| Summary: | 碩士 === 國立台灣工業技術學院 === 電機工程技術研究所 === 85 === This thesis presents the algorithms for collision detection in
a 3-Dgraphical environment simulated by a computer system, where
all the objectsare represented as polyhedral ones and perform
arbitrary translating and/orrotating motions. These algorithms
can be directly used for both convex andconcave objects which
consist of convex polygons. In the realisticapplications, there
require two kinds of solutions: time-interrupted andtime-
continuous collision detection; the former can detect the exact
positionof a collision event at a fixed time step, and the
latter can determine bothapproximate time and position of a
collision event. The algorithms first localize the object-to-
object collision events by the"space cell" method which divides
the 3-D environment into small cells. Inthis manner, only those
cells that intersect moving objects are examined inorder to
reduce the number of testing a pair of bounding volumes
surroundingthe objects. An azimuth-elevation map method is then
proposed to quicklyselect the polygons in the overlap region
between two candidate objects bypresorting their vertices in the
spherical coordinates system. Afterperforming that, a divide-
and-conquer method which takes advantage of thebounding box
representation is presented to moderate the number of
thepolygons needed to be checked by a polygon-to-polygon
intersection test. Todeal with the time-interrupted and time-
continuous collision detection, twopolygon-to-polygon
intersection testing methods based on a hierarchicalscheme are
developed to reduce unnecessary computation. All the
experiments are made by using the Microsoft Visual C/C++
4.0compiler under the operation system Microsoft Windows NT 4.0
of a personalcomputer with a Pentium Pro-180 CPU and 64M RAM. As
shown in the experiments,the time complexity of the space cell
method grows near linearly as theamount of objects increases.
When the bounding sphere of an object exactlyembraces its
occupied space, the azimuth-elevation map method is
moreefficient than the enumerative method for selecting all the
polygons withinor across the overlap region. The divide-and-
conquer method can economizelots of computing time as the
experiments reveal. The time-continuouscollision detection
algorithm is successfully verified, and also compared withthe
time-interrupted collision detection one to understand its
computationloading. So far, all the experimental results from
our proposed methods arevery encouraging.
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