1. A method for two-dimensional representation of an object using volume rendering, the method comprising: providing a representation of the object, in which values of a quantity characterizing the object are given at spatial points of the object; calculating, with a volume rendering technique without an illumination model or with a local illumination model, a blended color value for representation as pixels on a screen; simulating a ray emanating from a surface of the object for calculating the effect of shadows or the effect of ambient occlusion; calculating, a value for the effect of shadows or a value for the effect of ambient occlusion as a function of the ray; and combining the blended color value with the calculated value in order to obtain a blended color value that takes into account the effect of shadows or ambient occlusion.