I have a 3D volume and I need to set some parts of it to zero.
The problem is that I don't know how to refer to the parts I want. I know the shape of the area I want to crop, but I need that area revolved around the Z axis.
A picture's worth a thousand words:
The image shows the cross section of a 3D matrix in the XZ plane, in the middle is the Z axis. The area I want to select (or set to zero) in the volume is the red area, revolved around the green axis, the Z axis.
I'd rather have a solution that doesn't have a very big memory dependency (such as using meshgrid would) as these matrices can get quite big. Else, a meshgrid solution with cylindrical coordinates wouldn't be too difficult to make, as @Luis suggests.
How can I select this area?