The Poisson integral formula computes the value of a harmonic function in the interior of a disk as a weighted average of the function's values on the bounding circle. The Poisson kernel gives the weights assigned to the boundary data based on the (polar) coordinates of the point in the interior where the value of the function is to be computed. You can choose a point in the disk at which to evaluate the Poisson kernel along with its graph in either two or three dimensions.