glVertexAttribPointer causing Invalid Operation error despite having vao

Question

Probably a quick question as I'm probably messing up something silly.

I've been trying to get a rendering system working on my old laptop on my free time. I was having issues and thought that it had something to do with the original design of my program but now I'm not so sure if it's that. I've reduced my render call to a simple render triangle example and still get the error.

void RenderSystem::Render()
{
    glClear( GL_COLOR_BUFFER_BIT );
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray( vao );

    glUseProgram( shaderProgram );
    CheckForError();
    glEnableVertexAttribArray( coord3dAttrib );
    CheckForError();

    GLfloat triangle[] = {
        0.0, 0.8, 0.0,
        -0.8, -0.8, 0.0,
        0.8, -0.8, 0.0,
    };

    glVertexAttribPointer(
        coord3dAttrib,
        3,
        GL_FLOAT,
        GL_FALSE,
        0,
        triangle
    );
    CheckForError();

    glDrawArrays(GL_TRIANGLES, 0 , 3);
    CheckForError();

    glDisableVertexAttribArray( coord3dAttrib );
    CheckForError();

    SDL_GL_SwapWindow( window );
}

Ignore the excessive CheckForError function calls -- this was merely to pinpoint which function was causing the error. It definitely occurs right after my call to glVertexAttribPointer.

It should be worth noting that all of the shaders and programs have compiled properly. The context was initialized and is handled by SDL2 and there have been no errors with regards to the context initialization. The only weird error I get is an invalid enumerant when calling SDL_GL_SetSwapInterval(0) to turn off vsync.

Also, this laptop is an old laptop and I'm starting to consider the fact that maybe the drivers / hardware of this computer is too old to actually do this more modern style of GL rendering. In which case, is there a good way to test which version of GL I should run on this hardware? (I'm on Crunchbang, a linux debian distribution. Iirc, I've set up and installed a lot of drivers and headers properly so I would assume it should work but if driver issues cause this, I'll look into it more.)

Any clues? I'm assuming that I'm missing something basic as it has been a while since I last worked with OpenGL.

I'm not actually sure. I used to have a VBO but removed it when I wanted to simplify the rendering process. I'll try adding a VBO but when I had one before, it was still causing an Invalid Operation error. When I removed all of that to try and render a simple triangle, it still gave me the error. I saw a few posts online about how this error can occur when not having a VAO and re-added the VAO initialization call just to see if it would fix the error. — TheYokai
It's not valid to have a vertex attribute pointer point to client memory in a core profile. "If pointer is not NULL, a non-zero named buffer object must be bound to the GL_ARRAY_BUFFER target (see glBindBuffer), otherwise an error is generated. pointer is treated as a byte offset into the buffer object's data store. The buffer object binding (GL_ARRAY_BUFFER_BINDING) is saved as generic vertex attribute array state (GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING) for index index." That behavior is relaxed for a compatibility profile, but I don't know what kind of profile you have. — Andon M. Coleman
Right, when you put it like that, it makes way more sense. I'm trying to access a pool of memory that is inaccessible from the hardware. — TheYokai

lfn lfn · Accepted Answer · 2015-03-03T18:29:13

I think you are going wrong on your bindings. You need to generate a name to the VAO only once, bind and setup your buffer, and then use the assigned name to bind it later.

So, you should do the following.

Generate the name to your VAO variable in some initialization method (when you setup your buffers):

GLuint vao; // make this accessible in global scope or through some class
glGenVertexArrays(1, &vao);

Call the bind function as you did before, in your render method, using the previous assigned name to your variable vao:
```
glUseProgram( shaderProgram );
glBindVertexArray( vao );
```

I think this may be your answer, at last, this is how I'm used to see VAO being handled in books and tutorials.

glVertexAttribPointer causing Invalid Operation error despite having vao

1 Answers