We present an efficient raycasting algorithm for rendering Volumetric Depth Images (VDIs), and we show how it can be used in a remote visualization setting with VDIs generated and streamed from a remote server. VDIs are compact view-dependent volume representations that enable interactive visualization of large volumes at high frame rates by decoupling viewpoint changes from expensive rendering calculations. However, current rendering approaches for VDIs struggle with achieving interactive frame rates at high image resolutions. Here, we exploit the properties of perspective projection to simplify intersections of rays with the view-dependent frustums in a VDI and leverage spatial smoothness in the volume data to minimize memory accesses. Benchmarks show that responsive frame rates can be achieved close to the viewpoint of generation for HD display resolutions, providing high-fidelity approximate renderings of Gigabyte-sized volumes. We also propose a method to subsample the VDI for preview rendering, maintaining high frame rates even for large viewpoint deviations. We provide our implementation as an extension of an established open-source visualization library.

翻译：我们提出了一种高效的光线投射算法来渲染体深度图(VDIs)，并展示了在远程可视化场景中如何利用远程服务器生成并流式传输的VDI。VDI是一种紧凑的视角相关体表示方法，通过将视角变化与昂贵的渲染计算解耦，支持大体积数据的高帧率交互式可视化。然而，当前VDI的渲染方法难以在高图像分辨率下实现交互帧率。本研究利用透视投影的特性来简化光线与VDI中视角相关视锥体的相交计算，并利用体数据中的空间平滑性来最小化内存访问。基准测试表明，在HD显示分辨率下，生成视点附近可实现响应式帧率，从而为吉字节级体数据提供高保真近似渲染。我们还提出了一种用于预览渲染的VDI子采样方法，即使在大视角偏移下也能保持高帧率。我们将该实现作为成熟开源可视化库的扩展功能提供。