Masking Regions of the Viewer

If you want to mask the effect of the Text operation, the easiest way is to use a Roto node connected to the mask input:

1.

After connecting the Roto node, draw the mask in the Viewer. You can use any channel, but Roto defaults to the alpha channel.

2.

Select the mask channel from the Text node's mask dropdown menu, in this case rgba.alpha.

3.

To invert the mask as shown, check invert.

Standard masking.	Inverted masking.