Index: sansmodels/src/sans/models/c_models/c_models.cpp
===================================================================
--- sansmodels/src/sans/models/c_models/c_models.cpp	(revision 34c30203f24453aa528815f48e84a90b0bbd95be)
+++ sansmodels/src/sans/models/c_models/c_models.cpp	(revision 27fea3fd73c362e927fb15e5806e0a587260c5f3)
@@ -31,4 +31,5 @@
 void addCLamellarModel(PyObject *module);
 void addCLamellarFFHGModel(PyObject *module);
+void addCHollowCylinderModel(PyObject *module);
 
 
@@ -181,7 +182,9 @@
 	addCLamellarModel(m);
 	addCLamellarFFHGModel(m);
+	addCHollowCylinderModel(m);
 	addDisperser(m);
 	addCGaussian(m);
 	addCLorentzian(m);
 
+
 }
Index: sansmodels/src/sans/models/c_models/hollowcylinder.cpp
===================================================================
--- sansmodels/src/sans/models/c_models/hollowcylinder.cpp	(revision 27fea3fd73c362e927fb15e5806e0a587260c5f3)
+++ sansmodels/src/sans/models/c_models/hollowcylinder.cpp	(revision 27fea3fd73c362e927fb15e5806e0a587260c5f3)
@@ -0,0 +1,208 @@
+/**
+	This software was developed by the University of Tennessee as part of the
+	Distributed Data Analysis of Neutron Scattering Experiments (DANSE)
+	project funded by the US National Science Foundation.
+
+	If you use DANSE applications to do scientific research that leads to
+	publication, we ask that you acknowledge the use of the software with the
+	following sentence:
+
+	"This work benefited from DANSE software developed under NSF award DMR-0520547."
+
+	copyright 2008, University of Tennessee
+ */
+
+/**
+ * Scattering model classes
+ * The classes use the IGOR library found in
+ *   sansmodels/src/libigor
+ *
+ *	TODO: refactor so that we pull in the old sansmodels.c_extensions
+ */
+
+#include <math.h>
+#include "models.hh"
+#include "parameters.hh"
+#include <stdio.h>
+using namespace std;
+
+extern "C" {
+	#include "libCylinder.h"
+	#include "hollow_cylinder.h"
+}
+
+HollowCylinderModel :: HollowCylinderModel() {
+	scale      = Parameter(1.0);
+	core_radius = Parameter(20.0, true);
+	core_radius.set_min(0.0);
+	shell_radius  = Parameter(30.0, true);
+	shell_radius.set_min(0.0);
+	length     = Parameter(400.0, true);
+	length.set_min(0.0);
+	contrast  = Parameter(5.3e-6);
+	background = Parameter(0.0);
+	axis_theta = Parameter(0.0, true);
+	axis_phi   = Parameter(0.0, true);
+}
+
+/**
+ * Function to evaluate 1D scattering function
+ * The NIST IGOR library is used for the actual calculation.
+ * @param q: q-value
+ * @return: function value
+ */
+double HollowCylinderModel :: operator()(double q) {
+	double dp[6];
+
+	dp[0] = scale();
+	dp[1] = core_radius();
+	dp[2] = shell_radius();
+	dp[3] = length();
+	dp[4] = contrast();
+	dp[5] = background();
+
+	// Get the dispersion points for the core radius
+	vector<WeightPoint> weights_core_radius;
+	core_radius.get_weights(weights_core_radius);
+
+	// Get the dispersion points for the shell radius
+	vector<WeightPoint> weights_shell_radius;
+	shell_radius.get_weights(weights_shell_radius);
+
+	// Get the dispersion points for the length
+	vector<WeightPoint> weights_length;
+	length.get_weights(weights_length);
+
+	// Perform the computation, with all weight points
+	double sum = 0.0;
+	double norm = 0.0;
+
+	// Loop over core radius weight points
+	for(int i=0; i< (int)weights_core_radius.size(); i++) {
+		dp[1] = weights_core_radius[i].value;
+
+		// Loop over length weight points
+		for(int j=0; j< (int)weights_length.size(); j++) {
+			dp[3] = weights_length[j].value;
+
+			// Loop over shell radius weight points
+			for(int k=0; k< (int)weights_shell_radius.size(); k++) {
+				dp[2] = weights_shell_radius[k].value;
+
+				sum += weights_core_radius[i].weight
+					* weights_length[j].weight
+					* weights_shell_radius[k].weight
+					* HollowCylinder(dp, q);
+				norm += weights_core_radius[i].weight
+				* weights_length[j].weight
+				* weights_shell_radius[k].weight;
+			}
+		}
+	}
+	return sum/norm + background();
+}
+
+/**
+ * Function to evaluate 2D scattering function
+ * @param q_x: value of Q along x
+ * @param q_y: value of Q along y
+ * @return: function value
+ */
+double HollowCylinderModel :: operator()(double qx, double qy) {
+	HollowCylinderParameters dp;
+	// Fill parameter array
+	dp.scale      = scale();
+	dp.core_radius     = core_radius();
+	dp.shell_radius  = shell_radius();
+	dp.length     = length();
+	dp.contrast   = contrast();
+	dp.background = background();
+	dp.axis_theta = axis_theta();
+	dp.axis_phi   = axis_phi();
+
+	// Get the dispersion points for the core radius
+	vector<WeightPoint> weights_core_radius;
+	core_radius.get_weights(weights_core_radius);
+
+	// Get the dispersion points for the shell radius
+	vector<WeightPoint> weights_shell_radius;
+	shell_radius.get_weights(weights_shell_radius);
+
+	// Get the dispersion points for the length
+	vector<WeightPoint> weights_length;
+	length.get_weights(weights_length);
+
+	// Get angular averaging for theta
+	vector<WeightPoint> weights_theta;
+	axis_theta.get_weights(weights_theta);
+
+	// Get angular averaging for phi
+	vector<WeightPoint> weights_phi;
+	axis_phi.get_weights(weights_phi);
+
+	// Perform the computation, with all weight points
+	double sum = 0.0;
+	double norm = 0.0;
+
+	// Loop over core radius weight points
+	for(int i=0; i<(int)weights_core_radius.size(); i++) {
+		dp.core_radius = weights_core_radius[i].value;
+
+
+		// Loop over length weight points
+		for(int j=0; j<(int)weights_length.size(); j++) {
+			dp.length = weights_length[j].value;
+
+			// Loop over shell radius weight points
+			for(int m=0; m< (int)weights_shell_radius.size(); m++) {
+				dp.shell_radius = weights_shell_radius[m].value;
+
+			// Average over theta distribution
+			for(int k=0; k< (int)weights_theta.size(); k++) {
+				dp.axis_theta = weights_theta[k].value;
+
+				// Average over phi distribution
+				for(int l=0; l< (int)weights_phi.size(); l++) {
+					dp.axis_phi = weights_phi[l].value;
+
+					double _ptvalue = weights_core_radius[i].weight
+						* weights_length[j].weight
+						* weights_shell_radius[m].weight
+						* weights_theta[k].weight
+						* weights_phi[l].weight
+						* hollow_cylinder_analytical_2DXY(&dp, qx, qy);
+					if (weights_theta.size()>1) {
+						_ptvalue *= sin(weights_theta[k].value);
+					}
+					sum += _ptvalue;
+
+					norm += weights_core_radius[i].weight
+						* weights_length[j].weight
+						* weights_shell_radius[m].weight
+						* weights_theta[k].weight
+						* weights_phi[l].weight;
+
+				}
+			}
+			}
+		}
+	}
+	// Averaging in theta needs an extra normalization
+	// factor to account for the sin(theta) term in the
+	// integration (see documentation).
+	if (weights_theta.size()>1) norm = norm / asin(1.0);
+	return sum/norm + background();
+}
+
+/**
+ * Function to evaluate 2D scattering function
+ * @param pars: parameters of the  cylinder
+ * @param q: q-value
+ * @param phi: angle phi
+ * @return: function value
+ */
+double HollowCylinderModel :: evaluate_rphi(double q, double phi) {
+	double qx = q*cos(phi);
+	double qy = q*sin(phi);
+	return (*this).operator()(qx, qy);
+}
Index: sansmodels/src/sans/models/c_models/models.hh
===================================================================
--- sansmodels/src/sans/models/c_models/models.hh	(revision 34c30203f24453aa528815f48e84a90b0bbd95be)
+++ sansmodels/src/sans/models/c_models/models.hh	(revision 27fea3fd73c362e927fb15e5806e0a587260c5f3)
@@ -463,4 +463,23 @@
 	double evaluate_rphi(double q, double phi);
 };
-
+class HollowCylinderModel{
+public:
+	// Model parameters
+	Parameter scale;
+	Parameter core_radius;
+	Parameter shell_radius;
+	Parameter length;
+	Parameter contrast;
+	Parameter background;
+	Parameter axis_theta;
+	Parameter axis_phi;
+	
+	//Constructor
+	HollowCylinderModel();
+	
+	//Operators to get I(Q)
+	double operator()(double q);
+	double operator()(double qx , double qy);
+	double evaluate_rphi(double q, double phi);
+};
 #endif
