title =      "Visibility Computations for Real-Time Rendering in General
               3D Environments",
  author =     "Oliver Mattausch",
  year =       "2010",
  abstract =   "Visibility computations are essential operations in computer
               graphics, which are required for rendering acceleration in
               the form of visibility culling, as well as for computing
               realistic lighting. Visibility culling, which is the main
               focus of this thesis, aims to provide output sensitivity by
               sending only visible primitives to the hardware. Regardless
               of the rapid development of graphics hardware, it is of
               crucial importance for many applications like game
               development or architectural design, as the demands on the
               hardware regarding scene complexity increase accordingly.
               Solving the visibility problem has been an important
               research topic for many years, and countless methods have
               been proposed. Interestingly, there are still open research
               problems up to this day, and many algorithms are either
               impractical or only usable for specific scene
               configurations, preventing their widespread use. Visibility
               culling algorithms can be separated into algorithms for
               visibility preprocessing and online occlusion culling.
               Visibility computations are also required to solve complex
               lighting interactions in the scene, ranging from soft and
               hard shadows to ambient occlusion and full fledged global
               illumination. It is a big challenge to answer hundreds or
               thousands of visibility queries within a fraction of a
               second in order to reach real-time frame rates, which is one
               goal that we want to achieve in this thesis. The
               contribution of this thesis are four novel algorithms that
               provide solutions for efficient visibility interactions in
               order to achieve high-quality output-sensitive real-time
               rendering, and are general in the sense that they work with
               any kind of 3D scene configuration. First we present two
               methods dealing with the issue of automatically partitioning
               view space and object space into useful entities that are
               optimal for the subsequent visibility computations.
               Amazingly, this problem area was mostly ignored despite its
               importance, and view cells are mostly tweaked by hand in
               practice in order to reach optimal performance - a
               very time consuming task. The first algorithm specifically
               deals with the creation of an optimal view space partition
               into view cells using a cost heuristics and sparse
               visibility sampling. The second algorithm extends this
               approach to optimize both view space subdivision and object
               space subdivision simultaneously. Next we present a
               hierarchical online culling algorithm that eliminates most
               limitations of previous approaches, and is rendering engine
               friendly in the sense that it allows easy integration and
               efficient material sorting. It reduces the main problem of
               previous algorithms - the overhead due to many costly
               state changes and redundant hardware occlusion queries
               - to a minimum, obtaining up to three times speedup
               over previous work. At last we present an ambient occlusion
               algorithm which works in screen space, and show that
               high-quality shading with effectively hundreds of samples
               per pixel is possible in real time for both static and
               dynamic scenes by utilizing temporal coherence to reuse
               samples from previous frames.",
  address =    "Favoritenstrasse 9-11/186, A-1040 Vienna, Austria",
  school =     "Institute of Computer Graphics and Algorithms, Vienna
               University of Technology",
  month =      apr,
  keywords =   "3D rendering, real-time rendering, ambient occlusion,
               visibility, occlusion culling",