Direct volume rendering apparatus

The invention relates to a direct volume rendering apparatus for volume rendering a three-dimensional image data set. For each primary ray 10 of a plurality of primary rays, which traverse through the three-dimensional image data set and meet a respective pixel of a two-dimensional image in a two-dimensional image plane on which the three-dimensional image data set should be projected, colors and opacities are provided along the primary ray 10. Each primary ray 10 is subdivided into segments I, II, III, IV based on the opacities and/or colors along the respective primary ray 10, wherein, for each segment I, II, III, IV, a segment lighting value in accordance with a predetermined lighting calculation rule is calculated. The colors and segment lighting values are finally projected along the primary rays 10 onto the pixels based on a predetermined projection rule.