You can place composite shots inside other composite shots. This is called embedding.
Embedded composite shots can be 2D, 3D or 3D Unrolled. For detailed information on each of these layer states and how to switch between them, please read Working with layers.
Embedding has many uses.
If your composite shot has lots of layers and is becoming unwieldy, it can be useful to split the overall shot into several smaller composite shots.
For example, if you are working on a green screen shot and have 5 layers making up your background, it might be useful to have those 5 layers in their own composite shot. That way, once you're finished working on the background, it'll only take up a single layer in your main composite.
If you have been working in 3D, you can retain full 3D interactivity, even when using embedded composite shots, by setting its layer type to 3D Unrolled. For more information see Working with layers.
Embedding a composite shot can be a quick way to grade everything inside it in one go.
By applying your grading to the embedded composite shot itself, rather than to the individual layers inside it, all the layers will receive the same grade.
You can also grade a composite shot that has been placed on the Editor sequence, but this will not give you access to animation features.
You can also grade multiple layers at once using Grade layers.
Embedded composite shots that are set to 2D or 3D layer type are 'flattened', so that all the layers inside the composite shot are changed into a single layer.
Let's say you want to create a 3D particle effect in HitFilm and then composite it onto a computer monitor in your movie. Embedding a 3D composite shot makes this easy: you create the 3D particle effect inside the composite shot, then use the composite shot as a flattened 3D layer to display correctly on the computer monitor.
An embedded composite shot with its layer type set to 2D or 3D is essentially the same as exporting the composite shot and importing the rendered video file - except that you don't have to wait for anything to export, and you can re-open the composite shot at any point to make adjustments on the fly.
If you want to retain the full 3D positioning from the comp you should set it to 3D unrolled.
RECAP Embedding composite shots opens up creative possibilities and provides a useful way to keep projects tidy and organized.