A radial mask is parameterized by a 2D ellipse and enables to define a radial selection.
Note that similar and more evolved masks can be obtained by combining a Layer maskTurn any 2D generator into a maskRead More with a Radial GradientThis generator creates a linear gradient (by default from black to white), in a circle from the center to the edges of the layerRead More.
Related masks in 3D space are: SphereMask with a sphere shapeRead More and CylinderMask with a cylinder shapeRead More.
If you want to create a perfectly round radial mask, put Smode in pixel units and there you go :
Ellipse (Ellipse) : Ellipse defining the selection