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diff --git a/extern/bullet2/src/LinearMath/btPolarDecomposition.h b/extern/bullet2/src/LinearMath/btPolarDecomposition.h
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+++ b/extern/bullet2/src/LinearMath/btPolarDecomposition.h
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+#ifndef POLARDECOMPOSITION_H
+#define POLARDECOMPOSITION_H
+
+#include "btMatrix3x3.h"
+
+/**
+ * This class is used to compute the polar decomposition of a matrix. In
+ * general, the polar decomposition factorizes a matrix, A, into two parts: a
+ * unitary matrix (U) and a positive, semi-definite Hermitian matrix (H).
+ * However, in this particular implementation the original matrix, A, is
+ * required to be a square 3x3 matrix with real elements. This means that U will
+ * be an orthogonal matrix and H with be a positive-definite, symmetric matrix.
+ */
+class btPolarDecomposition
+{
+  public:
+    static const btScalar DEFAULT_TOLERANCE;
+    static const unsigned int DEFAULT_MAX_ITERATIONS;
+
+    /**
+     * Creates an instance with optional parameters.
+     *
+     * @param tolerance     - the tolerance used to determine convergence of the
+     *                        algorithm
+     * @param maxIterations - the maximum number of iterations used to achieve
+     *                        convergence
+     */
+    btPolarDecomposition(btScalar tolerance = DEFAULT_TOLERANCE, 
+      unsigned int maxIterations = DEFAULT_MAX_ITERATIONS);
+
+    /**
+     * Decomposes a matrix into orthogonal and symmetric, positive-definite
+     * parts. If the number of iterations returned by this function is equal to
+     * the maximum number of iterations, the algorithm has failed to converge.
+     *
+     * @param a - the original matrix
+     * @param u - the resulting orthogonal matrix
+     * @param h - the resulting symmetric matrix
+     *
+     * @return the number of iterations performed by the algorithm.
+     */
+    unsigned int decompose(const btMatrix3x3& a, btMatrix3x3& u, btMatrix3x3& h) const; 
+
+    /**
+     * Returns the maximum number of iterations that this algorithm will perform
+     * to achieve convergence.
+     *
+     * @return maximum number of iterations
+     */
+    unsigned int maxIterations() const;
+
+  private:
+    btScalar m_tolerance;
+    unsigned int m_maxIterations;
+};
+
+/**
+ * This functions decomposes the matrix 'a' into two parts: an orthogonal matrix
+ * 'u' and a symmetric, positive-definite matrix 'h'. If the number of
+ * iterations returned by this function is equal to
+ * btPolarDecomposition::DEFAULT_MAX_ITERATIONS, the algorithm has failed to
+ * converge.
+ *
+ * @param a - the original matrix
+ * @param u - the resulting orthogonal matrix
+ * @param h - the resulting symmetric matrix
+ *
+ * @return the number of iterations performed by the algorithm.
+ */
+unsigned int polarDecompose(const btMatrix3x3& a, btMatrix3x3& u, btMatrix3x3& h); 
+
+#endif // POLARDECOMPOSITION_H
+