2 Building the Profile 4
2 Building the Profile
2.1 Defining Support Points
To create the bottle's profile, you first create characteristic points with their coordinates as shown below in the (XOY)
plane. These points will be the supports that define the geometry of the profile.
(-myWidth / 2., 0 , 0)
(myWidth / 2., 0 , 0)
(-myWidth / 2., -myThickness / 4. , 0)
(myWidth / 2., myThickness / 4. , 0)
(0 , -myThickness / 2. , 0)
There are two classes to describe a 3D Cartesian point from its X, Y and Z coordinates in Open CASCADE
Technology:
• the primitive geometric gp_Pnt class
• the transient Geom_CartesianPoint class manipulated by handle
A handle is a type of smart pointer that provides automatic memory management. To choose the best class for this
application, consider the following:
• gp_Pnt is manipulated by value. Like all objects of its kind, it will have a limited lifetime.
• Geom_CartesianPoint is manipulated by handle and may have multiple references and a long lifetime.
Since all the points you will define are only used to create the profile's curves, an object with a limited lifetime will
do. Choose the gp_Pnt class. To instantiate a gp_Pnt object, just specify the X, Y, and Z coordinates of the points
in the global Cartesian coordinate system:
gp_Pnt aPnt1(-myWidth / 2., 0, 0);
gp_Pnt aPnt2(-myWidth / 2., -myThickness / 4., 0);
gp_Pnt aPnt3(0, -myThickness / 2., 0);
gp_Pnt aPnt4(myWidth / 2., -myThickness / 4., 0);
gp_Pnt aPnt5(myWidth / 2., 0, 0);
Once your objects are instantiated, you can use methods provided by the class to access and modify its data. For
example, to get the X coordinate of a point:
Standard_Real xValue1 = aPnt1.X();
2.2 Profile: Defining the Geometry
With the help of the previously defined points, you can compute a part of the bottle's profile geometry. As shown in
the figure below, it will consist of two segments and one arc.
(c) Open CASCADE 2019
