Classical volume rendering is computed by casting a bundle of parallel rays from a flat viewing plane onto the volume data set, and produces as such a spatially limited view of the objects in the data set. The method described in this paper is able to generate an overall planar view of an object that is topologically compatible with the sphere, by firing rays from a nearby surrounding surface and by unfolding this surface in a 2D plane, without introducing major distortions. It has been devised to facilitate the interpretation of the cerebral cortex. An initial surface consisting of two hemi-ellipsoids, one to cover the top and another one to surround the bottom of the brain, is interactively defined and deformed via a deformable model approach towards a dilated version of the cortical surface of the brain. During deformation, the nodes on the surface are continuously redistributed, to maintain a near homothetic mapping with the plane. Once the surface has converged to the dilated brain surface, rays are casted from the nodes, according to the normal of the surface at the node. The shading result, computed at the intersection of the rays with the original brain surface, is mapped via the near homothetic mapping to the plane. With this approach sulci can be followed in their entirety, so that it is much easier to derive their spatial relationship and to recognize them.