glVertexAttribPointer causing Invalid Operation OpenGL error in D

Question

I have a simple D application using DerelictGL3 and DerelictSDL2. I am trying to render a red triangle using vertex buffer objects however whenever I run glVertexAttribPointer(position, 2, GL_FLOAT, GL_FALSE, float.sizeof * 2, null);, glGetError() returns 1282 (Invalid Operation). The code is as follows...

app.d

import std.string;
import std.conv;
import std.stdio;
import std.file;
import std.c.stdlib;

import derelict.opengl3.gl3;
import derelict.sdl2.sdl;

void main() {
    DerelictSDL2.load();
    DerelictGL3.load();

    assert(SDL_Init(SDL_INIT_VIDEO) >= 0);

    auto vertex_shader = (cast(string) read("shaders/minimal.vert")).toStringz;
    auto fragment_shader = (cast(string) read("shaders/minimal.frag")).toStringz;

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

    auto final_param = SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN;
    auto window = SDL_CreateWindow("Triangle", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, final_param);

    assert(window);

    SDL_GL_CreateContext(window);

    DerelictGL3.reload();

    GLfloat[] vertices = [1, 1, 1, -1, -1, 1, -0.8, -1, 1];

    uint vbo;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, vertices.length * float.sizeof, vertices.ptr, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    auto program = glCreateProgram();

    auto vshader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vshader, 1, &vertex_shader, null);
    glCompileShader(vshader);
    glAttachShader(program, vshader);

    auto fshader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fshader, 1, &fragment_shader, null);
    glCompileShader(fshader);
    glAttachShader(program, fshader);

    glLinkProgram(program);
    glUseProgram(program);

    auto position = glGetAttribLocation(program, "position");

    auto close = false;

    check();

    while(!close) {
        SDL_Event event;
        while(SDL_PollEvent(&event)) {
            if(event.type == SDL_QUIT) close = true;
        }

        glClearColor(1, 0.4, 0.4, 1);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glEnableVertexAttribArray(position);
        check("before"); // Does not return error.
        glVertexAttribPointer(position, 2, GL_FLOAT, GL_FALSE, float.sizeof * 2, null); // <- Causing Invalid Operation GL error.
        check("after"); // Returns error.

        glDrawArrays(GL_TRIANGLES, 0, 3);

        SDL_GL_SwapWindow(window);
    }
}

void check(string msg="") {
    auto error = glGetError();
    assert(error == 0, msg ~ ":" ~ to!string(error));
}

shaders/minimal.vert

#version 120
attribute vec2 position;
void main(void) {
    gl_Position = vec4(position, 0, 1);
}

shaders/minimal.frag

#version 120
void main(void) {
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}

When ignoring the error, a red rectangle is rendered in the top right corner of the screen.

I'm not sure about that D specifc libraries and stuff. You do not explictely require a core or compatibility profile with SDL, and I don't know what SDL will do in that case. But if you end up with a GL3.x _core_ profile, vertex array objects are mandatory, and the error would be understandable, since you don't have a VAO bound when you set the pointer. — derhass, Aug 16 '14 at 12:00
You set stride to 2*float.sizeof, which would mean between each attribute are two unused floats. — weltensturm, Aug 19 '14 at 09:02
@derhass so can I not use VBOs without requiring a core or compatibility profile? Other examples I've seen include SDL in the same way as above but use VBOs. — Asraelite, Aug 19 '14 at 10:19
@Asraelite: I did not say that. I did not talk abot VBOs at all (you can use them in any profile), but _VAOs_, different thing. All I said was that you _must_ use VAOs in core profile, and that I don't know if SDL will create a core profile with the attributes you vae set. — derhass, Aug 19 '14 at 16:20
If you're using OpenGL 3.2 (as specified in your window creation), why are you using `#version 120` in your shaders? (OpenGL 3.2 uses `#version 150`). — James Zhu, Aug 31 '14 at 19:06

score 3 · Accepted Answer · answered Dec 08 '14 at 13:32

3

You're missing a VAO which is required in OpenGL 3.2. You can create it before other buffers like this:

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

answered Dec 08 '14 at 13:32

SurvivalMachine

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score 1 · Answer 2 · answered Aug 19 '14 at 18:44

What might help is enabling OpenGL debug logging, you can do it like this: https://github.com/d-gamedev-team/gfm/blob/master/opengl/gfm/opengl/opengl.d#L419

Some drivers like the NVIDIA one provide extensive warning when something go wrong, the problem might not be where you think it is.

glVertexAttribPointer causing Invalid Operation OpenGL error in D

2 Answers2