diff --git a/demos/opengl/gpuhelper.cpp b/demos/opengl/gpuhelper.cpp
new file mode 100644
index 0000000..fd236b1
--- /dev/null
+++ b/demos/opengl/gpuhelper.cpp
@@ -0,0 +1,126 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include "gpuhelper.h"
+#include "icosphere.h"
+#include <GL/glu.h>
+// PLEASE don't look at this old code... ;)
+
+#include <fstream>
+#include <algorithm>
+
+GpuHelper gpu;
+
+GpuHelper::GpuHelper()
+{
+    mVpWidth = mVpHeight = 0;
+    mCurrentMatrixTarget = 0;
+    mInitialized = false;
+}
+
+GpuHelper::~GpuHelper()
+{
+}
+
+void GpuHelper::pushProjectionMode2D(ProjectionMode2D pm)
+{
+    // switch to 2D projection
+    pushMatrix(Matrix4f::Identity(),GL_PROJECTION);
+
+    if(pm==PM_Normalized)
+    {
+        //glOrtho(-1., 1., -1., 1., 0., 1.);
+    }
+    else if(pm==PM_Viewport)
+    {
+        GLint vp[4];
+        glGetIntegerv(GL_VIEWPORT, vp);
+        glOrtho(0., vp[2], 0., vp[3], -1., 1.);
+    }
+
+    pushMatrix(Matrix4f::Identity(),GL_MODELVIEW);
+}
+
+void GpuHelper::popProjectionMode2D(void)
+{
+    popMatrix(GL_PROJECTION);
+    popMatrix(GL_MODELVIEW);
+}
+
+void GpuHelper::drawVector(const Vector3f& position, const Vector3f& vec, const Color& color, float aspect /* = 50.*/)
+{
+    static GLUquadricObj *cylindre = gluNewQuadric();
+    glColor4fv(color.data());
+    float length = vec.norm();
+    pushMatrix(GL_MODELVIEW);
+    glTranslatef(position.x(), position.y(), position.z());
+    Vector3f ax = Matrix3f::Identity().col(2).cross(vec);
+    ax.normalize();
+    Vector3f tmp = vec;
+    tmp.normalize();
+    float angle = 180.f/M_PI * acos(tmp.z());
+    if (angle>1e-3)
+        glRotatef(angle, ax.x(), ax.y(), ax.z());
+    gluCylinder(cylindre, length/aspect, length/aspect, 0.8*length, 10, 10);
+    glTranslatef(0.0,0.0,0.8*length);
+    gluCylinder(cylindre, 2.0*length/aspect, 0.0, 0.2*length, 10, 10);
+
+    popMatrix(GL_MODELVIEW);
+}
+
+void GpuHelper::drawVectorBox(const Vector3f& position, const Vector3f& vec, const Color& color, float aspect)
+{
+    static GLUquadricObj *cylindre = gluNewQuadric();
+    glColor4fv(color.data());
+    float length = vec.norm();
+    pushMatrix(GL_MODELVIEW);
+    glTranslatef(position.x(), position.y(), position.z());
+    Vector3f ax = Matrix3f::Identity().col(2).cross(vec);
+    ax.normalize();
+    Vector3f tmp = vec;
+    tmp.normalize();
+    float angle = 180.f/M_PI * acos(tmp.z());
+    if (angle>1e-3)
+        glRotatef(angle, ax.x(), ax.y(), ax.z());
+    gluCylinder(cylindre, length/aspect, length/aspect, 0.8*length, 10, 10);
+    glTranslatef(0.0,0.0,0.8*length);
+    glScalef(4.0*length/aspect,4.0*length/aspect,4.0*length/aspect);
+    drawUnitCube();
+    popMatrix(GL_MODELVIEW);
+}
+
+void GpuHelper::drawUnitCube(void)
+{
+    static float vertices[][3] = {
+        {-0.5,-0.5,-0.5},
+        { 0.5,-0.5,-0.5},
+        {-0.5, 0.5,-0.5},
+        { 0.5, 0.5,-0.5},
+        {-0.5,-0.5, 0.5},
+        { 0.5,-0.5, 0.5},
+        {-0.5, 0.5, 0.5},
+        { 0.5, 0.5, 0.5}};
+
+    glBegin(GL_QUADS);
+    glNormal3f(0,0,-1); glVertex3fv(vertices[0]); glVertex3fv(vertices[2]); glVertex3fv(vertices[3]); glVertex3fv(vertices[1]);
+    glNormal3f(0,0, 1); glVertex3fv(vertices[4]); glVertex3fv(vertices[5]); glVertex3fv(vertices[7]); glVertex3fv(vertices[6]);
+    glNormal3f(0,-1,0); glVertex3fv(vertices[0]); glVertex3fv(vertices[1]); glVertex3fv(vertices[5]); glVertex3fv(vertices[4]);
+    glNormal3f(0, 1,0); glVertex3fv(vertices[2]); glVertex3fv(vertices[6]); glVertex3fv(vertices[7]); glVertex3fv(vertices[3]);
+    glNormal3f(-1,0,0); glVertex3fv(vertices[0]); glVertex3fv(vertices[4]); glVertex3fv(vertices[6]); glVertex3fv(vertices[2]);
+    glNormal3f( 1,0,0); glVertex3fv(vertices[1]); glVertex3fv(vertices[3]); glVertex3fv(vertices[7]); glVertex3fv(vertices[5]);
+    glEnd();
+}
+
+void GpuHelper::drawUnitSphere(int level)
+{
+  static IcoSphere sphere;
+  sphere.draw(level);
+}
+
+