OpenGL Won't Render With Shaders Mac

Question

I'm trying to get OpenGL to render a basic triangle with shaders on my newer Macbook Pro with the M1 chip. I'm stuck using Qt Creator as well.

I was able to set it up and get a basic Fixed-Pipeline scene rendering, but when I changed the version to use modern OpenGL I get that the version is 4.1, even though I set it to 3.2.

Here's how I set the version:

    QSurfaceFormat format;
    format.setDepthBufferSize(24);
    format.setStencilBufferSize(8);
    format.setProfile(QSurfaceFormat::CoreProfile);
    format.setMajorVersion(3);
    format.setMinorVersion(2);
    QSurfaceFormat::setDefaultFormat(format);
    this->setFormat(format); // must be called before the widget or its parent window gets shown

When I print out the shader sources I can see that I'm getting exactly what I put into my vertex shader and fragment shader files, so I know that I'm loading in the files correctly. Here's how I'm using them inside of my Shader class:

programID = glCreateProgram(); // Creates the program ID
vs = glCreateShader(GL_VERTEX_SHADER); // Creates the vertex shader
fs = glCreateShader(GL_FRAGMENT_SHADER); // Creates the fragment shader

// Shader reading code removed...

    const char* vSrc = vSource.c_str();
    int size = vSource.size();
    glShaderSource(vs, 1, &vSrc, &size);
    glCompileShader(vs);

    int result;
    glGetShaderiv(vs, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE)
    {
        int length;
        glGetShaderiv(vs, GL_INFO_LOG_LENGTH, &length);
        char* msg = new char[length];
        glGetShaderInfoLog(vs, length, &length, msg);
        std::cout << "Vertex Shader Message:\n" << msg << std::endl;
        exit(1);
    }

    const char* fSrc = fSource.c_str();
    int size2 = fSource.size();
    glShaderSource(fs, 1, &fSrc, &size2);
    glCompileShader(fs);

    int result2;
    glGetShaderiv(fs, GL_COMPILE_STATUS, &result2);
    if (result2 == GL_FALSE)
    {
        int length;
        glGetShaderiv(fs, GL_INFO_LOG_LENGTH, &length);
        char* msg = new char[length];
        glGetShaderInfoLog(fs, length, &length, msg);
        std::cout << "Fragment Shader Message:\n" << msg << std::endl;
        exit(1);
    }


    glAttachShader(programID, vs);
    glAttachShader(programID, fs);
    glLinkProgram(programID);
    glValidateProgram(programID);

And then in my initOpenGL function I have:

    float positions[6] =
    {
        -0.5, -0.5,
         0.0,  0.5,
         0.5, -0.5
    };

    glGenBuffers(1, &currentBuffer); // Generates the buffer
    glBindBuffer(GL_ARRAY_BUFFER, currentBuffer); // Binds it before we use it
    glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW); // Sends the data to OpenGL

    glEnableVertexAttribArray(0); // Enables the buffer layout
    glBindBuffer(GL_ARRAY_BUFFER, currentBuffer);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0); // Tells OpenGL how we stored the data

    s = new Shader("main.vsh", "main.fsh");
    glUseProgram(s->getShaderID());

Then, I render the data with the following call in my render function:

    glDrawArrays(GL_TRIANGLES, 0, 3);

Here is the vertex shader code:

#version 410 core
layout (location = 0) in vec4 position;
void main()
{
    gl_Position = position;
}

Here is the fragment shader code:

#version 410 core
layout (location = 0) out vec4 color;
void main(void)
{
    color = vec4(1.0, 0.0, 0.0, 1.0);
}

Have you tried checking the return codes of the OpenGL functions to see what's going wrong? — Alan Birtles, May 07 '21 at 07:49

Rabbid76 · Accepted Answer · 2021-05-07T07:54:43.353

This is not a problem with the shaders. However in a core profile OpenGL Context you have to create Vertex Array Object, since the default VAO (0) is not valid. This is not optional:

GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

glEnableVertexAttribArray(0); // Enables the buffer layout
glBindBuffer(GL_ARRAY_BUFFER, currentBuffer);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0)

You have to bind the VAO before the vertex specification. The vertex specification is stored in the VAO.

The vertex specification stored in the currently bound VAO is used when drawing a mesh. Hence, you need to make sure the VAO is bound before the drawing command as well:

glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, 3);

OpenGL Won't Render With Shaders Mac

1 Answers1