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Instant relighting of volumetric data

During the visualization of volume data, changing the illumination condition provides us a way to reveal and emphasize the local structures within the volume. However, volume rendering with real-time lighting control is hard. It requires the re-computation of the amount of light received at each voxel after the attenuation, whenever the user changes the lighting condition. In this paper, we describe an image-based approach to relight (change the illumination) the volume in real time. The nature of image-based rendering decouples the rendering time complexity from the resolution of volume data. Hence, real-time relighting of volumetric data is possible even shadow (attenuation) is taken into account. Instead of re-computing all the lighting information, we pre-render (sample) a set of images (reference images) of the volumetric data under different illumination conditions. With these reference images, we are able to relight the volume under desired lighting condition by interpolating and superimposing pixel values. The relighting can be performed on ordinary PCs.