Metrics2 C++ Sample
Metrics is an MFC dialogue based application, which demonstrates calculation
of distances, and nearest points between two objects and usage of
IMetrics.Dist method. Metrics2 is an enhanced
version of Metrics sample. Metrics2 demonstrates
additionally how case when there are many points which have the same distance to
another object is handled. It also demonstrates usage of "Include Children"
property in distance calculations.
Source code for Metrics sample is available in Samples\VC\Metrics2 folder of
the installation directory. It is recommended to copy the folder to location
outside of the installation folder.
Running the application
The application expects the model to have at least two top level objects.
Names of the first and the second objects are displayed on the right hand side
of the form. The Calculate button calculates distances between the two objects
and displays the result in 3D view.
By default pairs of nearest points are rendered connected with a red segment
in 3D view. Check boxes in the Display group allow to turning on and off
rendering shortest distances, nearest points and normals.
When "Find All" check box is on, all pairs of nearest points (at the same
distances in this sample) are found and displayed.
More.
"Include Children" check box forces the algorithm to consider children of
both objects as single object with its parent. In the default Dist,glm model the
cylinder is a child of the box object.
The Move Object control group allows changing position and orientation of
either of the two objects. The movement is performed relative to the current
location and orientation of the local frame of the object. Show check box
displays or hides the local frame.
The "Is Closer Than" controls allow to determine whether the objects are
closer than the distance specified in the edit box.
File menu allows loading new and saving the current model.
Implementation
All DG Kernel related functionality is implemented inside the MetricsDlg
class. The DG Kernel related data is initialized inside InitModelInfo()
method, which uses GetModel
method of the DG Kernel control to obtain the root
interface of the hierarchy. ISection
interfaces, representing generic DG Kernel object, are obtained for the first
two top level objects of the model with the help of
IModel.GetEntity and stored in
m_iEntityFrom and m_iEntityTo member variables.
Calculation of distance is performed in OnCalculate() handler,
where IMetrics
interfaces are queried from relevant ISection
and IMetrics.Dist is called. The result of
the calculation is listed by returned IRelation
interface.
In this application the calculated nearest points are displayed in 3D view
with line segments and points. To improve performance of rendering
IRelation
is converted once to a pointer list and stored in m_pairList member.
This work is done by CompileNearestData method, where pairs of the relation
are iterated through, correspondent elements of the each per object list are
retrieved and converted to the actual type of IVertex.
The application uses ClientDraw
event, requested in OnInitDialog(), to add custom drawing of shortest
segments and other elements to the scene. The drawing is performed inside
OnClientDraw handler. In the OnClientDraw method the coordinates of each
vertex are obtained via IVertex.GetVertexCoord.
When rendering of normals, is requested they are obtained with a
IVertex.GetNormal call in
DrawNormals().
Work related to the "Is Closer than" group of controls is done in
OnCalculateCloserThan handler with the help of
IMetrics.IsCloserThan method.
Note that movements of the current object are performed in OnMoveObject
via IFrame2
rather than IFrame
to make movements relative to the current axes.
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