Small examples for game development in Qt, OpenGL, Box2D, Bullet Physics, OpenAL, and so on.

8Observer8

Custom OpenGL button for WebAssembly and Android

You cannot make the standard Qt button for WebAssembly because of this bug: https://bugreports.qt.io/browse/QTBUG-120651 (you can use the patch from the "Gerrit Reviews") But OpenGL allows to make custom GUI elements.

WebAssembly demo on free Netlify hosting (QOpenGLWindow)

QOpenGLWindow works on Android 7.1.2 in the mobile browser without problems. You can find a lot of GUI game assets on itch: https://itch.io/game-assets/tag-gui I use the following GUI game asset in this demo: https://wenrexa.itch.io/holoui I have used Free Texture Packer to pack to button textures to one texture + json-file. Text was added in GIMP.

Source code for Qt6 C++

The same demo for SDL3:

Click buttons with color ID using glReadPixels

Demo in the browser

This example uses the following GUI asset: https://wenrexa.itch.io/holoui. You can find a lot of GUI assets on itch: https://itch.io/game-assets/tag-gui I packed the GUI textures using Free Texture Packer to one texture + JSON. RapidJSON is used to parse the JSON file.

Tools: SDL3, Emscripten, C++, CMake, OpenGL ES 2.0, GLM, stb_image, Free Texture Packer, and RapidJSON

8Observer8

Activating the discrete GeForce of Radeon video card and OpenGL 3.3 Core profile on laptops

You can make it with the following code. The first one is for GeForce. The second one is for Radeon. If you can GeForce the second like with be ignored.

extern "C"
{
    __declspec(dllexport) unsigned long NvOptimusEnablement = 1;
    __declspec(dllexport) unsigned long AmdPowerXpressRequestHighPerformance = 1;
}

main.cpp

extern "C"
{
    __declspec(dllexport) unsigned long NvOptimusEnablement = 1;
    __declspec(dllexport) unsigned long AmdPowerXpressRequestHighPerformance = 1;
}

#include <QtGui/QOpenGLContext>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>
#include <QtOpenGL/QOpenGLWindow>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
    void initializeGL() override
    {
        initializeOpenGLFunctions();

        qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
        qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
        qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);
    }
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL)
    {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    }
    else
    {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    OpenGLWindow w;
    w.setFormat(fmt);
    w.show();
    return app.exec();
}

Output:

Requesting 3.3 core context
OpenGL version: 3.3.0 NVIDIA 391.35
GLSL version:  3.30 NVIDIA via Cg compiler
Vendor:  NVIDIA Corporation

By default the laptops with two video cards use the integrated video card:

main.cpp

#include <QtGui/QOpenGLContext>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>
#include <QtOpenGL/QOpenGLWindow>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
    void initializeGL() override
    {
        initializeOpenGLFunctions();

        qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
        qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
        qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);
    }
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL)
    {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    }
    else
    {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    OpenGLWindow w;
    w.setFormat(fmt);
    w.show();
    return app.exec();
}

Output:

Requesting 3.3 core context
OpenGL version: 3.1.0 - Build 9.17.10.4459
GLSL version:  1.40 - Intel Build 9.17.10.4459
Vendor:  Intel

8Observer8

Rotate a 3D vector around X, Y, Z axes

In my example, three vectors are rotated 10 degrees around the X, Y and Z axes:

Rotate the vector (0.f, 0.f, 1.f) 10 degrees around the X axis. Output: (0, -0.173648, 0.984808)
Rotate the vector (1.f, 0.f, 0.f) 10 degrees around the Y axis. Output: (0.984808, 0, -0.173648)
Rotate the vector (0.f, 1.f, 0.f) 10 degrees around the Z axis. Output: (-0.173648, 0.984808, 0)

#include <QtGlobal>
#include <QtMath>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QVector3D>
#include <QtOpenGL/QOpenGLWindow>
#include <QtWidgets/QApplication>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
    virtual void initializeGL() override
    {
        initializeOpenGLFunctions();

        // Rotate a 3D vector around the x-axis
        QVector3D vector1(0.f, 0.f, 1.f);
        QVector3D origin1(0.f, 0.f, 0.f);
        float r1 = qDegreesToRadians(10.f);
        QVector3D out1 = rotateX(vector1, origin1, r1);
        qDebug() << out1;

        // Rotate a 3D vector around the y-axis
        QVector3D vector2(1.f, 0.f, 0.f);
        QVector3D origin2(0.f, 0.f, 0.f);
        float r2 = qDegreesToRadians(10.f);
        QVector3D out2 = rotateY(vector2, origin2, r2);
        qDebug() << out2;

        // Rotate a 3D vector around the z-axis
        QVector3D vector3(0.f, 1.f, 0.f);
        QVector3D origin3(0.f, 0.f, 0.f);
        float r3 = qDegreesToRadians(10.f);
        QVector3D out3 = rotateZ(vector3, origin3, r3);
        qDebug() << out3;
    }

    QVector3D rotateX(const QVector3D &vector, const QVector3D &origin, float rad)
    {
        // Translate point to the origin
        QVector3D pos;
        pos.setX(vector.x() - origin.x());
        pos.setY(vector.y() - origin.y());
        pos.setZ(vector.z() - origin.z());

        // Perform rotation
        QVector3D rot;
        rot.setX(pos.x());
        rot.setY(pos.y() * qCos(rad) - pos.z() * qSin(rad));
        rot.setZ(pos.y() * qSin(rad) + pos.z() * qCos(rad));

        // Translate to correct position
        QVector3D out;
        out.setX(rot.x() + origin.x());
        out.setY(rot.y() + origin.y());
        out.setZ(rot.z() + origin.z());

        return out;
    }

    QVector3D rotateY(const QVector3D &vector, const QVector3D &origin, float rad)
    {
        // Translate point to the origin
        QVector3D pos;
        pos.setX(vector.x() - origin.x());
        pos.setY(vector.y() - origin.y());
        pos.setZ(vector.z() - origin.z());

        // Perform rotation
        QVector3D rot;
        rot.setX(pos.z() * qSin(rad) + pos.x() * qCos(rad));
        rot.setY(pos.y());
        rot.setZ(pos.z() * qCos(rad) - pos.x() * qSin(rad));

        // Translate to correct position
        QVector3D out;
        out.setX(rot.x() + origin.x());
        out.setY(rot.y() + origin.y());
        out.setZ(rot.z() + origin.z());

        return out;
    }

    QVector3D rotateZ(const QVector3D &vector, const QVector3D &origin, float rad)
    {
        // Translate point to the origin
        QVector3D pos;
        pos.setX(vector.x() - origin.x());
        pos.setY(vector.y() - origin.y());
        pos.setZ(vector.z() - origin.z());

        // Perform rotation
        QVector3D rot;
        rot.setX(pos.x() * qCos(rad) - pos.y() * qSin(rad));
        rot.setY(pos.x() * qSin(rad) + pos.y() * qCos(rad));
        rot.setZ(pos.z());

        // Translate to correct position
        QVector3D out;
        out.setX(rot.x() + origin.x());
        out.setY(rot.y() + origin.y());
        out.setZ(rot.z() + origin.z());

        return out;
    }
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    OpenGLWindow w;
    w.show();
    return app.exec();
}

pro

QT += core gui openglwidgets

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp

Source: https://glmatrix.net/docs/vec3.js.html#line564

Using GLM:

// Input vector
auto v = glm::vec3(0.f, 0.f, 1.f);
std::cout << v.x << ", " << v.y << ", " << v.z << std::endl;
// Rotation
auto rotationMatrix = glm::rotate(glm::mat4(1.f), glm::radians(10.f), glm::vec3{1.f, 0.f, 0.f});
auto newVector = rotationMatrix * glm::vec4(v, 0.f);
std::cout << newVector.x << ", " << newVector.y << ", " << newVector.z << std::endl;
// Output: 0, -0.173648, 0.984808

Stack Oveflow: https://stackoverflow.com/a/78633772/4159530

8Observer8

This post is deleted!

8Observer8

I have found two solutions how I can make the first person movement in the browser. Qt doesn't allow it because it is impossible to call emscripten_request_pointerlock() from Qt application: https://bugreports.qt.io/browse/QTBUG-126513

The solution is to use SDL3, Emscripten, and Bullet Physics: Click to run a demo in the browser

The demo allows to move with first person and third person view:

Baked shadows and textures using SDL3, Emscripten, OpenGL ES 2.0, Bullet Physics, and C++

Demo in the browser

8Observer8

Critical problems for WebAssembly

Background color of parent window is changed to black: https://bugreports.qt.io/browse/QTBUG-120651
emscripten_request_pointerlock() returns EMSCRIPTEN_RESULT_UNKNOWN_TARGET: https://bugreports.qt.io/browse/QTBUG-126513
Dealing with keyboard layout for input on Qt WebAssembly: https://forum.qt.io/post/790688

8Observer8

Transformed triangle in OpenGL 3.3 and Qt 6.9

Video: https://www.youtube.com/watch?v=AGHZsOrazEU

Source: https://github.com/8Observer8/basics-of-opengl33-and-qt6

8Observer8

Debug drawer for Box2D v3 using QPainter

It uses b2World_Draw to draw Box2D objects for debugging. You can just download and run it without compiling libs because it include libs for Windows (MinGW) and Android.

Source: https://github.com/8Observer8/debug-drawer-qpainter-box2dv3-qt6-cpp

8Observer8

Tank-transistor movement with Bullet Physics

View Live Wasm-Demo - you can control the tank-transistor with WASD-keys in the browser

Source code

8Observer8

Tutorials from Box2D/Box3D creator Erin Catto on the control character:

Rigid body character mover

Dynamic Character Mover : Box3D

8Observer8

Dear ImGui + Qt 6 + OpenGL 3.3 for Windows

Source code: https://github.com/ivan-enzhaev/imgui-opengl-test-qt6