4.2/4.3 compositor : "passepartout" or show render boundaries? (change from 4.0)

Question

In the 4.2 or 4.3 compositor (backdrop enabled), I create:

Image > Scale:Render Size:* > Viewer

When I select either "Fit" or "Crop" I see the full image on the backdrop, different sizes. It is surrounded by a white box if Viewer has been selected. There seems to be no indication of the (scene) render boundaries. If I do a full render, Image Editor : Render Result shows the actual output region. Toggling Fit/Crop then updates the Image Editor, but not the backdrop.

In 4.0, the scaled image appeared inside the scene render boundaries. This was much more convenient for making adjustments.

Maybe I'm missing something? I think I once had to change a setting due to noise on the compositor background - don't know where it was or if this is related.

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[Probably unrelated: A numerical Scale node before Scale:Render Size used to work in 4.0, now it seems to be overridden. But a preceding Translate works  -just duplicates the controls on Scale:Render Size.]

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Reply
  • Martin Bergwerf replied

    HI techworker1 ,

    I don't use the Compositor a lot (yet), but I think some of those changes might have to do with what is mentioned here: https://developer.blender.org/docs/release_notes/4.2/compositor/#breaking-changes 


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  • techworker1 replied

    spikeyxxx I'm sure you are correct (it is difficult to understand all the details).

    It seems that in the "new" compositor, Viewer is no longer a preview of what will appear in Composite. A pity, since it was a very convenient "trick".

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  • techworker1 replied

    I had always been creating a scene with Film:Transparent, then using Alpha Over to place it on top of a background image. That is simple and intuitive, but no longer seems to be the most efficient method.

    A slightly awkward alternative seems to avoid the difficulties.

    • Create scene with Film:Transparent
    • Put the Scene/View Layer into the TOP input of Mix (this sets "output size", per the documentation)
    • Invert the View Layer's Alpha - use it as the Mix factor.
    • Put the background image into the BOTTOM input of Mix
    • Uncheck "Use Alpha" on Viewer/Composite


    Now the Viewer/backdrop shows the scene/render bounds on the result. The background image can be translated/scaled as needed, and the Viewer/backdrop shows a preview of what will be rendered. Background does not need to be cropped separately.

    Sometimes an old dog must learn new tricks.

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