Roto Brush giving different result when rendered.

[King Doom]

Hi there,

I am using Adobe After Effects CC 2015.3, I am doing a project where I need to place a 3D Object in the scene, but there is a person moving in front of the camera, which is an issue, so either I could Key it out or make it a part of the video. So I decided to use masking and keep the person in the scene, but the the person will be moving in front of the 3D Object. I duplicated the footage and used Roto Brush method to Remove all the Background and keep the Person and adjusted it frame by frame so that he is in front of the 3D object but still distinct and looks pretty good. But there is a Problem, during the Composition every thing looks good, the person moving is perfectly keyed out and the scene is good to Render, But when I render using AE Best Settings and Lossless method, it shows some background (which should have been keyed out or Invisible) when the person comes in front of the 3D object.

I have even tried Rendering the whole Composition using AE "Lossless with Alpha" method but still getting the same result. Now what should I do remove those parts which do not exist when I watch in the AE Preview Tab, but somehow show in the Rendered video. I am using an Element 3D Plugin from VideoCopilot.net to insert the 3D Object.

I am using Windows 10-64 bit with an AMD Radeon HD Graphics 7600 M, probably not the best of the machine for AE, but it has no trouble while performing other AE functions.

I also tested by rendering only the RotoScoped footage in different setting including Lossless Tiff, but still getting a messy result when rendering compared what it shows in the preview.

Message was edited by: Arslan Ali

[Rick Gerard · Accepted solution]

My first guess is improper technique and failing to study up on how to use Rotobrush. I'm suspecting you did not freeze the Roto when you're finished.

Use the search help field to find help files and tutorials on using Roto brush.  You will find it at the top right corner of AE.

[Jeremy24242392rve3]

i know this thread is from 2016 but damn this response was back-handed as hell lol

[azzans69868199]

Hahaha right! How petty & unhelpful

[King Doom]

Thanks Rick Gerard, I was trying Roto Brush for the first time and didn't know it required FREEZE in the end to apply rotoscope to the footage.

It is much better now and the render does not look much different from the in-ae preview. But there are still some issues in the whole Roto Brush Tool, for example if Un-Freeze and change some values like Feather or Reduce Chatter, it messes the whole rotoscope and I have to do it all over again or use the last saved file to resume the previous work.

Anyways I will keep looking at adobe Help site to learn more about this tool.

Regards.

[Roei Tzoref]

just to make things clear - you should always freeze. it's a recommendation because rotobrush is a resource hog and will take a lot of memory and it also makes sure that the frames a saved in the project file so you won't get trouble when rendering and see a difference between what was previewed in after effects. 

as for feather and reduce chatter - these settings are applied after the propagation process (the only thing that is freezed) so what ever happened with your roto brush matte is not specifically related to freezing or un-freezing.

read all the articles and practice. it is quite long but it will save you time and frustration.

Roto Brush and Refine Matte in After Effects

After Effects Roto Brush, Refine Edge, and Refine Matte