diff --git a/Makefile b/Makefile
index e3308d6..99ed38e 100644
--- a/Makefile
+++ b/Makefile
@@ -32,7 +32,8 @@ debug:
 release:
 	make BUILDMODE=release all
 
-tests: all
+tests:
+	make BUILDMODE=${BUILDMODE} all
 	LD_LIBRARY_PATH=${BUILDPATH} CK_DEFAULT_TIMEOUT=30 ${BUILDPATH}/paysages-tests
 
 run_cli: all
diff --git a/src/rendering/clouds/clo_density.c b/src/rendering/clouds/clo_density.c
new file mode 100644
index 0000000..f967ae0
--- /dev/null
+++ b/src/rendering/clouds/clo_density.c
@@ -0,0 +1,66 @@
+#include "clo_density.h"
+
+#include "../tools.h"
+
+double cloudsGetLayerCoverage(CloudsLayerDefinition* layer, Vector3 location)
+{
+    if (layer->base_coverage == 0.0)
+    {
+        return 0.0;
+    }
+    else
+    {
+        double coverage = noiseGet2DTotal(layer->_coverage_noise, location.x / layer->shape_scaling, location.z / layer->shape_scaling);
+        coverage -= (1.0 - layer->base_coverage);
+
+        coverage *= curveGetValue(layer->_coverage_by_altitude, (location.y - layer->lower_altitude) / layer->thickness);
+
+        return (coverage <= 0.0) ? 0.0 : coverage;
+    }
+}
+
+double cloudsGetLayerDensity(CloudsLayerDefinition* layer, Vector3 location, double coverage)
+{
+    if (coverage == 0.0)
+    {
+        return 0.0;
+    }
+    else if (coverage == 1.0)
+    {
+        return 1.0;
+    }
+    else
+    {
+        double density = noiseGet3DTotal(layer->_shape_noise, location.x / layer->shape_scaling, location.y / layer->shape_scaling, location.z / layer->shape_scaling);
+        density -= (0.5 - coverage);
+        return (density <= 0.0) ? 0.0 : density;
+    }
+}
+
+static double _fakeGetDensity(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location)
+{
+    UNUSED(layer);
+    UNUSED(renderer);
+    UNUSED(location);
+
+    return 0.0;
+}
+
+void cloudsBindFakeDensityToRenderer(CloudsRenderer* renderer)
+{
+    renderer->getLayerDensity = _fakeGetDensity;
+}
+
+static double _realGetDensity(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location)
+{
+    UNUSED(renderer);
+
+    double coverage = cloudsGetLayerCoverage(layer, location);
+
+    return cloudsGetLayerDensity(layer, location, coverage);
+}
+
+void cloudsBindRealDensityToRenderer(CloudsRenderer* renderer)
+{
+    renderer->getLayerDensity = _realGetDensity;
+}
diff --git a/src/rendering/clouds/clo_density.h b/src/rendering/clouds/clo_density.h
new file mode 100644
index 0000000..afdf125
--- /dev/null
+++ b/src/rendering/clouds/clo_density.h
@@ -0,0 +1,45 @@
+#ifndef _PAYSAGES_CLOUDS_DENSITY_H_
+#define _PAYSAGES_CLOUDS_DENSITY_H_
+
+#include "public.h"
+
+/**
+ * Coverage/density management in a cloud layer.
+ */
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * Get the local coverage of a cloud layer [0.0;1.0]
+ *
+ * 0.0 means no cloud is present.
+ * 1.0 means full layer.
+ */
+double cloudsGetLayerCoverage(CloudsLayerDefinition* layer, Vector3 location);
+
+/**
+ * Get the local density of a cloud layer at a given point [0.0;1.0].
+ *
+ * 0.0 means no cloud is present.
+ * 1.0 means full density (deep inside cloud).
+ */
+double cloudsGetLayerDensity(CloudsLayerDefinition* layer, Vector3 location, double coverage);
+
+/*
+ * Bind fake density functions to a renderer.
+ */
+void cloudsBindFakeDensityToRenderer(CloudsRenderer* renderer);
+
+/*
+ * Bind real density functions to a renderer.
+ */
+void cloudsBindRealDensityToRenderer(CloudsRenderer* renderer);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/rendering/clouds/clo_rendering.c b/src/rendering/clouds/clo_rendering.c
index fc97f72..e5e8ada 100644
--- a/src/rendering/clouds/clo_rendering.c
+++ b/src/rendering/clouds/clo_rendering.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include "../tools.h"
 #include "../renderer.h"
+#include "clo_density.h"
 
 /******************** Fake ********************/
 static int _fakeAlterLight(Renderer* renderer, LightDefinition* light, Vector3 location)
@@ -23,21 +24,6 @@ static Color _fakeGetColor(Renderer* renderer, Color base, Vector3 start, Vector
     return base;
 }
 
-static CloudsInfo _fakeGetLayerInfo(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location)
-{
-    UNUSED(renderer);
-    UNUSED(layer);
-    UNUSED(location);
-
-    CloudsInfo result;
-
-    result.inside = 0;
-    result.density = 0.0;
-    result.distance_to_edge = 1.0;
-
-    return result;
-}
-
 /******************** Real ********************/
 /*static int _cmpLayer(const void* layer1, const void* layer2)
 {
@@ -89,7 +75,8 @@ static CloudsRenderer* _createRenderer()
 
     result->getColor = _fakeGetColor;
     result->alterLight = (FuncLightingAlterLight)_fakeAlterLight;
-    result->getLayerInfo = _fakeGetLayerInfo;
+
+    cloudsBindFakeDensityToRenderer(result);
 
     return result;
 }
@@ -106,7 +93,8 @@ static void _bindRenderer(Renderer* renderer, CloudsDefinition* definition)
 
     renderer->clouds->getColor = _getColor;
     renderer->clouds->alterLight = (FuncLightingAlterLight)_alterLight;
-    renderer->clouds->getLayerInfo = cloudsGetLayerInfo;
+
+    cloudsBindRealDensityToRenderer(renderer->clouds);
 
     lightingManagerRegisterFilter(renderer->lighting, (FuncLightingAlterLight)_alterLight, renderer);
 }
diff --git a/src/rendering/clouds/clo_tools.c b/src/rendering/clouds/clo_tools.c
index dd34015..cadf4c0 100644
--- a/src/rendering/clouds/clo_tools.c
+++ b/src/rendering/clouds/clo_tools.c
@@ -4,6 +4,7 @@
  * Clouds tools.
  */
 
+#include "clo_walking.h"
 #include "../renderer.h"
 #include "../tools.h"
 
@@ -46,179 +47,6 @@ static inline Vector3 _getNormal(CloudsLayerDefinition* layer, Vector3 position,
     return v3Normalize(result);
 }
 
-/**
- * Optimize the search limits in a layer.
- *
- * @param layer The cloud layer
- * @param start Start of the search to optimize
- * @param end End of the search to optimize
- * @return 0 if the search is useless
- */
-static int _optimizeSearchLimits(CloudsLayerDefinition* layer, Vector3* start, Vector3* end)
-{
-    Vector3 diff;
-
-    if (start->y > layer->lower_altitude + layer->thickness)
-    {
-        if (end->y >= layer->lower_altitude + layer->thickness)
-        {
-            return 0;
-        }
-        else
-        {
-            diff = v3Sub(*end, *start);
-            *start = v3Add(*start, v3Scale(diff, (layer->lower_altitude + layer->thickness - start->y) / diff.y));
-            if (end->y < layer->lower_altitude)
-            {
-                *end = v3Add(*end, v3Scale(diff, (layer->lower_altitude - end->y) / diff.y));
-            }
-        }
-    }
-    else if (start->y < layer->lower_altitude)
-    {
-        if (end->y <= layer->lower_altitude)
-        {
-            return 0;
-        }
-        else
-        {
-            diff = v3Sub(*end, *start);
-            *start = v3Add(*start, v3Scale(diff, (layer->lower_altitude - start->y) / diff.y));
-            if (end->y >= layer->lower_altitude + layer->thickness)
-            {
-                *end = v3Add(*end, v3Scale(diff, (layer->lower_altitude + layer->thickness - end->y) / diff.y));
-            }
-        }
-    }
-    else /* start is inside layer */
-    {
-        diff = v3Sub(*end, *start);
-        if (end->y > layer->lower_altitude + layer->thickness)
-        {
-            *end = v3Add(*start, v3Scale(diff, (layer->lower_altitude + layer->thickness - start->y) / diff.y));
-        }
-        else if (end->y < layer->lower_altitude)
-        {
-            *end = v3Add(*start, v3Scale(diff, (layer->lower_altitude - start->y) / diff.y));
-        }
-    }
-
-    /* TODO Limit the search length */
-    return 1;
-}
-
-/**
- * Go through the cloud layer to find segments (parts of the lookup that are likely to contain cloud).
- *
- * @param definition The cloud layer
- * @param renderer The renderer environment
- * @param start Start position of the lookup (already optimized)
- * @param direction Normalized direction of the lookup
- * @param max_segments Maximum number of segments to collect
- * @param max_inside_length Maximum length to spend inside the cloud
- * @param max_total_length Maximum lookup length
- * @param inside_length Resulting length inside cloud (sum of all segments length)
- * @param total_length Resulting lookup length
- * @param out_segments Allocated space to fill found segments
- * @return Number of segments found
- */
-static int _getPrimarySegments(CloudsLayerDefinition* definition, Renderer* renderer, Vector3 start, Vector3 direction, int max_segments, double max_inside_length, double max_total_length, double* inside_length, double* total_length, CloudSegment* out_segments)
-{
-    int inside, segment_count;
-    double current_total_length, current_inside_length;
-    double step_length, segment_length;
-    Vector3 walker, step, segment_start;
-    CloudsInfo info;
-    double render_precision;
-
-    if (max_segments <= 0)
-    {
-        return 0;
-    }
-
-    render_precision = 1.005 - 0.01 * (double)(renderer->render_quality * renderer->render_quality);
-    if (render_precision > max_total_length / 10.0)
-    {
-        render_precision = max_total_length / 10.0;
-    }
-    else if (render_precision < max_total_length / 10000.0)
-    {
-        render_precision = max_total_length / 10000.0;
-    }
-
-    segment_count = 0;
-    current_total_length = 0.0;
-    current_inside_length = 0.0;
-    segment_length = 0.0;
-    walker = start;
-    info = renderer->clouds->getLayerInfo(renderer, definition, start);
-    inside = info.inside;
-    step = v3Scale(direction, render_precision);
-
-    do
-    {
-        walker = v3Add(walker, step);
-        step_length = v3Norm(step);
-        current_total_length += step_length;
-
-        if (current_total_length >= max_total_length || current_inside_length > max_inside_length)
-        {
-            info.distance_to_edge = 0.0;
-            info.inside = 0;
-        }
-        else
-        {
-            info = renderer->clouds->getLayerInfo(renderer, definition, walker);
-        }
-
-        if (info.inside)
-        {
-            if (inside)
-            {
-                /* inside the cloud */
-                segment_length += step_length;
-                current_inside_length += step_length;
-            }
-            else
-            {
-                /* entering the cloud */
-                segment_length = step_length;
-                segment_start = walker;
-                current_inside_length += segment_length;
-                /* TODO Refine entry position */
-
-                inside = 1;
-            }
-        }
-        else
-        {
-            if (inside)
-            {
-                /* exiting the cloud */
-                segment_length += step_length;
-                current_inside_length += step_length;
-
-                out_segments->start = segment_start;
-                out_segments->end = walker;
-                out_segments->length = segment_length;
-                out_segments++;
-                if (++segment_count >= max_segments)
-                {
-                    break;
-                }
-                /* TODO Refine exit position */
-
-                inside = 0;
-            }
-        }
-        step = v3Scale(direction, (info.distance_to_edge < render_precision) ? render_precision : info.distance_to_edge);
-    } while (inside || (walker.y <= definition->lower_altitude + definition->thickness + 0.001 && walker.y >= definition->lower_altitude - 0.001 && current_total_length < max_total_length && current_inside_length < max_inside_length));
-
-    *total_length = current_total_length;
-    *inside_length = current_inside_length;
-    return segment_count;
-}
-
 static Color _applyLayerLighting(CloudsLayerDefinition* definition, Renderer* renderer, Vector3 location, double detail)
 {
     Vector3 normal;
@@ -262,32 +90,22 @@ static Color _applyLayerLighting(CloudsLayerDefinition* definition, Renderer* re
 Color cloudsApplyLayer(CloudsLayerDefinition* definition, Color base, Renderer* renderer, Vector3 start, Vector3 end)
 {
     int segment_count;
-    double max_length, total_length, inside_length;
-    Vector3 direction;
     Color col;
-    CloudSegment segments[MAX_SEGMENT_COUNT];
+    CloudPrimarySegment segments[MAX_SEGMENT_COUNT];
 
-    if (!_optimizeSearchLimits(definition, &start, &end))
-    {
-        return base;
-    }
-
-    direction = v3Sub(end, start);
-    max_length = v3Norm(direction);
-    direction = v3Normalize(direction);
-
-    segment_count = _getPrimarySegments(definition, renderer, start, direction, MAX_SEGMENT_COUNT, definition->transparencydepth * (double)renderer->render_quality, max_length, &inside_length, &total_length, segments);
+    segment_count = cloudsGetLayerPrimarySegments(renderer, definition, start, end, MAX_SEGMENT_COUNT, segments);
     /* TODO Crawl in segments for render */
 
     col = definition->material.base;
-    if (definition->transparencydepth == 0 || inside_length >= definition->transparencydepth)
+    col.a = 0.0;
+    /*if (definition->transparencydepth == 0 || inside_length >= definition->transparencydepth)
     {
         col.a = 1.0;
     }
     else
     {
         col.a = inside_length / definition->transparencydepth;
-    }
+    }*/
 
     col = renderer->atmosphere->applyAerialPerspective(renderer, start, col).final;
 
@@ -298,10 +116,10 @@ Color cloudsApplyLayer(CloudsLayerDefinition* definition, Color base, Renderer*
 
 Color cloudsLayerFilterLight(CloudsLayerDefinition* definition, Renderer* renderer, Color light, Vector3 location, Vector3 light_location, Vector3 direction_to_light)
 {
-    double inside_depth, total_depth, factor;
+    /*double inside_depth, total_depth, factor;
     CloudSegment segments[MAX_SEGMENT_COUNT];
 
-    if (!_optimizeSearchLimits(definition, &location, &light_location))
+    if (!cloudsOptimizeWalkingBounds(definition, &location, &light_location))
     {
         return light;
     }
@@ -325,93 +143,7 @@ Color cloudsLayerFilterLight(CloudsLayerDefinition* definition, Renderer* render
 
     light.r = light.r * factor;
     light.g = light.g * factor;
-    light.b = light.b * factor;
+    light.b = light.b * factor;*/
 
     return light;
 }
-
-/*
- * Get the coverage factor at the given location [0.0;1.0].
- * 0.0 means no cloud is present.
- * 1.0 means full layer.
- */
-static inline double _getLayerCoverage(CloudsLayerDefinition* layer, double x, double z)
-{
-    if (layer->base_coverage == 0.0)
-    {
-        return 0.0;
-    }
-    else
-    {
-        double coverage = noiseGet2DTotal(layer->_coverage_noise, x / layer->shape_scaling, z / layer->shape_scaling);
-        coverage -= (1.0 - layer->base_coverage);
-        return (coverage <= 0.0) ? 0.0 : coverage;
-    }
-}
-
-/*
- * Get the local density factor at the given location [0.0;1.0].
- * 0.0 means no cloud is present.
- * 1.0 means full density (deep inside cloud).
- */
-static inline double _getLayerDensity(CloudsLayerDefinition* layer, Vector3 location, double coverage)
-{
-    if (coverage == 0.0)
-    {
-        return 0.0;
-    }
-    else if (coverage == 1.0)
-    {
-        return 1.0;
-    }
-    else
-    {
-        double density = noiseGet3DTotal(layer->_shape_noise, location.x / layer->shape_scaling, location.y / layer->shape_scaling, location.z / layer->shape_scaling);
-        density -= (0.5 - coverage);
-        return (density <= 0.0) ? 0.0 : density;
-    }
-}
-
-CloudsInfo cloudsGetLayerInfo(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location)
-{
-    CloudsInfo result;
-
-    UNUSED(renderer);
-
-    result.density = 0.0;
-    result.distance_to_edge = 0.1;
-
-    /* Get coverage info */
-    double coverage = _getLayerCoverage(layer, location.x, location.z);
-    if (coverage <= 0.0)
-    {
-        /* TODO Distance to edge */
-    }
-    else
-    {
-        /* Apply altitude to coverage */
-        coverage *= curveGetValue(layer->_coverage_by_altitude, (location.y - layer->lower_altitude) / layer->thickness);
-        if (coverage <= 0.0)
-        {
-            /* TODO Distance to edge */
-        }
-        else
-        {
-            /* Get local density */
-            result.density = _getLayerDensity(layer, location, coverage);
-            if (result.density <= 0)
-            {
-                /* TODO Distance to edge */
-            }
-            else
-            {
-                /* TODO Distance to edge */
-            }
-        }
-    }
-
-    result.inside = (result.density > 0.0);
-
-    return result;
-}
-
diff --git a/src/rendering/clouds/clo_walking.c b/src/rendering/clouds/clo_walking.c
new file mode 100644
index 0000000..5efb929
--- /dev/null
+++ b/src/rendering/clouds/clo_walking.c
@@ -0,0 +1,157 @@
+#include "clo_walking.h"
+
+#include "../renderer.h"
+
+int cloudsOptimizeWalkingBounds(CloudsLayerDefinition* layer, Vector3* start, Vector3* end)
+{
+    Vector3 diff;
+
+    if (start->y > layer->lower_altitude + layer->thickness)
+    {
+        if (end->y >= layer->lower_altitude + layer->thickness)
+        {
+            return 0;
+        }
+        else
+        {
+            diff = v3Sub(*end, *start);
+            *start = v3Add(*start, v3Scale(diff, (layer->lower_altitude + layer->thickness - start->y) / diff.y));
+            if (end->y < layer->lower_altitude)
+            {
+                *end = v3Add(*end, v3Scale(diff, (layer->lower_altitude - end->y) / diff.y));
+            }
+        }
+    }
+    else if (start->y < layer->lower_altitude)
+    {
+        if (end->y <= layer->lower_altitude)
+        {
+            return 0;
+        }
+        else
+        {
+            diff = v3Sub(*end, *start);
+            *start = v3Add(*start, v3Scale(diff, (layer->lower_altitude - start->y) / diff.y));
+            if (end->y >= layer->lower_altitude + layer->thickness)
+            {
+                *end = v3Add(*end, v3Scale(diff, (layer->lower_altitude + layer->thickness - end->y) / diff.y));
+            }
+        }
+    }
+    else /* start is inside layer */
+    {
+        diff = v3Sub(*end, *start);
+        if (end->y > layer->lower_altitude + layer->thickness)
+        {
+            *end = v3Add(*start, v3Scale(diff, (layer->lower_altitude + layer->thickness - start->y) / diff.y));
+        }
+        else if (end->y < layer->lower_altitude)
+        {
+            *end = v3Add(*start, v3Scale(diff, (layer->lower_altitude - start->y) / diff.y));
+        }
+    }
+
+    /* TODO Limit the search length */
+    return 1;
+}
+
+int cloudsGetLayerPrimarySegments(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 start, Vector3 end, int max_segments, CloudPrimarySegment* out_segments)
+{
+    int inside, segment_count;
+    double step_length, segment_length;
+    Vector3 diff, walker, segment_start;
+    double render_precision, density;
+    double diff_length, progress;
+
+    if (max_segments <= 0)
+    {
+        return 0;
+    }
+
+    if (!cloudsOptimizeWalkingBounds(layer, &start, &end))
+    {
+        return 0;
+    }
+
+    diff = v3Sub(end, start);
+    diff_length = v3Norm(diff);
+
+    if (diff_length < 0.000001)
+    {
+        return 0;
+    }
+
+    render_precision = 1.005 - 0.01 * (double)(renderer->render_quality * renderer->render_quality);
+    /*if (render_precision > max_total_length / 10.0)
+    {
+        render_precision = max_total_length / 10.0;
+    }
+    else if (render_precision < max_total_length / 10000.0)
+    {
+        render_precision = max_total_length / 10000.0;
+    }*/
+
+    segment_count = 0;
+    segment_length = 0.0;
+    density = renderer->clouds->getLayerDensity(renderer, layer, start);
+    progress = 0.0;
+    step_length = render_precision;
+    inside = (density > 0.0);
+
+    do
+    {
+        progress += step_length;
+        walker = v3Add(start, v3Scale(diff, progress / diff_length));
+
+        if (progress >= diff_length)
+        {
+            density = 0.0;
+        }
+        else
+        {
+            density = renderer->clouds->getLayerDensity(renderer, layer, walker);
+        }
+
+        if (density > 0.0)
+        {
+            if (inside)
+            {
+                /* inside the cloud */
+                segment_length += step_length;
+            }
+            else
+            {
+                /* entering the cloud */
+                segment_length = step_length;
+                segment_start = v3Add(start, v3Scale(diff, (progress - step_length) / diff_length));
+                /* TODO Refine entry position */
+
+                inside = 1;
+            }
+        }
+        else
+        {
+            if (inside)
+            {
+                /* exiting the cloud */
+                segment_length += step_length;
+
+                out_segments->enter = segment_start;
+                out_segments->exit = walker;
+                out_segments->length = segment_length;
+                out_segments++;
+                if (++segment_count >= max_segments)
+                {
+                    break;
+                }
+                /* TODO Refine exit position */
+
+                inside = 0;
+            }
+        }
+        /* step = v3Scale(direction, (info.distance_to_edge < render_precision) ? render_precision : info.distance_to_edge); */
+    }
+    while (inside || (walker.y <= layer->lower_altitude + layer->thickness + 0.001 && walker.y >= layer->lower_altitude - 0.001 && progress < diff_length));
+
+    return segment_count;
+}
diff --git a/src/rendering/clouds/clo_walking.h b/src/rendering/clouds/clo_walking.h
new file mode 100644
index 0000000..2ad19b3
--- /dev/null
+++ b/src/rendering/clouds/clo_walking.h
@@ -0,0 +1,50 @@
+#ifndef _PAYSAGES_CLOUDS_WALKING_H_
+#define _PAYSAGES_CLOUDS_WALKING_H_
+
+#include "public.h"
+#include "../tools/euclid.h"
+
+/**
+ * Functions to walk through a cloud layer.
+ */
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+typedef struct
+{
+    Vector3 enter;
+    Vector3 exit;
+    double length;
+} CloudPrimarySegment;
+
+/**
+ * Optimize the search limits in a layer.
+ *
+ * @param layer The cloud layer
+ * @param start Start of the search to optimize
+ * @param end End of the search to optimize
+ * @return 0 if the search is useless
+ */
+int cloudsOptimizeWalkingBounds(CloudsLayerDefinition* layer, Vector3* start, Vector3* end);
+
+/**
+ * Go through the cloud layer to find segments (parts of the lookup that are likely to contain cloud).
+ *
+ * @param renderer The renderer environment
+ * @param layer The cloud layer
+ * @param start Start position of the lookup
+ * @param end End position of the lookup
+ * @param max_segments Maximum number of segments to collect
+ * @param out_segments Allocated space to fill found segments
+ * @return Number of segments found
+ */
+int cloudsGetLayerPrimarySegments(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 start, Vector3 end, int max_segments, CloudPrimarySegment* out_segments);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/rendering/clouds/private.h b/src/rendering/clouds/private.h
index bc597da..47c44bd 100644
--- a/src/rendering/clouds/private.h
+++ b/src/rendering/clouds/private.h
@@ -6,18 +6,9 @@
 #define CLOUDS_MAX_LAYERS 6
 #define MAX_SEGMENT_COUNT 100
 
-typedef struct
-{
-    Vector3 start;
-    Vector3 end;
-    double length;
-} CloudSegment;
-
 void cloudsLayerValidateDefinition(CloudsLayerDefinition* definition);
 
 Color cloudsLayerFilterLight(CloudsLayerDefinition* definition, Renderer* renderer, Color light, Vector3 location, Vector3 light_location, Vector3 direction_to_light);
 Color cloudsApplyLayer(CloudsLayerDefinition* definition, Color base, Renderer* renderer, Vector3 start, Vector3 end);
 
-CloudsInfo cloudsGetLayerInfo(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location);
-
 #endif
diff --git a/src/rendering/clouds/public.h b/src/rendering/clouds/public.h
index 9bb6016..beded50 100644
--- a/src/rendering/clouds/public.h
+++ b/src/rendering/clouds/public.h
@@ -59,15 +59,8 @@ typedef struct
     Layers* layers;
 } CloudsDefinition;
 
-typedef struct
-{
-    int inside;
-    double density;
-    double distance_to_edge;
-} CloudsInfo;
-
 typedef Color (*FuncCloudsGetColor)(Renderer* renderer, Color base, Vector3 start, Vector3 end);
-typedef CloudsInfo (*FuncCloudsGetLayerInfo)(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location);
+typedef double (*FuncCloudsGetLayerDensity)(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location);
 
 typedef struct
 {
@@ -75,7 +68,7 @@ typedef struct
 
     FuncCloudsGetColor getColor;
     FuncLightingAlterLight alterLight;
-    FuncCloudsGetLayerInfo getLayerInfo;
+    FuncCloudsGetLayerDensity getLayerDensity;
 } CloudsRenderer;
 
 
diff --git a/src/rendering/tools/euclid.h b/src/rendering/tools/euclid.h
index b5bbd6f..90f68a6 100644
--- a/src/rendering/tools/euclid.h
+++ b/src/rendering/tools/euclid.h
@@ -77,6 +77,11 @@ extern Vector3 VECTOR_SOUTH;
 extern Vector3 VECTOR_EAST;
 extern Vector3 VECTOR_WEST;
 
+static inline Vector3 v3(double x, double y, double z)
+{
+    Vector3 result = {x, y, z};
+    return result;
+};
 void v3Save(PackStream* stream, Vector3* v);
 void v3Load(PackStream* stream, Vector3* v);
 Vector3 v3Translate(Vector3 v1, double x, double y, double z);
diff --git a/src/testing/common.h b/src/testing/common.h
index 3aabbf5..daf3b82 100644
--- a/src/testing/common.h
+++ b/src/testing/common.h
@@ -35,10 +35,30 @@ static inline int _double_not_equals(double x, double y)
 {
     return fabs(x - y) >= 0.00000000001;
 }
+static inline int _double_greater(double x, double y)
+{
+    return _double_not_equals(x, y) || (x > y);
+}
+static inline int _double_greater_or_equal(double x, double y)
+{
+    return _double_equals(x, y) || (x >= y);
+}
+static inline int _double_less(double x, double y)
+{
+    return _double_not_equals(x, y) || (x < y);
+}
+static inline int _double_less_or_equal(double x, double y)
+{
+    return _double_equals(x, y) || (x <= y);
+}
 
 #define _ck_assert_double(F, X, O, Y) ck_assert_msg(F(X, Y), "Assertion '"#X#O#Y"' failed: "#X"=%f, "#Y"=%f", X, Y)
 #define ck_assert_double_eq(X, Y) _ck_assert_double(_double_equals, X, ==, Y)
 #define ck_assert_double_ne(X, Y) _ck_assert_double(_double_not_equals, X, !=, Y)
+#define ck_assert_double_gt(X, Y) _ck_assert_double(_double_greater, X, >, Y)
+#define ck_assert_double_lt(X, Y) _ck_assert_double(_double_greater_or_equal, X, >=, Y)
+#define ck_assert_double_gte(X, Y) _ck_assert_double(_double_less, X, <, Y)
+#define ck_assert_double_lte(X, Y) _ck_assert_double(_double_less_or_equal, X, <=, Y)
 
 
 /***** Generic comparison assertions *****/
@@ -56,4 +76,9 @@ static inline char* _ck_gen_##_type_##_str(char* buffer, _type_ X) { \
 static char _ck_gen_strbuf1[101];
 static char _ck_gen_strbuf2[101];
 
+
+/***** Some builtin comparisons *****/
+#define ck_assert_double_in_range(_double_, _x_, _y_) ck_assert_double_gte(_double_, _x_);ck_assert_double_lte(_double_, _y_)
+#define ck_assert_vector_values(_vector_, _x_, _y_, _z_) ck_assert_double_eq(_vector_.x, _x_);ck_assert_double_eq(_vector_.y, _y_);ck_assert_double_eq(_vector_.z, _z_)
+
 #endif
diff --git a/src/testing/main.c b/src/testing/main.c
index 5e32f3e..d66edc4 100644
--- a/src/testing/main.c
+++ b/src/testing/main.c
@@ -1,21 +1,30 @@
 #include <check.h>
 #include <stdlib.h>
 
+#include "rendering/main.h"
+
 extern void test_euclid_case(Suite* s);
 extern void test_camera_case(Suite* s);
+extern void test_clouds_case(Suite* s);
 
 int main(int argc, char** argv)
 {
     int number_failed;
     Suite *s = suite_create("rendering");
 
+    paysagesInit();
+
     /* TODO Find a way to automate this */
     test_euclid_case(s);
     test_camera_case(s);
+    test_clouds_case(s);
 
     SRunner *sr = srunner_create(s);
     srunner_run_all(sr, CK_NORMAL);
     number_failed = srunner_ntests_failed(sr);
     srunner_free(sr);
+
+    paysagesQuit();
+
     return (number_failed == 0) ? EXIT_SUCCESS : EXIT_FAILURE;
 }
diff --git a/src/testing/test_camera.c b/src/testing/test_camera.c
index 8c8ada9..6a8920a 100644
--- a/src/testing/test_camera.c
+++ b/src/testing/test_camera.c
@@ -2,8 +2,6 @@
 
 #include "rendering/camera.h"
 
-#define _checkVector(_vector_, _x_, _y_, _z_) ck_assert_double_eq(_vector_.x, _x_);ck_assert_double_eq(_vector_.y, _y_);ck_assert_double_eq(_vector_.z, _z_)
-
 START_TEST(test_camera_definition)
 {
     CameraDefinition* cam;
@@ -12,8 +10,8 @@ START_TEST(test_camera_definition)
     cameraSetLocationCoords(cam, 0.0, 1.0, 1.0);
     cameraSetTargetCoords(cam, 0.0, 0.0, 0.0);
 
-    _checkVector(cameraGetLocation(cam), 0.0, 1.0, 1.0);
-    _checkVector(cameraGetTarget(cam), 0.0, 0.0, 0.0);
+    ck_assert_vector_values(cameraGetLocation(cam), 0.0, 1.0, 1.0);
+    ck_assert_vector_values(cameraGetTarget(cam), 0.0, 0.0, 0.0);
 
     cameraDeleteDefinition(cam);
 }
diff --git a/src/testing/test_clouds.c b/src/testing/test_clouds.c
new file mode 100644
index 0000000..7ab715e
--- /dev/null
+++ b/src/testing/test_clouds.c
@@ -0,0 +1,252 @@
+#include "testing/common.h"
+
+#include "rendering/renderer.h"
+#include "rendering/tools.h"
+#include "rendering/clouds/public.h"
+#include "rendering/clouds/clo_density.h"
+#include "rendering/clouds/clo_walking.h"
+
+START_TEST(test_clouds_density)
+{
+    /* Setup */
+    double x, y, z;
+    CloudsLayerDefinition* layer;
+    layer = cloudsGetLayerType().callback_create();
+
+    /* Test default coverage (empty) */
+    for (x = -10.0; x < 10.0; x += 10.0)
+    {
+        for (y = -10.0; y < 10.0; y += 10.0)
+        {
+            for (z = -10.0; z < 10.0; z += 10.0)
+            {
+                ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, y, z)), 0.0);
+            }
+        }
+    }
+
+    /* Test coverage by altitude */
+    layer->base_coverage = 1.0;
+    layer->lower_altitude = -1.0;
+    layer->thickness = 2.0;
+    cloudsGetLayerType().callback_validate(layer);
+    layer->base_coverage = 1.0;
+    noiseForceValue(layer->_coverage_noise, 1.0);
+    for (x = -10.0; x < 10.0; x += 10.0)
+    {
+        for (z = -10.0; z < 10.0; z += 10.0)
+        {
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.0, z)), 1.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.5, z)), 0.5);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.5, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -0.5, z)), 0.5);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.5, z)), 0.0);
+        }
+    }
+    layer->base_coverage = 0.5;
+    noiseForceValue(layer->_coverage_noise, 1.0);
+    for (x = -10.0; x < 10.0; x += 10.0)
+    {
+        for (z = -10.0; z < 10.0; z += 10.0)
+        {
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.0, z)), 0.5);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.5, z)), 0.25);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.5, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -0.5, z)), 0.25);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.5, z)), 0.0);
+        }
+    }
+    layer->base_coverage = 1.0;
+    noiseForceValue(layer->_coverage_noise, 0.5);
+    for (x = -10.0; x < 10.0; x += 10.0)
+    {
+        for (z = -10.0; z < 10.0; z += 10.0)
+        {
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.0, z)), 0.5);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 0.5, z)), 0.25);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, 1.5, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -0.5, z)), 0.25);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.0, z)), 0.0);
+            ck_assert_double_eq(cloudsGetLayerCoverage(layer, v3(x, -1.5, z)), 0.0);
+        }
+    }
+
+    /* TODO Test fake renderer */
+
+    /* TODO Test real renderer */
+
+    /* Teardown */
+    cloudsGetLayerType().callback_delete(layer);
+}
+END_TEST
+
+START_TEST(test_clouds_walking_boundaries)
+{
+    Vector3 start, end;
+    int result;
+    CloudsLayerDefinition* layer;
+    layer = cloudsGetLayerType().callback_create();
+    layer->base_coverage = 1.0;
+    layer->lower_altitude = -1.0;
+    layer->thickness = 2.0;
+    cloudsGetLayerType().callback_validate(layer);
+
+    /* Basic cases */
+    start = v3(0.0, -3.0, 0.0);
+    end = v3(0.0, -2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, 2.0, 0.0);
+    end = v3(0.0, 3.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, -2.0, 0.0);
+    end = v3(0.0, 2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, -1.0, 0.0);
+    ck_assert_vector_values(end, 0.0, 1.0, 0.0);
+
+    start = v3(0.0, 0.0, 0.0);
+    end = v3(0.0, 2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, 0.0, 0.0);
+    ck_assert_vector_values(end, 0.0, 1.0, 0.0);
+
+    start = v3(0.0, -2.0, 0.0);
+    end = v3(0.0, 0.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, -1.0, 0.0);
+    ck_assert_vector_values(end, 0.0, 0.0, 0.0);
+
+    /* Basic cases (inverted) */
+    start = v3(0.0, -2.0, 0.0);
+    end = v3(0.0, -3.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, 3.0, 0.0);
+    end = v3(0.0, 2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, 2.0, 0.0);
+    end = v3(0.0, -2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, 1.0, 0.0);
+    ck_assert_vector_values(end, 0.0, -1.0, 0.0);
+
+    start = v3(0.0, 2.0, 0.0);
+    end = v3(0.0, 0.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, 1.0, 0.0);
+    ck_assert_vector_values(end, 0.0, 0.0, 0.0);
+
+    start = v3(0.0, 0.0, 0.0);
+    end = v3(0.0, -2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, 0.0, 0.0);
+    ck_assert_vector_values(end, 0.0, -1.0, 0.0);
+
+    /* Horizontal cases */
+    start = v3(0.0, 2.0, 0.0);
+    end = v3(10.0, 2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, 1.00001, 0.0);
+    end = v3(10.0, 1.00001, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, -1.00001, 0.0);
+    end = v3(10.0, -1.00001, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, -2.0, 0.0);
+    end = v3(10.0, -2.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 0);
+
+    start = v3(0.0, 0.0, 0.0);
+    end = v3(10.0, 0.0, 0.0);
+    result = cloudsOptimizeWalkingBounds(layer, &start, &end);
+    ck_assert_int_eq(result, 1);
+    ck_assert_vector_values(start, 0.0, 0.0, 0.0);
+    ck_assert_vector_values(end, 10.0, 0.0, 0.0);
+
+    cloudsGetLayerType().callback_delete(layer);
+}
+END_TEST
+
+static double _getLayerDensitySinX(Renderer* renderer, CloudsLayerDefinition* layer, Vector3 location)
+{
+    UNUSED(renderer);
+    UNUSED(layer);
+    double density = sin(location.x * (2.0 * M_PI));
+    return (density > 0.0) ? density : 0.0;
+}
+
+START_TEST(test_clouds_primary_segments)
+{
+    int segment_count, i;
+    CloudPrimarySegment segments[10];
+
+    CloudsLayerDefinition* layer;
+    layer = cloudsGetLayerType().callback_create();
+    layer->lower_altitude = -1.0;
+    layer->thickness = 2.0;
+    cloudsGetLayerType().callback_validate(layer);
+
+    Renderer* renderer;
+    renderer = rendererCreate();
+
+    renderer->render_quality = 8;
+    renderer->clouds->getLayerDensity = _getLayerDensitySinX;
+
+    segment_count = cloudsGetLayerPrimarySegments(renderer, layer, v3(-0.4, 0.0, 0.0), v3(1.9, 0.0, 0.0), 10, segments);
+    ck_assert_int_eq(segment_count, 2);
+    for (i = 0; i < segment_count; i++)
+    {
+        ck_assert_double_eq(segments[i].enter.y, 0.0);
+        ck_assert_double_eq(segments[i].enter.z, 0.0);
+        ck_assert_double_eq(segments[i].exit.y, 0.0);
+        ck_assert_double_eq(segments[i].exit.z, 0.0);
+    }
+    ck_assert_double_in_range(segments[0].enter.x, -0.5, 0.0);
+    ck_assert_double_in_range(segments[0].exit.x, 0.5, 1.0);
+    ck_assert_double_in_range(segments[0].length, 0.5, 1.5);
+    ck_assert_double_gte(segments[1].enter.x, segments[0].exit.x);
+    ck_assert_double_in_range(segments[1].enter.x, 0.5, 1.0);
+    ck_assert_double_in_range(segments[1].exit.x, 1.5, 2.0);
+    ck_assert_double_in_range(segments[1].length, 0.5, 1.5);
+
+    cloudsGetLayerType().callback_delete(layer);
+    rendererDelete(renderer);
+}
+END_TEST
+
+START_TEST(test_clouds_preview_color)
+{
+    Renderer* renderer = cloudsCreatePreviewColorRenderer();
+
+    /* TODO Test the density overriding */
+
+    rendererDelete(renderer);
+}
+END_TEST
+
+TEST_CASE(clouds, test_clouds_density, test_clouds_walking_boundaries, test_clouds_primary_segments, test_clouds_preview_color)