This mask is a Solid positioned with a
2D Placement. It has feather parameters that can operate on the four sides of the mask.
This mask can be used to create soft-edges when doing multiple video-projectors overlap. In this case, think to put the
Gamma parameter to a realistic value such as 2,2 for example.
Note that similar and more evolved masks can be obtained by combining a
Layer mask with a
Uniform.