C++ - Qt Framework - Using QOpenGLWidget to display a window for moving shapes with keyboard and mouse

In the past tutorials about Qt and OpenGL we saw how to deal with some basic tasks.

Let's see this time something a bit more advanced with the QOpenGLWidget class in order to display a scene from a window with a shape.

This shape (a cube) can be rotated, translated, zoomed with the keyboard and the mouse.

I added some options to change this cube into a colored or texured shape directly from the GUI.

You can also enable or stop the rotation of the cube.

And of couse reset the shape or camera view (both as well).

First of all

This tutorial uses Qt 5.

I also used some classes (Camera3D, Transform3D and Input) from this project : https://www.trentreed.net/blog/qt5-opengl-part-3b-camera-control/

I adapted it to my needs, so feel free to explore and use it if you want to.

I also changed, in the Input.h header, the line: 

friend class Window;

by

friend class BadprogOpenGLWidget;

All code of these 3 classes, except this line, have been kept from the original sources.

So only my code will be displayed in the following tutorial.

Thus, in our example we are going to use a QOpenGLWidget in order to demonstrate how to incorporate an OpenGL scene in a Qt Widget.

I divided the scene in 2 parts: one with colors and the other with textures.

To change it just click the radioButton of your choice.

By default the cube is rotating so it's possible to stop this rotation with a checkBox.

Furthermore you can reset the position of the cube and also the position of the camera by clicking on their respective pushButton.

I created 2 programs, one for the colors and the other for the texture.

Why? 

To keep things simple to get.

For the program 1 (the color mode) we have the cube created with "GL_TRIANGLE_STRIP" primitive.

Then I created shapes (still in the color mode) with the "GL_LINES" primitive.

You can see that the cube is hard coded when the shapes, from lines, are dynamically created with the method createVAO.

I won't explain anymore all the code because there are tons of things to say.

So I prefer you dive into it by yourself to really understand what's going on.

Code

BadprogOpenGLWidgetWithKeyboardAndMouse.pro

QT       += core gui opengl


greaterThan(QT_MAJOR_VERSION, 4): QT += widgets


CONFIG += c++11


# The following define makes your compiler emit warnings if you use

# any Qt feature that has been marked deprecated (the exact warnings

# depend on your compiler). Please consult the documentation of the

# deprecated API in order to know how to port your code away from it.

DEFINES += QT_DEPRECATED_WARNINGS


# You can also make your code fail to compile if it uses deprecated APIs.

# In order to do so, uncomment the following line.

# You can also select to disable deprecated APIs only up to a certain version of Qt.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += \

    badprogMainWindow.cpp \

    badprogOpenglWidget.cpp \

    camera3d.cpp \

    input.cpp \

    main.cpp \

    transform3d.cpp


HEADERS += \

    badprogMainWindow.h \

    badprogOpenglWidget.h \

    camera3d.h \

    input.h \

    transform3d.h


FORMS += \

    badprogMainWindow.ui


RESOURCES += \

    badprog.qrc


# Default rules for deployment.

qnx: target.path = /tmp/$${TARGET}/bin

else: unix:!android: target.path = /opt/$${TARGET}/bin

!isEmpty(target.path): INSTALLS += target

shader/shader_fragment_color.glsl

shader/shader_fragment_texture.glsl

shader/shader_vertex_color.glsl

shader/shader_vertex_texture.glsl

badprog.qrc

<RCC>

    <qresource prefix="/">

        <file alias="fragment_color">shader/shader_fragment_color.glsl</file>

        <file alias="fragment_texture">shader/shader_fragment_texture.glsl</file>

        <file alias="vertex_color">shader/shader_vertex_color.glsl</file>

        <file alias="vertex_texture">shader/shader_vertex_texture.glsl</file>

        <file alias="imageForTexture">image_for_texture.png</file>

    </qresource>

</RCC>

badprogMainWindow.cpp

badprogMainWindow.h

badprogMainWindow.ui

badprogOpenGLWidget.cpp

badprogOpenGLWidget.h

You also need an image for the texture.

In the code it's called "imageForTexture" from the badprog.qrc file.

Just add image_for_texture.png where there are other files.

Conclusion

If you see the window open then it's a good sign. 

Indeed, you are now able to add all widgets of your choice in your GUI to manipulate every kind of OpenGL shape.

Quite interesting.

Good job you did it.