Merged in DV510-merge-6.4.10 (pull request #322)

Merge master v 6.4.10 to DRTVWR-510

17 files changed, 506 insertions, 572 deletions

diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index c595a1c176..8d5a97d1cb 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -812,17 +812,6 @@
       <key>Value</key>
       <integer>0</integer>
     </map>
-    <key>FramePerSecondLimit</key>
-    <map>
-      <key>Comment</key>
-      <string>Controls upper limit of frames per second</string>
-      <key>Persist</key>
-      <integer>1</integer>
-      <key>Type</key>
-      <string>U32</string>
-      <key>Value</key>
-      <integer>120</integer>
-    </map>
     <key>BackgroundYieldTime</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/app_settings/shaders/class1/deferred/cloudsV.glsl b/indra/newview/app_settings/shaders/class1/deferred/cloudsV.glsl
index 495daa2db6..a132220bef 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/cloudsV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/cloudsV.glsl
@@ -80,7 +80,7 @@ void main()
 
 	// Texture coords
     // SL-13084 EEP added support for custom cloud textures -- flip them horizontally to match the preview of Clouds > Cloud Scroll
-	vary_texcoord0 = vec2( -texcoord0.x, texcoord0.y ); // See: LLSettingsVOSky::applySpecial
+    vary_texcoord0 = vec2(-texcoord0.x, texcoord0.y);  // See: LLSettingsVOSky::applySpecial
 
 	vary_texcoord0.xy -= 0.5;
 	vary_texcoord0.xy /= cloud_scale;
@@ -94,74 +94,65 @@ void main()
 	vary_texcoord3 = vary_texcoord1 * 16.;
 
 	// Get relative position
-	vec3 P = position.xyz - camPosLocal.xyz + vec3(0,50,0);
+    vec3 rel_pos = position.xyz - camPosLocal.xyz + vec3(0, 50, 0);
 
-    altitude_blend_factor = clamp((P.y + 512.0) / max_y, 0.0, 1.0);
+    altitude_blend_factor = clamp((rel_pos.y + 512.0) / max_y, 0.0, 1.0);
 
 	// Set altitude
-	if (P.y > 0.)
+    if (rel_pos.y > 0)
 	{
-		P *= (max_y / P.y);
+        rel_pos *= (max_y / rel_pos.y);
 	}
-	else
+    if (rel_pos.y < 0)
 	{
 		altitude_blend_factor = 0; // SL-11589 Fix clouds drooping below horizon
-		P *= (-32000. / P.y);
+        rel_pos *= (-32000. / rel_pos.y);
 	}
 
 	// Can normalize then
-	vec3 Pn = normalize(P);
-	float  Plen = length(P);
+    vec3  rel_pos_norm = normalize(rel_pos);
+    float rel_pos_len  = length(rel_pos);
 
 	// Initialize temp variables
-	vec4 temp1 = vec4(0.);
-	vec4 temp2 = vec4(0.);
-	vec4 blue_weight;
-	vec4 haze_weight;
-	//vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
 	vec4 sunlight = sunlight_color;
 	vec4 light_atten;
 
-    float dens_mul = density_multiplier;
-
 	// Sunlight attenuation effect (hue and brightness) due to atmosphere
 	// this is used later for sunlight modulation at various altitudes
-	light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
+    light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
 
 	// Calculate relative weights
-	temp1 = abs(blue_density) + vec4(abs(haze_density));
-	blue_weight = blue_density / temp1;
-	haze_weight = haze_density / temp1;
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = haze_density / combined_haze;
 
-	// Compute sunlight from P & lightnorm (for long rays like sky)
-	temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-	temp2.y = 1. / temp2.y;
-	sunlight *= exp( - light_atten * temp2.y);
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0., rel_pos_norm.y) + lightnorm.y);
+    sunlight *= exp(-light_atten * off_axis);
 
 	// Distance
-	temp2.z = Plen * dens_mul;
+    float density_dist = rel_pos_len * density_multiplier;
 
-	// Transparency (-> temp1)
-	// ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
 	// compiler gets confused.
-	temp1 = exp(-temp1 * temp2.z);
-
+    combined_haze = exp(-combined_haze * density_dist);
 
 	// Compute haze glow
-	temp2.x = dot(Pn, lightnorm.xyz);
-	temp2.x = 1. - temp2.x;
-		// temp2.x is 0 at the sun and increases away from sun
-	temp2.x = max(temp2.x, .001);	
+    float haze_glow = 1.0 - dot(rel_pos_norm, lightnorm.xyz);
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);
 		// Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-	temp2.x *= glow.x;
+    haze_glow *= glow.x;
 		// Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-	temp2.x = pow(temp2.x, glow.z);
+    haze_glow = pow(haze_glow, glow.z);
 		// glow.z should be negative, so we're doing a sort of (1 / "angle") function
 
-    temp2.x *= sun_moon_glow_factor;
+    haze_glow *= sun_moon_glow_factor;
 
 	// Add "minimum anti-solar illumination"
-	temp2.x += .25;
+    // For sun, add to glow.  For moon, remove glow entirely. SL-13768
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (haze_glow + 0.25);
 
 	// Increase ambient when there are more clouds
 	vec4 tmpAmbient = ambient_color;
@@ -171,29 +162,26 @@ void main()
 	sunlight *= (1. - cloud_shadow);
 
 	// Haze color below cloud
-	vec4 additiveColorBelowCloud = (	  blue_horizon * blue_weight * (sunlight + tmpAmbient)
-				+ (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-			 );	
+    vec4 additiveColorBelowCloud =
+        (blue_horizon * blue_weight * (sunlight + tmpAmbient) + (haze_horizon * haze_weight) * (sunlight * haze_glow + tmpAmbient));
 
 	// CLOUDS
-	temp2.y = max(0., lightnorm.y * 2.);
-	temp2.y = 1. / temp2.y;
-	sunlight *= exp( - light_atten * temp2.y);
+    off_axis = 1.0 / max(1e-6, lightnorm.y * 2.);
+    sunlight *= exp(-light_atten * off_axis);
 
 	// Cloud color out
-	vary_CloudColorSun = (sunlight * temp2.x) * cloud_color;
+    vary_CloudColorSun     = (sunlight * haze_glow) * cloud_color;
 	vary_CloudColorAmbient = tmpAmbient * cloud_color;
 	
 	// Attenuate cloud color by atmosphere
-	temp1 = sqrt(temp1);	//less atmos opacity (more transparency) below clouds
-	vary_CloudColorSun *= temp1;
-	vary_CloudColorAmbient *= temp1;
-	vec4 oHazeColorBelowCloud = additiveColorBelowCloud * (1. - temp1);
+    combined_haze = sqrt(combined_haze);  // less atmos opacity (more transparency) below clouds
+    vary_CloudColorSun *= combined_haze;
+    vary_CloudColorAmbient *= combined_haze;
+    vec4 oHazeColorBelowCloud = additiveColorBelowCloud * (1. - combined_haze);
 
 	// Make a nice cloud density based on the cloud_shadow value that was passed in.
 	vary_CloudDensity = 2. * (cloud_shadow - 0.25);
 
-
 	// Combine these to minimize register use
 	vary_CloudColorAmbient += oHazeColorBelowCloud;
 
@@ -202,4 +190,3 @@ void main()
 
 	// END CLOUDS
 }
-
diff --git a/indra/newview/app_settings/shaders/class1/deferred/fullbrightShinyF.glsl b/indra/newview/app_settings/shaders/class1/deferred/fullbrightShinyF.glsl
index 2d40e63eff..9fcee04c32 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/fullbrightShinyF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/fullbrightShinyF.glsl
@@ -64,28 +64,38 @@ void main()
 #else
 	vec4 color = texture2D(diffuseMap, vary_texcoord0.xy);
 #endif
-
+	
 	color.rgb *= vertex_color.rgb;
 
 	// SL-9632 HUDs are affected by Atmosphere
 	if (no_atmo == 0)
 	{
-		vec3 sunlit;
-		vec3 amblit;
-		vec3 additive;
-		vec3 atten;
+	vec3 sunlit;
+	vec3 amblit;
+	vec3 additive;
+	vec3 atten;
 		vec3 pos = vary_position.xyz/vary_position.w;
 
-		calcAtmosphericVars(pos.xyz, vec3(0), 1.0, sunlit, amblit, additive, atten, false);
-
-		vec3 envColor = textureCube(environmentMap, vary_texcoord1.xyz).rgb;
-		float env_intensity = vertex_color.a;
+	calcAtmosphericVars(pos.xyz, vec3(0), 1.0, sunlit, amblit, additive, atten, false);
+	
+	vec3 envColor = textureCube(environmentMap, vary_texcoord1.xyz).rgb;	
+	float env_intensity = vertex_color.a;
 
 	//color.rgb = srgb_to_linear(color.rgb);
 		color.rgb = mix(color.rgb, envColor.rgb, env_intensity);
-		color.rgb = fullbrightAtmosTransportFrag(color.rgb, additive, atten);
-		color.rgb = fullbrightScaleSoftClip(color.rgb);
+	color.rgb = fullbrightAtmosTransportFrag(color.rgb, additive, atten);
+	color.rgb = fullbrightScaleSoftClip(color.rgb);
+	}
+
+/*
+	// NOTE: HUD objects will be full bright. Uncomment if you want "some" environment lighting effecting these HUD objects.
+	else
+	{
+		vec3  envColor = textureCube(environmentMap, vary_texcoord1.xyz).rgb;
+		float env_intensity = vertex_color.a;
+		color.rgb = mix(color.rgb, envColor.rgb, env_intensity);
 	}
+*/
 
 	color.a = 1.0;
 
diff --git a/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl b/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
index 80f232948a..35068899ee 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
@@ -1,9 +1,9 @@
 /** 
- * @file moonF.glsl
+ * @file class1\deferred\moonF.glsl
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2005, Linden Research, Inc.
+ * Copyright (C) 2005, 2020 Linden Research, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -36,34 +36,33 @@ out vec4 frag_data[3];
 uniform vec4 color;
 uniform vec4 sunlight_color;
 uniform vec4 moonlight_color;
-uniform vec3 lumWeights;
+uniform vec3 moon_dir;
 uniform float moon_brightness;
-uniform float minLuminance;
 uniform sampler2D diffuseMap;
-uniform sampler2D altDiffuseMap;
-uniform float blend_factor; // interp factor between moon A/B
+
 VARYING vec2 vary_texcoord0;
 
 vec3 srgb_to_linear(vec3 c);
-void main() 
-{
-    vec4 moonA = texture2D(diffuseMap, vary_texcoord0.xy);
-    vec4 moonB = texture2D(altDiffuseMap, vary_texcoord0.xy);
-    vec4 c     = mix(moonA, moonB, blend_factor);
 
-    c.rgb = srgb_to_linear(c.rgb);
+/// Soft clips the light with a gamma correction
+vec3 scaleSoftClip(vec3 light);
 
-    // mix factor which blends when sunlight is brighter
-    // and shows true moon color at night
-    vec3 luma_weights = vec3(0.3, 0.5, 0.3);
+void main() 
+{
+    // Restore Pre-EEP alpha fade moon near horizon
+    float fade = 1.0;
+    if( moon_dir.z > 0 )
+        fade = clamp( moon_dir.z*moon_dir.z*4.0, 0.0, 1.0 );
 
-    vec4 light_color = max(sunlight_color, moonlight_color);
-    float mix = 1.0 - dot(normalize(light_color.rgb), luma_weights);
+    vec4 c      = texture2D(diffuseMap, vary_texcoord0.xy);
+//       c.rgb  = srgb_to_linear(c.rgb);
+         c.rgb *= moonlight_color.rgb;
+         c.rgb *= moon_brightness;
 
-    vec3 exp = vec3(1.0 - mix * moon_brightness) * 2.0  - 1.0;
-    c.rgb = pow(c.rgb, exp);
+         c.rgb *= fade;
+         c.a   *= fade;
 
-    //c.rgb *= moonlight_color.rgb;
+         c.rgb  = scaleSoftClip(c.rgb);
 
     frag_data[0] = vec4(c.rgb, c.a);
     frag_data[1] = vec4(0.0);
diff --git a/indra/newview/app_settings/shaders/class1/deferred/moonV.glsl b/indra/newview/app_settings/shaders/class1/deferred/moonV.glsl
index e1bac4f248..c4922afd7d 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/moonV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/moonV.glsl
@@ -1,9 +1,9 @@
 /** 
- * @file moonV.glsl
+ * @file class1\deferred\moonV.glsl
  *
   * $LicenseInfo:firstyear=2007&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2007, Linden Research, Inc.
+ * Copyright (C) 2007, 2020 Linden Research, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -32,18 +32,13 @@ ATTRIBUTE vec2 texcoord0;
 
 VARYING vec2 vary_texcoord0;
 
-void calcAtmospherics(vec3 eye_pos);
-
 void main()
 {
     //transform vertex
-    vec3 offset = vec3(0, 0, 50);
-    vec4 vert = vec4(position.xyz - offset, 1.0);
+    vec4 vert = vec4(position.xyz, 1.0);
     vec4 pos = (modelview_matrix * vert);
 
     gl_Position = modelview_projection_matrix*vert;
 
-    calcAtmospherics(pos.xyz);
-    
     vary_texcoord0 = (texture_matrix0 * vec4(texcoord0,0,1)).xy;
 }
diff --git a/indra/newview/app_settings/shaders/class1/deferred/skyV.glsl b/indra/newview/app_settings/shaders/class1/deferred/skyV.glsl
index ead754ec76..28a1faf24f 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/skyV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/skyV.glsl
@@ -1,24 +1,24 @@
-/** 
+/**
  * @file WLSkyV.glsl
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2005, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
@@ -37,13 +37,13 @@ VARYING vec4 vary_HazeColor;
 // Inputs
 uniform vec3 camPosLocal;
 
-uniform vec4 lightnorm;
-uniform vec4 sunlight_color;
-uniform vec4 moonlight_color;
-uniform int sun_up_factor;
-uniform vec4 ambient_color;
-uniform vec4 blue_horizon;
-uniform vec4 blue_density;
+uniform vec4  lightnorm;
+uniform vec4  sunlight_color;
+uniform vec4  moonlight_color;
+uniform int   sun_up_factor;
+uniform vec4  ambient_color;
+uniform vec4  blue_horizon;
+uniform vec4  blue_density;
 uniform float haze_horizon;
 uniform float haze_density;
 
@@ -52,7 +52,7 @@ uniform float density_multiplier;
 uniform float distance_multiplier;
 uniform float max_y;
 
-uniform vec4 glow;
+uniform vec4  glow;
 uniform float sun_moon_glow_factor;
 
 uniform vec4 cloud_color;
@@ -63,103 +63,91 @@ uniform vec4 cloud_color;
 //       indra\newview\lllegacyatmospherics.cpp
 void main()
 {
-
-	// World / view / projection
+    // World / view / projection
     vec4 pos = modelview_projection_matrix * vec4(position.xyz, 1.0);
 
-	gl_Position = pos;
-	
-	// Get relative position
-	vec3 P = position.xyz - camPosLocal.xyz + vec3(0,50,0);
-
-	// Set altitude
-	if (P.y > 0.)
-	{
-		P *= (max_y / P.y);
-	}
-	else
-	{
-		P *= (-32000. / P.y);
-	}
-
-	// Can normalize then
-	vec3 Pn = normalize(P);
-
-	float Plen = length(P);
-
-	// Initialize temp variables
-	vec4 temp1 = vec4(0.);
-	vec4 temp2 = vec4(0.);
-	vec4 blue_weight;
-	vec4 haze_weight;
-	vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
-	vec4 light_atten;
-
-    float dens_mul = density_multiplier;
-
-	// Sunlight attenuation effect (hue and brightness) due to atmosphere
-	// this is used later for sunlight modulation at various altitudes
-	light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
-
-	// Calculate relative weights
-	temp1 = abs(blue_density) + vec4(abs(haze_density));
-	blue_weight = blue_density / temp1;
-	haze_weight = haze_density / temp1;
-
-	// Compute sunlight from P & lightnorm (for long rays like sky)
-    temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-    temp2.y = 1. / temp2.y;
-    sunlight *= exp( - light_atten * temp2.y);
-
-	// Distance
-	temp2.z = Plen * dens_mul;
-
-	// Transparency (-> temp1)
-    // ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
-    // compiler gets confused.
-    temp1 = exp(-temp1 * temp2.z);
+    gl_Position = pos;
+
+    // Get relative position
+    vec3 rel_pos = position.xyz - camPosLocal.xyz + vec3(0, 50, 0);
+
+    // Adj position vector to clamp altitude
+    if (rel_pos.y > 0)
+    {
+        rel_pos *= (max_y / rel_pos.y);
+    }
+    if (rel_pos.y < 0)
+    {
+        rel_pos *= (-32000. / rel_pos.y);
+    }
+
+    // Can normalize then
+    vec3 rel_pos_norm = normalize(rel_pos);
 
-	// Compute haze glow
-	temp2.x = dot(Pn, lightnorm.xyz);
-	temp2.x = 1. - temp2.x;
-		// temp2.x is 0 at the sun and increases away from sun
-	temp2.x = max(temp2.x, .001);	
-		// Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-	temp2.x *= glow.x;
-		// Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-	temp2.x = pow(temp2.x, glow.z);
-		// glow.z should be negative, so we're doing a sort of (1 / "angle") function
+    float rel_pos_len = length(rel_pos);
 
-	// Add "minimum anti-solar illumination"
-	temp2.x += .25;
+    // Initialize temp variables
+    vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
+    vec4 light_atten;
 
-    vec4 color = (    blue_horizon * blue_weight * (sunlight + ambient_color)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + ambient_color)
-             );
+    // Sunlight attenuation effect (hue and brightness) due to atmosphere
+    // this is used later for sunlight modulation at various altitudes
+    light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
 
+    // Calculate relative weights
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = haze_density / combined_haze;
+
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0., rel_pos_norm.y) + lightnorm.y);
+    sunlight *= exp(-light_atten * off_axis);
+
+    // Distance
+    float density_dist = rel_pos_len * density_multiplier;
+
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
+    // compiler gets confused.
+    combined_haze = exp(-combined_haze * density_dist);
+
+    // Compute haze glow
+    float haze_glow = 1.0 - dot(rel_pos_norm, lightnorm.xyz);
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);
+    // Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
+    haze_glow *= glow.x;
+    // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
+    haze_glow = pow(haze_glow, glow.z);
+    // glow.z should be negative, so we're doing a sort of (1 / "angle") function
+
+    // Add "minimum anti-solar illumination"
+    // For sun, add to glow.  For moon, remove glow entirely. SL-13768
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (haze_glow + 0.25);
+
+    vec4 color =
+        (blue_horizon * blue_weight * (sunlight + ambient_color) + (haze_horizon * haze_weight) * (sunlight * haze_glow + ambient_color));
 
     // Final atmosphere additive
-    color *= (1. - temp1);
+    color *= (1. - combined_haze);
 
-	// Increase ambient when there are more clouds
-	vec4 tmpAmbient = ambient_color;
-	tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5; 
+    // Increase ambient when there are more clouds
+    vec4 tmpAmbient = ambient_color;
+    tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5;
 
-	// Dim sunlight by cloud shadow percentage
-	sunlight *= max(0.0, (1. - cloud_shadow));
+    // Dim sunlight by cloud shadow percentage
+    sunlight *= max(0.0, (1. - cloud_shadow));
 
-	// Haze color below cloud
-	vec4 additiveColorBelowCloud = (	  blue_horizon * blue_weight * (sunlight + tmpAmbient)
-				+ (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-			 );	
+    // Haze color below cloud
+    vec4 additiveColorBelowCloud =
+        (blue_horizon * blue_weight * (sunlight + tmpAmbient) + (haze_horizon * haze_weight) * (sunlight * haze_glow + tmpAmbient));
 
-	// Attenuate cloud color by atmosphere
-	temp1 = sqrt(temp1);	//less atmos opacity (more transparency) below clouds
+    // Attenuate cloud color by atmosphere
+    combined_haze = sqrt(combined_haze);  // less atmos opacity (more transparency) below clouds
 
-	// At horizon, blend high altitude sky color towards the darker color below the clouds
-	color += (additiveColorBelowCloud - color) * (1. - sqrt(temp1));
+    // At horizon, blend high altitude sky color towards the darker color below the clouds
+    color += (additiveColorBelowCloud - color) * (1. - sqrt(combined_haze));
 
     // Haze color above cloud
-	vary_HazeColor = color;	
+    vary_HazeColor = color;
 }
-
diff --git a/indra/newview/app_settings/shaders/class1/environment/encodeNormF.glsl b/indra/newview/app_settings/shaders/class1/environment/encodeNormF.glsl
index 50e781fa78..6cd2445522 100644
--- a/indra/newview/app_settings/shaders/class1/environment/encodeNormF.glsl
+++ b/indra/newview/app_settings/shaders/class1/environment/encodeNormF.glsl
@@ -23,6 +23,9 @@
  * $/LicenseInfo$
  */
 
+// Lambert Azimuthal Equal-Area projection
+// See: https://aras-p.info/texts/CompactNormalStorage.html
+// Also see: A_bit_more_deferred_-_CryEngine3.ppt
 vec2 encode_normal(vec3 n)
 {
 	float f = sqrt(8 * n.z + 8);
diff --git a/indra/newview/app_settings/shaders/class1/lighting/lightAlphaMaskF.glsl b/indra/newview/app_settings/shaders/class1/lighting/lightAlphaMaskF.glsl
index f665394b46..0bb48061e0 100644
--- a/indra/newview/app_settings/shaders/class1/lighting/lightAlphaMaskF.glsl
+++ b/indra/newview/app_settings/shaders/class1/lighting/lightAlphaMaskF.glsl
@@ -31,6 +31,9 @@ out vec4 frag_color;
 
 uniform float minimum_alpha;
 
+// render_hud_attachments() -> HUD objects set LLShaderMgr::NO_ATMO;
+uniform int no_atmo;
+
 vec3 atmosLighting(vec3 light);
 vec3 scaleSoftClip(vec3 light);
 
@@ -41,16 +44,19 @@ void default_lighting()
 {
 	vec4 color = diffuseLookup(vary_texcoord0.xy);
 	
-	color *= vertex_color;
-
 	if (color.a < minimum_alpha)
 	{
 		discard;
 	}
+	
+	color *= vertex_color;
 
-	color.rgb = atmosLighting(color.rgb);
-
-	color.rgb = scaleSoftClip(color.rgb);
+	// SL-9632 HUDs are affected by Atmosphere
+	if (no_atmo == 0)
+	{
+		color.rgb = atmosLighting(color.rgb);
+		color.rgb = scaleSoftClip(color.rgb);
+	}
 
 	frag_color = color;
 }
diff --git a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightAlphaMaskF.glsl b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightAlphaMaskF.glsl
index 46390e4a0e..1855cfceeb 100644
--- a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightAlphaMaskF.glsl
+++ b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightAlphaMaskF.glsl
@@ -30,7 +30,10 @@ out vec4 frag_color;
 #endif
 
 uniform float minimum_alpha;
-uniform float texture_gamma;
+uniform float texture_gamma; // either 1.0 or 2.2; see: "::TEXTURE_GAMMA"
+
+// render_hud_attachments() -> HUD objects set LLShaderMgr::NO_ATMO; used in LLDrawPoolAlpha::beginRenderPass()
+uniform int no_atmo;
 
 vec3 fullbrightAtmosTransport(vec3 light);
 vec3 fullbrightScaleSoftClip(vec3 light);
@@ -50,9 +53,17 @@ void fullbright_lighting()
 	color.rgb *= vertex_color.rgb;
 
 	color.rgb = pow(color.rgb, vec3(texture_gamma));
-	color.rgb = fullbrightAtmosTransport(color.rgb);
-	
-	color.rgb = fullbrightScaleSoftClip(color.rgb);
+
+	// SL-9632 HUDs are affected by Atmosphere
+	if (no_atmo == 0)
+	{
+		color.rgb = fullbrightAtmosTransport(color.rgb);
+		color.rgb = fullbrightScaleSoftClip(color.rgb);
+	}
+
+	//*TODO: Are we missing an inverse pow() here?
+	// class1\lighting\lightFullbrightF.glsl has:
+    //     color.rgb = pow(color.rgb, vec3(1.0/texture_gamma));
 
 	frag_color = color;
 }
diff --git a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightF.glsl b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightF.glsl
index b967709c57..5fcdf3107c 100644
--- a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightF.glsl
+++ b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightF.glsl
@@ -34,6 +34,9 @@ VARYING vec2 vary_texcoord0;
 
 uniform float texture_gamma;
 
+// render_hud_attachments() -> HUD objects set LLShaderMgr::NO_ATMO;
+uniform int no_atmo;
+
 vec3 fullbrightAtmosTransport(vec3 light);
 vec3 fullbrightScaleSoftClip(vec3 light);
 
@@ -43,9 +46,12 @@ void fullbright_lighting()
 	
 	color.rgb = pow(color.rgb, vec3(texture_gamma));
 
-	color.rgb = fullbrightAtmosTransport(color.rgb);
-	
-	color.rgb = fullbrightScaleSoftClip(color.rgb);
+	// SL-9632 HUDs are affected by Atmosphere
+	if (no_atmo == 0)
+	{
+		color.rgb = fullbrightAtmosTransport(color.rgb);
+		color.rgb = fullbrightScaleSoftClip(color.rgb);
+	}
 
 	color.rgb = pow(color.rgb, vec3(1.0/texture_gamma));
 
diff --git a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightShinyF.glsl b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightShinyF.glsl
index 3eaaa41866..5e966293c6 100644
--- a/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightShinyF.glsl
+++ b/indra/newview/app_settings/shaders/class1/lighting/lightFullbrightShinyF.glsl
@@ -48,17 +48,24 @@ void fullbright_shiny_lighting()
 {
 	vec4 color = diffuseLookup(vary_texcoord0.xy);
 	color.rgb *= vertex_color.rgb;
-
+	
 	// SL-9632 HUDs are affected by Atmosphere
 	if (no_atmo == 0)
 	{
+	vec3 envColor = textureCube(environmentMap, vary_texcoord1.xyz).rgb;	
+	color.rgb = mix(color.rgb, envColor.rgb, vertex_color.a*0.75); // MAGIC NUMBER SL-12574; ALM: Off, Quality > Low
+
+	color.rgb = fullbrightShinyAtmosTransport(color.rgb);
+	color.rgb = fullbrightScaleSoftClip(color.rgb);
+	}
+/*
+	// NOTE: HUD objects will be full bright. Uncomment if you want "some" environment lighting effecting these HUD objects.
+	else
+	{
 		vec3 envColor = textureCube(environmentMap, vary_texcoord1.xyz).rgb;
 		color.rgb = mix(color.rgb, envColor.rgb, vertex_color.a*0.75); // MAGIC NUMBER SL-12574; ALM: Off, Quality > Low
-
-		color.rgb = fullbrightShinyAtmosTransport(color.rgb);
-
-		color.rgb = fullbrightScaleSoftClip(color.rgb);
 	}
+*/
 
 	color.a = 1.0;
 
diff --git a/indra/newview/app_settings/shaders/class1/windlight/atmosphericsFuncs.glsl b/indra/newview/app_settings/shaders/class1/windlight/atmosphericsFuncs.glsl
index dcb02bd1c1..ea2690ba09 100644
--- a/indra/newview/app_settings/shaders/class1/windlight/atmosphericsFuncs.glsl
+++ b/indra/newview/app_settings/shaders/class1/windlight/atmosphericsFuncs.glsl
@@ -1,154 +1,134 @@
-/** 
+/**
  * @file class1\windlight\atmosphericsFuncs.glsl
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2019, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
-uniform vec4 lightnorm;
-uniform vec4 sunlight_color;
-uniform vec4 moonlight_color;
-uniform int sun_up_factor;
-uniform vec4 ambient_color;
-uniform vec4 blue_horizon;
-uniform vec4 blue_density;
+uniform vec4  lightnorm;
+uniform vec4  sunlight_color;
+uniform vec4  moonlight_color;
+uniform int   sun_up_factor;
+uniform vec4  ambient_color;
+uniform vec4  blue_horizon;
+uniform vec4  blue_density;
 uniform float haze_horizon;
 uniform float haze_density;
 uniform float cloud_shadow;
 uniform float density_multiplier;
 uniform float distance_multiplier;
 uniform float max_y;
-uniform vec4 glow;
+uniform vec4  glow;
 uniform float scene_light_strength;
-uniform mat3 ssao_effect_mat;
-uniform int no_atmo;
+uniform mat3  ssao_effect_mat;
+uniform int   no_atmo;
 uniform float sun_moon_glow_factor;
 
-float getAmbientClamp()
+float getAmbientClamp() { return 1.0f; }
+
+void calcAtmosphericVars(vec3 inPositionEye, vec3 light_dir, float ambFactor, out vec3 sunlit, out vec3 amblit, out vec3 additive,
+                         out vec3 atten, bool use_ao)
 {
-    return 1.0f;
-}
+    vec3 rel_pos = inPositionEye;
 
+    //(TERRAIN) limit altitude
+    if (abs(rel_pos.y) > max_y) rel_pos *= (max_y / rel_pos.y);
 
-void calcAtmosphericVars(vec3 inPositionEye, vec3 light_dir, float ambFactor, out vec3 sunlit, out vec3 amblit, out vec3 additive, out vec3 atten, bool use_ao) {
+    vec3  rel_pos_norm = normalize(rel_pos);
+    float rel_pos_len  = length(rel_pos);
+    vec4  sunlight     = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
 
-    vec3 P = inPositionEye;
-   
-    //(TERRAIN) limit altitude
-    if (P.y > max_y) P *= (max_y / P.y);
-    if (P.y < -max_y) P *= (-max_y / P.y); 
+    // sunlight attenuation effect (hue and brightness) due to atmosphere
+    // this is used later for sunlight modulation at various altitudes
+    vec4 light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
+    // I had thought blue_density and haze_density should have equal weighting,
+    // but attenuation due to haze_density tends to seem too strong
 
-    vec3 tmpLightnorm = lightnorm.xyz;
+    vec4 combined_haze = blue_density + vec4(haze_density);
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = vec4(haze_density) / combined_haze;
 
-    vec3 Pn = normalize(P);
-    float Plen = length(P);
+    //(TERRAIN) compute sunlight from lightnorm y component. Factor is roughly cosecant(sun elevation) (for short rays like terrain)
+    float above_horizon_factor = 1.0 / max(1e-6, lightnorm.y);
+    sunlight *= exp(-light_atten * above_horizon_factor);  // for sun [horizon..overhead] this maps to an exp curve [0..1]
+
+    // main atmospheric scattering line integral
+    float density_dist = rel_pos_len * density_multiplier;
 
-    vec4 temp1 = vec4(0);
-    vec3 temp2 = vec3(0);
-    vec4 blue_weight;
-    vec4 haze_weight;
-    vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
-    vec4 light_atten;
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist*distance_multiplier in a variable because the ati
+    // compiler gets confused.
+    combined_haze = exp(-combined_haze * density_dist * distance_multiplier);
 
-    float dens_mul = density_multiplier;
-    float dist_mul = distance_multiplier;
+    // final atmosphere attenuation factor
+    atten = combined_haze.rgb;
 
-    //sunlight attenuation effect (hue and brightness) due to atmosphere
-    //this is used later for sunlight modulation at various altitudes
-    light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
-        //I had thought blue_density and haze_density should have equal weighting,
-        //but attenuation due to haze_density tends to seem too strong
+    // compute haze glow
+    float haze_glow = dot(rel_pos_norm, lightnorm.xyz);
 
-    temp1 = blue_density + vec4(haze_density);
-    blue_weight = blue_density / temp1;
-    haze_weight = vec4(haze_density) / temp1;
+    // dampen sun additive contrib when not facing it...
+    // SL-13539: This "if" clause causes an "additive" white artifact at roughly 77 degreees.
+    //    if (length(light_dir) > 0.01)
+    haze_glow *= max(0.0f, dot(light_dir, rel_pos_norm));
 
-    //(TERRAIN) compute sunlight from lightnorm only (for short rays like terrain)
-    temp2.y = max(0.0, tmpLightnorm.y);
-    if (abs(temp2.y) > 0.000001f)
-    {
-        temp2.y = 1. / abs(temp2.y);
-    }
-    temp2.y = max(0.0000001f, temp2.y);
-    sunlight *= exp(-light_atten * temp2.y);
+    haze_glow = 1. - haze_glow;
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);  // set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
+    haze_glow *= glow.x;
+    // higher glow.x gives dimmer glow (because next step is 1 / "angle")
+    haze_glow = pow(haze_glow, glow.z);
+    // glow.z should be negative, so we're doing a sort of (1 / "angle") function
 
-    // main atmospheric scattering line integral
-    temp2.z = Plen * dens_mul;
+    // add "minimum anti-solar illumination"
+    haze_glow += .25;
 
-    // Transparency (-> temp1)
-    // ATI Bugfix -- can't store temp1*temp2.z*dist_mul in a variable because the ati
-    // compiler gets confused.
-    temp1 = exp(-temp1 * temp2.z * dist_mul);
+    haze_glow *= sun_moon_glow_factor;
 
-    //final atmosphere attenuation factor
-    atten = temp1.rgb;
-    
-    //compute haze glow
-    //(can use temp2.x as temp because we haven't used it yet)
-    temp2.x = dot(Pn, tmpLightnorm.xyz);
+    vec4 amb_color = ambient_color;
 
-    // dampen sun additive contrib when not facing it...
-    if (length(light_dir) > 0.01)
-    {
-        temp2.x *= max(0.0f, dot(light_dir, Pn));
-    }
-    temp2.x = 1. - temp2.x;
-        //temp2.x is 0 at the sun and increases away from sun
-    temp2.x = max(temp2.x, .001);    //was glow.y
-        //set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-    temp2.x *= glow.x;
-        //higher glow.x gives dimmer glow (because next step is 1 / "angle")
-    temp2.x = pow(temp2.x, glow.z);
-        //glow.z should be negative, so we're doing a sort of (1 / "angle") function
-
-    //add "minimum anti-solar illumination"
-    temp2.x += .25;
-
-    temp2.x *= sun_moon_glow_factor;
- 
-    vec4 amb_color = ambient_color; 
-    
-    //increase ambient when there are more clouds
+    // increase ambient when there are more clouds
     vec4 tmpAmbient = amb_color + (vec4(1.) - amb_color) * cloud_shadow * 0.5;
-    
+
     /*  decrease value and saturation (that in HSV, not HSL) for occluded areas
      * // for HSV color/geometry used here, see http://gimp-savvy.com/BOOK/index.html?node52.html
      * // The following line of code performs the equivalent of:
      * float ambAlpha = tmpAmbient.a;
      * float ambValue = dot(vec3(tmpAmbient), vec3(0.577)); // projection onto <1/rt(3), 1/rt(3), 1/rt(3)>, the neutral white-black axis
      * vec3 ambHueSat = vec3(tmpAmbient) - vec3(ambValue);
-     * tmpAmbient = vec4(RenderSSAOEffect.valueFactor * vec3(ambValue) + RenderSSAOEffect.saturationFactor *(1.0 - ambFactor) * ambHueSat, ambAlpha);
+     * tmpAmbient = vec4(RenderSSAOEffect.valueFactor * vec3(ambValue) + RenderSSAOEffect.saturationFactor *(1.0 - ambFactor) * ambHueSat,
+     * ambAlpha);
      */
     if (use_ao)
     {
         tmpAmbient = vec4(mix(ssao_effect_mat * tmpAmbient.rgb, tmpAmbient.rgb, ambFactor), tmpAmbient.a);
     }
 
-    //haze color
-        additive =
-        vec3(blue_horizon * blue_weight * (sunlight*(1.-cloud_shadow) + tmpAmbient)
-      + (haze_horizon * haze_weight) * (sunlight*(1.-cloud_shadow) * temp2.x
-          + tmpAmbient));
+    // Similar/Shared Algorithms:
+    //     indra\llinventory\llsettingssky.cpp                                        -- LLSettingsSky::calculateLightSettings()
+    //     indra\newview\app_settings\shaders\class1\windlight\atmosphericsFuncs.glsl -- calcAtmosphericVars()
+    // haze color
+    vec3 cs = sunlight.rgb * (1. - cloud_shadow);
+    additive = (blue_horizon.rgb * blue_weight.rgb) * (cs + tmpAmbient.rgb) + (haze_horizon * haze_weight.rgb) * (cs * haze_glow + tmpAmbient.rgb);
 
-    //brightness of surface both sunlight and ambient
+    // brightness of surface both sunlight and ambient
     sunlit = sunlight.rgb * 0.5;
     amblit = tmpAmbient.rgb * .25;
-    additive *= vec3(1.0 - temp1);
+    additive *= vec3(1.0 - combined_haze);
 }
diff --git a/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl b/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
index 24f3992e32..2425a2ad04 100644
--- a/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
+++ b/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
@@ -3,7 +3,7 @@
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2005, Linden Research, Inc.
+ * Copyright (C) 2005, 2020 Linden Research, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -36,28 +36,30 @@ out vec4 frag_color;
 uniform vec4 color;
 uniform vec4 sunlight_color;
 uniform vec4 moonlight_color;
-uniform vec3 lumWeights;
+uniform vec3 moon_dir;
 uniform float moon_brightness;
-uniform float minLuminance;
 uniform sampler2D diffuseMap;
-uniform sampler2D altDiffuseMap;
-uniform float blend_factor; // interp factor between moon A/B
+
 VARYING vec2 vary_texcoord0;
 
+vec3 scaleSoftClip(vec3 light);
+
 void main() 
 {
-    vec4 moonA = texture2D(diffuseMap, vary_texcoord0.xy);
-    vec4 moonB = texture2D(altDiffuseMap, vary_texcoord0.xy);
-    vec4 c     = mix(moonA, moonB, blend_factor);
+    // Restore Pre-EEP alpha fade moon near horizon
+    float fade = 1.0;
+    if( moon_dir.z > 0 )
+        fade = clamp( moon_dir.z*moon_dir.z*4.0, 0.0, 1.0 );
+
+    vec4 c     = texture2D(diffuseMap, vary_texcoord0.xy);
+//       c.rgb = pow(c.rgb, vec3(0.7f)); // can't use "srgb_to_linear(color.rgb)" as that is a deferred only function
+         c.rgb *= moonlight_color.rgb;
+         c.rgb *= moon_brightness;
 
-    // mix factor which blends when sunlight is brighter
-    // and shows true moon color at night
-    vec3 luma_weights = vec3(0.3, 0.5, 0.3);
-    float mix = 1.0f - dot(normalize(sunlight_color.rgb), luma_weights);
+         c.rgb *= fade;
+         c.a   *= fade;
 
-    vec3 exp = vec3(1.0 - mix * moon_brightness) * 2.0 - 1.0;
-    c.rgb = pow(c.rgb, exp);
-    //c.rgb *= moonlight_color.rgb;
+         c.rgb  = scaleSoftClip(c.rgb);
 
     frag_color = vec4(c.rgb, c.a);
 }
diff --git a/indra/newview/app_settings/shaders/class1/windlight/moonV.glsl b/indra/newview/app_settings/shaders/class1/windlight/moonV.glsl
index 8cd4b2ef47..2fceb5f743 100644
--- a/indra/newview/app_settings/shaders/class1/windlight/moonV.glsl
+++ b/indra/newview/app_settings/shaders/class1/windlight/moonV.glsl
@@ -3,7 +3,7 @@
  *
   * $LicenseInfo:firstyear=2007&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2007, Linden Research, Inc.
+ * Copyright (C) 2007, 2020 Linden Research, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -30,20 +30,15 @@ uniform mat4 modelview_projection_matrix;
 ATTRIBUTE vec3 position;
 ATTRIBUTE vec2 texcoord0;
 
-void calcAtmospherics(vec3 inPositionEye);
-
 VARYING vec2 vary_texcoord0;
 
 void main()
 {
     //transform vertex
-    vec3 offset = vec3(0, 0, 50);
-    vec4 vert = vec4(position.xyz - offset, 1.0);
+    vec4 vert = vec4(position.xyz, 1.0);
     vec4 pos = (modelview_matrix * vert);
 
     gl_Position = modelview_projection_matrix*vert;
     
     vary_texcoord0 = (texture_matrix0 * vec4(texcoord0,0,1)).xy;
-    
-    calcAtmospherics(pos.xyz);
 }
diff --git a/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl b/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
index 1dce85a83b..1485c515a4 100644
--- a/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
+++ b/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
@@ -1,24 +1,24 @@
-/** 
+/**
  * @file class2/deferred/skyF.glsl
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2005, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
@@ -32,13 +32,13 @@ uniform mat4 modelview_projection_matrix;
 // Inputs
 uniform vec3 camPosLocal;
 
-uniform vec4 lightnorm;
-uniform vec4 sunlight_color;
-uniform vec4 moonlight_color;
-uniform int sun_up_factor;
-uniform vec4 ambient_color;
-uniform vec4 blue_horizon;
-uniform vec4 blue_density;
+uniform vec4  lightnorm;
+uniform vec4  sunlight_color;
+uniform vec4  moonlight_color;
+uniform int   sun_up_factor;
+uniform vec4  ambient_color;
+uniform vec4  blue_horizon;
+uniform vec4  blue_density;
 uniform float haze_horizon;
 uniform float haze_density;
 
@@ -47,7 +47,7 @@ uniform float density_multiplier;
 uniform float distance_multiplier;
 uniform float max_y;
 
-uniform vec4 glow;
+uniform vec4  glow;
 uniform float sun_moon_glow_factor;
 
 uniform vec4 cloud_color;
@@ -73,16 +73,16 @@ uniform float ice_level;
 
 vec3 rainbow(float d)
 {
-   d = clamp(d, -1.0, 0.0);
-   float rad = (droplet_radius - 5.0f) / 1024.0f;
-   return pow(texture2D(rainbow_map, vec2(rad, d)).rgb, vec3(1.8)) * moisture_level;
+    d         = clamp(d, -1.0, 0.0);
+    float rad = (droplet_radius - 5.0f) / 1024.0f;
+    return pow(texture2D(rainbow_map, vec2(rad, d)).rgb, vec3(1.8)) * moisture_level;
 }
 
 vec3 halo22(float d)
 {
-   d = clamp(d, 0.1, 1.0);
-   float v = sqrt(clamp(1 - (d * d), 0, 1));
-   return texture2D(halo_map, vec2(0, v)).rgb * ice_level;
+    d       = clamp(d, 0.1, 1.0);
+    float v = sqrt(clamp(1 - (d * d), 0, 1));
+    return texture2D(halo_map, vec2(0, v)).rgb * ice_level;
 }
 
 /// Soft clips the light with a gamma correction
@@ -90,115 +90,96 @@ vec3 scaleSoftClip(vec3 light);
 
 void main()
 {
-
     // World / view / projection
-    // Get relative position
-    vec3 P = pos.xyz - camPosLocal.xyz + vec3(0,50,0);
+    // Get relative position (offset why?)
+    vec3 rel_pos = pos.xyz - camPosLocal.xyz + vec3(0, 50, 0);
 
-    // Set altitude
-    if (P.y > 0.)
+    // Adj position vector to clamp altitude
+    if (rel_pos.y > 0.)
     {
-        P *= (max_y / P.y);
+        rel_pos *= (max_y / rel_pos.y);
     }
-    else
+    if (rel_pos.y < 0.)
     {
-        P *= (-32000. / P.y);
+        rel_pos *= (-32000. / rel_pos.y);
     }
 
-    // Can normalize then
-    vec3 Pn = normalize(P);
-    float  Plen = length(P);
+    // Normalized
+    vec3  rel_pos_norm = normalize(rel_pos);
+    float rel_pos_len  = length(rel_pos);
 
     // Initialize temp variables
-    vec4 temp1 = vec4(0.);
-    vec4 temp2 = vec4(0.);
-    vec4 blue_weight;
-    vec4 haze_weight;
     vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
-    vec4 light_atten;
-
-    float dens_mul = density_multiplier;
 
     // Sunlight attenuation effect (hue and brightness) due to atmosphere
     // this is used later for sunlight modulation at various altitudes
-    light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
+    vec4 light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
 
     // Calculate relative weights
-    temp1 = abs(blue_density) + vec4(abs(haze_density));
-    blue_weight = blue_density / temp1;
-    haze_weight = haze_density / temp1;
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = haze_density / combined_haze;
 
-    // Compute sunlight from P & lightnorm (for long rays like sky)
-    temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-    temp2.y = 1. / temp2.y;
-    sunlight *= exp( - light_atten * temp2.y);
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0, rel_pos_norm.y) + lightnorm.y);
+    sunlight *= exp(-light_atten * off_axis);
 
     // Distance
-    temp2.z = Plen * dens_mul;
+    float density_dist = rel_pos_len * density_multiplier;
 
-    // Transparency (-> temp1)
-    // ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
     // compiler gets confused.
-    temp1 = exp(-temp1 * temp2.z);
+    combined_haze = exp(-combined_haze * density_dist);
 
     // Compute haze glow
-    temp2.x = dot(Pn, lightnorm.xyz);
-    temp2.x = 1. - temp2.x;
-        // temp2.x is 0 at the sun and increases away from sun
-    temp2.x = max(temp2.x, .001);   
-        // Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-    temp2.x *= glow.x;
-        // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-    temp2.x = pow(temp2.x, glow.z);
-        // glow.z should be negative, so we're doing a sort of (1 / "angle") function
+    float haze_glow = dot(rel_pos_norm, lightnorm.xyz);
+    haze_glow       = 1. - haze_glow;
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);
+    // Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
+    haze_glow *= glow.x;
+    // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
+    haze_glow = pow(haze_glow, glow.z);
+    // glow.z should be negative, so we're doing a sort of (1 / "angle") function
 
     // Add "minimum anti-solar illumination"
-    temp2.x += .25;
-
-    temp2.x *= sun_moon_glow_factor;
+    // For sun, add to glow.  For moon, remove glow entirely. SL-13768
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (sun_moon_glow_factor * (haze_glow + 0.25));
 
     // Haze color above cloud
-    vec4 color = (    blue_horizon * blue_weight * (sunlight + ambient_color)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + ambient_color)
-             ); 
+    vec4 color = blue_horizon * blue_weight * (sunlight + ambient_color) 
+               + haze_horizon * haze_weight * (sunlight * haze_glow + ambient_color);
 
     // Final atmosphere additive
-    color *= (1. - temp1);
+    color *= (1. - combined_haze);
 
     // Increase ambient when there are more clouds
-    vec4 tmpAmbient = ambient_color;
-    tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5; 
+    // TODO 9/20: DJH what does this do?  max(0,(1-ambient)) will change the color
+    vec4 ambient = ambient_color + max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5;
 
     // Dim sunlight by cloud shadow percentage
     sunlight *= max(0.0, (1. - cloud_shadow));
 
     // Haze color below cloud
-    vec4 additiveColorBelowCloud = (blue_horizon * blue_weight * (sunlight + tmpAmbient)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-             ); 
+    vec4 add_below_cloud = blue_horizon * blue_weight * (sunlight + ambient) 
+                         + haze_horizon * haze_weight * (sunlight * haze_glow + ambient);
 
-    
-    
     // Attenuate cloud color by atmosphere
-    temp1 = sqrt(temp1);    //less atmos opacity (more transparency) below clouds
+    combined_haze = sqrt(combined_haze);  // less atmos opacity (more transparency) below clouds
 
     // At horizon, blend high altitude sky color towards the darker color below the clouds
-    color += (additiveColorBelowCloud - color) * (1. - sqrt(temp1));
-    
-    float optic_d = dot(Pn, lightnorm.xyz);
-
-    vec3 halo_22 = halo22(optic_d);
+    color += (add_below_cloud - color) * (1. - sqrt(combined_haze));
 
+    float optic_d = dot(rel_pos_norm, lightnorm.xyz);
+    vec3  halo_22 = halo22(optic_d);
     color.rgb += rainbow(optic_d);
-
     color.rgb += halo_22;
-
     color.rgb *= 2.;
     color.rgb = scaleSoftClip(color.rgb);
 
-    /// Gamma correct for WL (soft clip effect).
+    // Gamma correct for WL (soft clip effect).
     frag_data[0] = vec4(color.rgb, 1.0);
-    frag_data[1] = vec4(0.0,0.0,0.0,0.0);
-    frag_data[2] = vec4(0.0,0.0,0.0,1.0); //1.0 in norm.w masks off fog
+    frag_data[1] = vec4(0.0, 0.0, 0.0, 0.0);
+    frag_data[2] = vec4(0.0, 0.0, 0.0, 1.0);  // 1.0 in norm.w masks off fog
 }
-
diff --git a/indra/newview/app_settings/shaders/class2/windlight/cloudsV.glsl b/indra/newview/app_settings/shaders/class2/windlight/cloudsV.glsl
index a4389f62dc..b004cc7ddd 100644
--- a/indra/newview/app_settings/shaders/class2/windlight/cloudsV.glsl
+++ b/indra/newview/app_settings/shaders/class2/windlight/cloudsV.glsl
@@ -78,90 +78,81 @@ void main()
 	// World / view / projection
 	gl_Position = modelview_projection_matrix * vec4(position.xyz, 1.0);
 
-	// Texture coords
+    // Texture coords
     // SL-13084 EEP added support for custom cloud textures -- flip them horizontally to match the preview of Clouds > Cloud Scroll
-	vary_texcoord0 = vec2( -texcoord0.x, texcoord0.y ); // See: LLSettingsVOSky::applySpecial
+    vary_texcoord0 = vec2(-texcoord0.x, texcoord0.y);  // See: LLSettingsVOSky::applySpecial
 
-	vary_texcoord0.xy -= 0.5;
-	vary_texcoord0.xy /= cloud_scale;
-	vary_texcoord0.xy += 0.5;
+    vary_texcoord0.xy -= 0.5;
+    vary_texcoord0.xy /= cloud_scale;
+    vary_texcoord0.xy += 0.5;
 
-	vary_texcoord1 = vary_texcoord0;
-	vary_texcoord1.x += lightnorm.x * 0.0125;
-	vary_texcoord1.y += lightnorm.z * 0.0125;
+    vary_texcoord1 = vary_texcoord0;
+    vary_texcoord1.x += lightnorm.x * 0.0125;
+    vary_texcoord1.y += lightnorm.z * 0.0125;
 
-	vary_texcoord2 = vary_texcoord0 * 16.;
-	vary_texcoord3 = vary_texcoord1 * 16.;
+    vary_texcoord2 = vary_texcoord0 * 16.;
+    vary_texcoord3 = vary_texcoord1 * 16.;
 
 	// Get relative position
-	vec3 P = position.xyz - camPosLocal.xyz + vec3(0,50,0);
+    vec3 rel_pos = position.xyz - camPosLocal.xyz + vec3(0, 50, 0);
 
     // fade clouds beyond a certain point so the bottom of the sky dome doesn't look silly at high altitude
-    altitude_blend_factor = clamp((P.y + 512.0) / max_y, 0.0, 1.0);
+    altitude_blend_factor = clamp((rel_pos.y + 512.0) / max_y, 0.0, 1.0);
 
-	// Set altitude
-	if (P.y > 0.)
+    // Adj position vector to clamp altitude
+    if (rel_pos.y > 0.)
 	{
-		P *= (max_y / P.y);
+        rel_pos *= (max_y / rel_pos.y);
 	}
-	else
+    if (rel_pos.y < 0.)
 	{
-		P *= (-32000. / P.y);
+        rel_pos *= (-32000. / rel_pos.y);
 	}
 
 	// Can normalize then
-	vec3 Pn = normalize(P);
-	float  Plen = length(P);
+    vec3  rel_pos_norm = normalize(rel_pos);
+    float rel_pos_len  = length(rel_pos);
 
 	// Initialize temp variables
-	vec4 temp1 = vec4(0.);
-	vec4 temp2 = vec4(0.);
-	vec4 blue_weight;
-	vec4 haze_weight;
-	//vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
 	vec4 sunlight = sunlight_color;
 	vec4 light_atten;
 
-    float dens_mul = density_multiplier;
-
 	// Sunlight attenuation effect (hue and brightness) due to atmosphere
 	// this is used later for sunlight modulation at various altitudes
-	light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
+    light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
 
 	// Calculate relative weights
-	temp1 = abs(blue_density) + vec4(abs(haze_density));
-	blue_weight = blue_density / temp1;
-	haze_weight = haze_density / temp1;
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = haze_density / combined_haze;
 
-	// Compute sunlight from P & lightnorm (for long rays like sky)
-	temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-	temp2.y = 1. / temp2.y;
-	sunlight *= exp( - light_atten * temp2.y);
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0., rel_pos_norm.y) + lightnorm.y);
+    sunlight *= exp(-light_atten * off_axis);
 
 	// Distance
-	temp2.z = Plen * dens_mul;
+    float density_dist = rel_pos_len * density_multiplier;
 
-	// Transparency (-> temp1)
-	// ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
 	// compiler gets confused.
-	temp1 = exp(-temp1 * temp2.z);
-
+    combined_haze = exp(-combined_haze * density_dist);
 
 	// Compute haze glow
-	temp2.x = dot(Pn, lightnorm.xyz);
-	temp2.x = 1. - temp2.x;
-		// temp2.x is 0 at the sun and increases away from sun
-	temp2.x = max(temp2.x, .001);	
+    float haze_glow = 1.0 - dot(rel_pos_norm, lightnorm.xyz);
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);
 		// Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-	temp2.x *= glow.x;
+    haze_glow *= glow.x;
 		// Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-	temp2.x = pow(temp2.x, glow.z);
+    haze_glow = pow(haze_glow, glow.z);
 		// glow.z should be negative, so we're doing a sort of (1 / "angle") function
 
-    temp2.x *= sun_moon_glow_factor;
+    haze_glow *= sun_moon_glow_factor;
 
 	// Add "minimum anti-solar illumination"
-	temp2.x += .25;
+    // For sun, add to glow.  For moon, remove glow entirely. SL-13768
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (haze_glow + 0.25);
 
 	// Increase ambient when there are more clouds
 	vec4 tmpAmbient = ambient_color;
@@ -171,29 +162,26 @@ void main()
 	sunlight *= (1. - cloud_shadow);
 
 	// Haze color below cloud
-	vec4 additiveColorBelowCloud = (	  blue_horizon * blue_weight * (sunlight + tmpAmbient)
-				+ (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-			 );	
+    vec4 additiveColorBelowCloud =
+        (blue_horizon * blue_weight * (sunlight + tmpAmbient) + (haze_horizon * haze_weight) * (sunlight * haze_glow + tmpAmbient));
 
 	// CLOUDS
-	temp2.y = max(0., lightnorm.y * 2.);
-	temp2.y = 1. / temp2.y;
-	sunlight *= exp( - light_atten * temp2.y);
+    off_axis = 1.0 / max(1e-6, lightnorm.y * 2.);
+    sunlight *= exp(-light_atten * off_axis);
 
 	// Cloud color out
-	vary_CloudColorSun = (sunlight * temp2.x) * cloud_color;
+    vary_CloudColorSun     = (sunlight * haze_glow) * cloud_color;
 	vary_CloudColorAmbient = tmpAmbient * cloud_color;
 	
 	// Attenuate cloud color by atmosphere
-	temp1 = sqrt(temp1);	//less atmos opacity (more transparency) below clouds
-	vary_CloudColorSun *= temp1;
-	vary_CloudColorAmbient *= temp1;
-	vec4 oHazeColorBelowCloud = additiveColorBelowCloud * (1. - temp1);
+    combined_haze = sqrt(combined_haze);  // less atmos opacity (more transparency) below clouds
+    vary_CloudColorSun *= combined_haze;
+    vary_CloudColorAmbient *= combined_haze;
+    vec4 oHazeColorBelowCloud = additiveColorBelowCloud * (1. - combined_haze);
 
 	// Make a nice cloud density based on the cloud_shadow value that was passed in.
 	vary_CloudDensity = 2. * (cloud_shadow - 0.25);
 
-
 	// Combine these to minimize register use
 	vary_CloudColorAmbient += oHazeColorBelowCloud;
 
@@ -202,4 +190,3 @@ void main()
 
 	// END CLOUDS
 }
-
diff --git a/indra/newview/app_settings/shaders/class2/windlight/skyV.glsl b/indra/newview/app_settings/shaders/class2/windlight/skyV.glsl
index 0d141342ce..a0a33b8642 100644
--- a/indra/newview/app_settings/shaders/class2/windlight/skyV.glsl
+++ b/indra/newview/app_settings/shaders/class2/windlight/skyV.glsl
@@ -1,28 +1,28 @@
-/** 
+/**
  * @file class2\wl\skyV.glsl
  *
  * $LicenseInfo:firstyear=2005&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2005, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
- 
+
 uniform mat4 modelview_projection_matrix;
 
 ATTRIBUTE vec3 position;
@@ -37,13 +37,13 @@ VARYING vec4 vary_HazeColor;
 // Inputs
 uniform vec3 camPosLocal;
 
-uniform vec4 lightnorm;
-uniform vec4 sunlight_color;
-uniform vec4 moonlight_color;
-uniform int sun_up_factor;
-uniform vec4 ambient_color;
-uniform vec4 blue_horizon;
-uniform vec4 blue_density;
+uniform vec4  lightnorm;
+uniform vec4  sunlight_color;
+uniform vec4  moonlight_color;
+uniform int   sun_up_factor;
+uniform vec4  ambient_color;
+uniform vec4  blue_horizon;
+uniform vec4  blue_density;
 uniform float haze_horizon;
 uniform float haze_density;
 
@@ -52,110 +52,98 @@ uniform float density_multiplier;
 uniform float distance_multiplier;
 uniform float max_y;
 
-uniform vec4 glow;
+uniform vec4  glow;
 uniform float sun_moon_glow_factor;
 
 uniform vec4 cloud_color;
 
 void main()
 {
-
-	// World / view / projection
+    // World / view / projection
     vec4 pos = modelview_projection_matrix * vec4(position.xyz, 1.0);
 
-	gl_Position = pos;
-	
-	// Get relative position
-	vec3 P = position.xyz - camPosLocal.xyz + vec3(0,50,0);
-
-	// Set altitude
-	if (P.y > 0.)
-	{
-		P *= (max_y / P.y);
-	}
-	else
-	{
-		P *= (-32000. / P.y);
-	}
-
-	// Can normalize then
-	vec3 Pn = normalize(P);
-
-	float Plen = length(P);
-
-	// Initialize temp variables
-	vec4 temp1 = vec4(0.);
-	vec4 temp2 = vec4(0.);
-	vec4 blue_weight;
-	vec4 haze_weight;
-	vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
-	vec4 light_atten;
-
-    float dens_mul = density_multiplier;
-
-	// Sunlight attenuation effect (hue and brightness) due to atmosphere
-	// this is used later for sunlight modulation at various altitudes
-	light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
-
-	// Calculate relative weights
-	temp1 = abs(blue_density) + vec4(abs(haze_density));
-	blue_weight = blue_density / temp1;
-	haze_weight = haze_density / temp1;
-
-	// Compute sunlight from P & lightnorm (for long rays like sky)
-    temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-    temp2.y = 1. / temp2.y;
-    sunlight *= exp( - light_atten * temp2.y);
-
-	// Distance
-	temp2.z = Plen * dens_mul;
-
-	// Transparency (-> temp1)
-    // ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
-    // compiler gets confused.
-    temp1 = exp(-temp1 * temp2.z);
+    gl_Position = pos;
+
+    // Get relative position
+    vec3 rel_pos = position.xyz - camPosLocal.xyz + vec3(0, 50, 0);
+
+    // Adj position vector to clamp altitude
+    if (rel_pos.y > 0.)
+    {
+        rel_pos *= (max_y / rel_pos.y);
+    }
+    if (rel_pos.y < 0.)
+    {
+        rel_pos *= (-32000. / rel_pos.y);
+    }
 
-	// Compute haze glow
-	temp2.x = dot(Pn, lightnorm.xyz);
-	temp2.x = 1. - temp2.x;
-		// temp2.x is 0 at the sun and increases away from sun
-	temp2.x = max(temp2.x, .001);	
-		// Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
-	temp2.x *= glow.x;
-		// Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-	temp2.x = pow(temp2.x, glow.z);
-		// glow.z should be negative, so we're doing a sort of (1 / "angle") function
+    // Can normalize then
+    vec3 rel_pos_norm = normalize(rel_pos);
 
-	// Add "minimum anti-solar illumination"
-	temp2.x += .25;
+    float rel_pos_len = length(rel_pos);
 
-    vec4 color = (    blue_horizon * blue_weight * (sunlight + ambient_color)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + ambient_color)
-             );
+    // Initialize temp variables
+    vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
+    vec4 light_atten;
 
+    // Sunlight attenuation effect (hue and brightness) due to atmosphere
+    // this is used later for sunlight modulation at various altitudes
+    light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
+
+    // Calculate relative weights
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight   = blue_density / combined_haze;
+    vec4 haze_weight   = haze_density / combined_haze;
+
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0., rel_pos_norm.y) + lightnorm.y);
+    sunlight *= exp(-light_atten * off_axis);
+
+    // Distance
+    float density_dist = rel_pos_len * density_multiplier;
+
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
+    // compiler gets confused.
+    combined_haze = exp(-combined_haze * density_dist);
+
+    // Compute haze glow
+    float haze_glow = 1.0 - dot(rel_pos_norm, lightnorm.xyz);
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);
+    // Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
+    haze_glow *= glow.x;
+    // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
+    haze_glow = pow(haze_glow, glow.z);
+    // glow.z should be negative, so we're doing a sort of (1 / "angle") function
+
+    // Add "minimum anti-solar illumination"
+    // For sun, add to glow.  For moon, remove glow entirely. SL-13768
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (haze_glow + 0.25);
+
+    vec4 color =
+        (blue_horizon * blue_weight * (sunlight + ambient_color) + (haze_horizon * haze_weight) * (sunlight * haze_glow + ambient_color));
 
     // Final atmosphere additive
-    color *= (1. - temp1);
+    color *= (1. - combined_haze);
 
-	// Increase ambient when there are more clouds
-	vec4 tmpAmbient = ambient_color;
-	tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5; 
+    // Increase ambient when there are more clouds
+    vec4 tmpAmbient = ambient_color;
+    tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5;
 
-	// Dim sunlight by cloud shadow percentage
-	sunlight *= max(0.0, (1. - cloud_shadow));
+    // Dim sunlight by cloud shadow percentage
+    sunlight *= max(0.0, (1. - cloud_shadow));
 
-	// Haze color below cloud
-	vec4 additiveColorBelowCloud = (	  blue_horizon * blue_weight * (sunlight + tmpAmbient)
-				+ (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-			 );	
+    // Haze color below cloud
+    vec4 additiveColorBelowCloud =
+        (blue_horizon * blue_weight * (sunlight + tmpAmbient) + (haze_horizon * haze_weight) * (sunlight * haze_glow + tmpAmbient));
 
-	// Attenuate cloud color by atmosphere
-	temp1 = sqrt(temp1);	//less atmos opacity (more transparency) below clouds
+    // Attenuate cloud color by atmosphere
+    combined_haze = sqrt(combined_haze);  // less atmos opacity (more transparency) below clouds
 
-	// At horizon, blend high altitude sky color towards the darker color below the clouds
-	color += (additiveColorBelowCloud - color) * (1. - sqrt(temp1));
+    // At horizon, blend high altitude sky color towards the darker color below the clouds
+    color += (additiveColorBelowCloud - color) * (1. - sqrt(combined_haze));
 
     // Haze color above cloud
-	vary_HazeColor = color;	
+    vary_HazeColor = color;
 }
-