Encapsulate frame buffers

core/CMakeLists.txt

@@ -23,6 +23,8 @@ target_sources(couchlib PUBLIC
   CollisionShape.h
   CollisionShape.cpp
   constants.h
+  Framebuffer.h
+  Framebuffer.cpp
   Index.h
   Index.cpp
   Input.h

core/Framebuffer.cpp

@@ -0,0 +1,79 @@
+/*
+  Dane Johnson <dane@danejohnson.org>
+ 
+  LICENSE
+ 
+  Couch  Copyright (C) 2021 Dane Johnson
+
+  This program comes with ABSOLUTELY NO WARRANTY; without event the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the GNU General Public License for details at
+  https://www.gnu.org/licenses/gpl-3.0.html
+  
+  This is free software, and you are welcome to redistribute it
+  under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+ 
+  DESCRIPTION
+   
+  Framebuffers are essentially just things that can be drawn to. They have
+  a number of settings that are set via stateful calls to OpenGL, so they
+  are wrapped here so they can be saved and restored in a stateless fashion.
+*/
+
+#include "Framebuffer.h"
+
+Framebuffer::Framebuffer() {
+  glGenFramebuffers(1, &fbo);
+}
+
+Framebuffer::Framebuffer(Id fbo) {
+  this->fbo = fbo;
+}
+
+Framebuffer::~Framebuffer() {
+  // If this isn't the default framebuffer.
+  if (fbo != 0) {
+    glDeleteFramebuffers(1, &fbo);
+  }
+}
+
+void Framebuffer::Enable() {
+  glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+  if (depthTest) {
+    glEnable(GL_DEPTH_TEST);
+  } else {
+    glDisable(GL_DEPTH_TEST);
+  }
+}
+
+
+void Framebuffer::Clear() {
+  glClearColor(clearColor.x, clearColor.y, clearColor.z, 1.0f);
+  glClear(clearFlags);
+}
+
+void Framebuffer::Bind() {
+  glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+}
+
+// Gotta initialize static members here so DLLs will
+// only create one instance.
+static FramebufferStack static_stack;
+
+void FramebufferStack::Save(Framebuffer *buffer) {
+  stack.push_back(curr);
+  curr = buffer;
+}
+
+void FramebufferStack::Restore() {
+  curr = stack.back();
+  stack.pop_back();
+
+  curr->Enable();
+}
+
+FramebufferStack *FramebufferStack::GetStack() {
+  return &static_stack;
+}

core/Framebuffer.h

@@ -0,0 +1,81 @@
+/**
+   @file
+   @author Dane Johnson <dane@danejohnson.org>
+ 
+   @section LICENSE
+ 
+   Couch  Copyright (C) 2021 Dane Johnson
+
+   This program comes with ABSOLUTELY NO WARRANTY; without event the
+   implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+   See the GNU General Public License for details at
+   https://www.gnu.org/licenses/gpl-3.0.html
+  
+   This is free software, and you are welcome to redistribute it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+ 
+   @section DESCRIPTION
+   
+   Framebuffers are essentially just things that can be drawn to. They have
+   a number of settings that are set via stateful calls to OpenGL, so they
+   are wrapped here so they can be saved and restored in a stateless fashion.
+*/
+
+#ifndef FRAMEBUFFER_H
+#define FRAMEBUFFER_H
+
+#include <vector>
+
+#include "types.h"
+
+class Framebuffer {
+public:
+  Framebuffer();
+  /**
+     If the frame buffer has already been initialized, you can pass it
+     in with this constructor
+     @param fbo the frame buffer object handle.
+  */
+  Framebuffer(Id fbo);
+  /** 
+      Apply the configuration for this framebuffer to the OpenGL state.
+  */
+  ~Framebuffer();
+  void Enable();
+  /** 
+      Clear out this framebuffer.
+  */
+  void Clear();
+  /**
+     Bind the texture without applying configuration.
+  */
+  void Bind();
+  /**
+     What clear color to draw to this frame buffer
+  */  
+  Vector3 clearColor = Vector3(0.0f, 0.0f, 1.0f);
+  /**
+     What bit(s) to clear in this buffer.
+  */
+  int clearFlags = GL_COLOR_BUFFER_BIT;
+  /**
+     Should we enable depth testing?
+  */
+  bool depthTest = false;
+private:
+  Id fbo;
+};
+
+class FramebufferStack {
+public:
+  void Save(Framebuffer *buffer);
+  void Restore();
+  Framebuffer *curr = new Framebuffer(0);  // Start with the default framebuffer
+  static FramebufferStack *GetStack();
+private:
+  std::vector<Framebuffer *> stack;
+};
+
+#endif /* FRAMEBUFFER_H */

core/Screen.cpp

@@ -33,8 +33,10 @@ Screen::Screen() {
   glBindVertexArray(0);
 
   // Setup frame buffers
-  glGenFramebuffers(1, &framebuffer);
-  glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+  framebuffer.clearColor = Vector3(1.0f, 0.0f, 0.0f);
+  framebuffer.clearFlags = GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT;
+  framebuffer.depthTest = true;
+  framebuffer.Bind();
 
   tex.width = width;
   tex.height = height;
@@ -59,14 +61,17 @@ Screen::Screen() {
     std::cerr << "Error setting up screen framebuffer." << std::endl;
     exit(1);
   }
-  glBindFramebuffer(GL_FRAMEBUFFER, 0);
+  FramebufferStack::GetStack()->curr->Bind();
 }
 
 void Screen::Enable() {
-  glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
-  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-  glEnable(GL_DEPTH_TEST);
+  FramebufferStack::GetStack()->Save(&framebuffer);
+  framebuffer.Enable();
+  framebuffer.Clear();
+}
+
+void Screen::Disable() {
+  FramebufferStack::GetStack()->Restore();
 }
 
 void Screen::Draw() {

core/Screen.h

@@ -7,6 +7,7 @@
 #include <GL/glew.h>
 
 #include "types.h"
+#include "Framebuffer.h"
 #include "Vertex.h"
 #include "Material.h"
 
@@ -14,13 +15,14 @@ class Screen {
 public:
   Screen();
   void Enable();
+  void Disable();
   void Draw();
   const int width = 640;
   const int height = 480;
   Texture tex;
 private:
   Id quad;
-  Id framebuffer;
+  Framebuffer framebuffer;
   Id renderbuffer;
 };
 

core/Window.cpp

@@ -32,14 +32,6 @@ bool Window::ShouldClose() {
   return glfwWindowShouldClose(glfwWindow);
 }
 
-void Window::Enable() {
-  glBindFramebuffer(GL_FRAMEBUFFER, 0);
-  glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
-  glClear(GL_COLOR_BUFFER_BIT);
-  glDisable(GL_DEPTH_TEST);
-  glViewport(0, 0, width, height);
-}
-
 void Window::Update() {
   glfwSwapBuffers(glfwWindow);
   glfwPollEvents();

core/Window.h

@@ -27,6 +27,8 @@
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>
 
+#include "Framebuffer.h"
+
 class Window {
 public:
   /**
@@ -37,10 +39,6 @@ public:
      @returns whether or not the user tried to close the window
   */
   bool ShouldClose();
-  /**
-     Begin rendering to the window
-   */
-  void Enable();
   /**
      Swap the buffers and poll for events
   */

core/couch.cpp

@@ -16,6 +16,7 @@
 #include "Shaders/SkyboxShader.h"
 
 #include "Screen.h"
+#include "Framebuffer.h"
 
 #include "Camera.h"
 #include "Input.h"
@@ -84,17 +85,21 @@ int main() {
   double delta = 0.0;
 
   while(!window.ShouldClose()) {
-    // Physics update()
+    // Physics update
     world->Step(delta);
-    
-    // Start rendering to texture;
-    screen.Enable();
 
-    // Call update function
+    // Script update
     lua->Update(delta);
+    
     // Delete freed nodes
     root->DoFree();
 
+    // Clear the default shader
+    FramebufferStack::GetStack()->curr->Clear();
+    
+    // Start rendering to screen
+    screen.Enable();
+
     shader->Use();
     shader->UpdateProjection(projection);
     Matrix view(1.0f);
@@ -133,11 +138,12 @@ int main() {
       glDepthFunc(GL_LESS);
     }
 
-    // Render to the window
-    window.Enable();
-    
+    // Stop rendering to texture
+    screen.Disable();
+
     screenShader->Use();
     screenShader->UpdateTex(screen.tex);
+    
     screen.Draw();
 
     window.Update();