Real-Time Ray Casting Rendering of Volume Clipping in Medical Visualization

This paper presents a real-time ray casting rendering algorithm for"volume clipping plane" as an extension of the conventional raycasting technique. For each viewing direction a (moderate) pre-processingstep is performed: the ray traverses the entire volume data (no earlyray termination). Its intensity and opacity contributions are dividedinto several segments which are then sorted and stored by depth. At eachsampling position along a segment, accumulated transparency and colorare stored at a moderate memory overhead. For visualizing real-timevolume clipping, only relevant segment contributions (maximum two) atthe location of the clipping plane are considered, thus reducing thecalculation to meet real-time requirements. Compared with the previouswork that involves time-consuming re-clipping, re-traversing andre-shading, the proposed method achieves quality identical to ray casting atreal-time speed. The performance is independent of the volume resolutionand/or the number of clipping planes along a given viewing direction.Therefore it is suitable for real-time "internal volume inspections",involving one or several cutting planes, typically applied e.g., inmedical visualization and material testing applications.