Implement skybox

shaders/sb_frag.glsl

@@ -0,0 +1,11 @@
+#version 330 core
+
+in vec3 uv_coords;
+
+uniform samplerCube cubemap;
+
+out vec4 color;
+
+void main() {
+  color = texture(cubemap, uv_coords);
+}

shaders/sb_vert.glsl

@@ -0,0 +1,16 @@
+#version 330 core
+
+layout(location=0) in vec3 position;
+layout(location=1) in vec3 normal;
+layout(location=2) in vec2 uv;
+
+uniform mat4 view;
+uniform mat4 projection;
+
+out vec3 uv_coords;
+
+void main() {
+  vec4 pos    = projection * view * vec4(position, 1.0);
+  gl_Position = pos.xyww;
+  uv_coords   = position;
+}

src/main.cc

@@ -144,6 +144,7 @@ struct FrameBuffer {
 
 FrameBuffer create_frame_buffer(unsigned int width, unsigned int height);
 void delete_frame_buffer(FrameBuffer &buffer);
+GLuint load_cubemap(std::vector<std::string> textures);
 
 int main() {
   if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
@@ -221,8 +222,36 @@ int main() {
     13, 15, 16
   };
 
-  Model backpack = {"models/suzanne/suzanne.obj"};
-  Mesh light     = {vertices, indices, {}};
+  Model suzanne = {"models/suzanne/suzanne.obj"};
+  Mesh light    = {vertices, indices, {}};
+
+  std::vector<Vertex> skybox_vertices = {
+    Vertex{glm::vec3(-1.0f,  1.0f, -1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3(-1.0f, -1.0f, -1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3( 1.0f, -1.0f, -1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3( 1.0f,  1.0f, -1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3(-1.0f, -1.0f,  1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3(-1.0f,  1.0f,  1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3( 1.0f, -1.0f,  1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+    Vertex{glm::vec3( 1.0f,  1.0f,  1.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(1.0f, 1.0f)},
+  };
+
+  std::vector<GLuint> skybox_indices = {
+    0, 1, 2,
+    2, 3, 0,
+    4, 1, 0,
+    0, 5, 4,
+    2, 6, 7,
+    7, 3, 2,
+    4, 5, 7,
+    7, 6, 4,
+    0, 3, 7,
+    7, 5, 0,
+    1, 4, 2,
+    2, 4, 6,
+  };
+
+  Mesh skybox = {skybox_vertices, skybox_indices, {}};
 
   std::vector<Vertex> screen_vertices = {
     Vertex{glm::vec3(-1.0f, -1.0f, 0.0f), glm::vec3(1.0f, 1.0f, 1.0f), glm::vec2(0.0f, 0.0f)},
@@ -240,6 +269,7 @@ int main() {
 
   Shader main_shader     {"shaders/vert.glsl",    "shaders/frag.glsl"};
   Shader light_shader    {"shaders/vert.glsl",    "shaders/light_frag.glsl"};
+  Shader skybox_shader   {"shaders/sb_vert.glsl", "shaders/sb_frag.glsl"};
   Shader post_processing {"shaders/pp_vert.glsl", "shaders/pp_frag.glsl"};
 
   const float camera_speed   = 25.0f;
@@ -262,6 +292,7 @@ int main() {
   main_shader.set_float("material.shininess", 32.0f);
 
   light_shader.set_mat4("projection", projection);
+  skybox_shader.set_mat4("projection", projection);
 
   std::vector<glm::vec3> point_light_positions = {
     glm::vec3( 0.7f,  0.2f,  2.0f),
@@ -317,6 +348,18 @@ int main() {
     memset(quadratic, 0, sizeof(quadratic));
   }
 
+  // Load cube map
+  std::vector<std::string> cube_map_textures = {
+    "images/skybox/right.jpg",
+    "images/skybox/left.jpg",
+    "images/skybox/top.jpg",
+    "images/skybox/bottom.jpg",
+    "images/skybox/front.jpg",
+    "images/skybox/back.jpg",
+  };
+
+  GLuint cubemap = load_cubemap(cube_map_textures);
+
   const float sensitivity   = 0.1f;
   int last_mouse_x          = WINDOW_HALF_WIDTH;
   int last_mouse_y          = WINDOW_HALF_HEIGHT;
@@ -402,13 +445,16 @@ int main() {
     main_shader.set_float("spot_light.outer_cutoff", glm::cos(glm::radians(17.5)));
     main_shader.set_mat4("view", view);
     light_shader.set_mat4("view", view);
+    skybox_shader.set_mat4("view", glm::mat4(glm::mat3(view)));
 
     // Main render pass
     glBindFramebuffer(GL_FRAMEBUFFER, offscreen_buffer.fbo);
 
     glClearColor(0.04f, 0.08f, 0.08f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
     glEnable(GL_DEPTH_TEST);
+    glDepthFunc(GL_LEQUAL);
     glEnable(GL_CULL_FACE);
 
     model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, 0.0f));
@@ -416,7 +462,7 @@ int main() {
     main_shader.activate();
     main_shader.set_mat4("model", model);
     main_shader.set_mat3("normal_mat", normal_mat);
-    backpack.draw(main_shader);
+    suzanne.draw(main_shader);
 
     // Draw light source
     for (int i = 0; i < point_light_positions.size(); ++i) {
@@ -428,6 +474,14 @@ int main() {
       light.draw(light_shader);
     }
 
+    // Draw skybox
+    glDisable(GL_CULL_FACE);
+    skybox_shader.activate();
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_CUBE_MAP, cubemap);
+    skybox_shader.set_int("cubemap", 0);
+    skybox.draw(skybox_shader);
+
     // wireframe mode
     // glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
 
@@ -816,3 +870,25 @@ void delete_frame_buffer(FrameBuffer &buffer) {
   glDeleteTextures(1, &buffer.color);
   glDeleteRenderbuffers(1, &buffer.depth_stencil);
 }
+
+GLuint load_cubemap(std::vector<std::string> textures) {
+  GLuint cubemap;
+  glGenTextures(1, &cubemap);
+  glBindTexture(GL_TEXTURE_CUBE_MAP, cubemap);
+
+  int width, height, channels;
+  uint8_t *tex;
+  for (unsigned int i = 0; i < textures.size(); ++i) {
+    tex = stbi_load(textures[i].c_str(), &width, &height, &channels, 0);
+    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, tex);
+    stbi_image_free(tex);
+  }
+
+  glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+
+  return cubemap;
+}