Use sun visibility for sunlight scattering (bug #7309)

CHANGELOG.md

@@ -69,6 +69,7 @@
     Bug #7284: "Your weapon has no effect." message doesn't always show when the player character attempts to attack
     Bug #7298: Water ripples from projectiles sometimes are not spawned
     Bug #7307: Alchemy "Magic Effect" search string does not match on tool tip for effects related to attributes
+    Bug #7309: Sunlight scattering is visible in inappropriate situations
     Bug #7322: Shadows don't cover groundcover depending on the view angle and perspective with compute scene bounds = primitives
     Bug #7413: Generated wilderness cells don't spawn fish
     Bug #7415: Unbreakable lock discrepancies

files/shaders/compatibility/water.frag

@@ -173,7 +173,7 @@ void main(void)
     vec3 waterColor = WATER_COLOR * sunFade;
 
     vec4 sunSpec = lcalcSpecular(0);
-    // alpha component is sun visibility; we want to start fading specularity when visibility is low
+    // alpha component is sun visibility; we want to start fading lighting effects when visibility is low
     sunSpec.a = min(1.0, sunSpec.a / SUN_SPEC_FADING_THRESHOLD);
 
     // artificial specularity to make rain ripples more noticeable
@@ -202,7 +202,7 @@ void main(void)
     float sunHeight = lVec.z;
     vec3 scatterColour = mix(SCATTER_COLOUR*vec3(1.0,0.4,0.0), SCATTER_COLOUR, clamp(1.0-exp(-sunHeight*SUN_EXT), 0.0, 1.0));
     vec3 lR = reflect(lVec, lNormal);
-    float lightScatter = clamp(dot(lVec,lNormal)*0.7+0.3, 0.0, 1.0) * clamp(dot(lR, vVec)*2.0-1.2, 0.0, 1.0) * SCATTER_AMOUNT * sunFade * clamp(1.0-exp(-sunHeight), 0.0, 1.0);
+    float lightScatter = clamp(dot(lVec,lNormal)*0.7+0.3, 0.0, 1.0) * clamp(dot(lR, vVec)*2.0-1.2, 0.0, 1.0) * SCATTER_AMOUNT * sunFade * sunSpec.a * clamp(1.0-exp(-sunHeight), 0.0, 1.0);
     gl_FragData[0].xyz = mix(mix(refraction,  scatterColour,  lightScatter), reflection, fresnel) + specular * sunSpec.rgb * sunSpec.a + rainSpecular;
     gl_FragData[0].w = 1.0;