opengl-playground/main.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include "glad/glad.h"
#include <GLFW/glfw3.h>
#include "lib.h"

#define STB_IMAGE_IMPLEMENTATION
#define STBI_FAILURE_USERMSG
#include "stb_image.h"

int SCREEN_WIDTH = 1024;
int SCREEN_HEIGHT = 768;

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

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

int main(void) {
    glfwInit();

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window =
        checkPtr(glfwCreateWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "Learn OpenGL", NULL, NULL),
                 "Error creating GLFW window");
    if (window == NULL) glfwTerminate();

    glfwMakeContextCurrent(window);

    checkCode(gladLoadGLLoader((GLADloadproc)glfwGetProcAddress), "Error initializing GLAD");

    glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);

    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    GLuint shaderProgram =
        compileShaderProgram("shaders/main.vert", "shaders/main.frag", NULL);

    stbi_set_flip_vertically_on_load(true);
    GLuint texture1, texture2;
    glGenTextures(1, &texture1);
    glBindTexture(GL_TEXTURE_2D, texture1);
    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_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    int w1, h1, c1;
    unsigned char* container = stbi_load("container.jpg", &w1, &h1, &c1, 0);
    if (container == NULL) {
        fprintf(stderr, "Failed to load image\n");
        exit(-1);
    }
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w1, h1, 0, GL_RGB,  GL_UNSIGNED_BYTE, container);
    glGenerateMipmap(GL_TEXTURE_2D);

    glGenTextures(1, &texture2);
    glBindTexture(GL_TEXTURE_2D, texture2);
    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_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    int w2, h2, c2;
    unsigned char* smiley = stbi_load("awesomeface.png", &w2, &h2, &c2, 0);
    if (smiley == NULL) {
        fprintf(stderr, "Failed to load image\n");
        exit(-1);
    }
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w2, h2, 0, GL_RGBA, GL_UNSIGNED_BYTE, smiley);
    glGenerateMipmap(GL_TEXTURE_2D);

    stbi_image_free(container);
    stbi_image_free(smiley);

    float v1[] = {
        // Position           // Color            // UV
         0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   2.0f, 2.0f,
         0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   2.0f, 0.0f,
        -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.0f, 0.0f,
        -0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   0.0f, 2.0f
    };

  unsigned int indices[] = {  
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };

    GLuint vaos[2];
    GLuint vbos[2];
    unsigned int EBO;
    glGenVertexArrays(2, vaos);
    glGenBuffers(1, &EBO);
    glGenBuffers(2, vbos);

    glBindVertexArray(vaos[0]);
    glBindBuffer(GL_ARRAY_BUFFER, vbos[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(v1), v1, 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, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3*sizeof(float)));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6*sizeof(float)));
    glEnableVertexAttribArray(2);

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

    glUseProgram(shaderProgram);
    int t1Loc = glGetUniformLocation(shaderProgram, "t1");
    glUniform1i(t1Loc, 0);
    int t2Loc = glGetUniformLocation(shaderProgram, "t2");
    glUniform1i(t2Loc, 1);

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

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

        float timeValue = glfwGetTime();
        float mix = (sin(timeValue) / 2.0f) + 0.5f;
        glUseProgram(shaderProgram);
        int offsetLoc = glGetUniformLocation(shaderProgram, "mixAmount");
        glUniform1f(offsetLoc, mix);

        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, texture1);
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, texture2);

        glBindVertexArray(vaos[0]);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(2, vaos);
    glDeleteBuffers(2, vbos);
    glDeleteProgram(shaderProgram);
    glfwTerminate();
    return 0;
}