This is my first question in this forum.
Sorry for my bad English, I am not a native speaker 🙂

I started programming with Java long ago and followed the 3D Java Game Dev series on YT from ThinMatrix. Nowadays I program with C++ and want to build my own little 3D Engine based on this former tutorial. I am at the point where I have to load a transformation matrix into the VertexShader in order to rotate, scale and increase the position of my squad. Therefore I programmed my own Mat4f struct. I already can rotate and scale my squad, the translate() Methode doesn’t work! The quad is not moving but gets scaled at the axis.

Here is the implementation for my Mat4f-struct:

Mat4f::Mat4f()
{
    setIdentity();
}

Mat4f::Mat4f(const float data[4][4])
{
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++)
            m_data[i][j] = data[i][j];
}

void Mat4f::setIdentity()
{
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++)
            m_data[i][j] = (i == j) ? 1.0f : 0.0f;
}

void Mat4f::print() const
{
    for (int i = 0; i < 4; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            std::cout << m_data[i][j] << " ";
        }
        std::cout << std::endl;
    }
}

void Mat4f::translate(const Vec3f& translation) {
   m_data[0][3] = translation.x;
   m_data[1][3] = translation.y;
   m_data[2][3] = translation.z;
 }

void Mat4f::rotate(float rx, float ry, float rz)
{
    float cosX = std::cos(rx);
        float sinX = std::sin(rx);
        float cosY = std::cos(ry);
        float sinY = std::sin(ry);
        float cosZ = std::cos(rz);
        float sinZ = std::sin(rz);

        float rot[4][4] = {
          { cosY * cosZ, -cosX * sinZ + sinX * cosY * sinZ, sinX * cosZ + cosX * cosY * sinZ, 0.0f },
          { cosY * sinZ, cosX * cosZ + sinX * cosY * sinZ, cosX * cosZ - sinX * cosY * sinZ, 0.0f },
          { -sinY, sinX * cosY, cosX * cosY, 0.0f },
          { 0.0f, 0.0f, 0.0f, 1.0f }
        };

        Mat4f tmp = *this * Mat4f(rot);
        *this = tmp;
}

void Mat4f::scale(float scale)
{
    float scaledMatrixData[4][4] = {
        {scale, 0.f, 0.f, 0.f},
        {0.f, scale, 0.f, 0.f},
        {0.f, 0.f, scale, 0.f},
        {0.f, 0.f, 0.f, 1.f}
    };
    
    Mat4f scaledMat(scaledMatrixData);
    *this *= scaledMat;
}

Mat4f Mat4f::operator*(const Mat4f& other) const
{
    Mat4f result;
    
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++)
        {
            float sum = 0.f;
            
            for (int k = 0; k < 4; k++)
                sum += m_data[i][k] * other.m_data[k][j];
            
            result.m_data[i][j] = sum;
        }
    
    return result;
}

void Mat4f::operator*=(const Mat4f& other)
{
    Mat4f result;

    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            float sum = 0.f;
            for (int k = 0; k < 4; k++) {
                sum += m_data[i][k] * other.m_data[k][j];
            }
            result.m_data[i][j] = sum;
        }
      }

      *this = result;
}

This is the function where I want to create my transformation matrix:

Mat4f createTransformationMatrix(const Vec3f& translation, float rx, float ry, float rz, float scale)
{
    Mat4f mat;
    mat.translate(translation);
    mat.rotate(rx, ry, rz);
    mat.scale(scale);
    
    return mat;
}

I load the matrix via glUniformMatrix4fv to the vertex Shader.

As mentioned, the rotation and scaling works just fine!
In the shader I simply multiply: gl_Position = transformationMatrix * vec4(position, 1.0);

I have a strong feeling, that something with the translate()-Method isn’t correct. But even after hours try to figure the error out with the help of AI, I cannot come to a conclusion xD

I am desperated…

Thanks for any help or advice 🙂