From b0568ca40495bf0c5891e68b0ccb448dfac7c135 Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Wed, 26 Jan 2022 23:03:35 +1100
Subject: [PATCH] [client] egl: use a sigmoid curve for nv

---
 client/renderers/EGL/shader/desktop_rgb.frag | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/client/renderers/EGL/shader/desktop_rgb.frag b/client/renderers/EGL/shader/desktop_rgb.frag
index 3dcd8f65..6b2c6f34 100644
--- a/client/renderers/EGL/shader/desktop_rgb.frag
+++ b/client/renderers/EGL/shader/desktop_rgb.frag
@@ -37,8 +37,9 @@ void main()
 
   if (nvGain > 0.0)
   {
-    highp float lumi = 1.0 - (0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b);
-    color *= 1.0 + lumi;
+    highp float lumi = (0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b);
+    if (lumi < 0.5)
+      color *= atanh((1.0 - lumi) * 2.0 - 1.0) + 1.0;
     color *= nvGain;
   }