Refactor, setup FBO, and render into ImGui window

imgui.ini

@@ -5,7 +5,7 @@ Collapsed=0
 
 [Window][Terrain Controls]
 Pos=0,19
-Size=1280,86
+Size=1498,94
 Collapsed=0
 DockId=0x00000001,0
 
@@ -19,11 +19,17 @@ Collapsed=0
 
 [Window][TerraVisor]
 Pos=0,0
-Size=1280,720
+Size=1498,720
 Collapsed=0
 
-[Docking][Data]
+[Window][Scene Window]
-DockSpace   ID=0x6F42A598 Window=0xE80F322C Pos=0,19 Size=1280,701 Split=Y
+Pos=0,115
-  DockNode  ID=0x00000001 Parent=0x6F42A598 SizeRef=1280,86 Selected=0xF69494A7
+Size=1498,605
-  DockNode  ID=0x00000002 Parent=0x6F42A598 SizeRef=1280,613 CentralNode=1
+Collapsed=0
+DockId=0x00000002,0
+
+[Docking][Data]
+DockSpace   ID=0x6F42A598 Window=0xE80F322C Pos=0,19 Size=1498,701 Split=Y Selected=0x9F2D9299
+  DockNode  ID=0x00000001 Parent=0x6F42A598 SizeRef=1280,94 Selected=0xF69494A7
+  DockNode  ID=0x00000002 Parent=0x6F42A598 SizeRef=1280,605 CentralNode=1 Selected=0x9F2D9299
 

include/scene.h

@@ -22,11 +22,15 @@ class Scene {
 
     private:
         void InitBuffers();
+        void InitQuadBuffers();
         void InitShaders();
 
         FBO fbo_;
+        FBO post_fbo_;
         GLuint shader_program_;
+        GLuint quad_shader_program_;
         GLuint vao_;
+        GLuint quad_vao_;
         float angle_;
         float scale_;
         float aspect_;

shaders/fragment.glsl

@@ -54,6 +54,6 @@ void main(void)
     // vec4 specular_term = atten*ks*Ls*pow(max(0.0, dot(rw, vw)), shininess);
 
     // fragcolor = ambient_term + diffuse_term + specular_term;
-    fragcolor = vec4(1.0, 0.0, 0.0, 1.0);
+    fragcolor = vec4(0.0, 0.0, 1.0, 1.0);
 }
 

shaders/quad_fragment.glsl

@@ -0,0 +1,12 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec2 TexCoord;
+
+uniform sampler2D screenTexture;
+
+void main()
+{
+    FragColor = texture(screenTexture, TexCoord);
+    //FragColor = vec4(vec3(1.0 - texture(screenTexture, TexCoord)), 1.0);
+}

shaders/quad_vertex.glsl

@@ -0,0 +1,12 @@
+#version 330 core
+layout(location = 0) in vec3 pos_attrib; //this variable holds the position of mesh vertices
+layout(location = 1) in vec2 tex_coord_attrib;
+layout(location = 2) in vec3 normal_attrib;  
+
+out vec2 TexCoord;
+
+void main()
+{
+    gl_Position = vec4(pos_attrib.xy, 0.0, 1.0);
+    TexCoord = tex_coord_attrib;
+}

source/fbo.cpp

@@ -19,6 +19,8 @@ void FBO::Init(int width, int height) {
     glGenTextures(1, &color_texture_id_);
     glBindTexture(GL_TEXTURE_2D, color_texture_id_);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     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, color_texture_id_, 0);

source/scene.cpp

@@ -27,16 +27,21 @@ namespace {
 const std::string kVertexShaderPath = "shaders/vertex.glsl";
 const std::string kFragmentShaderPath = "shaders/fragment.glsl";
 
+const std::string kQuadVertexPath = "shaders/quad_vertex.glsl";
+const std::string kQuadFragmentPath = "shaders/quad_fragment.glsl";
+
 } // namespace
 
 Scene::Scene(int width, int height) 
   : window_width(width),
     window_height(height),
     shader_program_(-1),
+    quad_shader_program_(-1),
     vao_(-1), 
+    quad_vao_(-1),
     angle_(0.0f), 
     scale_(1.0f), 
-    aspect_(1280.0f / 720.0f), 
+    aspect_(static_cast<float>(width) / static_cast<float>(height)), 
     near_z_(0.1f), far_z_(100.0f), 
     fov_(glm::pi<float>() / 4.0f) 
 {}
@@ -46,6 +51,7 @@ Scene::~Scene() {
     glDeleteVertexArrays(1, &vao_);
 
     fbo_.~FBO();
+    post_fbo_.~FBO();
 }
 
 void Scene::Init() {
@@ -55,9 +61,12 @@ void Scene::Init() {
     glEnable(GL_CULL_FACE);
 
     fbo_.Init(window_width, window_height);
+    post_fbo_.Init(window_width, window_height);
 
     InitBuffers();
     ReloadShader();
+    InitQuadBuffers();
+    quad_shader_program_ = InitShader(kQuadVertexPath.c_str(), kQuadFragmentPath.c_str());
 
     UpdateCamera();
     Uniforms::Init();
@@ -82,6 +91,34 @@ void Scene::InitBuffers() {
     glEnableVertexAttribArray(0);
 }
 
+void Scene::InitQuadBuffers() {
+    GLuint quad_vbo;
+    // Full-screen quad vertices (position and texture coordinates)
+    float quadVertices[] = {
+        // positions        // texCoords
+        -1.0f,  1.0f,  0.0f, 1.0f,  // Top-left
+        -1.0f, -1.0f,  0.0f, 0.0f,  // Bottom-left
+         1.0f,  1.0f,  1.0f, 1.0f,  // Top-right
+         1.0f, -1.0f,  1.0f, 0.0f   // Bottom-right
+    };
+
+    glGenVertexArrays(1, &quad_vao_);
+    glGenBuffers(1, &quad_vbo);
+    glBindVertexArray(quad_vao_);
+
+    glBindBuffer(GL_ARRAY_BUFFER, quad_vbo);
+    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)));
+
+    glBindVertexArray(0);
+}
+
+
 // Allows for runtime shader updates
 void Scene::ReloadShader() {
     GLuint new_shader = InitShader(kVertexShaderPath.c_str(), kFragmentShaderPath.c_str());
@@ -102,6 +139,8 @@ void Scene::Display(GLFWwindow* window) {
 
     fbo_.Bind();
 
+    glUseProgram(shader_program_);
+
     view_matrix_ = glm::lookAt(glm::vec3(Uniforms::SceneData.eye_w), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f));
     Uniforms::SceneData.PV = projection_matrix_ * view_matrix_; // Projection-View matrix
     Uniforms::BufferSceneData();
@@ -109,12 +148,30 @@ void Scene::Display(GLFWwindow* window) {
     glm::mat4 model_matrix = glm::rotate(angle_, glm::vec3(0.0f, 1.0f, 0.0f)) * glm::scale(glm::vec3(scale_));
     glUniformMatrix4fv(Uniforms::UniformLocs::M, 1, false, glm::value_ptr(model_matrix));
 
-    glUseProgram(shader_program_);
     glBindVertexArray(vao_);
     glDrawArrays(GL_TRIANGLES, 0, 3);
 
     fbo_.Unbind();
 
+    // post_fbo_ currently renders with a nasty artifact. Need to fix
+    post_fbo_.Bind();
+    glDisable(GL_DEPTH_TEST);
+
+    glUseProgram(quad_shader_program_);
+
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_2D, fbo_.GetColorTexture());
+
+    GLint screenTextureLoc = glGetUniformLocation(quad_shader_program_, "screenTexture");
+    glUniform1i(screenTextureLoc, 0);  // Texture unit 0
+
+    // Render the full-screen quad
+    glBindVertexArray(quad_vao_);
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+
+    post_fbo_.Unbind();
+    glEnable(GL_DEPTH_TEST);
+
     DrawGui(window);
     glfwSwapBuffers(window);
 }
@@ -177,6 +234,12 @@ void Scene::DrawGui(GLFWwindow* window) {
     ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
     ImGui::End();
 
+    // Draw FBO to ImGui window
+    ImGui::Begin("Scene Window");
+    ImVec2 windowSize = ImGui::GetContentRegionAvail();
+    ImGui::Image((void*)(intptr_t)post_fbo_.GetColorTexture(), windowSize, ImVec2(0, 1), ImVec2(1, 0));
+    ImGui::End();
+
     ImGui::Render();
     ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 }