From 451e872ddbe6db8bd8d6aa54ca0bf744dc5405e5 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Patrick=20Sch=C3=B6nberger?= <patrick.schoenberger@posteo.de>
Date: Wed, 3 Feb 2021 11:08:49 +0100
Subject: [PATCH] Screen Space SSS

---
 shaders/fbo_frag.glsl | 28 ++++++++++++++++++++++++----
 src/main.cpp          | 11 +++++++++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/shaders/fbo_frag.glsl b/shaders/fbo_frag.glsl
index cf1fafa..f6f12cd 100644
--- a/shaders/fbo_frag.glsl
+++ b/shaders/fbo_frag.glsl
@@ -4,10 +4,30 @@ out vec4 FragColor;
 in vec2 TexCoords;
 
 uniform sampler2D screenTexture;
+uniform int applySSSSS;
+uniform int N;
 
 void main()
-{ 
-    FragColor = vec4(
-        texture(screenTexture, TexCoords).rgb,
-        1.0);
+{
+    if (applySSSSS == 1) {
+        float x = 1.0/1600.0;
+        float y = 1.0/900.0;
+
+        float maxDist = N*N + N*N;
+
+        vec4 color = vec4(0, 0, 0, 1);
+        for (int i = -N; i <= N; i++) {
+            for (int j = -N; j <= N; j++) {
+                float dist = i*i + j*j;
+                vec4 newC = texture(screenTexture, TexCoords + vec2(i*x, j*y)) / (2*N*N);
+                float factor = 1 - (dist / maxDist);
+                factor = pow(factor, 2);
+                color += newC * factor;
+            }
+        }
+        FragColor = color;
+    }
+    else {
+        FragColor = texture(screenTexture, TexCoords);
+    }
 }
diff --git a/src/main.cpp b/src/main.cpp
index 41d5e76..4168c50 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -304,6 +304,8 @@ int main() {
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   //glBindTexture(GL_TEXTURE_2D, 0);
   glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, renderTexture, 0);
 
@@ -359,6 +361,8 @@ int main() {
   struct {
     bool wireframe = false;
     bool freecam = false;
+    bool sssss = false;
+    int N = 2;
   } options;
 
   sf::Clock deltaClock;
@@ -468,6 +472,9 @@ int main() {
     glClear(GL_COLOR_BUFFER_BIT);
     glUseProgram(screenShaderProgram);
 
+    glUniform1i(glGetUniformLocation(screenShaderProgram, "applySSSSS"), options.sssss);
+    glUniform1i(glGetUniformLocation(screenShaderProgram, "N"), options.N);
+
     glBindVertexArray(screenVAO);
     glBindTexture(GL_TEXTURE_2D, renderTexture);
     glDrawArrays(GL_TRIANGLES, 0, 6);
@@ -478,6 +485,10 @@ int main() {
     ImGui::Begin("Options");
     ImGui::Checkbox("Wireframe", &options.wireframe);
     ImGui::Checkbox("Free Cam", &options.freecam);
+    ImGui::Checkbox("SSSSS", &options.sssss);
+    if (options.sssss) {
+      ImGui::DragInt("N", &options.N, 0.05f, 1, 16);
+    }
     if (options.freecam) {
       ImGui::LabelText("Position", "%f %f %f", freeCam.pos.x, freeCam.pos.y, freeCam.pos.z);
       ImGui::LabelText("Rotation", "%f %f", freeCam.rot.x, freeCam.rot.y);
-- 
2.50.1