Browse Prior Art Database

Object Fuzz in Computer Graphics Systems

IP.com Disclosure Number: IPCOM000107960D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Lucas, B: AUTHOR

Abstract

Disclosed is a method, called object fuzz, applicable to computer graphics systems, of resolving the ambiguity as to which object should be visible that results when objects of different dimensionalities are defined to be coincident.

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Object Fuzz in Computer Graphics Systems

       Disclosed is a method, called object fuzz, applicable to
computer graphics systems, of resolving the ambiguity as to which
object should be visible that results when objects of different
dimensionalities are defined to be coincident.

      Consider a scene to be rendered by a computer graphics system
that consists of a planar surface with a line that is coincident with
the surface.  A standard z-buffered rendering system renders such a
scene as follows: associated with every pixel in the frame buffer is
not only a red, green, and blue value, but also a z-value
representing the distance from the camera of the closest object
visible at that pixel.  Rendering a scene consists of processing the
objects one by one, and for each object determining what pixels it
affects and the distance from the camera to the object at each of the
pixels that it affects.  A comparison is made for each pixel affected
between the distance from the camera to that object at that pixel and
the current z-value; if the object is closer, its color at that pixel
overrides the current color and z-value stored in the frame buffer
for that pixel.

      Unfortunately, if two objects that are intended to be
coincident are compared pixel-by-pixel for their distance from the
camera (z- value), it will be seen that sometimes one object appears
closer and sometimes the other object appears closer.  This is
because of the finite precision of computer arithmetic.  Because the
two coincident objects' z-values are, in effect, defined by two
different formulas (for example, the...