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Can you turn a mask off temporarily?
Hi –
I am working on a shot of a billboard across a highway. I have masked out the billboard so that I can replace it’s contents with a still image. The problem is, cars pass in front of the billboard. So I am rotoscoping the frames in which the billboard is partially obscured by a car, so that the car is not masked out of the video clip. That’s all going slowly, but successfully.
My problem is that I have a couple of sections in which the entire billboard is obscured by a larger vehicle. During these moments (15 frames or so), I want the mask to disappear entirely, since there is nothing to replace in the frame. Is there a way to turn it off temporarily and then turn it back on (after the large vehicle has passed)?
I feel like I should be able to keyframe the type of mask it is, so that I can switch from “subtract” to “none” and abck again, but that doesn’t seem to be possible. My other thought is to delete ALL of the vertex points, but I find that when I delete a vertex point in one frame, it also gets deleted on earlier frames, so that my previously drawn masks are ruined. (This seems like a major flaw in AE’s mask keyframing, by the way, but I recognize masks usually apply to similar shapes, not multiple and different ones, as with my cars.)
Finally, my other thought is to just start a new mask after each time the billboard is entirely obscured, but that means I still have to “turn off” the mask at a certain point, and I don’t know how to do that.
Sorry for verbosity, but hope that’s clear. Thanks!
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15 Replies
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Im not sure about turning it off temporarily but what you can do is drag it off the footage onto the grey area, set a keyframe and then go to the frame before the next time you want to use it, set a keyframe there and then continue rotoscoping.
Hope ive helped,
Pat Jaeger -
Thanks, Pat. That seems like a very workable solution, and one I probably should of thought of…
Rich
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Pat’s solution works well, untill you enable motionblur for the layer. Then you’ll see strange motionblur artefacts happening around the frames where you quickly animate the mask off-screen.
The alternative is to animate the mask opacity. Setting the mask opacity to 0 basically turns it off.
Bar3nd
Raamw3rk – digital storytelling and visual effects
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Maybe I’m missing something, or it’s not that big of a deal to you, but even though the billboard is fully obscured, wouldn’t there still be a few frames when the large vehicle is covering and uncovering the billboard? If I understand your situation correctly, it seems like it would be weird to completely turn the mask on and off, unless the car passes so quickly that you wouldn’t notice the sudden change anyway.. just thinkin..
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8core MacPro, 3.0 GHZ, 10GB RAM, OSX 10.5.2
DualCore G5 2.0 GHZ, 2GB RAM, OSX 10.4.11AE7 on both for now.
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Thanks, Barend. Unfortunately, I’d attempted to set opacity to zero, but I’m using a subtract mask to cut out a rectangle within the frame, so bringing opacity to zero removes everything outside of the mask (billboard), giving me a mostly black frame, which is not what I need.
Am I missing something? Should I not be using a subtract mask and drawing a rectangle around the billboard?
thanks
Rich -
You’re absolutely right, Jeremy. I am rotoscoping those “partial obscurations,” as the big vehicles enter and exit the “frame” of the billboard, just like when a car goes by and blocks part of the billboard. So I only want to turn the mask “off” for the frames when the billboard is entirely obscured. In essence, I am rotoscoping the mask to get smaller until it “disappears” and then get larger again until the vehicle has passed and the mask is the same size as the entire bllboard.
Rich
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Hi!
I would drag the original footage to the top of the comp and set it’s start when the mask should disappear and it’s end when the mask reappears, then continue rotoscoping the original footage.
Regards
Alejandro
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Sorry Richard, I misread your post. I was thinking along the same lines as Alejandro, in the sense of making a duplicate of the footage to cover the original whenever the billboard is completely obscured. Would that work for you?
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8core MacPro, 3.0 GHZ, 10GB RAM, OSX 10.5.2
DualCore G5 2.0 GHZ, 2GB RAM, OSX 10.4.11AE7 on both for now.
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Hi Richard
I think Jeremy and Alejandro have the right idea, by duping the orginal footage and droping your still in the middle. Another way (but this will cost you) is by using a program calleed: Mocha AE. Aharon Rabinowitz done a great tutorial on this program so you should check it out.
Basically Mocha lets you track your footage and then you can apply the four corner pins to your still frame.the best thing about this program is you can track the footage even when your four pins can’t be seen, so when the trucks pass by the billboard mocha will still track the exact point you choose (ie the four corners). Dont worry Aharon explains this far better than I can but you should check it out. Once you have the footage tracked and the still in place you then only have to mask the parts the trucks and cars pass by the billboard on the second copy of your orignal footage, sitting on top.
Hop this helps a little.
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Hi,
I might be mistaking, but it looks like this had become a lot more complicated then it should be..
My ‘simple’ method would be:
– Place a square mask around the entire layer and leave it on ‘add’ Having a full maks on ‘add’ as the first mask on your layer prevents masks that are set to substract from fading the entire layer.
– Place a second mask that masks out the billboard (or use your existing one) that will be put on ‘substract’
– Use a new mask for each car that passes, leave them on ‘add’ start creating them in the middle, outlining the front of the car, simply keyframe and grow them along untill the car is completely covering the frame. Set a new keyframe when te first frame of the car’s backside is in frame and follow and outline the back of the car until it (and the mask) is fully out of frame (needless to say that, at constant speed, this should only have to be 2 or 3 keyframes).
Just leave your mask standing there and create a new one for the next car, because reusing them will add the motion blur junk mentioned above.Or am I overseeing something here..
Good luck with it.
Job
Media100/after-effects/Combustion/FCP/Flint/Flame/Inferno..
Thank heavens; there’s a sign of progress here..
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