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Graphic Extend by Non-Manifold Geometric Model

IP.com Disclosure Number: IPCOM000112312D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 6 page(s) / 168K

Publishing Venue

IBM

Related People

Kuriyama, S: AUTHOR [+3]

Abstract

This article describes a concept of a graphics processing method using non-manifold model which makes the computations of clipping, visibility, pickability and hilighting fast. It increases interactively of an graphics application when a lot of graphics data are used. The non-manifold model is used as a graphics extent in the method.

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Graphic Extend by Non-Manifold Geometric Model

      This article describes a concept of a graphics processing
method using non-manifold model which makes the computations of
clipping, visibility, pickability and hilighting fast.  It increases
interactively of an graphics application when a lot of graphics data
are used.  The non-manifold model is used as a graphics extent in the
method.

      Computations of clipping, picking, highlighting and controlling
visibility about graphics primitives are important graphics processes
in an interactive graphics system.  Those computations are getting
heavier as the number of graphics primitives is increased.  There is
a method of using graphics extents to make this process fast.  It is
inefficient to process the graphics primitives such as polylines and
polygons individually.  By grouping the primitives using graphics
extent, the process tests the extent before checking the primitives.
This decreases the number of primitives to be processed [1].

      For example, in the case of the viewing clip in the three
dimensional world coordinate, the extent of the union of the
primitives is computed by traversing the primitives and finding the
maximum and the minimum of the x, y, and z coordinates.  The square
parallelepiped whose diagonal is the line with the maximum
coordinates,(x sub max , y sub max , z sub max ), and the minimum
coordinates, (x sub min , y sub min , z sub min )as the end points.
There are following three cases when the extent is checked in the
clipping process.

       The entire extent is outside of the viewing volume.

        There is a intersection of the extent and the viewing volume.

        The entire extent is inside of the viewing volume.

      Fig. 1 shows the those cases.  When the extent is outside of
the view volume the clipping does not need to be processed for the
primitives and none of the primitives is passed to the next graphic
process.  When there is the intersection, the clipping should be
processed and the processed data should be passed to the next graphic
process.  When the extent is inside of the view volume, the clipping
is not processed and the primitive data are passed to the next
graphic process.  As described above, the number of primitives to be
processed is decreased by using the extent and this leads the entire
graphics process faster.

      Concept

      Graphics extent by non-manifold model - 3D objects represented
by the B-rep are called manifold models.  The 3D models which cannot
be represented by the manifold models, such as an object with the
boundary line owned by more than three planes, are generally called
non-manifold models in CAD [2] One of the advantages of the
non-manifold models is the capability of representing space
partitioning.  The space partitioning structure is represented by
some cells as depicted in Fig. 3.  There are two spaces on the both
sides of the space partitioning p...