diff --git a/TODO b/TODO
index 1395bb5..2217f43 100644
--- a/TODO
+++ b/TODO
@@ -1,6 +1,5 @@
 Technology Preview 2 :
 - InputInt doesn't honor small_step.
-- Fix the fog impression when cloud layer overlaps with ground range.
 - Remove color gradations (replace with automatic boolean and simple colors).
 - Replace zone ranges with curves (with curve input and curve dialog).
 - Interface for textures thickness, slope_range and thickness_transparency (and correct slider ranges).
diff --git a/lib_paysages/atmosphere.c b/lib_paysages/atmosphere.c
index 3128f5f..f91dd39 100644
--- a/lib_paysages/atmosphere.c
+++ b/lib_paysages/atmosphere.c
@@ -87,6 +87,7 @@ Color atmosphereApply(AtmosphereDefinition* definition, Renderer* renderer, Vect
     Color mask = definition->color;
     double distance = v3Norm(v3Sub(renderer->camera_location, location));
     double value;
+    double alpha;
 
     if (distance < definition->distance_near)
     {
@@ -97,10 +98,15 @@ Color atmosphereApply(AtmosphereDefinition* definition, Renderer* renderer, Vect
         distance = definition->distance_far;
     }
 
+    alpha = base.a;
+    base.a = 1.0;
+    
     value = definition->full_mask * (distance - definition->distance_near) / (definition->distance_far - definition->distance_near);
+    
     mask.a = value;
-
     colorMask(&base, &mask);
+    
+    base.a = alpha;
 
     return base;
 }
diff --git a/lib_paysages/clouds.c b/lib_paysages/clouds.c
index aa9abb0..c89932a 100644
--- a/lib_paysages/clouds.c
+++ b/lib_paysages/clouds.c
@@ -169,7 +169,7 @@ CloudsLayerDefinition cloudsLayerCreateDefinition()
     result.base_coverage = 0.35;
     result.shape_noise = noiseCreateGenerator();
     noiseGenerateBaseNoise(result.shape_noise, 200000);
-    noiseAddLevelsSimple(result.shape_noise, 4, 1.0, 1.0);
+    noiseAddLevelsSimple(result.shape_noise, 5, 1.0, 1.0);
     result.edge_noise = noiseCreateGenerator();
     noiseGenerateBaseNoise(result.edge_noise, 800000);
     noiseAddLevelsSimple(result.edge_noise, 8, 1.0, 1.0);
@@ -575,7 +575,10 @@ Color cloudsGetLayerColor(CloudsLayerDefinition* definition, Renderer* renderer,
         col.a = 1.0;
     }
 
-    result = renderer->applyAtmosphere(renderer, start, result);
+    if (result.a > 0.000001)
+    {
+        result = renderer->applyAtmosphere(renderer, start, result);
+    }
 
     return result;
 }
@@ -602,7 +605,7 @@ Color cloudsGetColor(CloudsDefinition* definition, Renderer* renderer, Vector3 s
     for (i = 0; i < definition->nblayers; i++)
     {
         layer_color = cloudsGetLayerColor(layers + i, renderer, start, end);
-        if (layer_color.a > 0.0)
+        if (layer_color.a > 0.000001)
         {
             colorMask(&result, &layer_color);
         }
diff --git a/lib_paysages/system.c b/lib_paysages/system.c
index c2d64ec..e06b8fa 100644
--- a/lib_paysages/system.c
+++ b/lib_paysages/system.c
@@ -1,6 +1,8 @@
 #include "system.h"
 #include <unistd.h>
 
+/*#define DEBUG_ONETHREAD 1*/
+
 #ifdef WIN32
 #include <windows.h>
 #endif