OpenGL - Exception at clear Color

Question

I'm trying to open a window using glfw3, and paint the background blue. Here's my code:

#include <glad\glad.h>
#include <GLFW/glfw3.h>
GLFWwindow* window;
int main( void )
{
    int windowWidth = 1024;
    int windowHeight = 768;
    glfwInit();  
    glfwWindowHint(GLFW_SAMPLES, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    window = glfwCreateWindow( 1024, 768, "Tutorial 14 - Render To Texture", NULL, NULL);

    glfwMakeContextCurrent(window);

    glfwGetFramebufferSize(window, &windowWidth, &windowHeight);
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    glfwPollEvents();
    // Dark blue background
    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
    return 0;
}

At glClearColor, it throws

Unhandled exception at 0x74D2CB49 in rendertotexture.exe: 0xC0000005: Access violation executing location 0x00000000.

I already tried GLFW exception on glClearColor and glClear. I'm using Visual Studio 2017.

"I already tried [GLFW exception on glClearColor and glClear](https://stackoverflow.com/questions/45118349/glfw-exception-on-glclearcolor-and-glclear)."...then where's your `gladLoadGL()`/`gladLoadGLLoader()` call? — genpfault, Nov 15 '18 at 18:54
@QStollen: Did you call it after `glfwMakeContextCurrent` – it needs a OpenGL context bound to the current thread, in order to work. — datenwolf, Nov 15 '18 at 22:28

score 1 · Answer 1 · answered Nov 21 '18 at 05:20

You need to initialize glew and call glfwSwapBuffers(window).

See: https://www.glfw.org/docs/3.0/window.html

GLFW windows are always double buffered. That means that you have two rendering buffers; a front buffer and a back buffer. The front buffer is the one being displayed and the back buffer the one you render to.

When the entire frame has been rendered, it is time to swap the back and the front buffers in order to display what has been rendered and begin rendering a new frame. This is done with glfwSwapBuffers.

int main(void)
 {
    GLFWwindow* window;

    int windowWidth = 1024;
    int windowHeight = 768;
    glfwInit();
    glfwWindowHint(GLFW_SAMPLES, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    window = glfwCreateWindow(1024, 768, "Tutorial 14 - Render To Texture", NULL, NULL);

    glfwMakeContextCurrent(window);

    glewExperimental = true; // Needed in core profile
    if (glewInit() != GLEW_OK) {
       fprintf(stderr, "Failed to initialize GLEW\n");
    }

    glfwGetFramebufferSize(window, &windowWidth, &windowHeight);
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    while (!glfwWindowShouldClose(window))
    {
       glClear(GL_COLOR_BUFFER_BIT);
       glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
       glfwSwapBuffers(window);
       glfwPollEvents();
    }

    return 0;
}

OpenGL - Exception at clear Color

1 Answers1