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Jim Blinn's Corner: Notation, Notation, Notation by Jim Blinn

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Chapter Six

Calculating Screen Coverage

May 1996

u06-01-9781558608603

When drawing a 3D object, it is sometimes useful to find a rectangle on the screen that completely encloses the object. This can be used to minimize screen-update and z buffer–clear regions. If the entire object is visible within the screen boundaries, this calculation is easy. You just find the minimum and maximum x and y screen coordinates. If the object extends outside the screen boundaries in one or more coordinates, this calculation is a little trickier. Simply extending the enclosing boundaries to the entire screen dimensions is overly conservative. This chapter describes a way to determine a ...

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