How to get a imported Camera to work in perspective View

Hey Folks!

I am importing a Camera from Syntheyes into the GMask tracer. Works like a charme, can hook up my roto to the trackers from Syntheyes. But, when I switch to the F8 View to Key something with the tracer, my Roto is not seen through the imported Camera, but rather through the default Camera. Any idea how to force the object View (f8) into respecting the new Camera?

Many thanks,


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The Object View (F8) doesn’t update live when you select a different object in the Schematic / Manager. Could it be that you simply didn’t select the new Camera first? Try to select the new Camera and then reselect the Object view.

If that was the problem, you may want to give Alt-F8 a try. That version of the Object view will dynamically update based on the object selection.

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Hey Warren!

Thanks for the update. However, it doesn’t really solve the issue. For the Tracer Keyer to work, i need to have that particular GMask selected before entering the F8 View. If I select the Camera, i don’t have an active Gmask. What i am trying to achieve is the following: Have a Matchmove imported into the Gmask Tracer. Have a Gmask positioned in Space, “filmed” by that imported Camera and then apply a Tracer Keyer to that GMask. I’ll upload a video to illustrate what i am doing.

Many thanks,


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Go to the Mask submenu of the GMask object and change the Camera selection from Auto Frame to the desired Camera there (below the Blur setting).

Does that help?



That’s it! Thanks so much, Fred!!!


I feel foolish asking. BUT…
I have a camera. I have the gmask tracer set in space. I have selected the camera I want to use. The tracer looks lovely in F8. How do I get that matte out into F4 or as an output to use? I just see the shape of the gmask tracer I drew. There is a step I am missing some where. Thanks for any help on this.

Should I start a new thread for this? @ChrZap @fredwarren I could use your help.

Hi Brian,

Firstly, this all depends whether you created your mask in the Gmask Tracer node or the Action node.

If you used the Gmask Tracer node, you would need a background input as a source, and you draw your gmask tracker on top of that. Looking at the result view, you should see the black and white output of your Gmask. If you only see your background and not mask in the result view, press the 1 keystroke to toggle the outputs and you should see your black and white matte.

If you are using Action to create the Gmask and you want to output the matte from Action then the workflow will be different. For example, You have drawn your gmask in the F8 view as described. Normally Gmasks are part of the composite to cut holes in 3D objects and not the final outcome. But you can still change that with the following settings. Switch to the result view with F4 and go to the Render Outputs menu. With the viewport selected, switch the Render Pass Output Selections from COMP to MATTE. (remember to enable MATTE to get an output from the Action node). You should see a black frame with your mask shape but not white element to the mask. To force the mask into the output, change the GMASK setting from USE GMASK to GMASK ONLY. This renders the colour of the mask. You should now see the black and white matte you created and you can render this output.

Hope this helps

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Thanks for the explanation @La_Flame. I feel bad you spent time writing that out. My apologies for not being more clear.

I am looking at how to get the gmask tracer with an imported camera and a mask set in 3d space to use the tracer keying matte to work properly.

I can see the mask gui placed correctly when I set the camera box to the camera I am using. I can see the tracer front and back pickers make a matte for what I would like to be contained by the gmask. But when I check the output result in F4 it looks like the result is an offset BG image inside of the mask from the default camera.

I can’t figure out if it is a bug in 2021.2.1, an order of operations issue. ie. you have to draw the mask in F8 after you set the camera box to the desired camera in the mask node and the output settings, or if the tracers don’t like cameras produced outside of flame.

Any help would be great. There are obviously many many work around for this. But I am now fixated on making this work.

Thanks again Grant.

Maybe this will help illustrate my issue.

F8 looks great.I can see my matte and the keying that I need inside of the matte.

F4 is not showing a cut out of the F8 as you would expect.
I scaled the matte up 300% and I can see the keyed image off set from the original position.

Like this.

It does. But I have not. It is a gmask tracer node. I don’t think you can play with the UVs there.

Hi @ihatebrianwilliams

I haven’t had a chance to dig into this in more detail but when you look through the F8 view, you are looking at the media input that the Gmask is assigned to (see the number on the node matches the media list) and this ignores any other movement in the main 3D space. You are focusing the mask on the footage and not a 3D comp. This is why when you bring in an animated camera (any kind), the gmask is being offset by the movement of the camera.

My suggestion is to load your footage into the Gmask Tracer with the animated camera and NOT use the F8 object view. Draw your mask in the result view and if it is what I am thinking, it should stick as expected. Then the tracers should work.

Give that a try and let me know.