INTRODUCTION To

Qt

What is Qt?

❏Cross-platform application development framework.

❏Used to create graphical user interfaces.❏ It can be used with several different

programming languages.❏ “t” in Qt refers to toolkit which defines Qt

much better. Therefore, it can effectively be defined as a set of tools.

Qt TOOLS

❏ The main component is a set of libraries, written natively in C++. These libraries include: the core library providing the most important stuff, the GUI library providing the GUI components, the XML library.

❏ Meta Object Compiler(moc) used to handle Qt’s C++ extensions.This extends C++ a little bit, adding nice features like the signals/slots mechanism

❏ The GUI designer tool and the UIC. Qt Designer is a graphical tool to create GUIs visually and save them to XML files, and the UIC is a command-line tool to translate those XML files to C++ code.

❏Qt Linguist, tool to internationalize applications.Qt Linguist is a graphical tool for translator to edit those XML files and provide translations.

❏ The qmake tool, used to automate build process, so you don't have to run MOC, C++ compiler, UIC and other things manually.

❏ The Qt Creator, a graphical IDE to integrate all the stuff described above into a single environment.

qmake helps to create .pro file

Creating a Qt project

Go to File and select New

Select

Files generated

Examples

Similarly a 2D graphic such as a circle,ellipse

can be built

The code uses QPainter on QMainWindow. Circle drawing is done during gui decoration process , it is not drawn as an animation.Drawing empty circle on

QMainWindow involves subclassing of QMainWindow and overriding

paintEvent(QPaintEvent*) method.

using Coin3D and SoQt

3-D Graphics in Qt

❏Coin3D is a high level 3D graphics toolkit for developing cross-platform 3D visualizations.

❏ It uses scene graph data structures to render 3D graphics.

❏ Based on the de facto standard Open Inventor, Coin3D is a set of libraries for creating 3D graphics applications.

Coin3D

Few Steps to install

1. Download Coin-3.1.3.tar.gz fom https://bitbucket.org/Coin3D/coin/downloads.

2. Next unzip the file using the following commands:o cd /tmpo gzip -cd Coin-3.1.3.tar.gz | tar xvf -o mkdir coin-build

3. Run configure from the build directory:cd coin-build4. ../Coin-3.1.3/configure5. Build the Coin library:6. make7. Install the Coin library:8. make install

Just install:libsoqt40-dev

SoQt is a library which provides bridge between Coin3D visualistion and Qt 2D Graphical Interface.

Linking

Add in the pro file:

LIBS += -lCoin3D -lSoQt

Open Inventor

Open Inventor is a “scenegraph“ graphics API: All visible objects are stored in a scenegraph

Capabilities of Open Inventor

❏ Easy construction of 3D scenes❏User interaction❏ Animation

Scenegraph Anatomy

There are three kinds of nodes:

Group nodes: allow construction of trees

Property nodes: change the color / location / ... of the next object

Shapes: visible objects.

Common node types

❏Group nodes

SoGroup: SoSeparator..❏ Property nodes

Transform: SoTransform, SoRotation, ...

Appearance: SoMaterial….❏ Shape nodes

SoShape SoCone, SoCube,

Scene objects

class name prefix: So (scene object)❏ derived from SoNode❏ can be inserted directly into the scenegraph

Example:

root->addChild(new SoSphere)

# <Inventor/Qt/viewers/SoQtExaminerViewer.h>

#include <Inventor/nodes/SoSeparator.h>

#include <Inventor/nodes/SoCube.h>

int main(int argc, char ** argv)

{

QWidget * mainwin = SoQt::init(argc, argv, argv[0]);

SoSeparator * root = new SoSeparator;

root->ref();

SoCube *cube = new SoCube;

r

root->addChild(cube);

SoQtExaminerViewer * eviewer = new

SoQtExaminerViewer(mainwin);

eviewer->setSceneGraph(root);

eviewer->show();

SoQt::show(mainwin);

SoQt::mainLoop();

root->unref();

delete eviewer;

return 0;}

}

#include <Inventor/Qt/SoQt.h>: The SoQt class takes care of Qt initialisation.

# include<Inventor/Qt/viewers/SoQtExaminerViewer.h>It is the general purpose viewer to view the 3D object generated.

#include <Inventor/nodes/SoSeparator.h>

It is subclass of SoGroup class.

#include <Inventor/nodes/SoCube.h>This is the node for cube shape. It comes under the category of shape nodes.

❏ QWidget * mainwin = SoQt::init(argc, argv, argv[0]);

SoQt ::init with a string creates a QApplication and its main window, and returns its window handle.

❏ SoSeparator * root = new SoSeparator;

root->ref();

The root node of the scene graph is created here.❏ SoCube *cube = new SoCube;

root->addChild(cube);

A cube is added to the scene as a child to the root node.

❏ SoQtExaminerViewer(mainwin);

eviewer->setSceneGraph(root);

eviewer->show();

The ExaminerViewer class of the viewer is used for display of objects.

❏ SoQt::show(mainwin);

This pops up the main window.❏ SoQt::mainLoop();

Cleans up all static data allocated by the SoQt library on initialization.

Thank You