Real-Time Rendering, Third Edition, 3rd Edition

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670 14. Acceleration Algorithms

same plate, where the white rectangles are the portals and the mirror is

red. Note that it is only the objects inside any of the frustums that are

rendered.

There are many other uses for portals. Mirror reflections can be cre-

ated efficiently by transforming the viewer when the contents of a cell seen

through a portal are about to be rendered. That is, if the viewer looks at

a portal, then the viewer’s position and direction can be reflected in the

plane of that portal (see Section 9.3.1). Other transformations can be used

to create other effects, such as simple refractions.

14.5 Detail Culling

Detail culling is a technique that sacrifices quality for speed. The rationale

for detail culling is that small details in