The present invention is related to a method of digitally compensating distortions of rays of a light beam in tomography- based additive manufacturing, wherein said tomography-based additive manufacturing involves projecting light patterns from multiple angles into a container (22) comprising photoresponsive material, by simulating the path of the light rays through the container (22) and the photoresponsive material; and digitally compensating the light projections based on the simulated path of the light rays, so as to obtain modified light projections. The present invention is also related to a method and apparatus for preparing an object (24) in tomography-based additive manufacturing, employing said distortion compensation method.