added von mises distributionb

quick&dirty: added activity to the grid-walkers

math/distribution/VonMises.h

@@ -0,0 +1,56 @@
+#ifndef K_MATH_DISTRIBUTION_VONMISES_H
+#define K_MATH_DISTRIBUTION_VONMISES_H
+
+#include <cmath>
+#include <random>
+
+#include "../Math.h"
+#include "Bessel.h"
+#include "LUT.h"
+
+namespace Distribution {
+
+	/** von-mises distribution */
+	template <typename T> class VonMises {
+
+	private:
+
+		/** center of the distribution */
+		const T mu;
+
+		/** like 1.0/variance of the distribution */
+		const T kappa;
+
+		/** pre-calcuated look-up-table */
+		std::vector<T> lut;
+
+		/** helper for modified bessel I_0(kappa) */
+		Bessel<T> bessel;
+
+	public:
+
+		/** ctor */
+		VonMises(const T mu, const T kappa) : mu(mu), kappa(kappa) {
+
+		}
+
+		LUT<T> getLUT() const {
+			return LUT<T>(*this, -M_PI, +M_PI, 10000);
+		}
+
+		/** get probability for the given value */
+		T getProbability(const T _val) const {
+
+			const T val = Math::clamp((T)-M_PI, (T)+M_PI, _val);
+
+			return
+					std::exp(kappa * std::cos(val - mu)) /
+					(2 * M_PI * bessel.getModified(0, kappa));
+
+		}
+
+	};
+
+}
+
+#endif // K_MATH_DISTRIBUTION_VONMISES_H