OpenCV  4.10.0
Open Source Computer Vision
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Creating Widgets

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Goal

In this tutorial you will learn how to

  • Create your own widgets using WidgetAccessor and VTK.
  • Show your widget in the visualization window.

Code

You can download the code from here.

#ifndef USE_VTK
#include <iostream>
int main()
{
std::cout << "This sample requires direct compilation with VTK. Stop" << std::endl;
return 0;
}
#else
#include <opencv2/viz.hpp>
#include <iostream>
#include <vtkPoints.h>
#include <vtkTriangle.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkIdList.h>
#include <vtkActor.h>
#include <vtkProp.h>
using namespace cv;
using namespace std;
static void help()
{
cout
<< "--------------------------------------------------------------------------" << endl
<< "This program shows how to create a custom widget. You can create your own "
<< "widgets by extending Widget2D/Widget3D, and with the help of WidgetAccessor." << endl
<< "Usage:" << endl
<< "./creating_widgets" << endl
<< endl;
}
class WTriangle : public viz::Widget3D
{
public:
WTriangle(const Point3f &pt1, const Point3f &pt2, const Point3f &pt3, const viz::Color & color = viz::Color::white());
};
WTriangle::WTriangle(const Point3f &pt1, const Point3f &pt2, const Point3f &pt3, const viz::Color & color)
{
// Create a triangle
vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
points->InsertNextPoint(pt1.x, pt1.y, pt1.z);
points->InsertNextPoint(pt2.x, pt2.y, pt2.z);
points->InsertNextPoint(pt3.x, pt3.y, pt3.z);
vtkSmartPointer<vtkTriangle> triangle = vtkSmartPointer<vtkTriangle>::New();
triangle->GetPointIds()->SetId(0,0);
triangle->GetPointIds()->SetId(1,1);
triangle->GetPointIds()->SetId(2,2);
vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New();
cells->InsertNextCell(triangle);
// Create a polydata object
vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
// Add the geometry and topology to the polydata
polyData->SetPoints(points);
polyData->SetPolys(cells);
// Create mapper and actor
vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
#if VTK_MAJOR_VERSION <= 5
mapper->SetInput(polyData);
#else
mapper->SetInputData(polyData);
#endif
vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);
// Store this actor in the widget in order that visualizer can access it
viz::WidgetAccessor::setProp(*this, actor);
// Set the color of the widget. This has to be called after WidgetAccessor.
setColor(color);
}
int main()
{
help();
viz::Viz3d myWindow("Creating Widgets");
WTriangle tw(Point3f(0.0,0.0,0.0), Point3f(1.0,1.0,1.0), Point3f(0.0,1.0,0.0), viz::Color::red());
myWindow.showWidget("TRIANGLE", tw);
myWindow.spin();
return 0;
}
#endif
Template class for 3D points specified by its coordinates x, y and z.
Definition types.hpp:255
_Tp z
z coordinate of the 3D point
Definition types.hpp:286
_Tp x
x coordinate of the 3D point
Definition types.hpp:284
_Tp y
y coordinate of the 3D point
Definition types.hpp:285
This class represents color in BGR order.
Definition types.hpp:64
The Viz3d class represents a 3D visualizer window. This class is implicitly shared.
Definition viz3d.hpp:68
Base class of all 3D widgets.
Definition widgets.hpp:182
int main(int argc, char *argv[])
Definition highgui_qt.cpp:3
"black box" representation of the file storage associated with a file on disk.
Definition core.hpp:102
STL namespace.

Explanation

Here is the general structure of the program:

  • Extend Widget3D class to create a new 3D widget.
    class WTriangle : public viz::Widget3D
    {
    public:
    WTriangle(const Point3f &pt1, const Point3f &pt2, const Point3f &pt3, const viz::Color & color = viz::Color::white());
    };
  • Assign a VTK actor to the widget.
    // Store this actor in the widget in order that visualizer can access it
    viz::WidgetAccessor::setProp(*this, actor);
  • Set color of the widget.
    // Set the color of the widget. This has to be called after WidgetAccessor.
    setColor(color);
  • Construct a triangle widget and display it in the window.
    WTriangle tw(Point3f(0.0,0.0,0.0), Point3f(1.0,1.0,1.0), Point3f(0.0,1.0,0.0), viz::Color::red());
    myWindow.showWidget("TRIANGLE", tw);

Results

Here is the result of the program.