From 1c672e0f420f5b7b60c4ef5874c160d8d1791ef2 Mon Sep 17 00:00:00 2001
From: Cat Flynn <me@ktyl.dev>
Date: Sun, 26 Feb 2023 02:49:52 +0000
Subject: [PATCH] add denoise

---
 shader/quad/shader.frag | 48 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/shader/quad/shader.frag b/shader/quad/shader.frag
index cadfb1e..45921df 100644
--- a/shader/quad/shader.frag
+++ b/shader/quad/shader.frag
@@ -6,7 +6,53 @@ in vec2 TexCoord;
 
 uniform sampler2D ourTexture;
 
+#define INV_SQRT_OF_2PI 0.39894228040143267793994605993439  // 1.0/SQRT_OF_2PI
+#define INV_PI          0.31830988618379067153776752674503
+
+// https://github.com/BrutPitt/glslSmartDeNoise/blob/master/Shaders/frag.glsl
+vec4 denoise(sampler2D tex, vec2 uv, float sigma, float kSigma, float threshold)
+{
+    float radius = round(kSigma*sigma);
+    float radQ = radius*radius;
+
+    float invSigmaQx2 = .5 / (sigma*sigma);
+    float invSigmaQx2PI = INV_PI * invSigmaQx2;
+
+    float invThresholdSqx2 = .5 / (threshold*threshold);
+    float invThresholdSqrt2PI = INV_SQRT_OF_2PI / threshold;
+
+    vec4 centrPx = texture(tex,uv);
+
+    float zBuff = 0.0;
+    vec4 aBuff = vec4(0.0);
+    vec2 size = vec2(textureSize(tex, 0));
+
+    vec2 d;
+    for (d.x=-radius; d.x <= radius; d.x++)
+    {
+        float pt = sqrt(radQ-d.x*d.x);
+        for(d.y=-pt; d.y <= pt; d.y++)
+        {
+            float blurFactor = exp(-dot(d,d)*invSigmaQx2)*invSigmaQx2PI;
+
+            vec4 walkPx = texture(tex,uv+d/size);
+
+            vec4 dC = walkPx-centrPx;
+            float deltaFactor = exp(-dot(dC.rgb,dC.rgb) * invThresholdSqx2) * invThresholdSqrt2PI * blurFactor;
+
+            zBuff += deltaFactor;
+            aBuff += deltaFactor*walkPx;
+        }
+    }
+    return aBuff/zBuff;
+}
+
 void main()
 {
-    FragColor = texture(ourTexture, TexCoord);
+    float sigma = 2.2;
+    float kSigma = 10.0;
+    float threshold = 0.2;
+
+    FragColor = denoise(ourTexture, TexCoord, sigma, kSigma, threshold);
+    //FragColor = texture(ourTexture, TexCoord);
 }