1. A method, comprising: pre-computing, by a computing device having a processor, a plurality of coefficients for a given two-dimensional point on which a voxel of a three-dimensional object is projected, based on integer parts of coordinates of surrounding two-dimensional points with respect to the given two-dimensional point, the plurality of coefficients lacking inclusion of the coordinates; storing, by a non-transitory storage device, the plurality of coefficients; and computing, by the computing device during a back-projection operation that forms a reconstructed three-dimensional image, an intensity value at the given two-dimensional point; wherein the computing device computes the intensity value by reading the plurality of coefficients from the non-transitory storage device and combining the plurality of coefficients with the coordinates; wherein the method is performed by a Cone-Beam Computed Tomography system that includes the computing device and the non-transitory storage device.