Tutorial code for modern OpenGL rendering

CMakeLists.txt

@@ -6,8 +6,8 @@ set(CMAKE_CXX_STANDARD 17)
 find_package(OpenGL REQUIRED)
 find_package(glfw3 REQUIRED)
 
-add_executable(ecsgame main.cpp)
+add_executable(ecsgame glad.c main.cpp)
 
 include_directories(${OPENGL_INCLUDE_DIRS})
 
-target_link_libraries(ecsgame ${OPENGL_LIBRARY} glfw)
+target_link_libraries(ecsgame ${OPENGL_LIBRARY} glfw ${CMAKE_DL_LIBS})

README.md

@@ -1,3 +1,5 @@
 # ECSGame
 
 C++ ECS OpenGL game demo
+
+Some code adapted from Joey de Vries' (https://twitter.com/JoeyDeVriez) tutorials at https://learnopengl.com/About licensed under https://creativecommons.org/licenses/by-nc/4.0/.

main.cpp

@@ -1,9 +1,15 @@
 #include <iostream>
 #include "ECS.h"
+#include <glad/glad.h>
 #include <GLFW/glfw3.h>
+#include <GL/gl.h>
 
 using namespace ECS;
 
+
+World *world = World::createWorld();
+
+
 struct Position {
     Position(float x, float y, float z) : x(x), y(y), z(z) {}
 
@@ -14,16 +20,35 @@ struct Position {
     float z;
 };
 
+struct Movement {
+    Movement(float speedX, float speedY, float speedZ) : speedX(speedX), speedY(speedY), speedZ(speedZ) {}
+
+    float speedX;
+    float speedY;
+    float speedZ;
+
+    int movingX = 0;
+    int movingY = 0;
+    int movingZ = 0;
+
+    float velocityX = 0.0f;
+    float velocityY = 0.0f;
+    float velocityZ = 0.0f;
+};
+
+struct InputEvent {
+    int key;
+    int action;
+};
+
 class GravitySystem : public EntitySystem {
 public:
-    GravitySystem(float amount) {
+    explicit GravitySystem(float amount) {
         gravityAmount = amount;
     }
 
-    virtual ~GravitySystem() {}
+    void tick(World *pWorld, float deltaTime) override {
-
+        pWorld->each<Position>([&](Entity *ent, ComponentHandle<Position> position) {
-    virtual void tick(World *world, float deltaTime) override {
-        world->each<Position>([&](Entity *ent, ComponentHandle<Position> position) {
             position->y += gravityAmount * deltaTime;
         });
     }
@@ -32,25 +57,107 @@ private:
     float gravityAmount;
 };
 
-static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
+class PositionDebugOutputSystem : public EntitySystem {
-{
+public:
+    void tick(World *pWorld, float deltaTime) override {
+        pWorld->each<Position>([&](Entity *ent, ComponentHandle<Position> position) {
+            std::cout << ent->getEntityId() << ": "
+                      << position->x << ", "
+                      << position->y << ", "
+                      << position->z
+                      << std::endl;
+        });
+    }
+};
+
+class KeyboardMovementSystem : public EntitySystem, public EventSubscriber<InputEvent> {
+    void configure(World *pWorld) override {
+        pWorld->subscribe<InputEvent>(this);
+    }
+
+    void receive(World *pWorld, const InputEvent &event) override {
+        if (event.key == GLFW_KEY_W) {
+            world->each<Movement>([&](Entity *ent, ComponentHandle<Movement> movement) {
+                if (event.action == GLFW_PRESS) {
+                    movement->movingZ = -1;
+                } else if (event.action == GLFW_RELEASE) {
+                    movement->movingZ = 0;
+                }
+            });
+        } else if (event.key == GLFW_KEY_S) {
+            world->each<Movement>([&](Entity *ent, ComponentHandle<Movement> movement) {
+                if (event.action == GLFW_PRESS) {
+                    movement->movingZ = 1;
+                } else if (event.action == GLFW_RELEASE) {
+                    movement->movingZ = 0;
+                }
+            });
+        } else if (event.key == GLFW_KEY_A) {
+            world->each<Movement>([&](Entity *ent, ComponentHandle<Movement> movement) {
+                if (event.action == GLFW_PRESS) {
+                    movement->movingX = 1;
+                } else if (event.action == GLFW_RELEASE) {
+                    movement->movingX = 0;
+                }
+            });
+        } else if (event.key == GLFW_KEY_D) {
+            world->each<Movement>([&](Entity *ent, ComponentHandle<Movement> movement) {
+                if (event.action == GLFW_PRESS) {
+                    movement->movingX = -1;
+                } else if (event.action == GLFW_RELEASE) {
+                    movement->movingX = 0;
+                }
+            });
+        }
+        std::cout << "MyEvent was emitted!" << std::endl;
+    }
+
+    void tick(World *pWorld, float deltaTime) override {
+        pWorld->each<Position, Movement>(
+                [&](Entity *ent, ComponentHandle<Position> position, ComponentHandle<Movement> movement) {
+                    position->x += movement->movingX * movement->speedX * deltaTime;
+                    position->y += movement->movingY * movement->speedY * deltaTime;
+                    position->z += movement->movingZ * movement->speedZ * deltaTime;
+                });
+    }
+
+    void unconfigure(World *pWorld) override {
+        pWorld->unsubscribeAll(this);
+    }
+};
+
+
+static void key_callback(GLFWwindow *window, int key, int scancode, int action, int mods) {
     if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
         glfwSetWindowShouldClose(window, GLFW_TRUE);
+
+    world->emit<InputEvent>({key, action});
 }
 
+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(1.0f, 0.5f, 0.2f, 1.0f);\n"
+                                   "}\n\0";
+
 int main() {
-    World *world = World::createWorld();
     world->registerSystem(new GravitySystem(-9.8f));
+    world->registerSystem(new PositionDebugOutputSystem());
+    world->registerSystem(new KeyboardMovementSystem());
 
     Entity *ent = world->create();
-    ent->assign<Position>(0.f, 0.f, 0.f); // assign() takes arguments and passes them to the constructor
+    ent->assign<Position>(0.f, 0.f, 0.f);
-
+    ent->assign<Movement>(1.f, 1.f, 1.f);
-    world->tick(1.0f);
 
     ComponentHandle<Position> pos = ent->get<Position>();
 
-    std::cout << "y position after tick: " << pos->y << std::endl;
-
     GLFWwindow *window;
 
     /* Initialize the library */
@@ -69,11 +176,119 @@ int main() {
 
     glfwSetKeyCallback(window, key_callback);
 
+    // glad: load all OpenGL function pointers
+    // ---------------------------------------
+    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
+    {
+        std::cout << "Failed to initialize GLAD" << std::endl;
+        return -1;
+    }
+
+    // build and compile our shader program
+    // ------------------------------------
+    // vertex shader
+    int vertexShader = glCreateShader(GL_VERTEX_SHADER);
+    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
+    glCompileShader(vertexShader);
+    // check for shader compile errors
+    int success;
+    char infoLog[512];
+    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
+    if (!success)
+    {
+        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
+        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
+    }
+    // fragment shader
+    int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
+    glCompileShader(fragmentShader);
+    // check for shader compile errors
+    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
+    if (!success)
+    {
+        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
+        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
+    }
+    // link shaders
+    int shaderProgram = glCreateProgram();
+    glAttachShader(shaderProgram, vertexShader);
+    glAttachShader(shaderProgram, fragmentShader);
+    glLinkProgram(shaderProgram);
+    // check for linking errors
+    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
+    if (!success) {
+        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
+        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
+    }
+    glDeleteShader(vertexShader);
+    glDeleteShader(fragmentShader);
+
+    // set up vertex data (and buffer(s)) and configure vertex attributes
+    // ------------------------------------------------------------------
+    float vertices[] = {
+            0.5f,  0.5f, 0.0f,  // top right
+            0.5f, -0.5f, 0.0f,  // bottom right
+            -0.5f, -0.5f, 0.0f,  // bottom left
+            -0.5f,  0.5f, 0.0f   // top left
+    };
+    unsigned int indices[] = {  // note that we start from 0!
+            0, 1, 3,  // first Triangle
+            1, 2, 3   // second Triangle
+    };
+    unsigned int VBO, VAO, EBO;
+    glGenVertexArrays(1, &VAO);
+    glGenBuffers(1, &VBO);
+    glGenBuffers(1, &EBO);
+    // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
+    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);
+
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+    glEnableVertexAttribArray(0);
+
+    // note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    // remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
+    //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+    // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
+    // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
+    glBindVertexArray(0);
+
+    double timeInLastFrame = glfwGetTime();
+    double elapsed_time = 0.0;
+
     /* Loop until the user closes the window */
     while (!glfwWindowShouldClose(window)) {
+        // Delta time handling
+        double delta = glfwGetTime() - timeInLastFrame;
+        timeInLastFrame = glfwGetTime();
+        elapsed_time += delta;
+
+        std::cout << "Elapsed time: " << elapsed_time << std::endl;
+
+        world->tick(delta);
+
         /* Render here */
+        // render
+        // ------
+        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT);
 
+        // draw our first triangle
+        glUseProgram(shaderProgram);
+        glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
+        //glDrawArrays(GL_TRIANGLES, 0, 6);
+        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+        // glBindVertexArray(0); // no need to unbind it every time
+
         /* Swap front and back buffers */
         glfwSwapBuffers(window);