Purpose: Planning highly complex surgeries in virtual reality (VR) provides a user-friendly and natural way to navigate volumetric medical data and can improve the sense of depth and scale. Using ray marching-based volume rendering to display the data has several benefits over traditional mesh-based rendering, such as offering a more accurate and detailed visualization without the need for prior segmentation and meshing. However, volume rendering can be difficult to extend to support multiple intersecting volumes in a scene while maintaining a high enough update rate for a comfortable user experience in VR.

Methods: Upon loading a volume, a rough ad hoc segmentation is performed using a motion-tracked controller. The segmentation is not used to extract a surface mesh and does not need to precisely define the exact surfaces to be rendered, as it only serves to separate the volume into individual sub-volumes, which are rendered in multiple, consecutive volume rendering passes. For each pass, the ray lengths are written into the camera depth buffer at early ray termination and read in subsequent passes to ensure correct occlusion between individual volumes.

Results: We evaluate the performance of the multi-volume renderer using three different use cases and corresponding datasets. We show that the presented approach can avoid dropped frames at the typical update rate of 90 frames per second of a desktop-based VR system and, therefore, provide a comfortable user experience even in the presence of more than twenty individual volumes.

Conclusion: Our proof-of-concept implementation shows the feasibility of VR-based surgical planning systems, which require dynamic and direct manipulation of the original volumetric data without sacrificing rendering performance and user experience.

Keywords: Multi-volume rendering; Surgical planning; Virtual reality.

© 2025. The Author(s).

目的： 在虚拟现实（VR）中规划复杂的手术提供了一种用户友好的和自然的方式来导航体积医学数据，并且可以改善深度感和规模感。使用基于光线追踪的体渲染来显示数据，相比传统的网格基渲染有许多优点，例如提供了更准确和详细的可视化而无需事先分割和建模。然而，体渲染在支持场景中多个相交体积的同时保持足够高的更新率以提供舒适的VR用户体验方面可能会比较困难。

方法： 加载一个体积后，使用运动跟踪控制器进行粗略的手动分段处理。这种分割不用于提取表面网格，并且不需要精确定义要渲染的表面，因为它仅用于将体积分成单独的子体，在多个连续的体渲染通过中分别渲染这些子体。对于每个通过，光线长度在早期光线终止时写入相机深度缓冲区，并在后续通过中读取以确保各个体积之间的正确遮挡。

结果： 我们使用三个不同的用例和相应的数据集评估了多体积渲染器的性能。我们展示了所提出的方法可以在桌面VR系统的典型更新率为90帧每秒的情况下避免丢帧，因此即使在存在超过二十个独立体的情况中也能提供舒适的用户体验。

结论： 我们的概念验证实现表明，在不牺牲渲染性能和用户体验的前提下，基于VR的手术规划系统是可行的。