applying echo to an object isolated with rotobrush

[dv8kiwi]

This is a strange problem. I want to isolate and track a ball then apply an echo. I isolate first then add echo. 

When I add the echo with a negative time value the ball loses its rotobrush isolation and the and the echo is applied to the entire layer. Strangely when I add a positive value the echo works on the isolated area as expected. Of course I want the echo trail to follow the ball not precede it.

Any ideas why this is happening and any other possible ways to acheive this?

Thanks

[Rick Gerard · Accepted solution]

You are running into a render order problem. It is easy to solve. After you isolate the ball using Rotobrush, pre-compose the layer, then apply Echo to the pre-comp. If it took more than a few minutes to create the Rotobrushed ball layer, pre-compose, then use the Composition menu to  Pre-Render the layer. This will add the Roto-pre-comp to the Render Que, then render a lossless with alpha movie and replace the pre-comp with the rendered ball. Your AEP file will be more stable, and the file size will be much faster. The final comp with Echo applied will also render faster.

[dv8kiwi]

Thanks, that will definitely fix it. But I am having problems with pre-comp. I have a 2.25 minute clip but precomposing the rotobrush layer is taking hours. I did the actual render of the layer, which is the solution, and it took about an hour.. Any idea why precompose is taking so long? And is there anything I can do to track the progress of a precomposition? 

[Rick Gerard]

You probably did not freeze Rotobrush so it had to recalculate. You may also have failed to check the box that says to move all elements. 

[dv8kiwi]

Thanks, yes I did move all elements but didn't freeze. I didn't know about that or how to do it. I'll look it up. RTFM I guess 😄

[dv8kiwi]

Perfect. Got it 🙂