Height-based deformation and ray supersampling for colon unfolding

Virtual colon unfolding is a method to produce an unfold image from volume data. The previous method generates only 2D images casting rays from a central path toward the colon surface and maps the color value into 2D regular grid. However, since rays cannot be reached behind folds, some regions are not represented on the final image. In order to represent those areas adequately, we exploit a height field derived from ray casting. Since the problematic areas have high gradient in comparison to neighboring regions, the differences of height value in those areas are relatively large. Therefore, we can find problematic areas using the height field. To visualize those areas, we exploit supersampling method that casts additional rays toward perpendicular direction of the original rays. Experimental results show that our method represents colon folds accurately.