While you can use videomapping technics at layer’s level, you can do the same at canvas level. Working at this level may be very efficient, so you could separate your content (layer’s level) and how it is projected (canvas level).
 All the settings describe in this article are in the Output popup.

Per Output Mapping

A canvas is represented by one or more outputs. For each output, you can change the mapping by clicking on the gear icon :

As you can see, there are also options to tweak the color. The first option allows you to either display all the colors, or only the alpha as a grayscaled map. This option is especially interesting for color keyer (such as Blackmagic ATEM ones) :

The following options allows you to adjust the colorimetry of your output, which can be useful if your projectors are slightly different :

Last option is the curved one, to warp your output if your surface is not flat :

Canvas Mapping

By clicking the Mapping button, you can access to videomapping at canvas level :

In the first two tabs, Slice and Mapping, you can obviously adjust the slice and the mapping for the whole canvas, but also use a warping-grid.
 Combined with soft-edge (see this article : Soft-edge ), this can be practical for big building projection so all your content is correctly mapped, whatever you are doing with the layers.
 To learn more about warping, please refer to the dedicated article : Mapping


The tab Masks works in the same fashion as masks for layers :

Please note that such canvas masks are rendered after the canvas mapping.
 For more information about masks, please refer to the dedicated article : Masks


The tab Surfaces is all about defining mapping presets, so you could reuse them in your ptoject :

For more information about surfaces, please refer to the dedicated article : Surfaces