Preview hell - mask flickers on and off

Hi there,

Fusion drives me nuts! Or is it just me?

I have a shot where I have to remove a piece of metal underneath a car. I draw a polyline around it, track the area using a Planar Tracker, attach the Polyline to the foreground input, operation mode to corner pin (set my points to whole screen) and set the output to FG only.
Sometimes the mask stays opaque, sometimes it just flickers and starts to disappear from the right side.

I can cache the mask, I can cache the tracker but nothing helps!

What am I do wrong?

Without seeing the footage and seeing the track it's hard to tell.
I have experienced similar situations in the past, and usually this was when the size of the part that I tracked and the thing I put on top of it didn't quite match up.
Since you're saying you set the points to the whole screen it could be a part of it.
Just for the fun of it: try using a solid color background tool as the foreground input and then set the corner pin to something very close to the part you tracked and see if this makes a difference.

** update **

Upon reading your post again, it seems that you pipe your mask straight into the foreground input.
This will indeed cause trouble most likely, since masks aren't really images in Fusion as such.
The foreground input is meant for actual images. You can mask those images with a polyline of course, but feeding a mask into an image input is seldom recommended.

THAT DID THE JOB! Thank you
I just piped the Polygon into a bitmap node and everything works perfectly again. Thank you so much for the great tip!

Sorry but the problem appears again.
The outputs of my Planar Tracker nodes (FG only) sometimes just disappear for whatever reasons. The only chance to get them back is to toggle "Clipping mode" to Frame or Domain multiple times or just toggle "Enable" on and off.

Bildschirmfoto 2020-02-16 um 20.34.34.png (80.31 KiB) Viewed 1506 times

What is wrong?

Maybe you misunderstood me the last time, but piping a polyline into a bitmap node doesn't actually make it an image, since the bitmap node is still a mask (single channel black to white). You need to mask for example a Background tool and feed THAT into your foreground of the planar tracker to begin with.

You're absolutely right! My mistake.
You saved me, thanks

And it happens again

Bildschirmfoto 2020-02-24 um 20.32.56.png (50.36 KiB) Viewed 1403 times

When I play back the DACH_MERGE node where two planar-rotos come together, the mask flickers and is cropped in between and left and right.
Whan do I wrong?

Without seeing your footage and your tracks it's hard to tell. It could be that the tracks weren't good enough, so the images go wonky no matter what you do. So we really need more info than this.
Your flow is correct as far as I can tell, so it's either a bug, a bad track or user error. But you need to provide a little more info for us to be able to help you.

Without seeing your footage and your tracks it's hard to tell. It could be that the tracks weren't good enough, so the images go wonky no matter what you do. So we really need more info than this.
Your flow is correct as far as I can tell, so it's either a bug, a bad track or user error. But you need to provide a little more info for us to be able to help you.

Unfortunately I cannot post anything here because it's an ad and the footage is disclosed.

But I made a quick project where the issue occurs too.
You can download it here: https://f.io/EF0LidY1
The file tracking_failure.mov describes the problem.