Compositing Mode

Jey wrote on 4/28/2004, 7:18 AM

Question. Is it possible to use compositing mode to affect only the videotrack directly beneath the track on which the effect is applied? I.e. when I use compositing mode 'add' to adjust a videotrack, but the applied track has transparent portions, all my lower tracks become affected. Does anyone know how to prevent this?

Thanks.

Jey

Comments

chaboud wrote on 4/28/2004, 11:00 AM

Take a look at Parent/Child compositing.

Let's set up an example:

You have three tracks of interest. You plan on adding track 1 to track 2 and compositing all of that over track 3.

To do this, you set the composite mode of track 1 to "Add," but you find that track 1 is being added to the combination of tracks 2 and 3.

To solve this problem, press the "Make Compositing Child" button on Track 2. On the left side of track 1 you'll see a new motion button and compositing mode button. These are the motion and compositing mode for tracks 1 and 2 over track 3.

In essence, you can think of compositing children groups as parentheses. Without track 2 as a child, your composite would look like:
Track 1 is

C ▀ B + A (▀ represents the source alpha blend)

Which would combine C and B first and then add A to the result.

With track 2 set to be track 1's compositing child, you have:
C ▀ (B + A)

Which adds A to B and blends the result over C.

Cheesehole wrote on 4/28/2004, 11:07 AM

You should be able to accomplish this with Parent / Child compositing.

I'm assuming you have two tracks which you want to composite together using the ADD mode. Click the "Make Compositing Child" button on the lower of the two tracks. Now the "ADD" function doesn't affect tracks below your little composite group - it only affects the children added to the hierarchy.

EDIT: Thanks chaboud - you beat me to the punch. I like the detailed explanation.