Report Cao
Aerospace and Mechanical Engineering Department
Mechanical Computer-Aided-Design
Prof. Mr. Eric Béchet
Find one of the intersections between two
parametric surfaces.
ALARCÓN SOTO Pablo
Academic year 2011-2012
1. Index
1.1.Content index
1. Index ...................................................................................................................................... 2
1.1.
Content index ................................................................................................................ 2
1.2.
Figures index ................................................................................................................. 2
2. Introduction .......................................................................................................................... 3
3.
Creation of the algorithm ...................................................................................................... 3
3.1.
Examination of the curves ............................................................................................. 4
3.2. Computation of the first point ...................................................................................... 4
3.3.
Marching along the curve ............................................................................................. 5
4.
Results ................................................................................................................................... 7
5. Bibliography .......................................................................................................................... 9
1.2.Figures index
Figure 1 General view of the intersection……………………………………………………………………….4
Figure 2 Determination of the starting point…………………………………………………………………..5
Figure 3 Intersection curve, view 1………………………………………………………………………………..7 Figure 4 Intersection curve, view 2………………………………………………………………………………..8
Figure 5 Intersection curve, view 3………………………………………………………………………………..8
2. Introduction
Evaluate the intersection of parametric surfaces is a common operation in computer
design and solid modeling; this task is commonly known as the problem of surface to
surface intersection. In this work we will focus on the intersection between two
parametric surfaces defined as nbsplines surface.
To compute the intersection between two surfaces there are many different approach,
among which we can highlight the divide‐and‐conquer algorithm (where the surfaces are
subdivided into a great number of elements and the intersection of surfaces is
approximated by the intersection pairs of these elements) and the marching algorithm
(where one has to find an starting point on the intersection curve and then walk along the
intersection curve to get the successive points). We will focus our attention on the
marching methods because they are one of the simplest methods and moreover the
geometrical interpretation is easy to understand. Taking the definition given by Patrikalakis1 “Marching methods involve generation of
sequences of points of an intersection curve branch by stepping from a given point on the
required curve in a direction prescribed by the local differential geometry”, “However,
such methods are by themselves incomplete in that they require starting points (initial conditions) for every branch of the solution”. Considering that information we will
develop a simplified algorithm following the principle of the marching methods.
3. Creation of the algorithm
To create the algorithm we will follow in general terms the following steps.
Examine the curves to know in general terms the kind of intersection. ...
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