1. An image processing apparatus for generating an image of a scene, comprising: a first calculation unit configured to calculate spectral radiance data by performing ray tracing from a viewpoint for each pixel of an image of a scene, based on light source characteristics and object information in the scene; and a generation unit configured to perform either a spatial-based collection of the spectral radiance data or a wavelength-based collection of the spectral radiance data to generate preview data of the image of the scene, during performing of the ray tracing, wherein at least one of the calculation unit or the generation unit is implemented using a processor.