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14.9. Point Rendering 695
a surface element. A surfel is also a point-based primitive. An octree is
used to store the sampled surfels (position, normal, filtered texels). During
rendering, the surfels are projected onto the screen, and subsequently, a
visibility splatting algorithm is used to fill in any holes created.
Bærentzen [53] discusses using point-based models as substitutes for
objects in the distance. When triangles in a model each cover a pixel or less,
points can be faster to render as there is no triangle setup or interpolation.
Botsch et al. [130] use deferred shading techniques along with an elliptical
weighted average (EWA) filter to efficiently provide high quality.
Further Reading and Resources
The Inventor Mentor [1343] discusses the way scene graphs operate.
Abrash’s (now free) book [1] offers a thorough treatment of the use of
polygon-based BSP trees and their application in games such as Doom and
Quake. A thorough treatment of BSP trees and their history is also given by
James [597]. Though the focus is collision detection, Ericson’s book [315]
has relevant material about forming and using various space subdivision
schemes. A number of different view frustum culling optimizations (and
their combinations) are presented by Assarsson and M¨oller [48].
There is a wealth of literature about occlusion culling. Two good start-
ing places for early work on algorithms are the visibility surveys by Cohen-
Or et al. [185] and Durand [285]. Aila and Miettinen [4] describe the
architecture of a commercial, state-of-the-art culling system. An excellent
resource for information on levels of detail is the book Level of Detail for
3D Graphics by Luebke et al. [801]. A recent overview of research in the
area of rendering massive models is presented by Dietrich et al. [255].
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