SL-18190 Remove some (likely) superfluous color space conversions

indra/newview/app_settings/shaders/class2/windlight/atmosphericsF.glsl

@@ -32,23 +32,6 @@ uniform int no_atmo;
 vec3 srgb_to_linear(vec3 col);
 vec3 linear_to_srgb(vec3 col);
 
-vec3 atmosFragLightingLinear(vec3 light, vec3 additive, vec3 atten)
-{
-    if (no_atmo == 1)
-    {
-        return light;
-    }
-    
-    light = linear_to_srgb(light);
-    additive = linear_to_srgb(additive);
-    atten = linear_to_srgb(atten);
-    
-    light *= atten.r;
-    light += additive;
-    return srgb_to_linear(light);
-}
-
-
 vec3 atmosFragLighting(vec3 light, vec3 additive, vec3 atten)
 {
     if (no_atmo == 1)
@@ -60,6 +43,18 @@ vec3 atmosFragLighting(vec3 light, vec3 additive, vec3 atten)
     return light * 2.0;
 }
 
+vec3 atmosFragLightingLinear(vec3 light, vec3 additive, vec3 atten)
+{
+    if (no_atmo == 1)
+    {
+        return light;
+    }
+    
+    light *= atten.r;
+    light += additive;
+    return light;
+}
+
 vec3 atmosLighting(vec3 light)
 {
     return atmosFragLighting(light, getAdditiveColor(), getAtmosAttenuation());

indra/newview/app_settings/shaders/class2/windlight/gammaF.glsl

@@ -32,16 +32,15 @@ vec3 srgb_to_linear(vec3 col);
 vec3 linear_to_srgb(vec3 col);
 
 vec3 scaleSoftClipFragLinear(vec3 light)
-{
+{ // identical to non-linear version and that's probably close enough
     if (no_atmo == 1)
     {
         return light;
     }
-    light = linear_to_srgb(light);
     //soft clip effect:
     light = 1. - clamp(light, vec3(0.), vec3(1.));
     light = 1. - pow(light, vec3(gamma)); // s/b inverted already CPU-side
-    return srgb_to_linear(light);
+    return light;
 }
 
 vec3 scaleSoftClipFrag(vec3 light)

indra/newview/app_settings/shaders/class2/windlight/transportF.glsl

@@ -49,12 +49,9 @@ vec3 atmosTransport(vec3 light)
 
 vec3 fullbrightAtmosTransportFragLinear(vec3 light, vec3 additive, vec3 atten)
 {
-    light = linear_to_srgb(light);
-    additive = linear_to_srgb(additive);
-    atten = linear_to_srgb(atten);
-
+    // same as non-linear version, probably fine
     float brightness = dot(light.rgb * 0.5, vec3(0.3333)) + 0.1;    
-    return srgb_to_linear(mix(atmosTransportFrag(light.rgb, additive, atten), light.rgb + additive, brightness * brightness));
+    return mix(atmosTransportFrag(light.rgb, additive, atten), light.rgb + additive, brightness * brightness);
 }
 
 vec3 fullbrightAtmosTransportFrag(vec3 light, vec3 additive, vec3 atten)