main.cpp

#include <iostream>
#include <glad/glad.h>
#include <glfw3.h>
#include "shader.h"

// GL Mathematics
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <glm/gtx/string_cast.hpp>

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
float ratio = 0;

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);

    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
        ratio = fmin(1.0f, ratio + 0.001f);

    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
        ratio = fmax(0.0f, ratio - 0.001f);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}

int main()
{
    // the following snippet does the following: mat = 2 * I * Transform
    glm::mat4 mat = glm::mat4(1.0f); /// mat = I
    mat = glm::scale(mat, glm::vec3(2, 2, 2)); // mat = 2 * I
    mat = glm::translate(mat, glm::vec3(1.0f, 2.0f, 3.0f)); // mat = (2I) * Transform (INCORRECT)
    /*
    * The advised order of operations is:
    *   1) Scale
    *   2) Rotate
    *   3) Translate
    * The earliest operation should be the rightmost matrix and the last operation should be the leftmost matrix:
    *   M = Translate * Rotate * Scale
    * in GLM syntax:
    *   mat = translate(mat, ...)
    *   mat = rotate(mat, ...)
    *   mat = scale(mat, ...) 
    */

    // glfw: initialize and configure
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);


    // glfw window creation
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    shader shader("shader_source/shader.vert", "shader_source/shader.frag" );

    float vertices[] = {
        // positions          // colors           // texture coords
         0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f,   // top right
         0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f,   // bottom right
        -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.0f, 0.0f,   // bottom left
        -0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,   0.0f, 1.0f    // top left 
    };

    unsigned int indices[] = { 0, 1, 3, 
                               1, 2, 3 };

    unsigned int VAO, VBO, EBO;
    glGenVertexArrays(1, &VAO);

    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    glBindVertexArray(VAO);

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

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

    // vertex position
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    // vertex color
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    // vertex texture
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    /// texture handling
    unsigned int texture[2];
    glGenTextures(2, texture);
    
    // After activating a texture unit, a subsequent glBindTexture call will bind that texture to the currently active texture unit.
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture[0]);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    int width, height, nrChannels;
    stbi_set_flip_vertically_on_load(true);
    unsigned char* data = stbi_load("resources/textures/container.jpg", &width, &height, &nrChannels, 0);
    if (data) {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
        std::cout << "ERROR::FAILED TO LOAD TEXTURE" << std::endl;
    stbi_image_free(data);

    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, texture[1]);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    data = stbi_load("resources/textures/awesomeface.png", &width, &height, &nrChannels, 0);
    if (data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    stbi_image_free(data);

    // transformation
    glm::mat4 transf = glm::mat4(1.0);
    transf = glm::translate(transf, glm::vec3(0.25, 0.25, 0));
    transf = glm::rotate(transf, glm::radians(-30.0f), glm::vec3(0.0, 0.0, 1.0f));
    transf = glm::scale(transf, glm::vec3(0.5, 0.5, 1.0f));

    shader.use();
    shader.setInt("texture0", 0); // the first sampler references texture unit 0
    shader.setInt("texture1", 1); // the second sampler references texture unit 1

    // pass transform matrix to shader
    unsigned int transformLoc = glGetUniformLocation(shader.getID(), "transform");
    glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(transf));

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

        // render
        glClearColor(0.2f, 1.0f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        shader.setFloat("ratio", ratio);
        std::cout << ratio << std::endl;
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // glfw: terminate, clearing all previously allocated GLFW resources.
    glfwTerminate();
    return 0;

   
}