CODEWITHSUNDEEP
c++openglshaderglfw
Steve
Steve

Reputation: 6424

Why don't I need to load shaders when using GLFW?

According to a book I'm reading, vertex and fragment shaders are required for the newest versions of OpenGL, and if they're not provided, rendering will not happen properly.

I'm using the GLFW library (3.0.4), and in the spinning triangle Hello World type example, there is no code to load the GPU with these shaders. I cannot find anything that says whether GLFW provides default shaders or not...

Below is the example code I'm referring to. There are calls to glColor3f(), which might be involved.

Also, I notice that the OpenGL.org documentation doesn't seem to list glColor*() at all! Why is this?

#include "GLFW\glfw3.h"

static void error_callback(int error, const char* description)
{
    fputs(description, stderr);
}
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
}
int main(void)
{
    GLFWwindow* window;
    glfwSetErrorCallback(error_callback);
    if (!glfwInit())
        exit(EXIT_FAILURE);
    window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        exit(EXIT_FAILURE);
    }

    glfwMakeContextCurrent(window);

    glfwSetKeyCallback(window, key_callback);
    while (!glfwWindowShouldClose(window))
    {
        float ratio;
        int width, height;
        glfwGetFramebufferSize(window, &width, &height);
        ratio = width / (float)height;

        glViewport(0, 0, width, height);
        glClear(GL_COLOR_BUFFER_BIT);

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-ratio, ratio, -1.f, 1.f, 1.f, -1.f);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glRotatef((float)glfwGetTime() * 50.f, 0.f, 0.f, 1.f);

        glBegin(GL_TRIANGLES);
        glColor3f(1.f, 0.f, 0.f);
        glVertex3f(-0.6f, -0.4f, 0.f);
        glColor3f(0.f, 1.f, 0.f);
        glVertex3f(0.6f, -0.4f, 0.f);
        glColor3f(0.f, 0.f, 1.f);
        glVertex3f(0.f, 0.6f, 0.f);
        glEnd();

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwDestroyWindow(window);
    glfwTerminate();
    exit(EXIT_SUCCESS);
}

Upvotes: 1

Views: 1396

Answers (1)

ratchet freak
ratchet freak

Reputation: 48196

glBegin and glEnd indicate you use immediate mode aka the fixed function pipeline which predates shaders. That pipeline is also outdated and removed from 4.0+ core profiles.

Upvotes: 3

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