1. An image processing apparatus comprising: a calculator configured to calculate a correlation between a normal distribution of an object vertex corresponding to a first tile to be rendered and a light radiation direction of a first virtual point light (VPL) sampled in a three-dimensional (3D) space, based on a first vector representing a normal direction of the object vertex, and a second vector corresponding to a normal vector of the first VPL; and a determiner configured to determine the first VPL to be an indirect light source to be used to render the first tile in response to the correlation being greater than or equal to a first threshold value, the first VPL having a normal vector of which a dot product with the second vector is greater than or equal to a second threshold value, among VPLs sampled in the 3D space.