diff --git a/gui_qt/formclouds.cpp b/gui_qt/formclouds.cpp
index 7c907c6..186ff72 100644
--- a/gui_qt/formclouds.cpp
+++ b/gui_qt/formclouds.cpp
@@ -51,6 +51,89 @@ private:
     CloudsLayerDefinition _preview_layer;
 };
 
+class PreviewCloudsColor:public Preview
+{
+public:
+    PreviewCloudsColor(QWidget* parent):Preview(parent)
+    {
+        LightDefinition light;
+        
+        _preview_layer = cloudsLayerCreateDefinition();
+
+        _lighting = lightingCreateDefinition();
+        light.color = COLOR_WHITE;
+        light.amplitude = 0.0;
+        light.direction.x = 0.0;
+        light.direction.y = -0.4794;
+        light.direction.z = 0.8776;
+        light.filtered = 0;
+        light.masked = 1;
+        light.reflection = 1.0;
+        lightingAddLight(&_lighting, light);
+        lightingValidateDefinition(&_lighting);
+        
+        _renderer = rendererCreate();
+        _renderer.render_quality = 3;
+        _renderer.applyLightingToSurface = _applyLightingToSurface;
+        _renderer.maskLight = _maskLight;
+        _renderer.customData[0] = &_preview_layer;
+        _renderer.customData[1] = &_lighting;
+    }
+protected:
+    QColor getColor(double x, double y)
+    {
+        Vector3 start, end;
+        Color color_layer, result;
+
+        start.x = x;
+        start.y = y;
+        start.z = -100.0;
+        
+        end.x = x;
+        end.y = y;
+        end.z = 100.0;
+
+        result = COLOR_BLUE;
+        color_layer = cloudsGetLayerColor(&_preview_layer, &_renderer, start, end);
+        colorMask(&result, &color_layer);
+        return colorToQColor(result);
+    }
+    void updateData()
+    {
+        cloudsLayerCopyDefinition(&_layer, &_preview_layer);
+        _preview_layer.ymin = -100.0;
+        _preview_layer.ycenter = 0.0;
+        _preview_layer.ymax = 100.0;
+        _preview_layer.customcoverage = _coverageFunc;
+    }
+private:
+    Renderer _renderer;
+    CloudsLayerDefinition _preview_layer;
+    LightingDefinition _lighting;
+
+    static double _coverageFunc(CloudsLayerDefinition* layer, Vector3 position)
+    {
+        double dist = v3Norm(position);
+        
+        if (dist >= 100.0)
+        {
+            return 0.0;
+        }
+        else
+        {
+            return 1.0 - dist / 100.0;
+        }
+    }
+    static Color _applyLightingToSurface(Renderer* renderer, Vector3 location, Vector3 normal, SurfaceMaterial material)
+    {
+        return lightingApplyToSurface((LightingDefinition*)renderer->customData[1], renderer, location, normal, material);
+    }
+    static Color _maskLight(Renderer* renderer, Color light_color, Vector3 at_location, Vector3 light_location, Vector3 direction_to_light)
+    {
+        return cloudsLayerFilterLight((CloudsLayerDefinition*)renderer->customData[0], renderer, light_color, at_location, light_location, direction_to_light);
+    }
+};
+
 /**************** Form ****************/
 FormClouds::FormClouds(QWidget *parent):
     BaseForm(parent, false, true)
@@ -59,6 +142,7 @@ FormClouds::FormClouds(QWidget *parent):
     _layer = cloudsLayerCreateDefinition();
     
     addPreview(new PreviewCloudsCoverage(parent), "Layer coverage (no lighting)");
+    addPreview(new PreviewCloudsColor(parent), "Color and lighting");
 
     addInputDouble("Start altitude", &_layer.ymin, -10.0, 250.0, 0.5, 5.0);
     addInputDouble("Max density altitude", &_layer.ycenter, -10.0, 250.0, 0.5, 5.0);
diff --git a/lib_paysages/clouds.c b/lib_paysages/clouds.c
index 5bb3c33..bb60cbb 100644
--- a/lib_paysages/clouds.c
+++ b/lib_paysages/clouds.c
@@ -117,6 +117,29 @@ void cloudsValidateDefinition(CloudsDefinition* definition)
     }
 }
 
+static double _standardCoverageFunc(CloudsLayerDefinition* layer, Vector3 position)
+{
+    double inside;
+    
+    if (position.y > layer->ycenter)
+    {
+        inside = 1.0 - (position.y - layer->ycenter) / (layer->ymax - layer->ycenter);
+    }
+    else
+    {
+        inside = 1.0 - (layer->ycenter - position.y) / (layer->ycenter - layer->ymin);
+    }
+    
+    if (inside <= 0.0)
+    {
+        return 0.0;
+    }
+    else
+    {    
+        return layer->coverage * inside;
+    }
+}
+
 CloudsLayerDefinition cloudsLayerCreateDefinition()
 {
     CloudsLayerDefinition result;
@@ -133,6 +156,8 @@ CloudsLayerDefinition cloudsLayerCreateDefinition()
     result.ymin = 50.0;
     result.ycenter = 100.0;
     result.ymax = 200.0;
+    
+    result.customcoverage = _standardCoverageFunc;
 
     return result;
 }
@@ -188,8 +213,7 @@ int cloudsAddLayer(CloudsDefinition* definition)
     if (definition->nblayers < CLOUDS_MAX_LAYERS)
     {
         layer = definition->layers + definition->nblayers;
-        layer->noise = noiseCreateGenerator();
-        layer->coverage = 0.0;
+        *layer = cloudsLayerCreateDefinition();
 
         return definition->nblayers++;
     }
@@ -214,45 +238,47 @@ void cloudsDeleteLayer(CloudsDefinition* definition, int layer)
 
 static inline double _getDistanceToBorder(CloudsLayerDefinition* layer, Vector3 position)
 {
-    double val, min;
-
-    if (position.y > layer->ycenter)
-    {
-        min = (position.y - layer->ycenter) / (layer->ymax - layer->ycenter);
-    }
-    else
-    {
-        min = (layer->ycenter - position.y) / (layer->ycenter - layer->ymin);
-    }
+    double val;
 
     val = 0.5 * noiseGet3DTotal(layer->noise, position.x / layer->scaling, position.y / layer->scaling, position.z / layer->scaling) / noiseGetMaxValue(layer->noise);
 
-    return (val - 0.5 - min + layer->coverage) * layer->scaling;
+    return (val - 0.5 + layer->customcoverage(layer, position)) * layer->scaling;
 }
 
 static inline Vector3 _getNormal(CloudsLayerDefinition* layer, Vector3 position, double detail)
 {
     Vector3 result = {0.0, 0.0, 0.0};
+    Vector3 dposition;
     double val, dval;
     
-    val = noiseGet3DDetail(layer->noise, position.x / layer->scaling, position.y / layer->scaling, position.z / layer->scaling, detail);
+    val = _getDistanceToBorder(layer, position);
 
-    dval = val - noiseGet3DDetail(layer->noise, (position.x + detail) / layer->scaling, position.y / layer->scaling, position.z / layer->scaling, detail);
+    dposition.x = position.x + detail;
+    dposition.y = position.y;
+    dposition.z = position.z;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.x += dval;
 
-    dval = val - noiseGet3DDetail(layer->noise, (position.x - detail) / layer->scaling, position.y / layer->scaling, position.z / layer->scaling, detail);
+    dposition.x = position.x - detail;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.x -= dval;
 
-    dval = val - noiseGet3DDetail(layer->noise, position.x / layer->scaling, (position.y + detail) / layer->scaling, position.z / layer->scaling, detail);
+    dposition.x = position.x;
+    dposition.y = position.y + detail;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.y += dval;
 
-    dval = val - noiseGet3DDetail(layer->noise, position.x / layer->scaling, (position.y - detail) / layer->scaling, position.z / layer->scaling, detail);
+    dposition.y = position.y - detail;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.y -= dval;
 
-    dval = val - noiseGet3DDetail(layer->noise, position.x / layer->scaling, position.y / layer->scaling, (position.z + detail) / layer->scaling, detail);
+    dposition.y = position.y;
+    dposition.z = position.z + detail;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.z += dval;
 
-    dval = val - noiseGet3DDetail(layer->noise, position.x / layer->scaling, position.y / layer->scaling, (position.z - detail) / layer->scaling, detail);
+    dposition.z = position.z - detail;
+    dval = val - _getDistanceToBorder(layer, dposition);
     result.z -= dval;
 
     return v3Normalize(result);
diff --git a/lib_paysages/clouds.h b/lib_paysages/clouds.h
index f9371da..f8ed0dd 100644
--- a/lib_paysages/clouds.h
+++ b/lib_paysages/clouds.h
@@ -12,7 +12,11 @@ extern "C" {
 
 #define CLOUDS_MAX_LAYERS 6
 
-typedef struct
+typedef struct CloudsLayerDefinition CloudsLayerDefinition;
+    
+typedef double (*CloudCoverageFunc)(CloudsLayerDefinition* definition, Vector3 position);
+
+struct CloudsLayerDefinition
 {
     double ycenter;
     double ymin;
@@ -24,7 +28,8 @@ typedef struct
     double minimumlight;
     double scaling;
     double coverage;
-} CloudsLayerDefinition;
+    CloudCoverageFunc customcoverage;
+};
 
 typedef struct
 {