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 mask Turn any 2D generator into a mask Read More with a Radial Gradient This generator creates a linear gradient (by default from black to white), in a circle from the center to the edges of the layer Read More .
Related masks in 3D space are: Sphere Mask with a sphere shape Read More and Cylinder Mask with a cylinder shape Read More .
If you want to create a perfectly round radial mask, put Smode in pixel units and there you go :