First Steps in Hardware Two-Level Volume Rendering

We describe first steps toward implementing two-level volume rendering (abbreviated as 2lVR) on consumer PC graphics hardware. Two-level volume rendering allows to combine local per-object rendering modes, like direct volume rendering (DVR) and maximum intensity projection (MIP), with a global compositing mode for combining the contributions of different objects embedded in a segmented volume data set. In this way, the rendering mode most suitable to a specific kind of object can be used, e.g., MIP for the skin and DVR for the bones of a medical data set. The original implementation of 2lVR was done in the context of a fast and flexible software volume renderer, the RTVR library. In this paper, however, we present first steps toward achieving the flexibility of 2lVR in a volume renderer exploiting texture-mapping hardware, which will enable fast high-quality two-level volume rendering at high resolutions in the future.