opencv/doc/tutorials/viz/widget_pose/widget_pose.markdown

Pose of a widget

Goal

In this tutorial you will learn how to

• Add widgets to the visualization window
• Use Affine3 to set pose of a widget
• Rotating and translating a widget along an axis

Code

You can download the code from here . @code{.cpp} #include <opencv2/viz.hpp> #include <opencv2/calib3d.hpp> #include

using namespace cv; using namespace std;

/*

• @function main */ int main() { /// Create a window viz::Viz3d myWindow("Coordinate Frame");

  /// Add coordinate axes myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());

  /// Add line to represent (1,1,1) axis viz::WLine axis(Point3f(-1.0f,-1.0f,-1.0f), Point3f(1.0f,1.0f,1.0f)); axis.setRenderingProperty(viz::LINE_WIDTH, 4.0); myWindow.showWidget("Line Widget", axis);

  /// Construct a cube widget viz::WCube cube_widget(Point3f(0.5,0.5,0.0), Point3f(0.0,0.0,-0.5), true, viz::Color::blue()); cube_widget.setRenderingProperty(viz::LINE_WIDTH, 4.0);

  /// Display widget (update if already displayed) myWindow.showWidget("Cube Widget", cube_widget);

  /// Rodrigues vector Mat rot_vec = Mat::zeros(1,3,CV_32F); float translation_phase = 0.0, translation = 0.0; while(!myWindow.wasStopped()) { /* Rotation using rodrigues */ /// Rotate around (1,1,1) rot_vec.at(0,0) += CV_PI * 0.01f; rot_vec.at(0,1) += CV_PI * 0.01f; rot_vec.at(0,2) += CV_PI * 0.01f;

   /// Shift on (1,1,1)
   translation_phase += CV_PI * 0.01f;
   translation = sin(translation_phase);
  
   Mat rot_mat;
   Rodrigues(rot_vec, rot_mat);
  
   /// Construct pose
   Affine3f pose(rot_mat, Vec3f(translation, translation, translation));
  
   myWindow.setWidgetPose("Cube Widget", pose);
  
   myWindow.spinOnce(1, true);
  

  }

  return 0; } @endcode Explanation

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Here is the general structure of the program:

• Create a visualization window. @code{.cpp} /// Create a window viz::Viz3d myWindow("Coordinate Frame"); @endcode
• Show coordinate axes in the window using CoordinateSystemWidget. @code{.cpp} /// Add coordinate axes myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem()); @endcode
• Display a line representing the axis (1,1,1). @code{.cpp} /// Add line to represent (1,1,1) axis viz::WLine axis(Point3f(-1.0f,-1.0f,-1.0f), Point3f(1.0f,1.0f,1.0f)); axis.setRenderingProperty(viz::LINE_WIDTH, 4.0); myWindow.showWidget("Line Widget", axis); @endcode
• Construct a cube. @code{.cpp} /// Construct a cube widget viz::WCube cube_widget(Point3f(0.5,0.5,0.0), Point3f(0.0,0.0,-0.5), true, viz::Color::blue()); cube_widget.setRenderingProperty(viz::LINE_WIDTH, 4.0); myWindow.showWidget("Cube Widget", cube_widget); @endcode
• Create rotation matrix from rodrigues vector @code{.cpp} /// Rotate around (1,1,1) rot_vec.at(0,0) += CV_PI * 0.01f; rot_vec.at(0,1) += CV_PI * 0.01f; rot_vec.at(0,2) += CV_PI * 0.01f;

...

Mat rot_mat; Rodrigues(rot_vec, rot_mat); @endcode

• Use Affine3f to set pose of the cube. @code{.cpp} /// Construct pose Affine3f pose(rot_mat, Vec3f(translation, translation, translation)); myWindow.setWidgetPose("Cube Widget", pose); @endcode

• Animate the rotation using wasStopped and spinOnce @code{.cpp} while(!myWindow.wasStopped()) { ...

  myWindow.spinOnce(1, true); } @endcode Results

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Here is the result of the program.

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