diff --git a/modules/gems/joints.js b/modules/gems/joints.js
new file mode 100644
index 00000000..5022c79a
--- /dev/null
+++ b/modules/gems/joints.js
@@ -0,0 +1,40 @@
+
+export default class Joints {
+  
+  constructor() {
+    this.map = new Map();
+  }
+  
+  connect(a, b) {
+    let tuple = this.map.get(a);
+    if (!tuple) {
+      tuple = this.map.get(b);
+      if (!tuple) {
+        tuple = {
+          master: a,
+          linked: new Set()
+        };
+        this.map.set(b, tuple);
+      }
+      this.map.set(a, tuple);
+    }
+    tuple.linked.add(a);
+    tuple.linked.add(b);
+  }
+
+  connected(a, b) {
+    let set = this.map.get(a);
+    if (!set) {
+      return false;
+    }
+    return set.has(b);
+  }
+  
+  master(node) {
+    let tuple = this.map.get(node);
+    if (!tuple) {
+      return node;
+    }
+    return tuple.master;
+  }
+}
\ No newline at end of file
diff --git a/web/app/cad/sketch/sketchModel.js b/web/app/cad/sketch/sketchModel.js
index 0d4a815b..c30e8fd1 100644
--- a/web/app/cad/sketch/sketchModel.js
+++ b/web/app/cad/sketch/sketchModel.js
@@ -5,6 +5,7 @@ import {Point} from '../../brep/geom/point'
 import {LUT} from '../../math/bezier-cubic'
 import {distanceAB, isCCW, makeAngle0_360} from '../../math/math'
 import {normalizeCurveEnds} from '../../brep/geom/impl/nurbs-ext';
+import Vector from '../../../../modules/math/vector';
 
 const RESOLUTION = 20;
 
@@ -120,7 +121,8 @@ export class Arc extends SketchPrimitive {
     const yAxis = pointAtAngle(startAngle + Math.PI * 0.5);
 
     let arc = new verb.geom.Arc(_3dtr(this.c).data(), xAxis.data(), yAxis.data(), distanceAB(this.c, this.a), 0, Math.abs(angle));
-    return arc;
+    
+    return adjustEnds(arc, _3dtr(this.a), _3dtr(this.b))
   }
 }
 
@@ -181,7 +183,18 @@ export class EllipticalArc extends SketchPrimitive {
     points.push(bo);
     return points;
   }
+  
+  toVerbNurbs(plane, _3dtr) {
+    const xAxis = this.ep2.minus(this.ep1)._multiply(0.5);
+    const yAxis = new Vector(xAxis.y, xAxis.x)._normalize()._multiply(this.r) ;
+    const center = this.ep1.plus(xAxis);
 
+    const startAngle = makeAngle0_360(Math.atan2(this.a.y - center.y, this.a.x - center.x));
+    const endAngle = makeAngle0_360(Math.atan2(this.b.y - center.y, this.b.x - center.x));
+    
+    let arc = new verb.geom.EllipseArc(_3dtr(center).data(), _3dtr(xAxis).data(), _3dtr(yAxis).data(), startAngle, endAngle);
+    return adjustEnds(arc, _3dtr(this.a), _3dtr(this.b))
+  }
 }
 
 export class Circle extends SketchPrimitive {
@@ -329,3 +342,18 @@ class CompositeCurve {
   }
 }
 
+function adjustEnds(arc, a, b) {
+  let data = arc.asNurbs();
+
+  function setHomoPoint(homoPoint, vector) {
+    homoPoint[0] = vector.x * homoPoint[3];
+    homoPoint[1] = vector.y * homoPoint[3];
+    homoPoint[2] = vector.z * homoPoint[3];
+  }
+
+  setHomoPoint(data.controlPoints[0], a);
+  setHomoPoint(data.controlPoints[data.controlPoints.length - 1], b);
+
+  return new verb.geom.NurbsCurve(data);
+}
+
diff --git a/web/app/cad/sketch/sketchReader.js b/web/app/cad/sketch/sketchReader.js
index 5c6c3a42..9251aad6 100644
--- a/web/app/cad/sketch/sketchReader.js
+++ b/web/app/cad/sketch/sketchReader.js
@@ -4,6 +4,8 @@ import Vector from 'math/vector';
 import {Graph} from '../../math/graph'
 import * as math from '../../math/math'
 import {HashTable} from '../../utils/hashmap'
+import {Constraints} from '../../sketcher/parametric';
+import Joints from '../../../../modules/gems/joints';
 
 class SketchGeom {
 
@@ -45,6 +47,31 @@ export function ReadSketch(sketch, sketchId, readConstructionSegments) {
     return sketchId + "/" + obj.id;
   }
   const out = new SketchGeom();
+
+  let coiJoints = new Joints();
+  
+  if (sketch.constraints !== undefined) {
+    for (let i = 0; i < sketch.constraints.length; ++i) {
+      let c = sketch.constraints[i];
+      let name = c[0];
+      let ps = c[1];
+      if (name === 'coi') {
+        coiJoints.connect(ps[0], ps[1]);
+      }
+    }
+  }
+
+  let pointsById = new Map();
+  function ReadSketchPoint(arr) {
+    let pointId = arr[0];
+    pointId = coiJoints.master(pointId);
+    let point = pointsById.get(pointId);
+    if (!point) {
+      point = new Vector(readSketchFloat(arr[1][1]), readSketchFloat(arr[2][1]), 0);
+      pointsById.set(pointId, point);
+    }
+    return point;
+  }
   if (sketch.layers !== undefined) {
     for (let layer of sketch.layers) {
       const isConstructionLayer = layer.name === "_construction_";
@@ -89,10 +116,6 @@ export function ReadSketch(sketch, sketchId, readConstructionSegments) {
   return out;
 }
 
-export function ReadSketchPoint(arr) {
-  return new Vector(readSketchFloat(arr[1][1]), readSketchFloat(arr[2][1]), 0)
-}
-
 export function FetchContours(geom) {
   const contours = findClosedContours(geom.connections);
   for (let loop of geom.loops) {