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

摘要

This paper presents a real-time ray casting rendering algorithm for "volume clipping plane" as an extension of the conventional ray casting technique. For each viewing direction a (moderate) pre-processing step is performed: the ray traverses the entire volume data (no early ray termination). Its intensity and opacity contributions are divided into several segments which are then sorted and stored by depth. At each sampling position along a segment, accumulated transparency and color are stored at a moderate memory overhead. For visualizing real-time volume clipping, only relevant segment contributions (maximum two) at the location of the clipping plane are considered, thus reducing the calculation to meet real-time requirements. Compared with the previous work that involves time-consuming re-clipping, re-traversing and re-shading, the proposed method achieves quality identical to ray casting at real-time speed. The performance is independent of the volume resolution arid/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., in medical visualization and material testing applications.