Triple Depth Culling

Figure 1: Triple Depth Culling introduces controllable early depth testing for highly complex scenes with arbitrary shader operations. Virtual worlds feature increasing geometric and shading complexi-ties, resulting in a constant need for effective solutions to avoid ren-dering objects invisible for the viewer. This observation is partic-ularly true in the context of real-time rendering of highly occluded environments such as urban areas, landscapes or indoor scenes. This problem has been intensively researched in the past decades, resulting in numerous optimizations building upon the well-known Z-buffer technique. Among them, extensions of graphics hardware such as early Z-culling [Morein 2000] efficiently avoid shading most of invisible fragments. However, this technique is not applica-ble when the fragment shader discards fragments or modifies their depth value, or if alpha testing is enabled [nVidia 2008]. We introduce Triple Depth culling for fast and controllable per-pixel visibility at the fragment shading stage using multiple dept