diff --git a/src/render/software/FluidMediumInterface.cpp b/src/render/software/FluidMediumInterface.cpp
new file mode 100644
index 0000000..aa68a53
--- /dev/null
+++ b/src/render/software/FluidMediumInterface.cpp
@@ -0,0 +1 @@
+#include "FluidMediumInterface.h"
diff --git a/src/render/software/FluidMediumInterface.h b/src/render/software/FluidMediumInterface.h
new file mode 100644
index 0000000..7dc297e
--- /dev/null
+++ b/src/render/software/FluidMediumInterface.h
@@ -0,0 +1,27 @@
+#ifndef FLUIDMEDIUMINTERFACE_H
+#define FLUIDMEDIUMINTERFACE_H
+
+#include "software_global.h"
+
+namespace paysages {
+namespace basics {
+    class SpaceCoordinate;
+}
+namespace software {
+
+/*!
+ * \brief Interface to a fluid medium compatible class.
+ */
+class SOFTWARESHARED_EXPORT FluidMediumInterface
+{
+public:
+    /*!
+     * Return true if the object may interfere with the fluid medium on the given segment.
+     */
+    virtual bool mayInfluence(const SpaceCoordinate& start, const SpaceCoordinate& end) const = 0;
+};
+
+}
+}
+
+#endif // FLUIDMEDIUMINTERFACE_H
diff --git a/src/render/software/global/FluidMediumTraversal.cpp b/src/render/software/FluidMediumTraversal.cpp
similarity index 100%
rename from src/render/software/global/FluidMediumTraversal.cpp
rename to src/render/software/FluidMediumTraversal.cpp
diff --git a/src/render/software/global/FluidMediumTraversal.h b/src/render/software/FluidMediumTraversal.h
similarity index 90%
rename from src/render/software/global/FluidMediumTraversal.h
rename to src/render/software/FluidMediumTraversal.h
index 6ef2ca9..7341f57 100644
--- a/src/render/software/global/FluidMediumTraversal.h
+++ b/src/render/software/FluidMediumTraversal.h
@@ -24,10 +24,11 @@ class SOFTWARESHARED_EXPORT FluidMediumTraversal
 {
 public:
     FluidMediumTraversal(SoftwareRenderer *renderer);
+    virtual ~FluidMediumTraversal();
 
     void setCollector(FluidMediumCollector *collector);
 
-    virtual void getTraversedMedia(std::vector<FluidMediumInterface> &media);
+    virtual void getTraversedMedia(std::vector<FluidMediumInterface> &media, const SpaceCoordinates &start, const SpaceCoordinates &end);
 
     void collectHalfLine(const SpaceCoordinates &start, const Vector3 &direction);
     void collectSegment(const SpaceCoordinates &start, const SpaceCoordinates &end);
diff --git a/src/render/software/SoftwareRenderer.cpp b/src/render/software/SoftwareRenderer.cpp
index b246a4c..991240a 100644
--- a/src/render/software/SoftwareRenderer.cpp
+++ b/src/render/software/SoftwareRenderer.cpp
@@ -1,6 +1,6 @@
 #include "SoftwareRenderer.h"
 
-#include "global/FluidMediumTraversal.h"
+#include "FluidMediumTraversal.h"
 
 SoftwareRenderer::SoftwareRenderer(Scenery* scenery):
     scenery(scenery)
diff --git a/src/render/software/software.pro b/src/render/software/software.pro
index 9305e18..1356e79 100644
--- a/src/render/software/software.pro
+++ b/src/render/software/software.pro
@@ -14,11 +14,13 @@ DEFINES += SOFTWARE_LIBRARY
 include(../../common.pri)
 
 SOURCES += SoftwareRenderer.cpp \
-    global/FluidMediumTraversal.cpp
+    FluidMediumTraversal.cpp \
+    FluidMediumInterface.cpp
 
 HEADERS += SoftwareRenderer.h\
         software_global.h \
-    global/FluidMediumTraversal.h
+    FluidMediumTraversal.h \
+    FluidMediumInterface.h
 
 unix:!symbian {
     maemo5 {