From 825abab64306bdde79f1d44e2ce8a855a0feb77f Mon Sep 17 00:00:00 2001
From: Stuart Buchanan <stuart_d_buchanan@yahoo.co.uk>
Date: Wed, 25 Dec 2013 23:14:04 +0000
Subject: [PATCH] Fix for black clouds on ATI (bug 1160)

http://code.google.com/p/flightgear-bugs/issues/detail?id=1160

Fix by Emilian Huminiuc.
---
 Shaders/3dcloud.frag |  3 ++-
 Shaders/3dcloud.vert | 11 ++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/Shaders/3dcloud.frag b/Shaders/3dcloud.frag
index f63d464d7..6536e1344 100644
--- a/Shaders/3dcloud.frag
+++ b/Shaders/3dcloud.frag
@@ -1,5 +1,6 @@
 uniform sampler2D baseTexture;
 varying float fogFactor;
+varying vec4  cloudColor;
 
 void main(void)
 {
@@ -7,7 +8,7 @@ void main(void)
       if (base.a < 0.02)
         discard;
 
-      vec4 finalColor = base * gl_Color;
+      vec4 finalColor = base * cloudColor;
       gl_FragColor.rgb = mix(gl_Fog.color.rgb, finalColor.rgb, fogFactor );
       gl_FragColor.a = finalColor.a;
 }
diff --git a/Shaders/3dcloud.vert b/Shaders/3dcloud.vert
index f32f8c527..28455e34c 100644
--- a/Shaders/3dcloud.vert
+++ b/Shaders/3dcloud.vert
@@ -2,6 +2,7 @@
 #version 120
 
 varying float fogFactor;
+varying vec4  cloudColor;
 
 uniform float range; // From /sim/rendering/clouds3d-vis-range
 uniform float detail_range; // From /sim/rendering/clouds3d_detail-range
@@ -48,7 +49,7 @@ void main(void)
     // More than detail_range away, so discard all sprites on opposite side of
     // cloud center by shifting them beyond the view fustrum
     gl_Position = vec4(0.0,0.0,10.0,1.0);
-    gl_FrontColor.a = 0.0;
+    cloudColor = vec4(0.0);
   } else {
     // Determine a lighting normal based on the vertex position from the
     // center of the cloud, so that sprite on the opposite side of the cloud to the sun are darker.
@@ -70,17 +71,17 @@ void main(void)
                   
     // Final position of the sprite
     gl_Position = gl_ModelViewProjectionMatrix * gl_Position;    
-    gl_FrontColor = gl_LightSource[0].diffuse * shade + gl_FrontLightModelProduct.sceneColor;
+    cloudColor = gl_LightSource[0].diffuse * shade + gl_FrontLightModelProduct.sceneColor;
     
     if ((fogCoord > (0.9 * detail_range)) && (fogCoord > center_dist) && (shade_factor < 0.7)) {
       // cloudlet is almost at the detail range, so fade it out.
-      gl_FrontColor.a = 1.0 - smoothstep(0.9 * detail_range, detail_range, fogCoord);
+      cloudColor.a = 1.0 - smoothstep(0.9 * detail_range, detail_range, fogCoord);
     } else {
       // As we get within 100m of the sprite, it is faded out. Equally at large distances it also fades out.
-      gl_FrontColor.a = min(smoothstep(10.0, 100.0, fogCoord), 1.0 - smoothstep(0.9 * range, range, fogCoord));    
+      cloudColor.a = min(smoothstep(10.0, 100.0, fogCoord), 1.0 - smoothstep(0.9 * range, range, fogCoord));
     }
     
-    gl_BackColor = gl_FrontColor;
+    //gl_BackColor = cloudColor;
 
     // Fog doesn't affect clouds as much as other objects.
     fogFactor = exp( -gl_Fog.density * fogCoord * 0.5);