After Effects Roto brush slow propagation and span adjustment

[kpblocher2]

Generally work has gone smoothly with Roto Brush 2 in AE 17.5, but I'm about halfway through a 900-frame shot, and suddenly each corrective stroke causes a 30-second delay while it propagates the change. (I had previously jumped through the shot, beginning about halfway through, and applied Roto Brush strokes every five frames, and experienced the same long delays after each stroke.) I've tried narrowing the Roto Brush & Refine Edge span, but as soon as I make a new stroke, the span automatically expands back out to the full length of the shot. I've tried freezing and unfreezing propagation, which doesn't solve my problem. For bonus points, can someone explain how I can get propagation to go back towards the head of the shot? It always indicates it's going towards the end of the shot. Thank you in advance for any suggestions!

[Peru Bob]

I've moved this from the Using the Community forum (which is the forum for issues using the forums) to the AE forum so that proper help can be offered.

[kpblocher2]

Thank you, Peru Bob. I suspected I was posting to the wrong place, but it being my first time, I wasn’t sure how to navigate to the proper place. I appreciate the help.

[kpblocher2]

Correction to my original post: It appears the delay after making a correction stroke is while AE is rendering the correction, not propagating. If I jump the gun and prematurely try to add another stroke, it says I need to wait until the current frame finishes rendering. But is there a way to eliminate, or greatly reduce, this long delay?

[Rick Gerard]

Processing time depends on the shot, the codec, the frame size, and the size of the matte. Faster systems help. Making sure that you have at least 4GB of ram allocated to other apps and your ram allotment for Adobe apps is an even number also helps. Starting at frame zero and analyzing a frame at a time to check for errors and corrections also helps. Just letting Rotobrush propagate and then going back to fix problems isn't going to save you any time. 

[kpblocher2]

Thanks for the reply and advice, Rick. That’s good to know about not going back to fix problems. I had misunderstood the instructions, which may have been for Roto Brush 1. Interestingly, the slowdown happens about halfway through the shot, which is about where I started jumping in five-frame increments.
It turns out that I've solved my problem by duplicating my footage layer, removing Roto Brush from the new copy, and creating a part 2 by trimming the tail of the original and the head of the copy. Then I started Roto Brush from scratch on the new part 2, and it's working great - very fast. From this experience, I'm assuming that there was only 400 frames or so of capacity for the system to deal with this particular shot.
For the record, I have a 2.7 GHz 12-Core Intel Xeon E5 system, with 52 GB RAM allocated to AE, and 12 GB to others. My material is a 1080p DNxHD115 export from Avid Media Composer. And yes, it’s a big, complicated matte.
 
Thanks again for your feedback.

[default81wv2r5yxgv4]

Amazing KP, that worked perfectly....after 4 hours of trying to figure out what was wrong with my system.

[Hugo5C8F]

Hi there,

I'm having a similar problem with the propagation, too. Let me simplify. I use the rotobrush once and it takes forever for it to load on After Effects 18.2.1, like over ten minutes. I have to save the project, close it and open it again just to use the rotobrush. Why is this happening? Is there a problem with the 18.2.1 version? Do you guys know any way that I can fix that?

[bartv8954217]

I have a 1080 P clip, 1200 frames, takes hours and hours to rotobrush.
Been running it for 5 hours now with 12 gig ram allocated to ae.
Freezing also takes ages, over 3 hours in right now.

[Rick Gerard]

1200 frames is an eternity in almost any movie. The average time between cuts is now around 4 seconds. Is there any way to cut up the clip? Is there any way to use procedural mattes or animated masks to simplify the Rotobrush workload?

I try and never work on any frames in AE that will not end up in the final edit. I learned to do that in the early 1970s when I was hand painting mattes on acetate animation cells to replace the sky in a shot I was working on for a documentary. My partner in the project had been doing visual effects for more than 20 years. I never forgot the advice to edit first, then do the visual effects. A great deal of the ways After Effects works with its multi-plane and animation capabilities come directly from the work and patents of Max Fleischer in about 1915. 

[Huân36353748wc3x]

Thank you Mr.Gerald, this helped me