Welfenlab - Leibniz 
                        Universitšt Hannover Welfenlab Leibniz Universitšt Hannover

Illustrative Volume Rendering with Lit Sphere Mapping using additional Segment Information

Johannes Wahle, Leibniz Universität Hannover, Studienarbeit
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Ray-Casting is a widespread method to visualize volumetric data, e.g. medical data. The basic idea is to follow an imaginary ray from the point of view through the volume data set. For each pixel in the resulting image one ray is send to determine the color of that pixel. This technique is thus - not only by name - closely related to the concepts stemming from the field of Ray Tracing.

Besides a preferably realistic view with established light models like Goraud- or Phong-Shading, there also exist procedures with focus on illustration. One of these methods following a rather artistic approach is Lit Sphere Shading. Sloan et al. introduced this concept in 2001, where they proposed a method based on shading techniques used by illustrators. The artists use shading drafts in the form of a projected hemisphere, to give their image a certain style of drawing. In the process the color shading is applied to a disc that contains all possible normal directions as color information.

One Problem of image creation via an intensity value based transfer function is, is the fact that different forms of tissue (due to the utilized data source e.g. CT, MRT, PET, ...) may yield similar intensity values. In the course of this work different approaches to incorporate existing segment information shall be examined, compared and integrated into YaDiV, the volume visualization platform developed in the institute for Graphical Data Processing.

Kontakt: Karl-Ingo Friese

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