From d29377269030a32dd39b9c297433d56ee170859b Mon Sep 17 00:00:00 2001
From: Cyberarm <matthewlikesrobots@gmail.com>
Date: Wed, 25 Mar 2020 09:18:06 -0500
Subject: [PATCH] Initial work on using framebuffer from GBuffer

---
 lib/renderer/g_buffer.rb            | 55 +++++++++++++++++++++++++++++
 lib/renderer/opengl_renderer.rb     | 29 +++++++++++++--
 lib/renderer/renderer.rb            |  2 +-
 shaders/fragment/render_screen.glsl | 10 ++++++
 shaders/vertex/render_screen.glsl   | 10 ++++++
 5 files changed, 103 insertions(+), 3 deletions(-)
 create mode 100644 shaders/fragment/render_screen.glsl
 create mode 100644 shaders/vertex/render_screen.glsl

diff --git a/lib/renderer/g_buffer.rb b/lib/renderer/g_buffer.rb
index 3cee155..d683e61 100644
--- a/lib/renderer/g_buffer.rb
+++ b/lib/renderer/g_buffer.rb
@@ -2,13 +2,36 @@ class IMICFPS
   class GBuffer
     include CommonMethods
 
+    attr_reader :screen_vbo, :vertices, :uvs
     def initialize
       @framebuffer = nil
       @buffers = [:position, :diffuse, :normal, :texcoord]
       @textures = {}
+      @screen_vbo = nil
       @ready = false
 
+      @vertices = [
+        -1.0, -1.0, 0,
+        1.0,  -1.0, 0,
+        -1.0,  1.0, 0,
+        
+        -1.0,  1.0, 0,
+        1.0,  -1.0, 0,
+        1.0,   1.0, 0,
+    ].freeze
+
+      @uvs = [
+        0, 1,
+        1, 1,
+        0, 0,
+
+        0, 0,
+        1, 1,
+        1, 0
+      ].freeze
+
       create_framebuffer
+      create_screen_vbo
     end
 
     def create_framebuffer
@@ -72,6 +95,30 @@ class IMICFPS
       glDrawBuffers(draw_buffers.size, draw_buffers.pack("I*"))
     end
 
+    def create_screen_vbo
+      buffer = ' ' * 8
+      glGenVertexArrays(1, buffer)
+      @screen_vbo = buffer.unpack('L2').first
+
+      buffer = " " * 4
+      glGenBuffers(1, buffer)
+      @positions_buffer_id = buffer.unpack('L2').first
+
+      buffer = " " * 4
+      glGenBuffers(1, buffer)
+      @uvs_buffer_id = buffer.unpack('L2').first
+
+      glBindVertexArray(@screen_vbo)
+      glBindBuffer(GL_ARRAY_BUFFER, @positions_buffer_id)
+      glBufferData(GL_ARRAY_BUFFER, @vertices.size * Fiddle::SIZEOF_FLOAT, @vertices.pack("f*"), GL_STATIC_DRAW);
+      glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nil)
+
+      glBindBuffer(GL_ARRAY_BUFFER, @uvs_buffer_id)
+      glBufferData(GL_ARRAY_BUFFER, @uvs.size * Fiddle::SIZEOF_FLOAT, @uvs.pack("f*"), GL_STATIC_DRAW);
+      glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, nil)
+
+    end
+
     def bind_for_writing
       glBindFramebuffer(GL_DRAW_FRAMEBUFFER, @framebuffer)
     end
@@ -88,12 +135,20 @@ class IMICFPS
       glBindFramebuffer(GL_FRAMEBUFFER, 0)
     end
 
+    def texture(type)
+      @textures[type]
+    end
+
     def clean_up
       glDeleteFramebuffers(@framebuffer)
 
       @textures.values.each do |id|
         glDeleteTextures(id)
       end
+
+      glDeleteBuffers(@positions_buffer_id)
+      glDeleteBuffers(@uvs_buffer_id)
+      glDeleteVertexArrays(@screen_vbo)
     end
   end
 end
\ No newline at end of file
diff --git a/lib/renderer/opengl_renderer.rb b/lib/renderer/opengl_renderer.rb
index 7d56fed..11b73e8 100644
--- a/lib/renderer/opengl_renderer.rb
+++ b/lib/renderer/opengl_renderer.rb
@@ -10,10 +10,10 @@ class IMICFPS
 
     def render(camera, lights, entities)
       if Shader.available?("default")
-        # @g_buffer.bind_for_writing
+        @g_buffer.bind_for_writing
         gl_error?
 
-        # glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
+        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
 
         Shader.use("default") do |shader|
           lights.each_with_index do |light, i|
@@ -46,6 +46,11 @@ class IMICFPS
 
         @g_buffer.unbind_framebuffer
         gl_error?
+
+        lighting(lights)
+        post_processing
+        render_framebuffer
+        gl_error?
       else
         puts "Shader 'default' failed to compile, using immediate mode for rendering..." unless @@immediate_mode_warning
         @@immediate_mode_warning = true
@@ -76,6 +81,26 @@ class IMICFPS
       gl_error?
     end
 
+    def lighting(lights)
+    end
+
+    def post_processing
+    end
+
+    def render_framebuffer
+      if Shader.available?("render_screen")
+        Shader.use("render_screen") do |shader|
+          glBindVertexArray(@g_buffer.screen_vbo)
+          glEnableVertexAttribArray(0)
+          glEnableVertexAttribArray(1)
+          
+          glDisable(GL_DEPTH_TEST)
+          glBindTexture(GL_TEXTURE_2D, @g_buffer.texture(:diffuse))
+          glDrawArrays(GL_TRIANGLES, 0, @g_buffer.vertices.size)
+        end
+      end
+    end
+
     def draw_model(model, shader)
       glBindVertexArray(model.vertex_array_id)
       glEnableVertexAttribArray(0)
diff --git a/lib/renderer/renderer.rb b/lib/renderer/renderer.rb
index 3ca54bf..66b213e 100644
--- a/lib/renderer/renderer.rb
+++ b/lib/renderer/renderer.rb
@@ -10,7 +10,7 @@ class IMICFPS
     end
 
     def preload_default_shaders
-      shaders = ["default"]
+      shaders = ["default", "render_screen"]
       shaders.each do |shader|
         Shader.new(
           name: shader,
diff --git a/shaders/fragment/render_screen.glsl b/shaders/fragment/render_screen.glsl
new file mode 100644
index 0000000..672b2eb
--- /dev/null
+++ b/shaders/fragment/render_screen.glsl
@@ -0,0 +1,10 @@
+#version 330 core
+out vec4 FragColor;
+  
+in vec2 outTexCoords;
+
+uniform sampler2D screenTexture;
+
+void main() { 
+  FragColor = texture(screenTexture, outTexCoords);
+}
\ No newline at end of file
diff --git a/shaders/vertex/render_screen.glsl b/shaders/vertex/render_screen.glsl
new file mode 100644
index 0000000..6acd275
--- /dev/null
+++ b/shaders/vertex/render_screen.glsl
@@ -0,0 +1,10 @@
+#version 330 core
+layout (location = 0) in vec2 inPosition;
+layout (location = 1) in vec2 inTexCoords;
+
+out vec2 outTexCoords;
+
+void main() {
+  gl_Position = vec4(inPosition.x, inPosition.y, inPosition.z, 1.0); 
+  outTexCoords = inTexCoords;
+}  
\ No newline at end of file