The present invention relates to a method and a device for visualizing surface-like structures in volumetric data sets, including defining local coordinate systems at sample points of the volumetric data set, transforming external parameters from a global coordinate system into the local coordinate systems, calculating the gradient vector components (Gai, Gbi, Gci) within the local coordinate systems of the sample points, and using the gradient vector components (Gai, Gbi, Gci) for calculating a surface normal at a given position of the volumetric data set, where the surface normal is important for conventional illumination models such as the Blinn-Phong shading model, preferably, the present invention is also calculating the external parameters from the global coordinate system at the given position by using the transformed external parameters of the local coordinate systems of the sample points, where the shading or illumination at the given position is then done by using a conventional illumination model, thereby using the calculated surface normal at the given position and the calculated external parameters at the given position.