QOpenGLShaderProgram add QOpenGLShader uniform location -1

  • Hi there,

    I'm playing around with the triangle example. What I saw is that if I use the QOpenGLShader classes to create the vertex and fragment shaders (instead of add the source string directly) and then add them to a QOpenGLShaderProgram object, getting the uniform location of the matrix returns -1.

    Here it is the code:

    '''void TriangleWindow::initialize()

      QOpenGLShader *vertexShader = new QOpenGLShader(QOpenGLShader::Vertex);
    if (!vertexShader->compileSourceFile(QDir::currentPath() + "/vertexshader.vert"))
        qDebug() << vertexShader->log();
    QOpenGLShader *fragmentShader = new QOpenGLShader(QOpenGLShader::Fragment);
    if (!fragmentShader->compileSourceFile(QDir::currentPath() + "/fragmentshader.frag"))
        qDebug() << fragmentShader->log();
    m_program = new QOpenGLShaderProgram(this);
    if (!m_program->addShader(vertexShader)) qDebug() << "Cannot add vertex shader\n";
    if (!m_program->addShader(fragmentShader)) qDebug() << "Cannot add fragment shader\n";
    if (!m_program->link())
    qDebug() << m_program->log();
    m_posAttr = m_program->attributeLocation("posAttr");
    if (m_posAttr == -1) qDebug() << "Cannot find position\n";
    m_colAttr = m_program->attributeLocation("colAttr");
    if (m_colAttr == -1) qDebug() << "Cannot find colors\n";
    m_matrixUniform = m_program->uniformLocation("matrix");
    if (m_matrixUniform == -1) qDebug() << "Cannot find matrix\n";'''

    Am I doing somthing wrong? The shader files hold exactly the same code as the shader string of the example.


  • I found my problem. It was my mistake

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    What mistake was it ? That may help other users

  • Hi,

    I feel very bad for saying this. I was reading another shader file were the uniform matrix variable wasn't used. And the compiler gets rid of those variables. It was a very stupid mistake!!


  • Lifetime Qt Champion

    Don't worry, that kind of things can happen

    Happy coding !

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