MAINT-8838 render a sun disc if the texture(s) are provided by WL settings (default is no sun disc and just haze)

Refactor sky texture optimization to retain building the cubemap used by shiny.

13 files changed, 383 insertions, 61 deletions

diff --git a/indra/llinventory/llsettingsdaycycle.cpp b/indra/llinventory/llsettingsdaycycle.cpp
index 2534d5f0f1..5e6d5597e4 100644
--- a/indra/llinventory/llsettingsdaycycle.cpp
+++ b/indra/llinventory/llsettingsdaycycle.cpp
@@ -683,7 +683,7 @@ LLSettingsDay::CycleTrack_t::value_type LLSettingsDay::getSettingsNearKeyframe(c
 
     F32 dist = get_wrapping_distance(startframe, (*it).first);
 
-    LL_DEBUGS("LAPRAS") << "[" << startframe << " ... " << keyframe << " -> " << (*it).first << "@" << dist << LL_ENDL;
+    //LL_DEBUGS("LAPRAS") << "[" << startframe << " ... " << keyframe << " -> " << (*it).first << "@" << dist << LL_ENDL;
 
     if (dist <= (fudge * 2.0f))
         return (*it);
diff --git a/indra/llinventory/llsettingssky.cpp b/indra/llinventory/llsettingssky.cpp
index 0b6ad66a0c..d73ae5721a 100644
--- a/indra/llinventory/llsettingssky.cpp
+++ b/indra/llinventory/llsettingssky.cpp
@@ -640,7 +640,7 @@ LLSD LLSettingsSky::defaults(const LLSettingsBase::TrackPosition& position)
         dfltsetting[SETTING_BLOOM_TEXTUREID]    = IMG_BLOOM1;
         dfltsetting[SETTING_CLOUD_TEXTUREID]    = GetDefaultCloudNoiseTextureId();
         dfltsetting[SETTING_MOON_TEXTUREID]     = GetDefaultMoonTextureId();
-        dfltsetting[SETTING_SUN_TEXTUREID]      = LLUUID::null; // GetDefaultSunTextureId();
+        dfltsetting[SETTING_SUN_TEXTUREID]      = GetDefaultSunTextureId();
 
         dfltsetting[SETTING_TYPE] = "sky";
 
@@ -1092,7 +1092,8 @@ LLUUID LLSettingsSky::GetDefaultAssetId()
 
 LLUUID LLSettingsSky::GetDefaultSunTextureId()
 {
-    return DEFAULT_SUN_ID;
+    //return DEFAULT_SUN_ID;
+    return LLUUID::null;
 }
 
 LLUUID LLSettingsSky::GetDefaultMoonTextureId()
diff --git a/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl b/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
index b0fca8ddee..6562b86aaf 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/moonF.glsl
@@ -49,7 +49,7 @@ void main()
 {
 	vec4 moonA = texture2D(diffuseMap, vary_texcoord0.xy);
 	vec4 moonB = texture2D(altDiffuseMap, vary_texcoord0.xy);
-    vec4 c     = mix(moonA, moonB, blend_factor);
+    vec4 c     = mix(moonB, moonA, blend_factor);
 
 	c.rgb = pow(c.rgb, vec3(0.7f));
 	c.rgb = fullbrightAtmosTransport(c.rgb);
diff --git a/indra/newview/app_settings/shaders/class1/deferred/sunDiscF.glsl b/indra/newview/app_settings/shaders/class1/deferred/sunDiscF.glsl
new file mode 100644
index 0000000000..d2e3be2720
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/deferred/sunDiscF.glsl
@@ -0,0 +1,55 @@
+/** 
+ * @file sunDiscF.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
+ * $/LicenseInfo$
+ */
+ 
+#extension GL_ARB_texture_rectangle : enable
+
+/*[EXTRA_CODE_HERE]*/
+
+#ifdef DEFINE_GL_FRAGCOLOR
+out vec4 frag_color;
+#else
+#define frag_color gl_FragColor
+#endif
+
+vec3 fullbrightAtmosTransport(vec3 light);
+vec3 fullbrightScaleSoftClip(vec3 light);
+
+uniform sampler2D diffuseMap;
+uniform sampler2D altDiffuseMap;
+uniform float blend_factor; // interp factor between sunDisc A/B
+VARYING vec2 vary_texcoord0;
+
+void main() 
+{
+	vec4 sunDiscA = texture2D(diffuseMap, vary_texcoord0.xy);
+	vec4 sunDiscB = texture2D(altDiffuseMap, vary_texcoord0.xy);
+    vec4 c     = mix(sunDiscB, sunDiscA, blend_factor);
+
+	c.rgb = pow(c.rgb, vec3(0.7f));
+	c.rgb = fullbrightAtmosTransport(c.rgb);
+    c.rgb = fullbrightScaleSoftClip(c.rgb);
+	frag_color = c;
+}
+
diff --git a/indra/newview/app_settings/shaders/class1/deferred/sunDiscV.glsl b/indra/newview/app_settings/shaders/class1/deferred/sunDiscV.glsl
new file mode 100644
index 0000000000..3bf50ddd0a
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/deferred/sunDiscV.glsl
@@ -0,0 +1,44 @@
+/** 
+ * @file sunDiscV.glsl
+ *
+  * $LicenseInfo:firstyear=2007&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2007, 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 texture_matrix0;
+uniform mat4 modelview_matrix;
+uniform mat4 modelview_projection_matrix;
+
+ATTRIBUTE vec3 position;
+ATTRIBUTE vec2 texcoord0;
+
+VARYING vec2 vary_texcoord0;
+
+void main()
+{
+	//transform vertex
+	vec4 vert = vec4(position.xyz, 1.0);
+	vec4 pos = (modelview_matrix * vert);
+
+	gl_Position = modelview_projection_matrix*vec4(position.xyz, 1.0);
+	
+	vary_texcoord0 = (texture_matrix0 * vec4(texcoord0,0,1)).xy;
+}
diff --git a/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl b/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
index 933625986c..480a0e1dc4 100644
--- a/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
+++ b/indra/newview/app_settings/shaders/class1/windlight/moonF.glsl
@@ -49,7 +49,7 @@ void main()
 {
 	vec4 moonA = texture2D(diffuseMap, vary_texcoord0.xy);
 	vec4 moonB = texture2D(altDiffuseMap, vary_texcoord0.xy);
-    vec4 c     = mix(moonA, moonB, blend_factor);
+    vec4 c     = mix(moonB, moonA, blend_factor);
 
     c.rgb = pow(c.rgb, vec3(0.45f));
 	c.rgb = fullbrightAtmosTransport(c.rgb);
diff --git a/indra/newview/app_settings/shaders/class1/windlight/sunDiscF.glsl b/indra/newview/app_settings/shaders/class1/windlight/sunDiscF.glsl
new file mode 100644
index 0000000000..0eb32b69b8
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/windlight/sunDiscF.glsl
@@ -0,0 +1,54 @@
+/** 
+ * @file sunDiscF.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
+ * $/LicenseInfo$
+ */
+ 
+#extension GL_ARB_texture_rectangle : enable
+
+/*[EXTRA_CODE_HERE]*/
+
+#ifdef DEFINE_GL_FRAGCOLOR
+out vec4 frag_color;
+#else
+#define frag_color gl_FragColor
+#endif
+
+vec3 fullbrightAtmosTransport(vec3 light);
+vec3 fullbrightScaleSoftClip(vec3 light);
+
+uniform sampler2D diffuseMap;
+uniform sampler2D altDiffuseMap;
+uniform float blend_factor; // interp factor between sun A/B
+VARYING vec2 vary_texcoord0;
+
+void main() 
+{
+	vec4 sunA = texture2D(diffuseMap, vary_texcoord0.xy);
+	vec4 sunB = texture2D(altDiffuseMap, vary_texcoord0.xy);
+    vec4 c     = mix(sunB, sunA, blend_factor);
+    c.rgb = pow(c.rgb, vec3(0.45f));
+	c.rgb = fullbrightAtmosTransport(c.rgb);
+    c.rgb = fullbrightScaleSoftClip(c.rgb);
+	frag_color = c;
+}
+
diff --git a/indra/newview/app_settings/shaders/class1/windlight/sunDiscV.glsl b/indra/newview/app_settings/shaders/class1/windlight/sunDiscV.glsl
new file mode 100644
index 0000000000..3bf50ddd0a
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/windlight/sunDiscV.glsl
@@ -0,0 +1,44 @@
+/** 
+ * @file sunDiscV.glsl
+ *
+  * $LicenseInfo:firstyear=2007&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2007, 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 texture_matrix0;
+uniform mat4 modelview_matrix;
+uniform mat4 modelview_projection_matrix;
+
+ATTRIBUTE vec3 position;
+ATTRIBUTE vec2 texcoord0;
+
+VARYING vec2 vary_texcoord0;
+
+void main()
+{
+	//transform vertex
+	vec4 vert = vec4(position.xyz, 1.0);
+	vec4 pos = (modelview_matrix * vert);
+
+	gl_Position = modelview_projection_matrix*vec4(position.xyz, 1.0);
+	
+	vary_texcoord0 = (texture_matrix0 * vec4(texcoord0,0,1)).xy;
+}
diff --git a/indra/newview/lldrawpoolwlsky.cpp b/indra/newview/lldrawpoolwlsky.cpp
index cf4d63149c..9f8511a937 100644
--- a/indra/newview/lldrawpoolwlsky.cpp
+++ b/indra/newview/lldrawpoolwlsky.cpp
@@ -48,8 +48,9 @@ static LLStaticHashedString sCamPosLocal("camPosLocal");
 static LLStaticHashedString sCustomAlpha("custom_alpha");
 
 static LLGLSLShader* cloud_shader = NULL;
-static LLGLSLShader* sky_shader = NULL;
-static LLGLSLShader* moon_shader = NULL;
+static LLGLSLShader* sky_shader   = NULL;
+static LLGLSLShader* sun_shader   = NULL;
+static LLGLSLShader* moon_shader  = NULL;
 
 LLDrawPoolWLSky::LLDrawPoolWLSky(void) :
 	LLDrawPool(POOL_WL_SKY)
@@ -77,6 +78,11 @@ void LLDrawPoolWLSky::beginRenderPass( S32 pass )
 				&gObjectFullbrightNoColorWaterProgram :
 				&gWLCloudProgram;
 
+    sun_shader =
+			LLPipeline::sUnderWaterRender ?
+				&gObjectFullbrightNoColorWaterProgram :
+				&gWLSunProgram;
+
     moon_shader =
 			LLPipeline::sUnderWaterRender ?
 				&gObjectFullbrightNoColorWaterProgram :
@@ -91,6 +97,12 @@ void LLDrawPoolWLSky::beginDeferredPass(S32 pass)
 {
 	sky_shader = &gDeferredWLSkyProgram;
 	cloud_shader = &gDeferredWLCloudProgram;
+
+    sun_shader =
+			LLPipeline::sUnderWaterRender ?
+				&gObjectFullbrightNoColorWaterProgram :
+				&gDeferredWLSunProgram;
+
     moon_shader =
 			LLPipeline::sUnderWaterRender ?
 				&gObjectFullbrightNoColorWaterProgram :
@@ -300,53 +312,116 @@ void LLDrawPoolWLSky::renderHeavenlyBodies()
 	LLGLEnable blend_on(GL_BLEND);
 	gPipeline.disableLights();
 
-#if 0 // when we want to re-add a texture sun disc, here's where to do it.
 	LLFace * face = gSky.mVOSkyp->mFace[LLVOSky::FACE_SUN];
-	if (gSky.mVOSkyp->getSun().getDraw() && face->getGeomCount())
+
+    F32 blend_factor = LLEnvironment::instance().getCurrentSky()->getBlendFactor();
+    bool can_use_vertex_shaders = gPipeline.canUseVertexShaders();
+
+	if (gSky.mVOSkyp->getSun().getDraw() && face && face->getGeomCount())
 	{
-		LLViewerTexture * tex  = face->getTexture();
-		gGL.getTexUnit(0)->bind(tex);
-		LLColor4 color(gSky.mVOSkyp->getSun().getInterpColor());
-		LLFacePool::LLOverrideFaceColor color_override(this, color);
-		face->renderIndexed();
+		LLViewerTexture* tex_a = face->getTexture(LLRender::DIFFUSE_MAP);
+        LLViewerTexture* tex_b = face->getTexture(LLRender::ALTERNATE_DIFFUSE_MAP);
+
+        // if we even have sun disc textures to work with...
+        if (tex_a || tex_b)
+        {
+            // if and only if we have a texture defined, render the sun disc
+            if (can_use_vertex_shaders)
+		    {
+			    sun_shader->bind();
+            }
+
+            if (tex_a && (!tex_b || (tex_a == tex_b)))
+            {
+                // Bind current and next sun textures
+		        gGL.getTexUnit(0)->bind(tex_a);
+                gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+                blend_factor = 0;
+            }
+            else if (tex_b && !tex_a)
+            {
+                gGL.getTexUnit(0)->bind(tex_b);
+                gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+                blend_factor = 0;
+            }
+            else if (tex_b != tex_a)
+            {
+                gGL.getTexUnit(0)->bind(tex_a);
+                gGL.getTexUnit(1)->bind(tex_b);
+            }
+
+		    LLColor4 color(gSky.mVOSkyp->getSun().getInterpColor());
+
+            if (can_use_vertex_shaders)
+		    {
+                sun_shader->uniform4fv(LLShaderMgr::DIFFUSE_COLOR, 1, color.mV);
+                sun_shader->uniform1f(LLShaderMgr::BLEND_FACTOR, blend_factor);
+		    }
+
+		    LLFacePool::LLOverrideFaceColor color_override(this, color);
+		    face->renderIndexed();
+
+            gGL.getTexUnit(0)->unbind(LLTexUnit::TT_TEXTURE);
+            gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+
+            if (can_use_vertex_shaders)
+		    {
+			    sun_shader->unbind();
+            }
+        }
 	}
-#endif
 
-	LLFace * face = gSky.mVOSkyp->mFace[LLVOSky::FACE_MOON];
+	face = gSky.mVOSkyp->mFace[LLVOSky::FACE_MOON];
 
-	if (gSky.mVOSkyp->getMoon().getDraw() && face->getGeomCount() && moon_shader)
-	{
-		// *NOTE: even though we already bound this texture above for the
-		// stars register combiners, we bind again here for defensive reasons,
-		// since LLImageGL::bind detects that it's a noop, and optimizes it out.
-		gGL.getTexUnit(0)->bind(face->getTexture());
-		LLColor4 color(gSky.mVOSkyp->getMoon().getInterpColor());
+	if (gSky.mVOSkyp->getMoon().getDraw() && face && face->getTexture(LLRender::DIFFUSE_MAP) && face->getGeomCount() && moon_shader)
+	{        
+        LLViewerTexture* tex_a = face->getTexture(LLRender::DIFFUSE_MAP);
+        LLViewerTexture* tex_b = face->getTexture(LLRender::ALTERNATE_DIFFUSE_MAP);
 
-		/*F32 a = gSky.mVOSkyp->getMoon().getDirection().mV[2];
-		if (a > 0.f)
-		{
-			a = a*a*4.f;
-		}			
-		color.mV[3] = llclamp(a, 0.f, 1.f);*/
+		LLColor4 color(gSky.mVOSkyp->getMoon().getInterpColor());
 		
-		if (gPipeline.canUseVertexShaders())
+        if (can_use_vertex_shaders)
 		{
 			moon_shader->bind();
-            moon_shader->uniform4fv(LLShaderMgr::DIFFUSE_COLOR, 1, color.mV);
-            moon_shader->uniform3fv(LLShaderMgr::GLOW_LUM_WEIGHTS, 1, LLPipeline::RenderGlowLumWeights.mV);
-            F32 blend_factor = LLEnvironment::instance().getCurrentSky()->getBlendFactor();
+        }
+
+        if (tex_a && (!tex_b || (tex_a == tex_b)))
+        {
+            // Bind current and next sun textures
+		    gGL.getTexUnit(0)->bind(tex_a);
+            gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+            blend_factor = 0;
+        }
+        else if (tex_b && !tex_a)
+        {
+            gGL.getTexUnit(0)->bind(tex_b);
+            gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+            blend_factor = 0;
+        }
+        else if (tex_b != tex_a)
+        {
+            gGL.getTexUnit(0)->bind(tex_a);
+            gGL.getTexUnit(1)->bind(tex_b);
+        }
+
+        if (can_use_vertex_shaders)
+		{
+            moon_shader->uniform4fv(LLShaderMgr::DIFFUSE_COLOR, 1, color.mV);                
             moon_shader->uniform1f(LLShaderMgr::BLEND_FACTOR, blend_factor);
-		}
+        }
 
 		LLFacePool::LLOverrideFaceColor color_override(this, color);
 		
 		face->renderIndexed();
 
-		if (gPipeline.canUseVertexShaders())
+        gGL.getTexUnit(0)->unbind(LLTexUnit::TT_TEXTURE);
+        gGL.getTexUnit(1)->unbind(LLTexUnit::TT_TEXTURE);
+
+		if (can_use_vertex_shaders)
 		{
 			moon_shader->unbind();
 		}
-	}
+	}    
 }
 
 void LLDrawPoolWLSky::renderDeferred(S32 pass)
@@ -383,12 +458,6 @@ void LLDrawPoolWLSky::renderDeferred(S32 pass)
 	        gGL.pushMatrix();
 		    gGL.translatef(origin.mV[0], origin.mV[1], origin.mV[2]);
 
-		    // *NOTE: have to bind moon textures here since register combiners blending in
-		    // renderStars() requires something to be bound and we might as well only
-		    // bind the moon textures once.		
-		    gGL.getTexUnit(0)->bind(gSky.mVOSkyp->mFace[LLVOSky::FACE_MOON]->getTexture(LLRender::DIFFUSE_MAP));
-            gGL.getTexUnit(1)->bind(gSky.mVOSkyp->mFace[LLVOSky::FACE_MOON]->getTexture(LLRender::ALTERNATE_DIFFUSE_MAP));
-
 		    renderHeavenlyBodies();	        
         }
     }    
diff --git a/indra/newview/llviewershadermgr.cpp b/indra/newview/llviewershadermgr.cpp
index ea97765e5b..cd378c0a56 100644
--- a/indra/newview/llviewershadermgr.cpp
+++ b/indra/newview/llviewershadermgr.cpp
@@ -176,6 +176,7 @@ LLGLSLShader		gImpostorProgram;
 // WindLight shader handles
 LLGLSLShader			gWLSkyProgram;
 LLGLSLShader			gWLCloudProgram;
+LLGLSLShader			gWLSunProgram;
 LLGLSLShader			gWLMoonProgram;
 
 // Effects Shaders
@@ -232,6 +233,7 @@ LLGLSLShader			gFXAAProgram;
 LLGLSLShader			gDeferredPostNoDoFProgram;
 LLGLSLShader			gDeferredWLSkyProgram;
 LLGLSLShader			gDeferredWLCloudProgram;
+LLGLSLShader			gDeferredWLSunProgram;
 LLGLSLShader			gDeferredWLMoonProgram;
 LLGLSLShader			gDeferredStarProgram;
 LLGLSLShader			gDeferredFullbrightShinyProgram;
@@ -251,6 +253,7 @@ LLViewerShaderMgr::LLViewerShaderMgr() :
 	//ONLY shaders that need WL Param management should be added here
 	mShaderList.push_back(&gWLSkyProgram);
 	mShaderList.push_back(&gWLCloudProgram);
+    mShaderList.push_back(&gWLSunProgram);
     mShaderList.push_back(&gWLMoonProgram);
 	mShaderList.push_back(&gAvatarProgram);
 	mShaderList.push_back(&gObjectShinyProgram);
@@ -345,6 +348,7 @@ LLViewerShaderMgr::LLViewerShaderMgr() :
 	mShaderList.push_back(&gDeferredWLSkyProgram);
 	mShaderList.push_back(&gDeferredWLCloudProgram);
     mShaderList.push_back(&gDeferredWLMoonProgram);
+    mShaderList.push_back(&gDeferredWLSunProgram);
 }
 
 LLViewerShaderMgr::~LLViewerShaderMgr()
@@ -831,6 +835,7 @@ void LLViewerShaderMgr::unloadShaders()
 
 	gWLSkyProgram.unload();
 	gWLCloudProgram.unload();
+    gWLSunProgram.unload();
     gWLMoonProgram.unload();
 
 	gPostColorFilterProgram.unload();
@@ -1213,6 +1218,7 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
 		gDeferredUnderWaterProgram.unload();
 		gDeferredWLSkyProgram.unload();
 		gDeferredWLCloudProgram.unload();
+        gDeferredWLSunProgram.unload();
         gDeferredWLMoonProgram.unload();
 		gDeferredStarProgram.unload();
 		gDeferredFullbrightShinyProgram.unload();
@@ -2159,6 +2165,24 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
 
     if (success)
 	{
+		gDeferredWLSunProgram.mName = "Deferred Windlight Sun Program";
+        gDeferredWLSunProgram.mFeatures.calculatesAtmospherics = true;
+		gDeferredWLSunProgram.mFeatures.hasTransport = true;
+        gDeferredWLSunProgram.mFeatures.hasGamma = true;
+		gDeferredWLSunProgram.mFeatures.hasAtmospherics = true;
+        gDeferredWLSunProgram.mFeatures.isFullbright = true;
+		gDeferredWLSunProgram.mFeatures.disableTextureIndex = true;
+		gDeferredWLSunProgram.mShaderFiles.clear();
+		gDeferredWLSunProgram.mShaderFiles.push_back(make_pair("deferred/sunDiscV.glsl", GL_VERTEX_SHADER_ARB));
+		gDeferredWLSunProgram.mShaderFiles.push_back(make_pair("deferred/sunDiscF.glsl", GL_FRAGMENT_SHADER_ARB));
+		gDeferredWLSunProgram.mShaderLevel = mVertexShaderLevel[SHADER_DEFERRED];
+		gDeferredWLSunProgram.mShaderGroup = LLGLSLShader::SG_SKY;
+		success = gDeferredWLSunProgram.createShader(NULL, NULL);
+        llassert(success);
+	}
+
+    if (success)
+	{
 		gDeferredWLMoonProgram.mName = "Deferred Windlight Moon Program";
         gDeferredWLMoonProgram.mFeatures.calculatesAtmospherics = true;
 		gDeferredWLMoonProgram.mFeatures.hasTransport = true;
@@ -2171,10 +2195,6 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
 		gDeferredWLMoonProgram.mShaderFiles.push_back(make_pair("deferred/moonF.glsl", GL_FRAGMENT_SHADER_ARB));
 		gDeferredWLMoonProgram.mShaderLevel = mVertexShaderLevel[SHADER_DEFERRED];
 		gDeferredWLMoonProgram.mShaderGroup = LLGLSLShader::SG_SKY;
-        if (mVertexShaderLevel[SHADER_WINDLIGHT] >= 3)
-        {
-            gDeferredWLSkyProgram.mExtraLinkObject = gAtmosphere->getAtmosphericShaderForLink();
-        }
 		success = gDeferredWLMoonProgram.createShader(NULL, NULL);
         llassert(success);
 	}
@@ -3510,6 +3530,7 @@ BOOL LLViewerShaderMgr::loadShadersWindLight()
 	{
 		gWLSkyProgram.unload();
 		gWLCloudProgram.unload();
+        gWLSunProgram.unload();
         gWLMoonProgram.unload();
 		gDownsampleMinMaxDepthRectProgram.unload();
         gInscatterRectProgram.unload();
@@ -3548,6 +3569,24 @@ BOOL LLViewerShaderMgr::loadShadersWindLight()
 
     if (success && (mVertexShaderLevel[SHADER_WINDLIGHT] < 3))
 	{
+		gWLSunProgram.mName = "Windlight Sun Program";
+		gWLSunProgram.mShaderFiles.clear();
+		gWLSunProgram.mFeatures.calculatesAtmospherics = true;
+		gWLSunProgram.mFeatures.hasTransport = true;
+        gWLSunProgram.mFeatures.hasGamma = true;
+		gWLSunProgram.mFeatures.hasAtmospherics = true;
+        gWLSunProgram.mFeatures.isFullbright = true;
+		gWLSunProgram.mFeatures.disableTextureIndex = true;
+		gWLSunProgram.mShaderGroup = LLGLSLShader::SG_SKY;
+		gWLSunProgram.mShaderFiles.push_back(make_pair("windlight/sunDiscV.glsl", GL_VERTEX_SHADER_ARB));
+		gWLSunProgram.mShaderFiles.push_back(make_pair("windlight/sunDiscF.glsl", GL_FRAGMENT_SHADER_ARB));
+		gWLSunProgram.mShaderLevel = mVertexShaderLevel[SHADER_WINDLIGHT];
+		gWLSunProgram.mShaderGroup = LLGLSLShader::SG_SKY;
+		success = gWLSunProgram.createShader(NULL, NULL);
+	}
+
+    if (success && (mVertexShaderLevel[SHADER_WINDLIGHT] < 3))
+	{
 		gWLMoonProgram.mName = "Windlight Moon Program";
 		gWLMoonProgram.mShaderFiles.clear();
 		gWLMoonProgram.mFeatures.calculatesAtmospherics = true;
diff --git a/indra/newview/llviewershadermgr.h b/indra/newview/llviewershadermgr.h
index fc788b944b..250f8f1ee3 100644
--- a/indra/newview/llviewershadermgr.h
+++ b/indra/newview/llviewershadermgr.h
@@ -261,6 +261,7 @@ extern LLGLSLShader			gImpostorProgram;
 // WindLight shader handles
 extern LLGLSLShader			gWLSkyProgram;
 extern LLGLSLShader			gWLCloudProgram;
+extern LLGLSLShader			gWLSunProgram;
 extern LLGLSLShader			gWLMoonProgram;
 
 // Post Process Shaders
@@ -316,6 +317,7 @@ extern LLGLSLShader			gDeferredAvatarEyesProgram;
 extern LLGLSLShader			gDeferredAvatarAlphaProgram;
 extern LLGLSLShader			gDeferredWLSkyProgram;
 extern LLGLSLShader			gDeferredWLCloudProgram;
+extern LLGLSLShader			gDeferredWLSunProgram;
 extern LLGLSLShader			gDeferredWLMoonProgram;
 extern LLGLSLShader			gDeferredStarProgram;
 extern LLGLSLShader			gDeferredFullbrightShinyProgram;
diff --git a/indra/newview/llvosky.cpp b/indra/newview/llvosky.cpp
index 1a721c7370..b57652e3f5 100644
--- a/indra/newview/llvosky.cpp
+++ b/indra/newview/llvosky.cpp
@@ -427,7 +427,7 @@ void LLVOSky::init()
 		for (S32 tile = 0; tile < NUM_TILES; ++tile)
 		{
 			initSkyTextureDirs(side, tile);
-			createSkyTexture(side, tile);
+			createSkyTexture(side, tile, false);
 		}
 	}
 
@@ -556,7 +556,7 @@ void LLVOSky::initSkyTextureDirs(const S32 side, const S32 tile)
 	}
 }
 
-void LLVOSky::createSkyTexture(const S32 side, const S32 tile)
+void LLVOSky::createSkyTexture(const S32 side, const S32 tile, bool use_windlight_shaders)
 {
 	S32 tile_x = tile % NUM_TILES_X;
 	S32 tile_y = tile / NUM_TILES_X;
@@ -569,7 +569,10 @@ void LLVOSky::createSkyTexture(const S32 side, const S32 tile)
 	{
 		for (x = tile_x_pos; x < (tile_x_pos + sTileResX); ++x)
 		{
-			mSkyTex[side].setPixel(m_legacyAtmospherics.calcSkyColorInDir(mSkyTex[side].getDir(x, y)), x, y);
+            if (use_windlight_shaders)
+            {
+			    mSkyTex[side].setPixel(m_legacyAtmospherics.calcSkyColorInDir(mSkyTex[side].getDir(x, y)), x, y);
+            }
 			mShinyTex[side].setPixel(m_legacyAtmospherics.calcSkyColorInDir(mSkyTex[side].getDir(x, y), true), x, y);
 		}
 	}
@@ -652,7 +655,9 @@ bool LLVOSky::updateSky()
         mForceUpdate = mForceUpdate || color_changed;
         mForceUpdate = mForceUpdate || !mInitialized;
 
-        if ((mForceUpdate) && (forceupdThrottle.hasExpired()) && (!gPipeline.canUseWindLightShaders()))
+        bool use_windlight_shaders = gPipeline.canUseWindLightShaders();
+
+        if (mForceUpdate && forceupdThrottle.hasExpired())
 		{
             LL_RECORD_BLOCK_TIME(FTM_VOSKY_UPDATEFORCED);
 
@@ -674,16 +679,21 @@ bool LLVOSky::updateSky()
 					{
 						for (int tile = 0; tile < NUM_TILES; tile++) 
 						{
-							createSkyTexture(side, tile);
+							createSkyTexture(side, tile, use_windlight_shaders);
 						}
 					}
 
 					for (int side = 0; side < 6; side++) 
 					{
-						LLImageRaw* raw1 = mSkyTex[side].getImageRaw(TRUE);
-						LLImageRaw* raw2 = mSkyTex[side].getImageRaw(FALSE);
-						raw2->copy(raw1);
-						mSkyTex[side].createGLImage(mSkyTex[side].getWhich(FALSE));
+                        LLImageRaw* raw1 = nullptr;
+                        LLImageRaw* raw2 = nullptr;
+                        if (use_windlight_shaders)
+                        {
+						    raw1 = mSkyTex[side].getImageRaw(TRUE);
+						    raw2 = mSkyTex[side].getImageRaw(FALSE);
+						    raw2->copy(raw1);
+						    mSkyTex[side].createGLImage(mSkyTex[side].getWhich(FALSE));
+                        }
 
 						raw1 = mShinyTex[side].getImageRaw(TRUE);
 						raw2 = mShinyTex[side].getImageRaw(FALSE);
@@ -695,7 +705,10 @@ bool LLVOSky::updateSky()
 			        // update the sky texture
 			        for (S32 i = 0; i < 6; ++i)
 			        {
-				        mSkyTex[i].create(1.0f);
+                        if (use_windlight_shaders)
+                        {
+				            mSkyTex[i].create(1.0f);
+                        }
 				        mShinyTex[i].create(1.0f);
 			        }
 
@@ -778,8 +791,9 @@ LLDrawable *LLVOSky::createDrawable(LLPipeline *pipeline)
 
 void LLVOSky::setSunTextures(const LLUUID& sun_texture, const LLUUID& sun_texture_next)
 {
-    mSunTexturep[0] = LLViewerTextureManager::getFetchedTexture(sun_texture, FTT_DEFAULT, TRUE, LLGLTexture::BOOST_UI);
-    mSunTexturep[1] = LLViewerTextureManager::getFetchedTexture(sun_texture_next, FTT_DEFAULT, TRUE, LLGLTexture::BOOST_UI);
+    // We test the UUIDs here because we explicitly do not want the default image returned by getFetchedTexture in that case...
+    mSunTexturep[0] = sun_texture.isNull() ? nullptr : LLViewerTextureManager::getFetchedTexture(sun_texture, FTT_DEFAULT, TRUE, LLGLTexture::BOOST_UI);
+    mSunTexturep[1] = sun_texture_next.isNull() ? nullptr : LLViewerTextureManager::getFetchedTexture(sun_texture_next, FTT_DEFAULT, TRUE, LLGLTexture::BOOST_UI);
 
     if (mFace[FACE_SUN])
     {
@@ -791,9 +805,9 @@ void LLVOSky::setSunTextures(const LLUUID& sun_texture, const LLUUID& sun_textur
     
         if (mSunTexturep[1])
         {
-	        mSunTexturep[1]->setAddressMode(LLTexUnit::TAM_CLAMP);
-            mFace[FACE_SUN]->setTexture(LLRender::ALTERNATE_DIFFUSE_MAP, mSunTexturep[1]);
+	        mSunTexturep[1]->setAddressMode(LLTexUnit::TAM_CLAMP);            
         }
+        mFace[FACE_SUN]->setTexture(LLRender::ALTERNATE_DIFFUSE_MAP, mSunTexturep[1]);
     }
 }
 
diff --git a/indra/newview/llvosky.h b/indra/newview/llvosky.h
index 5294addcec..a9a59681ff 100644
--- a/indra/newview/llvosky.h
+++ b/indra/newview/llvosky.h
@@ -289,7 +289,7 @@ protected:
 	void updateDirections(void);
 
 	void initSkyTextureDirs(const S32 side, const S32 tile);
-	void createSkyTexture(const S32 side, const S32 tile);
+	void createSkyTexture(const S32 side, const S32 tile, bool use_windlight_shaders);
 
 	LLPointer<LLViewerFetchedTexture> mSunTexturep[2];
 	LLPointer<LLViewerFetchedTexture> mMoonTexturep[2];