ROS knowledge: the structure of the rviz library librviz

One 、 summary

        RViz Not just a visual application , It is also a library ！ Through the link librviz.so（ Or whatever name your operating system likes to call it ）, You can access... In your own application RViz Most of the functions .

         This tutorial shows a very simple example , It creates a 3D Visual widgets (rviz::RenderPanel), Programmatically create a new grid display , And then use Qt The slider control adjusts the properties of several meshes . The application is called “myviz”.

         The source code for this tutorial is located in librviz_tutorial In bag . You can view the source code directly , perhaps （ If you use Ubuntu） You can like this apt-get Install precompiled Debian software package ：

sudo apt-get install ros-hydro-visualization-tutorials

Two 、The Code

 myviz The code file is : src/main.cpp, src/myviz.h,  src/myviz.cpp.

2.1 main.cpp analysis

         This “myviz” Example main() It's simple , It just initializes ROS, Create a QApplication, Create top-level widgets （ The type is “MyViz”）, Show it , And run Qt The event loop . 

#include <QApplication>
#include <ros/ros.h>
#include "myviz.h"

int main(int argc, char **argv)
{
  if( !ros::isInitialized() )
  {
    ros::init( argc, argv, "myviz", ros::init_options::AnonymousName );
  }

  QApplication app( argc, argv );

  MyViz* myviz = new MyViz();
  myviz->show();

  app.exec();
  delete myviz;
}

2.2 myviz.h explain

        “MyViz” Class implements the top-level part of this example .

class MyViz: public QWidget
{
Q_OBJECT
public:
  MyViz( QWidget* parent = 0 );
  virtual ~MyViz();

private Q_SLOTS:
  void setThickness( int thickness_percent );
  void setCellSize( int cell_size_percent );

private:
  rviz::VisualizationManager* manager_;
  rviz::RenderPanel* render_panel_;
  rviz::Display* grid_;
};

         Only joined Q_OBJECT, Can be used QT Medium signal and slot Mechanism , and Q_OBJECT To be placed at the front of the class . 

         The signal and slot are Qt application development The basis of , It connects two unrelated objects , Slot and ordinary C++ The function is the same , It's just that when it's connected to the signal , When sending a signal , The slot will be called automatically. Only when you join Q_OBJECT, You can use QT Medium signal and slot Mechanism .

2. 3 myviz.cpp explain

The full text of myviz.cpp is here: src/myviz.cpp

MyViz Constructor for . This completes most of the work of the class .

MyViz::MyViz( QWidget* parent )
  : QWidget( parent )
{
   

Build and lay out label and slider controls .

QLabel* thickness_label = new QLabel( "Line Thickness" );
QSlider* thickness_slider = new QSlider( Qt::Horizontal );
thickness_slider->setMinimum( 1 );
thickness_slider->setMaximum( 100 );
QLabel* cell_size_label = new QLabel( "Cell Size" );
QSlider* cell_size_slider = new QSlider( Qt::Horizontal );
cell_size_slider->setMinimum( 1 );
cell_size_slider->setMaximum( 100 );
QGridLayout* controls_layout = new QGridLayout();
controls_layout->addWidget( thickness_label, 0, 0 );
controls_layout->addWidget( thickness_slider, 0, 1 );
controls_layout->addWidget( cell_size_label, 1, 0 );
controls_layout->addWidget( cell_size_slider, 1, 1 );

Build and lay out rendering panels .

render_panel_ = new rviz::RenderPanel();
QVBoxLayout* main_layout = new QVBoxLayout;
main_layout->addLayout( controls_layout );
main_layout->addWidget( render_panel_ );

Set this MyViz Top level layout of widgets .

setLayout( main_layout );

Carry signal / Slot connection .

connect( thickness_slider, SIGNAL( valueChanged( int )), this, SLOT( setThickness( int )));
connect( cell_size_slider, SIGNAL( valueChanged( int )), this, SLOT( setCellSize( int )));

Next, we initialize the main RViz class .

VisualizationManager yes Display Object's container , Including the main Ogre scene , contain ViewController etc. . It's very important , We may use it every time librviz You need one at a time .

manager_ = new rviz::VisualizationManager( render_panel_ );
render_panel_->initialize( manager_->getSceneManager(), manager_ );
manager_->initialize();
manager_->startUpdate();

Create a grid display .

grid_ = manager_->createDisplay( "rviz/Grid", "adjustable grid", true );
ROS_ASSERT( grid_ != NULL );

Configure... In the way we like GridDisplay.

grid_->subProp( "Line Style" )->setValue( "Billboards" );
grid_->subProp( "Color" )->setValue( Qt::yellow );

Initialize slider value .

  thickness_slider->setValue( 25 );
  cell_size_slider->setValue( 10 );
}

destructor .

MyViz::~MyViz()
{
  delete manager_;
}

This function is a connection to QSlider Of valueChanged() The signal Qt Slot . It does this by changing the shape of the mesh “ Line width ” Property to set the lineweight of the mesh .

void MyViz::setThickness( int thickness_percent )
{
  if( grid_ != NULL )
  {
    grid_->subProp( "Line Style" )->subProp( "Line Width" )->setValue( thickness_percent / 100.0f );
  }
}

This function is a connection to QSlider Of valueChanged() The signal Qt Slot . It does this by changing the shape of the mesh “ Cell size ” Property to set the cell size of the grid .

void MyViz::setCellSize( int cell_size_percent )
{
  if( grid_ != NULL )
  {
    grid_->subProp( "Cell Size" )->setValue( cell_size_percent / 10.0f );
  }
}

3、 ... and 、 perform

After compiling ：

rosrun librviz_tutorial myviz