From 5e3ea358578e2a6b4a857daaf86ca72c56ba16ec Mon Sep 17 00:00:00 2001
From: Sanjeet Suhag <suhagsanjeet@gmail.com>
Date: Wed, 16 Mar 2022 11:25:02 -0400
Subject: [PATCH] Fix tonemapping, HSB bug #1

---
 Source/Shaders/SkyAtmosphereFS.glsl | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/Source/Shaders/SkyAtmosphereFS.glsl b/Source/Shaders/SkyAtmosphereFS.glsl
index 34a261864226..79a06fd09f9e 100644
--- a/Source/Shaders/SkyAtmosphereFS.glsl
+++ b/Source/Shaders/SkyAtmosphereFS.glsl
@@ -1,5 +1,7 @@
 varying vec3 v_outerPositionWC;
 
+uniform vec3 u_hsbShift;
+
 #ifndef PER_FRAGMENT_ATMOSPHERE
 varying vec3 v_mieColor;
 varying vec3 v_rayleighColor;
@@ -29,5 +31,24 @@ void main (void)
     opacity = v_opacity;
 #endif
 
-    gl_FragColor = computeAtmosphereColor(v_outerPositionWC, lightDirection, rayleighColor, mieColor, opacity);
+    vec4 color = computeAtmosphereColor(v_outerPositionWC, lightDirection, rayleighColor, mieColor, opacity);
+
+#ifdef COLOR_CORRECT
+    // Convert rgb color to hsb
+    vec3 hsb = czm_RGBToHSB(color.rgb);
+    // Perform hsb shift
+    hsb.x += u_hsbShift.x; // hue
+    hsb.y = clamp(hsb.y + u_hsbShift.y, 0.0, 1.0); // saturation
+    hsb.z = hsb.z > czm_epsilon7 ? hsb.z + u_hsbShift.z : 0.0; // brightness
+    // Convert shifted hsb back to rgb
+    color.rgb = czm_HSBToRGB(hsb);
+#endif
+
+    // Apply tonemapping
+    float exposure = 1.0;
+    color = vec4(1.0 - exp(-exposure * color));
+    float gamma = 0.8;
+    color = pow(color, vec4(1.0 / gamma));
+
+    gl_FragColor= color;
 }