Added Inventor plugin, submitted by Sean Spicer, Written by Vivek (c) Magic-Earth.

To compile in do a setenv/export USE_COIN or USE_INVENTOR.

src/osgPlugins/Inventor/PendulumCallback.cpp

@@ -0,0 +1,54 @@
+#include <osg/MatrixTransform>
+
+#include "PendulumCallback.h"
+
+PendulumCallback::PendulumCallback(const osg::Vec3& axis, 
+                                         float startAngle, float endAngle,
+                                         float frequency)
+{
+    _axis = axis;
+    _startAngle = startAngle;
+    _endAngle = endAngle;
+    _frequency = frequency;
+    
+    _previousTraversalNumber = -1;
+    _previousTime = -1.0;
+    _angle = 0.0;
+}
+
+void PendulumCallback::operator() (osg::Node* node, osg::NodeVisitor* nv)
+{
+    if (!nv)
+        return;
+
+    osg::MatrixTransform* transform = dynamic_cast<osg::MatrixTransform*>(node);
+    if (!transform)
+        return;
+
+    const osg::FrameStamp* fs = nv->getFrameStamp();
+    if (!fs) 
+        return; 
+    
+    // ensure that we do not operate on this node more than
+    // once during this traversal.  This is an issue since node
+    // can be shared between multiple parents.
+    if (nv->getTraversalNumber()!=_previousTraversalNumber)
+    {
+        double currentTime = fs->getReferenceTime();
+        _angle += (currentTime - _previousTime) * 2 * M_PI * _frequency;
+        
+        double frac = 0.5 + 0.5 * sin(_angle);
+        double rotAngle = _endAngle  - _startAngle - M_PI 
+                + (1.0 - frac) * _startAngle + frac * _endAngle;
+
+        // update the specified transform
+        transform->setMatrix(osg::Matrix::rotate(rotAngle, _axis));
+            
+        _previousTraversalNumber = nv->getTraversalNumber();
+        _previousTime = currentTime;
+    }
+
+    // must call any nested node callbacks and continue subgraph traversal.
+    traverse(node,nv);
+
+}