In the integral equations that arise in potential theory it is necessary to evaluate the solid angle subtended at a point r on the surface by each element of area of the surface. If the surface is approximated by a set of triangles then those triangles that contain the point r as a vertex require special attention, and this is referred to as the "auto solid angle" problem. We give an exact formula for evaluating the auto solid angle, and a prescription for apportioning it amongst the vertices of these triangles.
"Computation of the return current in encephalography: the auto solid angle", Proc. SPIE 1351, Digital Image Synthesis and Inverse Optics, (1 November 1990); doi: 10.1117/12.23650; https://doi.org/10.1117/12.23650