From 95d698146179437211c42bd09c2e9f225754cf63 Mon Sep 17 00:00:00 2001
From: Peder Bergebakken Sundt <pbsds@hotmail.com>
Date: Sun, 7 Apr 2019 00:03:03 +0200
Subject: [PATCH] Add support for fog into the scene shader

---
 res/shaders/simple.frag | 18 +++++++++++++++---
 src/renderlogic.cpp     | 15 +++++++++++----
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/res/shaders/simple.frag b/res/shaders/simple.frag
index 6317240..ac22e86 100644
--- a/res/shaders/simple.frag
+++ b/res/shaders/simple.frag
@@ -27,6 +27,9 @@ uniform vec3 specular_color;
 uniform vec3 emissive_color;
 uniform vec3 backlight_color;
 
+uniform vec3 fog_color;
+uniform float fog_strength;
+
 uniform bool isIlluminated;
 uniform bool isTextured;
 uniform bool isVertexColored;
@@ -138,7 +141,15 @@ vec3 phong(vec3 basecolor, vec3 nnormal) {
     return basecolor + specular_color * specular_component;
 }
 
+const float near = 0.1;
+const float far  = 5000.0;
+float linearDepth() {
+    float z = gl_FragCoord.z * 2.0 - 1.0;
+    return (2.0 * near * far) / (far + near - z * (far - near));
+}
+
 void main() {
+
     vec3 nnormal = get_nnormal(); // normalized normal
     vec4 c = vec4(vec3(1.0), opacity);
     if (isVertexColored)    c *= color;
@@ -152,8 +163,9 @@ void main() {
     }
     if (backlight_strength > 0.05)
         c.rgb += backlight_color * clamp((dot(normalize(vertex), nnormal) + backlight_strength) / backlight_strength, 0, 1);
-    //c.rgb = diffuse_color;
-    //c.rgb = emissive_color;
-    //c.rgb = specular_color;
+
+    float fog = linearDepth()/1500;
+    c.rgb = mix(c.rgb, fog_color, pow(fog,1.2)*fog_strength);
+    
     color_out = c;
 }
diff --git a/src/renderlogic.cpp b/src/renderlogic.cpp
index 40da540..3a84387 100644
--- a/src/renderlogic.cpp
+++ b/src/renderlogic.cpp
@@ -30,6 +30,9 @@ sf::SoundBuffer* buffer;
 Gloom::Shader* current_shader = nullptr;
 Gloom::Shader* prev_shader = nullptr; // The last shader to glDrawElements
 
+// uniforms in the scene
+vec3  fog_color = vec3(0);
+float fog_strength = 0;
 
 // the framebuffer we render the scene to before post-processing
 GLuint framebufferID = 0;
@@ -246,14 +249,18 @@ void renderNode(SceneNode* node, Gloom::Shader* parent_shader, vector<NodeDistSh
         case GEOMETRY:
             if (transparent_nodes!=nullptr && node->has_transparancy()) {
                 // defer to sorted pass later on
-                //transparent_nodes->emplace_back(node, s, glm::length(vec3(node->MVP[3])));
-                //transparent_nodes->push_back({node, s, glm::length(vec3(node->MVP[3]))});
                 transparent_nodes->emplace_back(node, s, glm::length(vec3(node->MVP*vec4(0,0,0,1))));
-                //transparent_nodes->push_back({node, s, glm::length(vec3(node->MVP*vec4(0,0,0,1)))});
             }
             else if(node->vertexArrayObjectID != -1) {
                 if (node->opacity <= 0.05) break;
-                // load uniforms
+                
+                // load scene uniforms
+                if (shader_changed) { // guaranteed at start of every frame, due to post_shader
+                    glUniform3fv(s->location("fog_color"), 1, glm::value_ptr(fog_color));
+                    glUniform1f( s->location("fog_strength"), fog_strength);
+                }
+                
+                // load material uniforms
                 um4fv(MVP);
                 um4fv(MV);
                 um4fv(MVnormal);