diff --git a/simgear/scene/model/Makefile.am b/simgear/scene/model/Makefile.am
index 3734733b..4ab768d6 100644
--- a/simgear/scene/model/Makefile.am
+++ b/simgear/scene/model/Makefile.am
@@ -6,6 +6,7 @@ noinst_HEADERS =
 
 include_HEADERS = \
 	animation.hxx \
+	flash.hxx \
 	location.hxx \
 	model.hxx \
 	modellib.hxx \
@@ -13,6 +14,7 @@ include_HEADERS = \
 
 libsgmodel_a_SOURCES = \
 	animation.cxx \
+	flash.cxx \
 	location.cxx \
 	model.cxx \
 	modellib.cxx \
diff --git a/simgear/scene/model/animation.cxx b/simgear/scene/model/animation.cxx
index ac305760..6ced0858 100644
--- a/simgear/scene/model/animation.cxx
+++ b/simgear/scene/model/animation.cxx
@@ -16,7 +16,7 @@
 #include <simgear/props/props.hxx>
 
 #include "animation.hxx"
-
+#include "flash.hxx"
 
 
 ////////////////////////////////////////////////////////////////////////
@@ -190,8 +190,14 @@ SGAnimation::init ()
 {
 }
 
-void
+int
 SGAnimation::update()
+{
+    return 1;
+}
+
+void
+SGAnimation::restore()
 {
 }
 
@@ -255,7 +261,7 @@ SGRangeAnimation::~SGRangeAnimation ()
 {
 }
 
-void
+int
 SGRangeAnimation::update()
 {
     float ranges[2];
@@ -275,6 +281,7 @@ SGRangeAnimation::update()
     if (upd) {
        ((ssgRangeSelector *)_branch)->setRanges(ranges, 2);
     }
+  return 1;
 }
 
 
@@ -313,13 +320,14 @@ SGSelectAnimation::~SGSelectAnimation ()
   delete _condition;
 }
 
-void
+int
 SGSelectAnimation::update()
 {
   if (_condition != 0 && _condition->test()) 
       ((ssgSelector *)_branch)->select(0xffff);
   else
       ((ssgSelector *)_branch)->select(0x0000);
+  return 1;
 }
 
 
@@ -372,7 +380,7 @@ SGSpinAnimation::~SGSpinAnimation ()
 {
 }
 
-void
+int
 SGSpinAnimation::update()
 {
   double dt = sim_time_sec - _last_time_sec;
@@ -386,6 +394,7 @@ SGSpinAnimation::update()
     _position_deg -= 360.0;
   set_rotation(_matrix, _position_deg, _center, _axis);
   ((ssgTransform *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -406,7 +415,7 @@ SGTimedAnimation::~SGTimedAnimation ()
 {
 }
 
-void
+int
 SGTimedAnimation::update()
 {
     if ((sim_time_sec - _last_time_sec) >= _duration_sec) {
@@ -416,6 +425,7 @@ SGTimedAnimation::update()
             _step = 0;
         ((ssgSelector *)getBranch())->selectStep(_step);
     }
+  return 1;
 }
 
 
@@ -473,7 +483,7 @@ SGRotateAnimation::~SGRotateAnimation ()
   delete _table;
 }
 
-void
+int
 SGRotateAnimation::update()
 {
   if (_table == 0) {
@@ -487,6 +497,7 @@ SGRotateAnimation::update()
   }
   set_rotation(_matrix, _position_deg, _center, _axis);
   ((ssgTransform *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -514,7 +525,7 @@ SGBlendAnimation::~SGBlendAnimation ()
     delete _table;
 }
 
-void
+int
 SGBlendAnimation::update()
 {
   double _blend;
@@ -534,6 +545,7 @@ SGBlendAnimation::update()
     _prev_value = _blend;
     change_alpha( _branch, _blend );
   }
+  return 1;
 }
 
 
@@ -566,7 +578,7 @@ SGTranslateAnimation::~SGTranslateAnimation ()
   delete _table;
 }
 
-void
+int
 SGTranslateAnimation::update()
 {
   if (_table == 0) {
@@ -580,6 +592,7 @@ SGTranslateAnimation::update()
   }
   set_translation(_matrix, _position_m, _axis);
   ((ssgTransform *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -619,7 +632,7 @@ SGScaleAnimation::~SGScaleAnimation ()
   delete _table;
 }
 
-void
+int
 SGScaleAnimation::update()
 {
   if (_table == 0) {
@@ -654,6 +667,7 @@ SGScaleAnimation::update()
 
   set_scale(_matrix, _x_scale, _y_scale, _z_scale );
   ((ssgTransform *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -688,7 +702,7 @@ SGTexRotateAnimation::~SGTexRotateAnimation ()
   delete _table;
 }
 
-void
+int
 SGTexRotateAnimation::update()
 {
   if (_table == 0) {
@@ -702,6 +716,7 @@ SGTexRotateAnimation::update()
   }
   set_rotation(_matrix, _position_deg, _center, _axis);
   ((ssgTexTrans *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -735,7 +750,7 @@ SGTexTranslateAnimation::~SGTexTranslateAnimation ()
   delete _table;
 }
 
-void
+int
 SGTexTranslateAnimation::update()
 {
   if (_table == 0) {
@@ -749,6 +764,7 @@ SGTexTranslateAnimation::update()
   }
   set_translation(_matrix, _position, _axis);
   ((ssgTexTrans *)_branch)->setTransform(_matrix);
+  return 1;
 }
 
 
@@ -825,7 +841,7 @@ SGTexMultipleAnimation::~SGTexMultipleAnimation ()
   delete _transform;
 }
 
-void
+int
 SGTexMultipleAnimation::update()
 {
   int i;
@@ -866,6 +882,7 @@ SGTexMultipleAnimation::update()
     }
   }
   ((ssgTexTrans *)_branch)->setTransform(tmatrix);
+  return 1;
 }
 
 
@@ -904,4 +921,39 @@ void SGAlphaTestAnimation::setAlphaClampToBranch(ssgBranch *b, float clamp)
   }
 }
 
+
+
+////////////////////////////////////////////////////////////////////////
+// Implementation of SGFlashAnimation
+////////////////////////////////////////////////////////////////////////
+SGFlashAnimation::SGFlashAnimation(SGPropertyNode_ptr props)
+  : SGAnimation( props, new SGFlash )
+{
+  sgVec3 axis;
+  axis[0] = props->getFloatValue("axis/x", 0);
+  axis[1] = props->getFloatValue("axis/y", 0);
+  axis[2] = props->getFloatValue("axis/z", 1);
+  ((SGFlash *)_branch)->setAxis( axis );
+
+  sgVec3 center;
+  center[0] = props->getFloatValue("center/x-m", 0);
+  center[1] = props->getFloatValue("center/y-m", 0);
+  center[2] = props->getFloatValue("center/z-m", 0);
+  ((SGFlash *)_branch)->setCenter( center );
+
+  float offset = props->getFloatValue("offset", 0.0);
+  float factor = props->getFloatValue("factor", 1.0);
+  float power = props->getFloatValue("power", 1.0);
+  bool two_sides = props->getBoolValue("two-sides", false);
+  ((SGFlash *)_branch)->setParameters( power, factor, offset, two_sides );
+
+  float v_min = props->getFloatValue("min", 0.0);
+  float v_max = props->getFloatValue("max", 1.0);
+  ((SGFlash *)_branch)->setClampValues( v_min, v_max );
+}
+
+SGFlashAnimation::~SGFlashAnimation()
+{
+}
+
 // end of animation.cxx
diff --git a/simgear/scene/model/animation.hxx b/simgear/scene/model/animation.hxx
index c0c7fc39..76259c98 100644
--- a/simgear/scene/model/animation.hxx
+++ b/simgear/scene/model/animation.hxx
@@ -65,7 +65,12 @@ public:
   /**
    * Update the animation.
    */
-  virtual void update();
+  virtual int update();
+
+  /**
+   * Restore the state after the animation.
+   */
+  virtual void restore();
 
   /**
    * Set the value of sim_time_sec.  This needs to be called every
@@ -102,7 +107,7 @@ public:
   SGRangeAnimation (SGPropertyNode *prop_root,
                     SGPropertyNode_ptr props);
   virtual ~SGRangeAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _min_prop;
   SGPropertyNode_ptr _max_prop;
@@ -133,7 +138,7 @@ public:
   SGSelectAnimation( SGPropertyNode *prop_root,
                    SGPropertyNode_ptr props );
   virtual ~SGSelectAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGCondition * _condition;
 };
@@ -151,7 +156,7 @@ public:
                  SGPropertyNode_ptr props,
                  double sim_time_sec );
   virtual ~SGSpinAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _factor;
@@ -171,7 +176,7 @@ class SGTimedAnimation : public SGAnimation
 public:
     SGTimedAnimation (SGPropertyNode_ptr props);
     virtual ~SGTimedAnimation ();
-    virtual void update();
+    virtual int update();
 private:
     double _duration_sec;
     double _last_time_sec;
@@ -189,7 +194,7 @@ class SGRotateAnimation : public SGAnimation
 public:
   SGRotateAnimation( SGPropertyNode *prop_root, SGPropertyNode_ptr props );
   virtual ~SGRotateAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _offset_deg;
@@ -215,7 +220,7 @@ public:
   SGTranslateAnimation( SGPropertyNode *prop_root,
                       SGPropertyNode_ptr props );
   virtual ~SGTranslateAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _offset_m;
@@ -239,7 +244,7 @@ public:
   SGBlendAnimation( SGPropertyNode *prop_root,
                       SGPropertyNode_ptr props );
   virtual ~SGBlendAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   SGInterpTable * _table;
@@ -261,7 +266,7 @@ public:
   SGScaleAnimation( SGPropertyNode *prop_root,
                         SGPropertyNode_ptr props );
   virtual ~SGScaleAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _x_factor;
@@ -299,7 +304,7 @@ class SGTexRotateAnimation : public SGAnimation
 public:
   SGTexRotateAnimation( SGPropertyNode *prop_root, SGPropertyNode_ptr props );
   virtual ~SGTexRotateAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _offset_deg;
@@ -325,7 +330,7 @@ public:
   SGTexTranslateAnimation( SGPropertyNode *prop_root,
                       SGPropertyNode_ptr props );
   virtual ~SGTexTranslateAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   SGPropertyNode_ptr _prop;
   double _offset;
@@ -354,7 +359,7 @@ public:
   SGTexMultipleAnimation( SGPropertyNode *prop_root,
                       SGPropertyNode_ptr props );
   virtual ~SGTexMultipleAnimation ();
-  virtual void update();
+  virtual int update();
 private:
   class TexTransform
     {
@@ -382,7 +387,7 @@ private:
 
 
 /**
- * An animation to enable the alpha test 
+ * An "animation" to enable the alpha test 
  */
 class SGAlphaTestAnimation : public SGAnimation
 {
@@ -396,4 +401,16 @@ private:
 };
 
 
+/**
+ * An "animation" that compute a scale according to 
+ * the angle between an axis and the view direction
+ */
+class SGFlashAnimation : public SGAnimation
+{
+public:
+  SGFlashAnimation(SGPropertyNode_ptr props);
+  virtual ~SGFlashAnimation ();
+};
+
+
 #endif // _SG_ANIMATION_HXX
diff --git a/simgear/scene/model/flash.cxx b/simgear/scene/model/flash.cxx
new file mode 100755
index 00000000..9e75421d
--- /dev/null
+++ b/simgear/scene/model/flash.cxx
@@ -0,0 +1,147 @@
+/*
+     $Id$
+*/
+
+#include "plib/ssg.h"
+#include "flash.hxx"
+void _ssgPushMatrix ( sgMat4 m );
+void _ssgPopMatrix  ();
+void _ssgReadInt     ( FILE *fd,                int   *var );
+void _ssgWriteInt    ( FILE *fd, const          int    var );
+extern sgMat4 _ssgOpenGLAxisSwapMatrix;
+
+void SGFlash::copy_from( SGFlash *src, int clone_flags )
+{
+  ssgBranch::copy_from( src, clone_flags );
+  sgCopyVec3( _center, src->_center );
+  sgCopyVec3( _axis, src->_axis );
+  _power = src->_power;
+  _factor = src->_factor;
+  _offset = src->_offset;
+  _min_v = src->_min_v;
+  _max_v = src->_max_v;
+  _two_sides = src->_two_sides;
+}
+
+ssgBase *SGFlash::clone( int clone_flags )
+{
+  SGFlash *b = new SGFlash;
+  b -> copy_from( this, clone_flags );
+  return b;
+}
+
+
+SGFlash::SGFlash()
+{
+  type = ssgTypeBranch();
+}
+
+SGFlash::~SGFlash()
+{
+}
+
+void SGFlash::setAxis( sgVec3 axis )
+{
+  sgCopyVec3( _axis, axis );
+  sgNormalizeVec3( _axis );
+}
+
+void SGFlash::setCenter( sgVec3 center )
+{
+  sgCopyVec3( _center, center );
+}
+
+void SGFlash::setParameters( float power, float factor, float offset, bool two_sides )
+{
+  _power = power;
+  _factor = factor;
+  _offset = offset;
+  _two_sides = two_sides;
+}
+
+void SGFlash::setClampValues( float min_v, float max_v )
+{
+  _min_v = min_v;
+  _max_v = max_v;
+}
+
+void SGFlash::cull( sgFrustum *f, sgMat4 m, int test_needed )
+{
+  if ( ! preTravTests( &test_needed, SSGTRAV_CULL ) )
+    return;
+
+  sgVec3 transformed_axis;
+  sgXformVec3( transformed_axis, _axis, m );
+  sgNormalizeVec3( transformed_axis );
+
+  float cos_angle = transformed_axis[ 2 ]; // z component, through the screen
+  float scale_factor = 0.f;
+  if ( _two_sides && cos_angle < 0 )
+    scale_factor = _factor * (float)pow( -cos_angle, _power ) + _offset;
+  else if ( cos_angle > 0 )
+    scale_factor = _factor * (float)pow( cos_angle, _power ) + _offset;
+
+  if ( scale_factor < _min_v )
+      scale_factor = _min_v;
+  if ( scale_factor > _max_v )
+      scale_factor = _max_v;
+
+  sgMat4 tmp, transform;
+  sgMakeIdentMat4( transform );
+  transform[0][0] = scale_factor;
+  transform[1][1] = scale_factor;
+  transform[2][2] = scale_factor;
+  transform[3][0] = _center[0] * ( 1 - scale_factor );
+  transform[3][1] = _center[1] * ( 1 - scale_factor );
+  transform[3][2] = _center[2] * ( 1 - scale_factor );
+
+  sgCopyMat4( tmp, m );
+  sgPreMultMat4( tmp, transform );
+
+  _ssgPushMatrix( tmp );
+  glPushMatrix();
+  glLoadMatrixf( (float *) tmp );
+
+  for ( ssgEntity *e = getKid ( 0 ); e != NULL; e = getNextKid() )
+    e -> cull( f, tmp, test_needed );
+
+  glPopMatrix();
+  _ssgPopMatrix();
+
+  postTravTests( SSGTRAV_CULL );
+}
+
+
+void SGFlash::hot( sgVec3 s, sgMat4 m, int test_needed )
+{
+  ssgBranch::hot( s, m, test_needed );
+}
+
+void SGFlash::los( sgVec3 s, sgMat4 m, int test_needed )
+{
+  ssgBranch::los( s, m, test_needed );
+}
+
+
+void SGFlash::isect( sgSphere *s, sgMat4 m, int test_needed )
+{
+  ssgBranch::isect( s, m, test_needed );
+}
+
+
+
+int SGFlash::load( FILE *fd )
+{
+//  _ssgReadInt( fd, & point_rotate );
+
+  return ssgBranch::load(fd);
+}
+
+int SGFlash::save( FILE *fd )
+{
+//  _ssgWriteInt( fd, point_rotate );
+
+  return ssgBranch::save(fd);
+}
+
+const char *SGFlash::getTypeName (void) { return "SGFlash"; }
diff --git a/simgear/scene/model/flash.hxx b/simgear/scene/model/flash.hxx
new file mode 100755
index 00000000..f94fef03
--- /dev/null
+++ b/simgear/scene/model/flash.hxx
@@ -0,0 +1,29 @@
+
+class SGFlash : public ssgBranch
+{
+public:
+    virtual ssgBase *clone( int clone_flags = 0 );
+    SGFlash();
+    virtual ~SGFlash(void);
+
+    void setAxis( sgVec3 axis );
+    void setCenter( sgVec3 center );
+    void setParameters( float power, float factor, float offset, bool two_sides );
+    void setClampValues( float min_v, float max_v );
+
+    virtual const char *getTypeName(void);
+    virtual int load( FILE *fd );
+    virtual int save( FILE *fd );
+    virtual void cull( sgFrustum *f, sgMat4 m, int test_needed );
+    virtual void isect( sgSphere *s, sgMat4 m, int test_needed );
+    virtual void hot( sgVec3 s, sgMat4 m, int test_needed );
+    virtual void los( sgVec3 s, sgMat4 m, int test_needed );
+
+protected:
+    virtual void copy_from( SGFlash *src, int clone_flags );
+
+private:
+    sgVec3 _axis, _center;
+    float _power, _factor, _offset, _min_v, _max_v;
+    bool _two_sides;
+};
diff --git a/simgear/scene/model/model.cxx b/simgear/scene/model/model.cxx
index be5d9f48..3e6d508b 100644
--- a/simgear/scene/model/model.cxx
+++ b/simgear/scene/model/model.cxx
@@ -52,8 +52,17 @@ model_filter_callback (ssgEntity * entity, int mask)
 static int
 animation_callback (ssgEntity * entity, int mask)
 {
-    ((SGAnimation *)entity->getUserData())->update();
-    return true;
+    return ((SGAnimation *)entity->getUserData())->update();
+}
+
+/**
+ * Callback to restore the state after an animation.
+ */
+static int
+restore_callback (ssgEntity * entity, int mask)
+{
+    ((SGAnimation *)entity->getUserData())->restore();
+    return 1;
 }
 
 
@@ -145,6 +154,8 @@ sgMakeAnimation( ssgBranch * model,
     animation = new SGBlendAnimation(prop_root, node);
   } else if (!strcmp("alpha-test", type)) {
     animation = new SGAlphaTestAnimation(node);
+  } else if (!strcmp("flash", type)) {
+    animation = new SGFlashAnimation(node);
   } else {
     animation = new SGNullAnimation(node);
     SG_LOG(SG_INPUT, SG_WARN, "Unknown animation type " << type);
@@ -188,6 +199,7 @@ sgMakeAnimation( ssgBranch * model,
   animation->init();
   branch->setUserData(animation);
   branch->setTravCallback(SSG_CALLBACK_PRETRAV, animation_callback);
+  branch->setTravCallback(SSG_CALLBACK_POSTTRAV, restore_callback);
 }