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Alex DeJesus
Alex DeJesus
430 posts
Jul 25, 2008
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Roto Brush only works for a few frames

May 29, 2012 11:26 PM

Tags: #rotobrush

CS6 After Effects. I am trying to remove the background behind a person in a shot about 1 1/2 minutes long. The roto brush tool does a good job of selecting the area. It replaces the background area with black. But it doesn't seem to want to propagate past the first few frames. I am working in the layer panel. I watched a couple of tutorials. 

 

I have to page down 3 to four times for it to advance one frame. After about the 6th frame it has stopped applying the roto brush. The background has reappeared in the frame. RAM preview plays the clip as if no effect is applied.

 

I have never done any rotoscoping, so I'm not sure if it is meant for this purpose or for this long a clip. In the tutorial, the clip used is only 11 seconds. Mine is 1 1/2 minutes

 

Addtn: Now I see that you have to drag the span slider across the timeline first. Now it seems to be rendering. However, the program is freezing after each ten frames or so. Looks like I'll let this one work overnight.

1774 Views   8 Replies   Latest reply: Mylenium, May 31, 2012 2:32 AM
 
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  • Mylenium
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    1. Mylenium,
    May 29, 2012 11:32 PM   in reply to Alex DeJesus
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    Screeenshots tell a lot... Manually having to set the spans is not the way it's designed to work and such excessive render times point to otehr issues.

     

    Mylenium

     
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  • Alex DeJesus
    430 posts
    Jul 25, 2008
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    2. Alex DeJesus,
    May 29, 2012 11:35 PM   in reply to Alex DeJesus
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    I understand that I need to modify the mask every so often as it seems to lose track. However, it seems to catch on after a while. The tutorial does not explain what to do with the span slider. Since I want to affect the entire clip, is it correct to span across from the beginning and then RAM preview? Or should I span across smaller segments at a time?

     
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  • Alex DeJesus
    430 posts
    Jul 25, 2008
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    3. Alex DeJesus,
    May 29, 2012 11:46 PM   in reply to Mylenium
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    Rotobrush tool.jpgWell, it was working for a while, but froze again after hitting second mark on the timeline. I notice quite a few people have posted similar issues with this tool. Seems it only works 10 frames at a time.

     
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  • Alex DeJesus
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    Jul 25, 2008
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    4. Alex DeJesus,
    May 30, 2012 8:05 PM   in reply to Alex DeJesus
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    Rotobrush tool 2.jpgSure wish I could get an answer on this one.

    As you can see, it does a decent job of refining initially. But if I go from one frame to the next, I have to redraw stroke or two. How close should I get with the brush?

     

    Rendering is slow.And I have 32 GB RAM. Rendering this effect pushes half of it.The little green bar creeps along For a clip this length, I can be here all week at this rate. It's weird watching this render. It kind of goes in spurts. Then it locks up. I see a yellow candy cane pattern along top of the timeline. I don't dare hit the 'freeze' button again because it crashed the computer twice already.

     

    As a test I rendered out a short segment of this clip - 15 seconds. The matte came out pretty rough, not good enough to use. I literally have to go frame by frame with this thing.

     

    I hae a serious problem. I have this and one other clip to process tonight on a deadline, and at this rate, it simply will not happen.

     
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  • Alex DeJesus
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    Jul 25, 2008
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    5. Alex DeJesus,
    May 30, 2012 8:23 PM   in reply to Alex DeJesus
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    So, it's an hour later and still rendering out a 15 second portion of my clip. I can't imagine this will end. Am I asking too much?

     
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  • Mylenium
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    6. Mylenium,
    May 30, 2012 11:18 PM   in reply to Alex DeJesus
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    I'm afraid I have no answer for you. this sounds completely insane. I have rotobrushed 10 minute clips and the propagation would take at most twice that long, so having it sit there for hours on a one minute clip just isn't right. Anything specific to the footage? Have you tried with a completely different footage to compare results?

     

    Mylenium

     
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  • Alex DeJesus
    430 posts
    Jul 25, 2008
    Currently Being Moderated
    7. Alex DeJesus,
    May 31, 2012 1:53 AM   in reply to Mylenium
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    Thanks for checking in. I may have other problemks. I found a stash of temp files on my system drive that have been collecting for a few days. I suspect there is more somewhere because 120 GB SSD is at 75% capacity. I have set up my prefs to store all cache files on a separate drive, but these files keep collecting on the system drive.

    As for the Rotobrush, the render did finally end. I brought the clip into Premiere, but not usable. There is a color tinge around the subject's hair that I can't get rid of. I'd have to go back and reaccomplish the roto, but I don't have the time to do the entire length of the clip - would take a couple of days Temp files.jpg

     
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  • Mylenium
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    8. Mylenium,
    May 31, 2012 2:32 AM   in reply to Alex DeJesus
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    Well, you info tells a lot. It would seem that AE is decoding your footage over and over to extract the current frame and produce the temp frame. I recommend you convert the file to something else. I'm sure things will work like a snap once you do.

     

    Mylenium

     
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