1. A method implemented by a computing device, the method comprising: rendering a two-dimensional (2D) image that includes first and second sets of image objects in which a distance of the second set of image object to a light source is less than a distance of the first set of image objects to the light source, the rendering including: assigning one or more values to the first set of image objects to indicate a level of light for each image object in the first set of objects; calculating one or more values to indicate a level of light for the second set of image objects based, at least in part, on the one or more values assigned to the first set of image objects; and rendering the 2D image to include the first and second sets of image objects.