The shooting and bouncing rays (SBR) method in computational electromagnetics was first developed for computation of radar cross section (RCS).
The first step in the SBR method is to use geometrical optics (GO, ray-tracing) for computing equivalent currents, either on metallic structures or on an exit aperture.
The scattered field is thereafter computed by integrating these currents using physical optics (PO), by the Kirchhoff's diffraction formula.
on a perfect electrical conductor (PEC) is related to the incident magnetic field
[2] Since the approximation described above assumes that the radius of curvature is large compared to the wavelength, the diffraction from edges needs to be handled separately.