for what I need.”

Totally true. This is the sort of thing that’s a lot more straightforward with a nodal compositor than a layer-based compositor. Good luck with the rest of your project!

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events

Reply to this Discussion! Login or Sign Up

Creative Communities of the World Forums