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+====== Coordinates for Polyhedra ======
+=== This page explains how the coordinates for objects of type Polytope<Coord> in application polytope work. ===
+Each polyhedron can be written as the Minkowski sum of a convex polytope (spanned by points $a, b, c,...$) and a cone (generated by the rays $r, s, t,...$). If the polyhedron is bounded, i.e. it is a polytope, then the cone is empty.
+Suppose our polyhedron lives in a $d$-space $V$.
+In order to obtain a unified view on the polytope and the cone section of a polyhedron, we embed $V$ as an affine subspace of a $(d+1)$-space $W$ such that the image of $V$ contains the point $(1,0,0,...,0)$ and it is parallel to the subspace spanned by the last $d$ unit vectors.
+Points from both sections can now be identified with infinite rays through the origin in $W$. Facets are identified with the a hyperplane containing the image of the facet in $V$ and the origin in $W$. This hyperplane is represented by a normal vector.
+Note that a facet defining hyperplane is not uniquely determined if the polyhedron is not full-dimensional.
+<html><img src="/lib/exe/fetch.php?media=tutorials/release/4.11/coordinates/coord.gif" style="float: right" width=326></html><html><img></html>
+A vertex is incident with a facet if and only if the scalar product of their representatives in $W$ is zero.
+The polytope point $a=(ay,az)$ is modelled as the infinite ray from the origin $(0,0,0)$ through the point $(1,ay,az)$, i.e. the set of all non-negative multiples of $(1,ay,az)$. The cone point $r=(ry,rz)$ becomes the ray through $(0,ry,rz)$.
+The facet containing the points $a$ and $c$ is represented by an (oriented) normal vector of the (hyper-)plane spanned by $a$, $c$, and the origin. If $d=2$, as in the picture, the normal vector can be computed as the cross product of $a$ and $c$. The normal vector will be oriented such that it points towards the interior of the polyhedron.
+According to this model two points in $W$ are identical to polymake if they differ by a positive multiple. In particular, for a polytope point in the input data it is not required that the first coordinate is //1//; it just has to be some positive number.
+Notice, that //by definition// the combinatorics (encoded as ''%%VERTICES_IN_FACETS%%'') of an arbitrary polyhedron is the combinatorics of a polytope which is projectively equivalent to quotient of the orginal polyhedron modulo its lineality space.
+===== An example =====
+The following defines the positive orthant in 3-space. It has only one vertex, the origin, and three rays pointing into the three coordinate directions. The distinction between these comes from our choice of the homogenizing coordinate.
+<code perl>
+> $p=new Polytope(POINTS=>[[1,0,0,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]]);
+</code>
+This lists the facet coordinates.
+<code perl>
+> print $p->FACETS;
+0 0 0
+1 0 0
+0 1 0
+0 0 1
+</code>
+Each line describes one linear inequality. The encoding is as follows: $(a_0,a_1,...,a_d)$ is the inequality $a_0 + a_1 x_1 + ... + a_d x_d \ge 0$. This way a point in (oriented) homogeneous coordinates satisfies an inequality if and only if the scalar product of the point with the inequality gives a non-negative value. (Use the command ''%%print_constraints($m)%%'' to display the inequalities of the matrix ''%%$m%%'' in a nice way.)
+Clearly, the polyhedron is unbounded.
+<code perl>
+> print $p->BOUNDED;
+false
+</code>
+Yet, the combinatorial data describe a 3-simplex.
+<code perl>
+> print $p->VERTICES_IN_FACETS;
+{1 2 3}
+{0 2 3}
+{0 1 3}
+{0 1 2}
+</code>
+The rays span the //face at infinity//.
+<code perl>
+> print $p->FAR_FACE;
+{1 2 3}
+</code>
+By the way, unbounded polyhedra can be visualized just like bounded ones. ''%%polymake%%'' automatically chooses a bounding box.
+<code perl>
+> $p->VISUAL;
+</code>
+<HTML>
+<!--
+polymake for knusper
+Thu Mar  3 00:30:06 2022
+p_bounded
+-->
+<html>
+   <head>
+      <meta charset=utf-8>
+      <title>p_bounded</title>
+      <style>
+/*
+// COMMON_CODE_BLOCK_BEGIN
+*/
+         html {overflow: scroll;}
+         strong{font-size: 18px;}
+         canvas { z-index: 8; }
+         input[type='radio'] {margin-left:0;}
+         input[type='checkbox'] {margin-right:7px; margin-left: 0px; padding-left:0px;}
+         .group{padding-bottom: 15px;}
+         .settings * {z-index: 11; }
+         .settings{z-index: 10; font-family: Arial, Helvetica, sans-serif; margin-left: 30px; visibility: hidden; width: 14em; height: 96%; border: solid 1px silver; padding: 2px; overflow-y: scroll; box-sizing: border-box; background-color: white; position: absolute;}
+         .indented{margin-left: 20px; margin-top: 10px; padding-bottom: 0px;}
+         .shownObjectsList{overflow: auto; max-width: 150px; max-height: 150px;}
+         .showSettingsButton{visibility: visible; z-index: 12; position: absolute }
+         .hideSettingsButton{visibility: hidden; z-index: 12; position: absolute; opacity: 0.5}
+         button{margin-left: 0; margin-top: 10px}
+         img{cursor: pointer;}
+         .suboption{padding-top: 15px;}
+         #model31762941772 { width: 100%; height: 100%; }
+         .threejs_container { width: 100%; height: 75vh;}
+         .settings{max-height: 74vh}
+         input[type=range] {
+           -webkit-appearance: none;
+           padding:0;
+           width:90%;
+           margin-left: auto;
+           margin-right: auto;
+           margin-top: 15px;
+           margin-bottom: 15px;
+           display: block;
+         }
+         input[type=range]:focus {
+           outline: none;
+         }
+         input[type=range]::-webkit-slider-runnable-track {
+           height: 4px;
+           cursor: pointer;
+           animate: 0.2s;
+           box-shadow: 0px 0px 0px #000000;
+           background: #E3E3E3;
+           border-radius: 0px;
+           border: 0px solid #000000;
+         }
+         input[type=range]::-webkit-slider-thumb {
+           box-shadow: 1px 1px 2px #B8B8B8;
+           border: 1px solid #ABABAB;
+           height: 13px;
+           width: 25px;
+           border-radius: 20px;
+           background: #E0E0E0;
+           cursor: pointer;
+           -webkit-appearance: none;
+           margin-top: -5px;
+         }
+         input[type=range]:focus::-webkit-slider-runnable-track {
+           background: #E3E3E3;
+         }
+         input[type=range]::-moz-range-track {
+           height: 4px;
+           cursor: pointer;
+           animate: 0.2s;
+           box-shadow: 0px 0px 0px #000000;
+           background: #E3E3E3;
+           border-radius: 0px;
+           border: 0px solid #000000;
+         }
+         input[type=range]::-moz-range-thumb {
+           box-shadow: 1px 1px 2px #B8B8B8;
+           border: 1px solid #ABABAB;
+           height: 13px;
+           width: 25px;
+           border-radius: 20px;
+           background: #E0E0E0;
+           cursor: pointer;
+         }
+         input[type=range]::-ms-track {
+           height: 4px;
+           cursor: pointer;
+           animate: 0.2s;
+           background: transparent;
+           border-color: transparent;
+           color: transparent;
+         }
+         input[type=range]::-ms-fill-lower {
+           background: #E3E3E3;
+           border: 0px solid #000000;
+           border-radius: 0px;
+           box-shadow: 0px 0px 0px #000000;
+         }
+         input[type=range]::-ms-fill-upper {
+           background: #E3E3E3;
+           border: 0px solid #000000;
+           border-radius: 0px;
+           box-shadow: 0px 0px 0px #000000;
+         }
+         input[type=range]::-ms-thumb {
+           box-shadow: 1px 1px 2px #B8B8B8;
+           border: 1px solid #ABABAB;
+           height: 13px;
+           width: 25px;
+           border-radius: 20px;
+           background: #E0E0E0;
+           cursor: pointer;
+         }
+         input[type=range]:focus::-ms-fill-lower {
+           background: #E3E3E3;
+         }
+         input[type=range]:focus::-ms-fill-upper {
+           background: #E3E3E3;
+         }
+/*
+// COMMON_CODE_BLOCK_END
+*/
+		</style>
+   </head>
+<body>
+   <div class='threejs_container'>
+		<div id='settings_0' class='settings'>
+			<div class=group id='transparency_0' class='transparency'>
+				<strong>Transparency</strong>
+				<input id='transparencyRange_0' type='range' min=0 max=1 step=0.01 value=0>
+            <div class=indented><input id='depthWriteCheckbox_0' type='checkbox'>depthWrite</div>
+			</div>
+			<div class=group id='rotation_0'>
+				<strong>Rotation</strong>
+				<div class=indented>
+					<div><input type='checkbox' id='changeRotationX_0'> x-axis</div>
+					<div><input type='checkbox' id='changeRotationY_0'> y-axis</div>
+					<div><input type='checkbox' id='changeRotationZ_0'> z-axis</div>
+					<button id='resetButton_0'>Reset</button>
+				</div>
+				<div class=suboption>Rotation speed</div>
+				<input id='rotationSpeedRange_0' type='range' min=0 max=5 step=0.01 value=2>
+			</div>
+			<div class=group id='display_0'>
+				<strong>Display</strong>
+				<div class=indented>
+					<div id='shownObjectTypesList_0' class='shownObjectsList'></div>
+				</div>
+				<div class=suboption>Objects</div>
+				<div class=indented>
+				   <div id='shownObjectsList_0' class='shownObjectsList'></div>
+				</div>
+			</div>
+         <div class=group id='camera_0'>
+            <strong>Camera</strong>
+            <div class=indented>
+               <form>
+                  <select id="cameraType_0">
+                     <option value='perspective' selected> Perspective<br></option>
+                     <option value='orthographic' > Orthographic<br></option>
+                  </select>
+               </form>
+            </div>
+         </div>
+			<div class=group id='svg_0'>
+				<strong>SVG</strong>
+				<div class=indented>
+					<form>
+						<input type="radio" name='screenshotMode' value='download' id='download_0' checked> Download<br>
+						<input type="radio" name='screenshotMode' value='tab' id='tab_0' > New tab<br>
+					</form>
+					<button id='takeScreenshot_0'>Screenshot</button>
+				</div>
+			</div>
+		</div>	<!-- end of settings -->
+		<img id='hideSettingsButton_0' class='hideSettingsButton' src='/kernelspecs/r118/polymake/close.svg' width=20px">
+		<img id='showSettingsButton_0' class='showSettingsButton' src='/kernelspecs/r118/polymake/menu.svg' width=20px">
+<div id="model31762941772"></div>
+</div>
+   <script>
+    requirejs.config({
+      paths: {
+        three: '/kernelspecs/r118/polymake/three',
+        TrackballControls: '/kernelspecs/r118/polymake/TrackballControls',
+        OrbitControls: '/kernelspecs/r118/polymake/OrbitControls',
+        Projector: '/kernelspecs/r118/polymake/Projector',
+        SVGRenderer: '/kernelspecs/r118/polymake/SVGRenderer',
+        WEBGL: '/kernelspecs/r118/polymake/WebGL',
+      },
+      shim: {
+        'three': { exports: 'THREE'},
+        'SVGRenderer': { deps: [ 'three' ], exports: 'THREE.SVGRenderer' },
+        'WEBGL': { deps: [ 'three' ], exports: 'THREE.WEBGL' },
+        'Projector': { deps: [ 'three' ], exports: 'THREE.Projector' },
+        'TrackballControls': { deps: [ 'three' ], exports: 'THREE.TrackballControls' },
+        'OrbitControls': { deps: [ 'three' ], exports: 'THREE.OrbitControls' },
+      }
+    });
+    require(['three'],function(THREE){
+        window.THREE = THREE;
+      require(['TrackballControls', 'OrbitControls', 'Projector', 'SVGRenderer', 'WEBGL'],
+               function(TrackballControls, OrbitControls, Projector, SVGRenderer, WEBGL) {
+    THREE.TrackballControls = TrackballControls;
+    THREE.OrbitControls = OrbitControls;
+    THREE.Projector = Projector;
+    THREE.SVGRenderer = SVGRenderer;
+    THREE.WEBGL = WEBGL;
+// COMMON_CODE_BLOCK_BEGIN
+const intervalLength = 25; // for automatic animations
+const explodableModel = false;
+const modelContains = { points: false, pointlabels: false, lines: false, edgelabels: false, faces: false, arrowheads: false };
+const foldables = [];
+var three = document.getElementById("model31762941772");
+var scene = new THREE.Scene();
+var renderer = new THREE.WebGLRenderer( { antialias: true } );
+var svgRenderer = new THREE.SVGRenderer( { antialias: true } );
+renderer.setPixelRatio( window.devicePixelRatio );
+renderer.setClearColor(0xFFFFFF, 1);
+svgRenderer.setClearColor(0xFFFFFF, 1);
+three.appendChild(renderer.domElement);
+var frustumSize = 4;
+var cameras = [new THREE.PerspectiveCamera(75, 1, 0.1, 1000), new THREE.OrthographicCamera()];
+cameras.forEach(function(cam) {
+    cam.position.set(0, 0, 5);
+    cam.lookAt(0, 0, 0);
+    cam.up.set(0, 1, 0);
+});
+var controls = [new THREE.TrackballControls(cameras[0], three), new THREE.OrbitControls(cameras[1], three)];
+var camera, control;
+controls[0].zoomSpeed = 0.2;
+controls[0].rotateSpeed = 4;
+// class to allow move points together with labels and spheres
+var PMPoint = function (x,y,z) {
+   this.vector = new THREE.Vector3(x,y,z);
+   this.sprite = null;
+   this.sphere = null;
+}
+PMPoint.prototype.addLabel = function(labelsprite) {
+   this.sprite = labelsprite;
+   this.sprite.position.copy(this.vector);
+}
+PMPoint.prototype.addSphere = function(spheremesh) {
+   this.sphere = spheremesh;
+   this.sphere.position.copy(this.vector);
+}
+PMPoint.prototype.set = function(x,y,z) {
+   this.vector.set(x,y,z);
+   if (this.sprite) {
+      this.sprite.position.copy(this.vector);
+   }
+   if (this.sphere) {
+      this.sphere.position.copy(this.vector);
+   }
+}
+PMPoint.prototype.radius = function() {
+   if (this.sphere) {
+      return this.sphere.geometry.parameters.radius;
+   } else {
+      return 0;
+   }
+};
+// select the target node
+var target = document.querySelector('#model31762941772');
+// create an observer instance
+var observer = new MutationObserver(function(mutations) {
+   mutations.forEach(function(mutation) {
+      if (mutation.removedNodes && mutation.removedNodes.length > 0) {
+         cancelAnimationFrame(renderId);
+         observer.disconnect();
+         console.log("cancelled frame "+renderId);
+      }
+   });
+});
+// configuration of the observer:
+var config = { childList: true, characterData: true }
+// pass in the target node, as well as the observer options
+while (target) {
+   if (target.className=="output") {
+      observer.observe(target, config);
+      break;
+   }
+   target = target.parentNode;
+}
+// COMMON_CODE_BLOCK_END
+var obj0 = new THREE.Object3D();
+obj0.name = "p_bounded";
+obj0.userData.explodable = 1;
+obj0.userData.points = [];
+obj0.userData.points.push(new PMPoint(1, 1, 0));
+obj0.userData.points.push(new PMPoint(0, 1, 0));
+obj0.userData.points.push(new PMPoint(0, 0, 0));
+obj0.userData.points.push(new PMPoint(1, 0, 0));
+obj0.userData.points.push(new PMPoint(0, 0, 1));
+obj0.userData.points.push(new PMPoint(1, 0, 1));
+obj0.userData.points.push(new PMPoint(0, 1, 1));
+obj0.userData.points.push(new PMPoint(1, 1, 1));
+obj0.userData.pointradii = [0, 0, 0.02, 0, 0, 0, 0, 0];
+   <!-- Vertex style -->
+obj0.userData.pointmaterial = new THREE.MeshBasicMaterial( { color: 0xFF0000, side: THREE.DoubleSide, transparent: false } );
+obj0.userData.pointlabels = [" ", " ", "0", " ", " ", " ", " ", " "];
+obj0.userData.edgeindices = [0, 1, 1, 2, 0, 3, 2, 3, 2, 4, 3, 5, 4, 5, 1, 6, 4, 6, 0, 7, 5, 7, 6, 7];
+   <!-- Edge style -->
+obj0.userData.edgematerial = new THREE.LineBasicMaterial( { color: 0x000000, linewidth: 1.5, transparent: false } );
+obj0.userData.facets = [[2, 4, 6, 1], [5, 4, 2, 3], [2, 1, 0, 3], [7, 5, 3, 0], [1, 6, 7, 0], [6, 4, 5, 7]];
+   <!-- Facet style -->
+obj0.userData.facetmaterial = [new THREE.MeshBasicMaterial( { color: 0x77EC9E, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } ),
+new THREE.MeshBasicMaterial( { color: 0x77EC9E, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } ),
+new THREE.MeshBasicMaterial( { color: 0x77EC9E, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } ),
+new THREE.MeshBasicMaterial( { color: 0xFF0000, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } ),
+new THREE.MeshBasicMaterial( { color: 0xFF0000, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } ),
+new THREE.MeshBasicMaterial( { color: 0xFF0000, depthFunc: THREE.LessDepth, depthWrite: false, opacity: 1, polygonOffset: true, polygonOffsetFactor: 1, polygonOffsetUnits: 0.5, side: THREE.DoubleSide, transparent: true } )];
+init_object(obj0);
+scene.add(obj0);
+// COMMON_CODE_BLOCK_BEGIN
+function textSpriteMaterial(message, parameters) {
+    if ( parameters === undefined ) parameters = {};
+    var fontface = "Helvetica";
+    var fontsize = parameters.hasOwnProperty("fontsize") ? parameters["fontsize"] : 15;
+    fontsize = fontsize*10;
+    var lines = message.split('\\n');
+    var size = 512;
+    for(var i = 0; i<lines.length; i++){
+        var tmp = lines[i].length;
+        while(tmp*fontsize > size){
+           fontsize--;
+        }
+    }
+    var canvas = document.createElement('canvas');
+    canvas.width = size;
+    canvas.height = size;
+    var context = canvas.getContext('2d');
+    context.fillStyle = "rgba(255, 255, 255, 0)";
+    context.fill();
+    context.font = fontsize + "px " + fontface;
+    // text color
+    context.fillStyle = "rgba(0, 0, 0, 1.0)";
+     for(var i = 0; i<lines.length; i++){
+        context.fillText(lines[i], size/2, size/2+i*fontsize);
+     }
+    // canvas contents will be used for a texture
+    var texture = new THREE.Texture(canvas);
+    texture.needsUpdate = true;
+    var spriteMaterial = new THREE.SpriteMaterial({map: texture, depthTest: true, depthWrite: false, polygonOffset: true, polygonOffsetFactor: -1, polygonOffsetUnits: 1 });
+    return spriteMaterial;
+}
+// ---------------------- INITIALIZING OBJECTS--------------------------------------
+// ---------------------------------------------------------------------------------
+function init_object(obj) {
+    if (obj.userData.hasOwnProperty("pointmaterial")) {
+        init_points(obj);
+        modelContains.points = true;
+    }
+    if (obj.userData.hasOwnProperty("pointlabels")) {
+        init_pointlabels(obj);
+        modelContains.pointlabels = true;
+    }
+    if (obj.userData.hasOwnProperty("edgematerial")) {
+        init_lines(obj);
+        modelContains.lines = true;
+    }
+    if (obj.userData.hasOwnProperty("edgelabels")) {
+        init_edgelabels(obj);
+        modelContains.edgelabels = true;
+    }
+    if (obj.userData.hasOwnProperty("arrowstyle")) {
+        init_arrowheads(obj);
+        modelContains.arrowheads = true;
+    }
+    if (obj.userData.hasOwnProperty("facetmaterial")) {
+        init_faces(obj);
+        modelContains.faces = true;
+    }
+}
+function init_points(obj) {
+    var pointgroup = new THREE.Group();
+    pointgroup.name = "points";
+    var points = obj.userData.points;
+    var radii = obj.userData.pointradii;
+    var materials = obj.userData.pointmaterial;
+    var geometry,material;
+    if (!Array.isArray(radii)) {
+        geometry = new THREE.SphereBufferGeometry(radii);
+    }
+    if (!Array.isArray(materials)) {
+        material = materials;
+    }
+    for (var i=0; i<points.length; i++) {
+        var point = points[i];
+        if (Array.isArray(radii)) {
+            if (radii[i] == 0) {
+                continue;
+            }
+            geometry = new THREE.SphereBufferGeometry(radii[i]);
+        }
+        if (Array.isArray(materials)) {
+            material = materials[i];
+        }
+        var sphere = new THREE.Mesh(geometry, material);
+        point.addSphere(sphere);
+        pointgroup.add(sphere);
+    }
+    obj.add(pointgroup);
+}
+function init_pointlabels(obj) {
+    var points = obj.userData.points;
+    var labels = obj.userData.pointlabels;
+    var pointlabels = new THREE.Group();
+    pointlabels.name = "pointlabels";
+    if (Array.isArray(labels)) {
+        for (var i=0; i<points.length; i++) {
+            var point = points[i];
+            var spriteMaterial = textSpriteMaterial( labels[i] );
+	        var sprite = new THREE.Sprite(spriteMaterial);
+            point.addLabel(sprite);
+            pointlabels.add(sprite);
+        }
+    } else {
+        var spriteMaterial = textSpriteMaterial( labels );
+        for (var i=0; i<points.length; i++) {
+            var point = points[i];
+	        var sprite = new THREE.Sprite(spriteMaterial);
+            point.addLabel(sprite);
+            pointlabels.add(sprite);
+        }
+    }
+    obj.add(pointlabels);
+}
+function init_lines(obj) {
+    var edgeindices = obj.userData.edgeindices;
+    var points = obj.userData.points;
+    var materials = obj.userData.edgematerial;
+    var geometry = new THREE.BufferGeometry();
+    var bufarr = new Float32Array( obj.userData.edgeindices.length * 3 );
+    var bufattr = new THREE.Float32BufferAttribute( bufarr, 3 );
+    var geometry = new THREE.BufferGeometry();
+    geometry.setAttribute('position', bufattr);
+    if (Array.isArray(materials)) {
+        for (var i=0; i<materials.length; i++) {
+            geometry.addGroup(2*i,2,i);
+        }
+    }
+    var lines = new THREE.LineSegments(geometry, materials);
+    lines.name = "lines";
+    obj.add(lines);
+    updateEdgesPosition(obj);
+}
+function init_edgelabels(obj) {
+    var points = obj.userData.points;
+    var edgeindices = obj.userData.edgeindices;
+    var labels = obj.userData.edgelabels;
+    var edgelabels = new THREE.Group();
+    edgelabels.name = "edgelabels";
+    if (Array.isArray(labels)) {
+        for (var i=0; i<edgeindices.length/2; i++) {
+            var spriteMaterial = textSpriteMaterial( labels[i] );
+            var sprite = new THREE.Sprite(spriteMaterial);
+            sprite.position.copy(new THREE.Vector3().addVectors(points[edgeindices[2*i]].vector,points[edgeindices[2*i+1]].vector).multiplyScalar(0.5));
+            edgelabels.add(sprite);
+        }
+    } else {
+        var spriteMaterial = textSpriteMaterial( labels );
+        for (var i=0; i<edgeindices.length/2; i++) {
+            var sprite = new THREE.Sprite(spriteMaterial);
+            sprite.position.copy(new THREE.Vector3().addVectors(points[edgeindices[2*i]].vector,points[edgeindices[2*i+1]].vector).multiplyScalar(0.5));
+            edgelabels.add(sprite);
+        }
+    }
+    obj.add(edgelabels);
+}
+function init_arrowheads(obj) {
+    var arrowheads = new THREE.Group();
+    arrowheads.name = "arrowheads";
+    var arrowstyle = obj.userData.arrowstyle;
+    var edgeindices = obj.userData.edgeindices;
+    var edgematerials = obj.userData.edgematerial;
+    var points = obj.userData.points;
+    var material;
+    if (!Array.isArray(edgematerials)) {
+        material = new THREE.MeshBasicMaterial( {color: edgematerials.color} );
+    }
+    for (var i=0; i<edgeindices.length; i=i+2) {
+        var start = points[edgeindices[i]];
+        var end = points[edgeindices[i+1]];
+        var dist = start.vector.distanceTo( end.vector ) - start.radius() - end.radius();
+        if (dist <= 0) {
+            continue;
+        }
+        var dir = new THREE.Vector3().subVectors(end.vector,start.vector);
+        dir.normalize();
+        var axis = new THREE.Vector3().set(dir.z,0,-dir.x);
+        axis.normalize();
+        var radians = Math.acos( dir.y );
+        var radius = dist/25;
+        var height = dist/5;
+        var geometry = new THREE.ConeBufferGeometry(radius,height);
+        var position = new THREE.Vector3().addVectors(start.vector,dir.clone().multiplyScalar(start.radius()+dist-height/2));
+        if (Array.isArray(edgematerials)) {
+            material = new THREE.MeshBasicMaterial( {color: edgematerials[i].color} );
+        }
+        var cone = new THREE.Mesh( geometry, material );
+        cone.quaternion.setFromAxisAngle(axis,radians);;
+        cone.position.copy(position);;
+        arrowheads.add(cone);
+    }
+    obj.add(arrowheads);
+}
+function init_faces(obj) {
+    var points = obj.userData.points;
+    var facets = obj.userData.facets;
+    obj.userData.triangleindices = [];
+    for (var i=0; i<facets.length; i++) {
+        facet = facets[i];
+        for (var t=0; t<facet.length-2; t++) {
+            obj.userData.triangleindices.push(facet[0],facet[t+1],facet[t+2]);
+        }
+    }
+    var bufarr = new Float32Array( obj.userData.triangleindices.length * 3 );
+    var bufattr = new THREE.Float32BufferAttribute(bufarr,3);
+    var materials = obj.userData.facetmaterial;
+    var geometry = new THREE.BufferGeometry();
+    var frontmaterials = [];
+    var backmaterials = [];
+    geometry.setAttribute('position',bufattr);
+    if (Array.isArray(materials)) {
+        var tricount = 0;
+        var facet;
+        for (var i=0; i<facets.length; i++) {
+            facet = facets[i];
+            geometry.addGroup(tricount,(facet.length-2)*3,i);
+            tricount += (facet.length-2)*3;
+        }
+        for (var j=0; j<materials.length; j++) {
+            var fmat = materials[j].clone()
+            fmat.side = THREE.FrontSide;
+            frontmaterials.push(fmat);
+            var bmat = materials[j].clone()
+            bmat.side = THREE.BackSide;
+            backmaterials.push(bmat);
+            obj.userData.facetmaterial = frontmaterials.concat(backmaterials);
+        }
+    } else if (materials instanceof THREE.Material) {
+        frontmaterials = materials.clone()
+        frontmaterials.side = THREE.FrontSide;
+        backmaterials = materials.clone()
+        backmaterials.side = THREE.BackSide;
+        obj.userData.facetmaterial = [frontmaterials, backmaterials];
+    }
+    // duplicating the object with front and back should avoid transparency issues
+    var backmesh = new THREE.Mesh(geometry, backmaterials);
+    // meshname is used to show/hide objects
+    backmesh.name = "backfaces";
+    obj.add(backmesh);
+    var frontmesh = new THREE.Mesh(geometry, frontmaterials);
+    frontmesh.name = "frontfaces";
+    obj.add(frontmesh);
+    updateFacesPosition(obj);
+}
+// //INITIALIZING
+function updateFacesPosition(obj) {
+    var points = obj.userData.points;
+    var indices = obj.userData.triangleindices;
+    var faces = obj.getObjectByName("frontfaces");
+    var ba = faces.geometry.getAttribute("position");
+    for (var i=0; i<indices.length; i++) {
+        ba.setXYZ(i, points[indices[i]].vector.x, points[indices[i]].vector.y ,points[indices[i]].vector.z);
+    }
+    faces.geometry.attributes.position.needsUpdate = true;
+}
+function updateEdgesPosition(obj) {
+    var points = obj.userData.points;
+    var indices = obj.userData.edgeindices;
+    var lines = obj.getObjectByName("lines");
+    var ba = lines.geometry.getAttribute("position");
+    for (var i=0; i<indices.length; i++) {
+        ba.setXYZ(i, points[indices[i]].vector.x, points[indices[i]].vector.y ,points[indices[i]].vector.z);
+    }
+    lines.geometry.attributes.position.needsUpdate = true;
+}
+function onWindowResize() {
+    renderer.setSize( three.clientWidth, three.clientHeight );
+    svgRenderer.setSize( three.clientWidth, three.clientHeight );
+    updateCamera();
+}
+function updateCamera() {
+    var width = three.clientWidth;
+    var height = three.clientHeight;
+    var aspect = width / height;
+    if (camera.type == "OrthographicCamera") {
+        camera.left = frustumSize * aspect / - 2;
+        camera.right = frustumSize * aspect / 2;
+        camera.top = frustumSize / 2;
+        camera.bottom = - frustumSize / 2;
+    } else if (camera.type == "PerspectiveCamera") {
+        camera.aspect = aspect;
+    }
+    camera.updateProjectionMatrix();
+}
+function changeCamera(event) {
+    var selindex = event.currentTarget.selectedIndex;
+    camera = cameras[selindex];
+    control = controls[selindex];
+    control.enabled = true;
+    for (var i=0; i<controls.length; i++) {
+        if (i!=selindex) {
+            controls[i].enabled = false;
+        }
+    }
+    updateCamera();
+}
+var camtypenode = document.getElementById('cameraType_0');
+camtypenode.onchange = changeCamera;
+camtypenode.dispatchEvent(new Event('change'));
+onWindowResize();
+window.addEventListener('resize', onWindowResize);
+var xRotationEnabled = false;
+var yRotationEnabled = false;
+var zRotationEnabled = false;
+var rotationSpeedFactor = 1;
+var settingsShown = false;
+var labelsShown = true;
+var intervals = [];
+var timeouts = [];
+var explodingSpeed = 0.05;
+var explodeScale = 0.000001;
+var XMLS = new XMLSerializer();
+var svgElement;
+var renderId;
+var render = function () {
+	renderId = requestAnimationFrame(render);
+//	comment in for automatic explosion
+//	explode(updateFactor());
+    var phi = 0.02 * rotationSpeedFactor;
+    if (xRotationEnabled) {
+        scene.rotation.x += phi;
+    }
+    if (yRotationEnabled) {
+        scene.rotation.y += phi;
+    }
+    if (zRotationEnabled) {
+        scene.rotation.z += phi;
+    }
+    control.update();
+    renderer.render(scene, camera);
+};
+if ( THREE.WEBGL.isWebGLAvailable() ) {
+	render();
+} else {
+	var warning = WEBGL.getWebGLErrorMessage();
+	three.appendChild( warning );
+}
+function changeTransparency() {
+    var opacity = 1-Number(event.currentTarget.value);
+    for (var i=0; i<scene.children.length; i++) {
+        child = scene.children[i];
+        if ( child.userData.hasOwnProperty("facetmaterial") ) {
+            if (Array.isArray(child.userData.facetmaterial)) {
+                for (var j=0; j<child.userData.facetmaterial.length; j++) {
+                    child.userData.facetmaterial[j].opacity = opacity;
+                }
+            } else {
+                child.userData.facetmaterial.opacity = opacity;
+            }
+        }
+    }
+}
+function toggleDepthWrite(event) {
+    depthwrite = event.currentTarget.checked;
+    for (var i=0; i<scene.children.length; i++) {
+        child = scene.children[i];
+        if ( child.userData.hasOwnProperty("facetmaterial") ) {
+            if (Array.isArray(child.userData.facetmaterial)) {
+                for (var j=0; j<child.userData.facetmaterial.length; j++) {
+                    child.userData.facetmaterial[j].depthWrite = depthwrite;
+                }
+            } else {
+                child.userData.facetmaterial.depthWrite = depthWrite;
+            }
+        }
+    }
+}
+function changeRotationX(event){
+    xRotationEnabled = event.currentTarget.checked;
+}
+function changeRotationY(event){
+    yRotationEnabled = event.currentTarget.checked;
+}
+function changeRotationZ(event){
+    zRotationEnabled = event.currentTarget.checked;
+}
+function changeRotationSpeedFactor(event){
+    rotationSpeedFactor = Number(event.currentTarget.value);
+}
+function resetScene(){
+    scene.rotation.set(0,0,0);
+    camera.position.set(0,0,5);
+    camera.up.set(0,1,0);
+}
+function showSettings(event){
+    document.getElementById('settings_0').style.visibility = 'visible';
+    document.getElementById('showSettingsButton_0').style.visibility = 'hidden';
+    document.getElementById('hideSettingsButton_0').style.visibility = 'visible';
+    settingsShown = true;
+}
+function hideSettings(event){
+    document.getElementById('settings_0').style.visibility = 'hidden';
+    document.getElementById('showSettingsButton_0').style.visibility = 'visible';
+    document.getElementById('hideSettingsButton_0').style.visibility = 'hidden';
+    settingsShown = false;
+}
+var pos = 150* Math.PI;
+function updateFactor() {
+    pos++;
+    return Math.sin(.01*pos)+1;
+}
+// ------------------------ FOLDING ------------------------------------------------
+// ---------------------------------------------------------------------------------
+// rotate point p around axis defined by points p1 and p2 by given angle
+function rotate(p, p1, p2, angle ){
+    angle = -angle;
+    var x = p.x, y = p.y, z = p.z,
+    a = p1.x, b = p1.y, c = p1.z,
+    u = p2.x-p1.x, v = p2.y-p1.y, w = p2.z-p1.z;
+    var result = [];
+    var L = u*u + v*v + w*w;
+    var sqrt = Math.sqrt;
+    var cos = Math.cos;
+    var sin = Math.sin;
+    result[0] = ((a*(v*v+w*w)-u*(b*v+c*w-u*x-v*y-w*z))*(1-cos(angle))+L*x*cos(angle)+sqrt(L)*(-c*v+b*w-w*y+v*z)*sin(angle))/L;
+    result[1] = ((b*(u*u+w*w)-v*(a*u+c*w-u*x-v*y-w*z))*(1-cos(angle))+L*y*cos(angle)+sqrt(L)*(c*u-a*w+w*x-u*z)*sin(angle))/L;
+    result[2] = ((c*(u*u+v*v)-w*(a*u+b*v-u*x-v*y-w*z))*(1-cos(angle))+L*z*cos(angle)+sqrt(L)*(-b*u+a*v-v*x+u*y)*sin(angle))/L;
+    return result;
+}
+var fold = function(event){
+    var obj = foldables[Number(event.currentTarget.name)];
+    var foldvalue = Number(event.currentTarget.value);
+    var scale = foldvalue - obj.userData.oldscale;
+    for (var j=0; j<obj.userData.axes.length; j++) {
+        rotateVertices(obj, j, scale);
+    }
+    update(obj);
+    obj.userData.oldscale += scale;
+    lookAtBarycenter(obj);
+}
+function lookAtBarycenter(obj){
+    control.target = barycenter(obj);
+}
+function barycenter(obj) {
+    var center = new THREE.Vector3(0,0,0);
+    var points = obj.userData.points;
+    for (var i=0; i<points.length; i++){
+        center.add(points[i].vector);
+    }
+    center.divideScalar(points.length);
+    return center;
+}
+function rotateVertices(obj, edge, scale) {
+    var axes = obj.userData.axes;
+    var subtrees = obj.userData.subtrees;
+    var points = obj.userData.points;
+    var angles = obj.userData.angles;
+    if (edge < axes.length){
+        for (var j=0; j<subtrees[edge].length; j++){
+            var rotP = rotate(points[subtrees[edge][j]].vector, points[axes[edge][0]].vector,points[axes[edge][1]].vector, scale * (Math.PI - angles[edge]));
+            points[subtrees[edge][j]].set(rotP[0],rotP[1],rotP[2]);
+        }
+    }
+}
+function update(obj) {
+   updateFacesPosition(obj);
+   updateEdgesPosition(obj);
+}
+if (foldables.length) {
+    var settings = document.getElementById('settings_0');
+    var foldDiv = document.createElement('div');
+    foldDiv.id = 'fold_0';
+    var title = document.createElement('strong');
+    title.innerHTML = 'Fold';
+    foldDiv.appendChild(title);
+    foldDiv.className = 'group';
+    for (var i=0; i<foldables.length; i++) {
+        var range = document.createElement('input');
+        range.type = 'range';
+        range.min = 0;
+        range.max = 1;
+        range.value = 0;
+        range.step = 0.001;
+        range.name = String(i);
+        range.oninput = fold;
+        foldDiv.appendChild(range);
+    }
+    lookAtBarycenter(foldables[0]);
+    settings.insertBefore(foldDiv,settings.childNodes[0]);
+}
+// ---------------------- EXPLOSION ------------------------------------------------
+// ---------------------------------------------------------------------------------
+if (explodableModel) {
+    for (var i=0; i<scene.children.length; i++) {
+        obj = scene.children[i];
+        if ( obj.userData.explodable ) {
+            computeCentroid(obj);
+        }
+    }
+    document.getElementById('explodeRange_0').oninput = triggerExplode;
+    document.getElementById('explodeCheckbox_0').onchange = triggerAutomaticExplode;
+    document.getElementById('explodingSpeedRange_0').oninput = setExplodingSpeed;
+    explode(0.000001);
+}
+function computeCentroid(obj) {
+    centroid = new THREE.Vector3();
+    obj.userData.points.forEach(function(pmpoint) {
+        centroid.add(pmpoint.vector);
+    });
+    centroid.divideScalar(obj.userData.points.length);
+    obj.userData.centroid = centroid;
+}
+function explode(factor) {
+    for (var i=0; i<scene.children.length; i++) {
+        var obj = scene.children[i];
+        if (obj.userData.hasOwnProperty("centroid")) {
+            var c = obj.userData.centroid;
+            obj.position.set(c.x*factor, c.y*factor, c.z*factor);
+        }
+    }
+}
+function triggerExplode(event){
+    explodeScale = Number(event.currentTarget.value);
+    explode(explodeScale);
+}
+function setExplodingSpeed(event){
+    explodingSpeed = Number(event.currentTarget.value);
+}
+function triggerAutomaticExplode(event){
+    if (event.currentTarget.checked){
+        startExploding();
+    } else {
+        clearIntervals();
+    }
+}
+function startExploding(){
+    intervals.push(setInterval(explodingInterval, 25));
+}
+function explodingInterval(){
+    explodeScale += explodingSpeed;
+    if (explodeScale <= 6){
+        explode(explodeScale);
+    }
+    else{
+        explode(6);
+        explodeScale = 6;
+        clearIntervals();
+        timeouts.push(setTimeout(startUnexploding, 3000));
+    }
+    document.getElementById('explodeRange_0').value = explodeScale;
+}
+function startUnexploding(){
+    intervals.push(setInterval(unexplodingInterval, 25));
+}
+function unexplodingInterval(){
+    explodeScale -= explodingSpeed;
+    if (explodeScale >= 0){
+        explode(explodeScale);
+    }
+    else {
+        explode(0);
+        explodeScale = 0;
+        clearIntervals();
+        timeouts.push(setTimeout(startExploding, 3000));
+    }
+    document.getElementById('explodeRange_0').value = explodeScale;
+}
+function clearIntervals(){
+    intervals.forEach(function(interval){
+        clearInterval(interval);
+    });
+    intervals = [];
+    timeouts.forEach(function(timeout){
+        clearTimeout(timeout);
+    });
+    timeouts = [];
+}
+// ---------------------- DISPLAY --------------------------------------------------
+// ---------------------------------------------------------------------------------
+const objectTypeInnerHTMLs = { points: "Points", pointlabels: "Point labels", lines: "Edges", edgelabels: "Edge labels", faces: "Faces", arrowheads: "Arrow heads" };
+const objectTypeVisible = {};
+Object.assign(objectTypeVisible,modelContains);
+const sortedObjectTypeKeys = Object.keys(objectTypeInnerHTMLs).sort();
+const shownObjectTypesList = document.getElementById('shownObjectTypesList_0');
+function setVisibility(bool,objname) {
+    for (var i=0; i<scene.children.length; i++){
+        var obj = scene.children[i].getObjectByName(objname);
+        if (obj) {
+            obj.visible = bool;
+        }
+    }
+}
+function toggleObjectTypeVisibility(event){
+    var name = event.currentTarget.name;
+    var checked = event.currentTarget.checked;
+    objectTypeVisible[name] = checked;
+    if (name == "faces") {
+        setVisibility(checked,"frontfaces");
+        setVisibility(checked,"backfaces");
+    } else {
+        setVisibility(checked,name);
+    }
+}
+for (var i=0; i<sortedObjectTypeKeys.length; i++){
+    var key = sortedObjectTypeKeys[i];
+    if (modelContains[key]) {
+        var objTypeNode = document.createElement('span');
+        objTypeNode.innerHTML = objectTypeInnerHTMLs[key] + '<br>';
+        var checkbox = document.createElement('input');
+        checkbox.type = 'checkbox';
+        checkbox.checked = true;
+        checkbox.name = key;
+        checkbox.onchange = toggleObjectTypeVisibility;
+        shownObjectTypesList.appendChild(checkbox);
+        shownObjectTypesList.appendChild(objTypeNode);
+    }
+}
+// ------------------------------------------------------
+function toggleObjectVisibility(event){
+    var nr = Number(event.currentTarget.name);
+    scene.children[nr].visible = event.currentTarget.checked;
+}
+// append checkboxes for displaying or hiding objects
+var shownObjectsList = document.getElementById('shownObjectsList_0');
+for (var i=0; i<scene.children.length; i++){
+    obj = scene.children[i];
+    var objNode = document.createElement('span');
+    objNode.innerHTML = obj.name + '<br>';
+    var checkbox = document.createElement('input');
+    checkbox.type = 'checkbox';
+    checkbox.checked = true;
+    checkbox.name = String(i);
+    checkbox.onchange = toggleObjectVisibility;
+    shownObjectsList.appendChild(checkbox);
+    shownObjectsList.appendChild(objNode);
+}
+// ---------------------- SVG ------------------------------------------------------
+// ---------------------------------------------------------------------------------
+function takeSvgScreenshot() {
+    if (objectTypeVisible["pointlabels"]) {
+        setVisibility(false,"pointlabels");
+    }
+    if (objectTypeVisible["edgelabels"]) {
+        setVisibility(false,"edgelabels");
+    }
+    svgRenderer.render(scene,camera);
+    svgElement = XMLS.serializeToString(svgRenderer.domElement);
+    if (objectTypeVisible["pointlabels"]) {
+        setVisibility(true,"pointlabels");
+    }
+    if (objectTypeVisible["edgelabels"]) {
+        setVisibility(true,"edgelabels");
+    }
+    if (document.getElementById('tab_0').checked){
+        //show in new tab
+        var myWindow = window.open("","");
+        myWindow.document.body.innerHTML = svgElement;
+    } else{
+        // download svg file
+        download("screenshot.svg", svgElement);
+    }
+}
+function download(filename, text) {
+    var element = document.createElement('a');
+    element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
+    element.setAttribute('download', filename);
+    element.style.display = 'none';
+    document.body.appendChild(element);
+    element.click();
+    document.body.removeChild(element);
+}
+document.getElementById('transparencyRange_0').oninput = changeTransparency;
+document.getElementById('depthWriteCheckbox_0').onchange = toggleDepthWrite;
+document.getElementById('changeRotationX_0').onchange = changeRotationX;
+document.getElementById('changeRotationY_0').onchange = changeRotationY;
+document.getElementById('changeRotationZ_0').onchange = changeRotationZ;
+document.getElementById('resetButton_0').onclick = resetScene;
+document.getElementById('rotationSpeedRange_0').oninput = changeRotationSpeedFactor;
+document.getElementById('takeScreenshot_0').onclick = takeSvgScreenshot;
+document.getElementById('showSettingsButton_0').onclick = showSettings;
+document.getElementById('hideSettingsButton_0').onclick = hideSettings;
+// ------------------ SHORTCUTS --------------------------------------------
+// -------------------------------------------------------------------------
+/**
+ * http://www.openjs.com/scripts/events/keyboard_shortcuts/
+ * Version : 2.01.B
+ * By Binny V A
+ * License : BSD
+ */
+shortcut = {
+	'all_shortcuts':{},//All the shortcuts are stored in this array
+	'add': function(shortcut_combination,callback,opt) {
+		//Provide a set of default options
+		var default_options = {
+			'type':'keydown',
+			'propagate':false,
+			'disable_in_input':false,
+			'target':document,
+			'keycode':false
+		}
+		if(!opt) opt = default_options;
+		else {
+			for(var dfo in default_options) {
+				if(typeof opt[dfo] == 'undefined') opt[dfo] = default_options[dfo];
+			}
+		}
+		var ele = opt.target;
+		if(typeof opt.target == 'string') ele = document.getElementById(opt.target);
+		var ths = this;
+		shortcut_combination = shortcut_combination.toLowerCase();
+		//The function to be called at keypress
+		var func = function(e) {
+			e = e || window.event;
+			if(opt['disable_in_input']) { //Don't enable shortcut keys in Input, Textarea fields
+				var element;
+				if(e.target) element=e.target;
+				else if(e.srcElement) element=e.srcElement;
+				if(element.nodeType==3) element=element.parentNode;
+				if(element.tagName == 'INPUT' || element.tagName == 'TEXTAREA') return;
+			}
+			//Find Which key is pressed
+			if (e.keyCode) code = e.keyCode;
+			else if (e.which) code = e.which;
+			var character = String.fromCharCode(code).toLowerCase();
+			if(code == 188) character=","; //If the user presses , when the type is onkeydown
+			if(code == 190) character="."; //If the user presses , when the type is onkeydown
+			var keys = shortcut_combination.split("+");
+			//Key Pressed - counts the number of valid keypresses - if it is same as the number of keys, the shortcut function is invoked
+			var kp = 0;
+			//Work around for stupid Shift key bug created by using lowercase - as a result the shift+num combination was broken
+			var shift_nums = {
+				"`":"~",
+				"1":"!",
+				"2":"@",
+				"3":"#",
+				"4":"$",
+				"5":"%",
+				"6":"^",
+				"7":"&",
+				"8":"*",
+				"9":"(",
+				"0":")",
+				"-":"_",
+				"=":"+",
+				";":":",
+				"'":"\"",
+				",":"<",
+				".":">",
+				"/":"?",
+				"\\":"|"
+			}
+			//Special Keys - and their codes
+			var special_keys = {
+				'esc':27,
+				'escape':27,
+				'tab':9,
+				'space':32,
+				'return':13,
+				'enter':13,
+				'backspace':8,
+				'scrolllock':145,
+				'scroll_lock':145,
+				'scroll':145,
+				'capslock':20,
+				'caps_lock':20,
+				'caps':20,
+				'numlock':144,
+				'num_lock':144,
+				'num':144,
+				'pause':19,
+				'break':19,
+				'insert':45,
+				'home':36,
+				'delete':46,
+				'end':35,
+				'pageup':33,
+				'page_up':33,
+				'pu':33,
+				'pagedown':34,
+				'page_down':34,
+				'pd':34,
+				'left':37,
+				'up':38,
+				'right':39,
+				'down':40,
+				'f1':112,
+				'f2':113,
+				'f3':114,
+				'f4':115,
+				'f5':116,
+				'f6':117,
+				'f7':118,
+				'f8':119,
+				'f9':120,
+				'f10':121,
+				'f11':122,
+				'f12':123
+			}
+			var modifiers = {
+				shift: { wanted:false, pressed:false},
+				ctrl : { wanted:false, pressed:false},
+				alt  : { wanted:false, pressed:false},
+				meta : { wanted:false, pressed:false}	//Meta is Mac specific
+			};
+			if(e.ctrlKey)	modifiers.ctrl.pressed = true;
+			if(e.shiftKey)	modifiers.shift.pressed = true;
+			if(e.altKey)	modifiers.alt.pressed = true;
+			if(e.metaKey)   modifiers.meta.pressed = true;
+			for(var i=0; k=keys[i],i<keys.length; i++) {
+				//Modifiers
+				if(k == 'ctrl' || k == 'control') {
+					kp++;
+					modifiers.ctrl.wanted = true;
+				} else if(k == 'shift') {
+					kp++;
+					modifiers.shift.wanted = true;
+				} else if(k == 'alt') {
+					kp++;
+					modifiers.alt.wanted = true;
+				} else if(k == 'meta') {
+					kp++;
+					modifiers.meta.wanted = true;
+				} else if(k.length > 1) { //If it is a special key
+					if(special_keys[k] == code) kp++;
+				} else if(opt['keycode']) {
+					if(opt['keycode'] == code) kp++;
+				} else { //The special keys did not match
+					if(character == k) kp++;
+					else {
+						if(shift_nums[character] && e.shiftKey) { //Stupid Shift key bug created by using lowercase
+							character = shift_nums[character];
+							if(character == k) kp++;
+						}
+					}
+				}
+			}
+			if(kp == keys.length &&
+						modifiers.ctrl.pressed == modifiers.ctrl.wanted &&
+						modifiers.shift.pressed == modifiers.shift.wanted &&
+						modifiers.alt.pressed == modifiers.alt.wanted &&
+						modifiers.meta.pressed == modifiers.meta.wanted) {
+				callback(e);
+				if(!opt['propagate']) { //Stop the event
+					//e.cancelBubble is supported by IE - this will kill the bubbling process.
+					e.cancelBubble = true;
+					e.returnValue = false;
+					//e.stopPropagation works in Firefox.
+					if (e.stopPropagation) {
+						e.stopPropagation();
+						e.preventDefault();
+					}
+					return false;
+				}
+			}
+		}
+		this.all_shortcuts[shortcut_combination] = {
+			'callback':func,
+			'target':ele,
+			'event': opt['type']
+		};
+		//Attach the function with the event
+		if(ele.addEventListener) ele.addEventListener(opt['type'], func, false);
+		else if(ele.attachEvent) ele.attachEvent('on'+opt['type'], func);
+		else ele['on'+opt['type']] = func;
+	},
+	//Remove the shortcut - just specify the shortcut and I will remove the binding
+	'remove':function(shortcut_combination) {
+		shortcut_combination = shortcut_combination.toLowerCase();
+		var binding = this.all_shortcuts[shortcut_combination];
+		delete(this.all_shortcuts[shortcut_combination])
+		if(!binding) return;
+		var type = binding['event'];
+		var ele = binding['target'];
+		var callback = binding['callback'];
+		if(ele.detachEvent) ele.detachEvent('on'+type, callback);
+		else if(ele.removeEventListener) ele.removeEventListener(type, callback, false);
+		else ele['on'+type] = false;
+	}
+}
+shortcut.add("Alt+Left",function() {
+	var event = new Event('click');
+	if (settingsShown){
+		document.getElementById('hideSettingsButton_0').dispatchEvent(event);
+	} else {
+		document.getElementById('showSettingsButton_0').dispatchEvent(event);
+	}
+});
+// COMMON_CODE_BLOCK_END
+});});
+      </script>
+   </body>
+</html>
+</HTML>
+===== Internal treatment of polytope generators =====
+As described above polyhedra in ''%%polymake%%'' are modelled as the intersection of a cone with the affine hyperplane defined by $x_0=1$. Hence, infinitely many cones give rise to the same polytope. The algorithms in ''%%polymake%%'' usually work with the //homogenized cone// ''%%homog(P)%%'' of a polyhedron. Hence, ''%%polymake%%'' takes care about the correct canonicalization of user input of polytope generators in the following way:
+In order to construct ''%%homog(P)%%'', the cone defining the polyhedron is intersected with the hyperplane $H_0: x_0=0$. The rays defining the bounded part $(R_b)$ and rays with $x_0=0$ $(R_0)$ are just inherited. To obtain the rest of the generators for the unbounded part, it is necessary to carry out a "dual Fourier-Motzkin procedure": Any two rays with different signs are linearly combined to a new ray that is contained in $H_0$. All these rays together with the rays in $R_b$ and $R_0$ then define the //homogenized cone// ''%%homog(P)%%''.
+===== Other coefficients =====
+polymake has limited support for other ordered fields for coefficients of polytopes (and linear programs). An example are quadratic extensions to the rationals. As an example we show how to construct a regular triangle.
+<code perl>
+> $t=new QuadraticExtension(0,1/2,3);
+</code>
+This gives the number $ \sqrt{3}/2 $. More generally, you can construct the value $ a+b\sqrt{r} $ via ''%%QuadraticExtension(a, b, r)%%''. Note that currently polymake is restricted to computing with single extensions, i.e., you cannot mix distinct square roots.
+<code perl>
+> print $t*$t;
+/4
+> $triangle = new Polytope<QuadraticExtension>(POINTS=>[[1,0,1],[1,$t,-1/2],[1,-$t,-1/2]]);
+</code>
+That regular triangle can be treated like any polytope. The following computes the area, which results in $ \frac{3}{4}\sqrt{3} $.
+<code perl>
+> print $triangle->VOLUME;
++3/4r3
+</code>