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Partially obscuring objects on a path that appear/reappear

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Michelle ChristenaPartially obscuring objects on a path that appear/reappear
by on May 25, 2014 at 11:45:06 pm

Hello there, I have a bit of a complicated issue with a project that I'm working on in AE. This is my first time using the program, but I'm a seasoned Adobe user. I have AE CS6. My project lays out like this:

I have a video of two guys tossing a "glowing orb" which is created in AE back and forth. They move it between their hands, behind their backs, and behind their bodies. I have my orb created and am working on creating the path that the orb will follow. The problem that I'm running into is masks. There are times when parts of the orb will be hidden because it's behind their hand or part of their leg. Other times, the orb will be completely hidden because it's behind their back or body. If I create a mask I'm not sure how to only have that mask active for the few seconds that it may be behind one of their backs before essentially becoming obsolete. Due to the complicated nature of the ways the orb needs to be hidden/visible especially partially I'm not quite sure how to handle this. If I could use an eraser brush for the orb for certain frames before it returns back to normal that would be perfect. After trying to find a solution on the internet, I figured I'd ask specifically. Thanks for your help!


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Darby EdelenRe: Partially obscuring objects on a path that appear/reappear
by on May 26, 2014 at 3:31:33 am

You have a few options for this sort of thing.

1) Keyframe your mask opacity.

2) Roto your subjects, place them in front of the orb layer and selectively mask or keyframe opacity.

3) Use the erase functionality of the brush tool.

The best solution will depend largely on the footage in question (e.g. how many times is the orb obscured vs. not).

Darby Edelen


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Michelle ChristenaRe: Partially obscuring objects on a path that appear/reappear
by on May 26, 2014 at 12:45:44 pm

I've tried keyframing mask opacity and it just changes the opacity for the entire time versus using the keyframes which is what got me frustrated. I would say it spends equal time being partially hidden vs not considering their hands will be holding it and almost always something will be infront of it. Can you use the erase brush for only a few frames?


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Darby EdelenRe: Partially obscuring objects on a path that appear/reappear
by on May 26, 2014 at 4:27:42 pm

Can you describe how the mask opacity is working in more detail? It should work for this.

You can specify the duration of the brush strokes, so each stroke has an in point and an out point. If the subject is moving a lot then you'd probably need to use single frame strokes. In that case it might be better to try option 2 maybe with the rotobrush.

Darby Edelen


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Michelle ChristenaRe: Partially obscuring objects on a path that appear/reappear
by on May 26, 2014 at 5:21:20 pm

I will give the rotobrush a try and look into the brush strokes. When I was working with the mask opacity I would set keyframes, and turn on the stop watch.. I had 4 keyframes. I set the first keyframe to 0% opacity, set the next to 100%, and then the third to 100%, and the fourth to 0% so that the mask was only visible in the short amount of time I needed it to completely obscure items beneath it. Any time I would change the mask opacity at that point, it would change it for all of them so I wasn't sure what I was doing wrong. Considering I would end up having probably 300 masks before it's all said and done the other two options may work better lol.


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Darby EdelenRe: Partially obscuring objects on a path that appear/reappear
by on May 27, 2014 at 4:26:51 pm

[Michelle Christena] "I set the first keyframe to 0% opacity, set the next to 100%, and then the third to 100%, and the fourth to 0% so that the mask was only visible in the short amount of time I needed it to completely obscure items beneath it. Any time I would change the mask opacity at that point, it would change it for all of them so I wasn't sure what I was doing wrong."

Did this change all of the keyframe values or change all of the mask opacity values?

If the former then make sure you don't have any keyframes selected (or only have the ones you want to modify selected).

If the latter then make sure that you are animating the "Mask Opacity" property (not the layer's "Opacity" property) and also that you only have the one Mask Opacity property you want to modify selected.

Also, here are some shortcuts you might find useful when working with masks. With a layer selected press:

m - To reveal Mask Shape properties
f - To reveal Mask Feather properties
tt - To reveal Mask Opacity properties (tap t twice as opposed to tapping t once for the layer opacity)
mm - To reveal all Mask properties (includes all of the above + Mask Expansion)

Darby Edelen


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