main.cpp

#include <iostream>
#include <glad/glad.h>
#include <GLFW/glfw3.h>
void processInput(GLFWwindow *window);
void framebuffer_size_callback(GLFWwindow* window, int width, int height);

const char *vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 aPos;\n"
    "void main()\n"
    "{\n"
    "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
    "}\0";

const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"	FragColor = vec4(0.8f, 0.3f, 0.02f, 1.0f);\n"
"}\n\0";


int main() {
    //initialise the glfw
    glfwInit();

    //no clue yet
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);


    //making the points of the triangle
    //we use a range of -1 to 1, with the limit of the range being the border of the window
    //also, as openGL is a 3d renderer, the third coordinate is the z axis.
    GLfloat points[] = {
        -0.5f, -0.5f, 0.0f, //lower left corner
        -0.25f, 0.0f, 0.0f, // mid left
        0.0f, -0.5f, 0.0f, // low mid
        0.5f, -0.5f, 0.0f, //low right
        0.25f, 0.0f, 0.0f, // mid right
        0.0f, 0.5f, 0.0f // top mid
    };

    GLuint indices[] ={
        0, 1, 2, // POSITIONING OF THE FIRST TRIANGLE
        2, 3, 4, // POSITIONING OF THE SECOND TRIANGLE
        1, 4, 5 // POSITIONING OF THE THIRD TRIANGLE
    };


    //just error checks and for debugging
    GLFWwindow* window = glfwCreateWindow(800, 600, "Triangle", NULL, NULL);
    if (window == NULL) {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    //just little error checks to give a reason for progam failing
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }


    glViewport(0, 0, 800, 600);

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    GLuint shaderProgram = glCreateProgram();

    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);


    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);


    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    GLuint VAO, VBO, EBO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);


    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);


    glClearColor(0.5f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);


    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

    while (!glfwWindowShouldClose(window)) {
        //input
        processInput(window);

        //funny
        glClearColor(0.5f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glUseProgram(shaderProgram);
        glBindVertexArray(VAO);
        //glDrawArrays(GL_TRIANGLES, 0, 3); FOR ONE TRIANGLE
        glDrawElements(GL_TRIANGLES, 9, GL_UNSIGNED_INT, 0);
        //check for events
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);
    glDeleteProgram(shaderProgram);





    glfwDestroyWindow(window);
    glfwTerminate();
    return 0;
    // TIP See CLion help at <a href="https://www.jetbrains.com/help/clion/">jetbrains.com/help/clion/</a>. Also, you can try interactive lessons for CLion by selecting 'Help | Learn IDE Features' from the main menu.
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
    glViewport(0, 0, width, height);
}

void processInput(GLFWwindow *window) {
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}