1. An image processing apparatus, comprising: a storage processor configured to store a lookup table (LUT) including information on corresponding relationships between an occlusion vector of at least one point of a 3-dimensional (3D) object and a spherical harmonics (SH) coefficient; a rendering processor configured to determine a first SH coefficient using the LUT and to determine a pixel value of a first point using the determined first SH coefficient; and a computation processor comprising; an LUT update processor configured to update the LUT based on the first SH coefficient; and an SH coefficient computation processor configured to compute the first SH coefficient by projecting an occlusion map to at least one SH basis.