First edit for framebuffers but it's slapped together and doesn't work yet.

21-framebuffers/config.json

@@ -8,6 +8,10 @@
       "vertex_path": "shaders/19-vert.glsl",
       "frag_path": "shaders/19-lightsource.frag.glsl"
     },
+    "screen_shader": {
+      "vertex_path": "shaders/21-screen.vert.glsl",
+      "frag_path": "shaders/21-screen.frag.glsl"
+    },
     "materials": {
       "default": {
         "ambient": [0.5, 0.5, 0.5],
@@ -57,11 +61,11 @@
         "rotation": {"angle": 90.0, "axes": [1.0,0.0,0.0]},
         "scale": 1.0,
         "material": "default"},
-      {"model": "window", "position": [1.75,  0.25,  0.25],
+      {"model": "window", "position": [1.5,  0.25,  0.0],
         "rotation": {"angle": 90.0, "axes": [1.0,0.0,0.0]},
         "scale": 1.0,
         "material": "shiny"},
-      {"model": "window", "position": [1.5,  0.25,  0.0],
+      {"model": "window", "position": [1.75,  0.25,  0.25],
         "rotation": {"angle": 90.0, "axes": [1.0,0.0,0.0]},
         "scale": 1.0,
         "material": "shiny"}

21-framebuffers/shaders/21-screen.frag.glsl

@@ -0,0 +1,11 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec2 TexCoords;
+
+uniform sampler2D screenTexture;
+
+void main()
+{
+    FragColor = texture(screenTexture, TexCoords);
+}

21-framebuffers/shaders/21-screen.vert.glsl

@@ -0,0 +1,11 @@
+#version 330 core
+layout (location = 0) in vec2 aPos;
+layout (location = 1) in vec2 aTexCoords;
+
+out vec2 TexCoords;
+
+void main()
+{
+    gl_Position = vec4(aPos.x, aPos.y, 0.0, 1.0);
+    TexCoords = aTexCoords;
+}

21-framebuffers/src/components.hpp

@@ -102,7 +102,7 @@ namespace components {
 
   struct Scene {
     components::Shader shader;
-    components::Shader light_shader;
+    components::Shader screen_shader;
     std::unordered_map<std::string, Material> materials;
     std::unordered_map<std::string, Model> models;
     std::vector<Thing> things;
@@ -110,5 +110,5 @@ namespace components {
     Lighting light;
   };
 
-  ENROLL_COMPONENT(Scene, shader, light_shader, materials, models, things, camera, light);
+  ENROLL_COMPONENT(Scene, shader, screen_shader, materials, models, things, camera, light);
 }

21-framebuffers/src/main.cpp

@@ -10,6 +10,10 @@ void init_glfw() {
   glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
   glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
   glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+
+#ifdef __APPLE__
+  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+#endif
 }
 
 void framebuffer_size_callback(GLFWwindow *, int width, int height) {

21-framebuffers/src/scene.cpp

@@ -34,15 +34,19 @@ void Scene::draw_thing(Shader& with_shader, Thing& thing)
 }
 
 void Scene::render(GLFWwindow* window) {
-  glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-
   glm::mat4 view = camera.look_at();
   glm::mat4 projection = glm::mat4(1.0f);
 
   // fov, aspect, near plane, far plane
   projection = glm::perspective(glm::radians(camera.fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
 
+  // framebuffer stuff here
+  glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+  glEnable(GL_DEPTH_TEST);
+  glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
+  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+  // render the scene
   shader.use();
   shader.setMat4("view", view);
   shader.setMat4("projection", projection);
@@ -50,6 +54,19 @@ void Scene::render(GLFWwindow* window) {
   for(auto& thing : things) {
     draw_thing(shader, thing);
   }
+
+  // disable the frame buffer
+  glBindFramebuffer(GL_FRAMEBUFFER, 0);
+  glDisable(GL_DEPTH_TEST);
+
+  glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+  glClear(GL_COLOR_BUFFER_BIT);
+
+  // render the screen quad
+  screen_shader.use();
+  glBindVertexArray(quadVAO);
+  glBindTexture(GL_TEXTURE_2D, textureColorBuffer);
+  glDrawArrays(GL_TRIANGLES, 0, 6);
 }
 
 void Scene::cleanup() {

21-framebuffers/src/scene.hpp

@@ -26,7 +26,7 @@ struct Thing {
 
 struct Scene {
   Shader shader;
-  Shader light_shader;
+  Shader screen_shader;
 
   std::unordered_map<std::string, components::Material> materials;
   Camera camera;
@@ -36,10 +36,27 @@ struct Scene {
 
   float deltaTime = 0.0f;
   float lastFrame = 0.0f;
+  unsigned int framebuffer = 0;
+  unsigned int textureColorBuffer = 0;
+  unsigned int quadVAO = 0;
+  unsigned int quadVBO = 0;
+  unsigned int rbo = 0;
+
+  float quadVertices[24] = {
+    // vertex attributes for a quad that fills the entire screen in Normalized Device Coordinates.
+    // positions   // texCoords
+    -1.0f,  1.0f,  0.0f, 1.0f,
+    -1.0f, -1.0f,  0.0f, 0.0f,
+    1.0f, -1.0f,  1.0f, 0.0f,
+
+    -1.0f,  1.0f,  0.0f, 1.0f,
+    1.0f, -1.0f,  1.0f, 0.0f,
+    1.0f,  1.0f,  1.0f, 1.0f
+  };
 
   Scene(components::Scene& config):
     shader{config.shader.vertex_path, config.shader.frag_path},
-    light_shader{config.light_shader.vertex_path, config.shader.frag_path},
+    screen_shader{config.screen_shader.vertex_path, config.shader.frag_path},
     materials{config.materials},
     camera{
       .position=config.camera.position,
@@ -64,8 +81,46 @@ struct Scene {
           thing.scale);
     }
 
+    // screen quadVAO
+    glGenVertexArrays(1, &quadVAO);
+    glGenBuffers(1, &quadVBO);
+    glBindVertexArray(quadVAO);
+    glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
+    glEnableVertexAttribArray(0);
+    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
+    glEnableVertexAttribArray(1);
+    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2 * sizeof(float)));
+
+
+    // framebuffer config
+    glGenFramebuffers(1, &framebuffer);
+    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+
+    // create a color attachment texture
+    glGenTextures(1, &textureColorBuffer);
+    glBindTexture(GL_TEXTURE_2D, textureColorBuffer);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, SCR_WIDTH, SCR_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureColorBuffer, 0);
+
+    // create renderbuffer object for depth and stencil attachment
+    glGenRenderbuffers(1, &rbo);
+    glBindRenderbuffer(GL_RENDERBUFFER, rbo);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, SCR_WIDTH, SCR_HEIGHT);
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);
+
+    glBindRenderbuffer(GL_RENDERBUFFER, 0);
+
+    dbc::check(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE, "Frame buffer not complete.");
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
     shader.use();
     shader.apply_lighting(light);
+
+    screen_shader.use();
+    screen_shader.setInt("screenTexture", 0);
   }
 
   void update();

21-framebuffers/tests/config.json

@@ -72,7 +72,7 @@
         "material": "default"
       },
   "shader_test": {
-    "vertex_path": "shaders/16-vert.glsl",
-    "frag_path": "shaders/16-frag.glsl"
+    "vertex_path": "shaders/19-vert.glsl",
+    "frag_path": "shaders/19-frag.glsl"
   }
 }