From 2dca8a0aa69981bc2a81c4a68f9061aef861f0ea Mon Sep 17 00:00:00 2001
From: Pushkar Joshi
Date: Wed, 6 Jun 2012 15:01:10 -0700
Subject: enable gradients for brush stroke (in authoring as well as runtime)

---
 js/lib/geom/brush-stroke.js | 1406 ++++++++++++++++++++++---------------------
 1 file changed, 732 insertions(+), 674 deletions(-)

(limited to 'js/lib/geom')

diff --git a/js/lib/geom/brush-stroke.js b/js/lib/geom/brush-stroke.js
index 09a7023c..b2e56149 100755
--- a/js/lib/geom/brush-stroke.js
+++ b/js/lib/geom/brush-stroke.js
@@ -65,777 +65,835 @@ var BrushStroke = function GLBrushStroke() {
     this._planeMatInv = null;
     this._planeCenter = null;
     this._dragPlane = null;
+}; //BrushStroke class defition
 
-    /////////////////////////////////////////////////////////
-    // Property Accessors/Setters
-    /////////////////////////////////////////////////////////
-    this.setCanvas = function(c) {
-        this._canvas = c;
+BrushStroke.prototype = Object.create(GeomObj, {});
+
+/////////////////////////////////////////////////////////
+// Property Accessors/Setters
+/////////////////////////////////////////////////////////
+BrushStroke.prototype.setCanvas = function(c) {
+    this._canvas = c;
+};
+
+BrushStroke.prototype.setWorld = function (world) {
+    this._world = world;
+};
+
+BrushStroke.prototype.getWorld = function () {
+    return this._world;
+};
+
+BrushStroke.prototype.geomType = function () {
+    return this.GEOM_TYPE_BRUSH_STROKE;
+};
+
+BrushStroke.prototype.setDrawingTool = function (tool) {
+    this._drawingTool = tool;
+};
+
+BrushStroke.prototype.getDrawingTool = function () {
+    return this._drawingTool;
+};
+
+BrushStroke.prototype.setPlaneMatrix = function(planeMat){
+    this._planeMat = planeMat;
+};
+
+BrushStroke.prototype.setPlaneMatrixInverse = function(planeMatInv){
+    this._planeMatInv = planeMatInv;
+};
+
+BrushStroke.prototype.setPlaneCenter = function(pc){
+    this._planeCenter = pc;
+};
+
+BrushStroke.prototype.setDragPlane = function(p){
+    this._dragPlane = p;
+};
+
+BrushStroke.prototype.getNumPoints = function () {
+    if (this._LocalPoints.length)
+        return this._LocalPoints.length;
+    else
+        return this._Points.length;
+};
+
+BrushStroke.prototype.getPoint = function (index) {
+    return this._Points[index].slice(0);
+};
+
+BrushStroke.prototype.addPoint = function (pt) {
+    //add the point only if it is some epsilon away from the previous point
+    var numPoints = this._Points.length;
+    if (numPoints>0) {
+        var threshold = this._MIN_SAMPLE_DISTANCE_THRESHOLD;
+        var prevPt = this._Points[numPoints-1];
+        var diffPt = [prevPt[0]-pt[0], prevPt[1]-pt[1]];
+        var diffPtMag = Math.sqrt(diffPt[0]*diffPt[0] + diffPt[1]*diffPt[1]);
+        if (diffPtMag>threshold){
+            this._Points.push(pt);
+            this._isDirty=true;
+            this._isInit = false;
+        }
+    } else {
+        this._Points.push(pt);
+        this._isDirty=true;
+        this._isInit = false;
     }
+};
 
-    this.setWorld = function (world) {
-        this._world = world;
-    };
+BrushStroke.prototype.insertPoint = function(pt, index){
+    this._Points.splice(index, 0, pt);
+    this._isDirty=true;
+    this._isInit = false;
+};
 
-    this.getWorld = function () {
-        return this._world;
-    };
+BrushStroke.prototype.isDirty = function(){
+    return this._isDirty;
+};
 
-    this.geomType = function () {
-        return this.GEOM_TYPE_BRUSH_STROKE;
-    };
+BrushStroke.prototype.makeDirty = function(){
+    this._isDirty=true;
+};
 
-    this.setDrawingTool = function (tool) {
-        this._drawingTool = tool;
-    };
+BrushStroke.prototype.getStageWorldCenter = function() {
+    return this._stageWorldCenter;
+};
 
-    this.getDrawingTool = function () {
-        return this._drawingTool;
-    };
+BrushStroke.prototype.getBBoxMin = function () {
+    return this._BBoxMin;
+};
 
-    this.setPlaneMatrix = function(planeMat){
-        this._planeMat = planeMat;
-    };
+BrushStroke.prototype.getBBoxMax = function () {
+    return this._BBoxMax;
+};
 
-    this.setPlaneMatrixInverse = function(planeMatInv){
-        this._planeMatInv = planeMatInv;
-    };
+BrushStroke.prototype.getStrokeWidth = function () {
+    return this._strokeWidth;
+};
 
-    this.setPlaneCenter = function(pc){
-        this._planeCenter = pc;
-    };
+BrushStroke.prototype.setStrokeWidth = function (w) {
+    this._strokeWidth = w;
+    if (this._strokeWidth<1) {
+        this._strokeWidth = 1;
+    }
+    this._isDirty=true;
+};
 
-    this.setDragPlane = function(p){
-        this._dragPlane = p;
-    };
+BrushStroke.prototype.getStrokeMaterial = function () {
+    return this._strokeMaterial;
+};
 
-    this.getNumPoints = function () {
-        if (this._LocalPoints.length)
-            return this._LocalPoints.length;
-        else
-            return this._Points.length;
-    };
+BrushStroke.prototype.setStrokeMaterial = function (m) {
+    this._strokeMaterial = m; this._isDirty = true;
+};
 
-    this.getPoint = function (index) {
-        return this._Points[index].slice(0);
-    };
+BrushStroke.prototype.getStrokeColor = function () {
+    return this._strokeColor;
+};
 
-    this.addPoint = function (pt) {
-        //add the point only if it is some epsilon away from the previous point
-        var numPoints = this._Points.length;
-        if (numPoints>0) {
-            var threshold = this._MIN_SAMPLE_DISTANCE_THRESHOLD;
-            var prevPt = this._Points[numPoints-1];
-            var diffPt = [prevPt[0]-pt[0], prevPt[1]-pt[1]];
-            var diffPtMag = Math.sqrt(diffPt[0]*diffPt[0] + diffPt[1]*diffPt[1]);
-            if (diffPtMag>threshold){
-                this._Points.push(pt);
-                this._isDirty=true;
-                this._isInit = false;
-            }
-        } else {
-            this._Points.push(pt);
-            this._isDirty=true;
-            this._isInit = false;
-        }
-    };
-    
-    this.insertPoint = function(pt, index){
-        this._Points.splice(index, 0, pt);
-        this._isDirty=true;
-        this._isInit = false;
-    };
+BrushStroke.prototype.setStrokeColor = function (c) {
+    this._strokeColor = c; this._isDirty = true;
+};
 
-    this.isDirty = function(){
-        return this._isDirty;
-    };
+BrushStroke.prototype.setFillColor = function(c){
+    return;
+}; //NO-OP for now as we have no fill region
 
-    this.makeDirty = function(){
-        this._isDirty=true;
-    };
+BrushStroke.prototype.setSecondStrokeColor = function(c){
+    this._secondStrokeColor=c; this._isDirty = true;
+};
 
-    this.getStageWorldCenter = function() {
-        return this._stageWorldCenter;
-    };
+BrushStroke.prototype.setStrokeHardness = function(h){
+    if (this._strokeHardness!==h){
+        this._strokeHardness=h;
+        this._isDirty = true;
+    }
+};
+BrushStroke.prototype.getStrokeHardness = function(){
+    return this._strokeHardness;
+};
+
+BrushStroke.prototype.setDoSmoothing = function(s){
+    if (this._strokeDoSmoothing!==s) {
+        this._strokeDoSmoothing = s;
+        this._isDirty = true;
+    }
+};
 
-    this.getBBoxMin = function () {
-        return this._BBoxMin;
-    };
+BrushStroke.prototype.getDoSmoothing = function(){
+    return this._strokeDoSmoothing;
+};
 
-    this.getBBoxMax = function () {
-        return this._BBoxMax;
-    };
+BrushStroke.prototype.setSmoothingAmount = function(a){
+    if (this._strokeAmountSmoothing!==a) {
+        this._strokeAmountSmoothing = a;
+        this._isDirty = true;
+    }
+};
 
-    this.getStrokeWidth = function () {
-        return this._strokeWidth;
-    };
+BrushStroke.prototype.getSmoothingAmount = function(){
+    return this._strokeAmountSmoothing;
+};
 
-    this.setStrokeWidth = function (w) {
-        this._strokeWidth = w;
-        if (this._strokeWidth<1) {
-            this._strokeWidth = 1;
-        }
-        this._isDirty=true;
-    };
+BrushStroke.prototype.setStrokeUseCalligraphic = function(c){
+    if (this._strokeUseCalligraphic!==c){
+        this._strokeUseCalligraphic = c;
+        this._isDirty = true;
+    }
+};
 
-    this.getStrokeMaterial = function () {
-        return this._strokeMaterial;
+BrushStroke.prototype.setStrokeAngle = function(a){
+    if (this._strokeAngle!==a){
+        this._strokeAngle = a;
+        this._isDirty = true;
     };
+};
 
-    this.setStrokeMaterial = function (m) {
-        this._strokeMaterial = m; this._isDirty = true;
-    };
+BrushStroke.prototype.getStrokeUseCalligraphic = function(){
+    return this._strokeUseCalligraphic;
+};
 
-    this.getStrokeColor = function () {
-        return this._strokeColor;
-    };
+BrushStroke.prototype.getStrokeAngle = function(){
+    return this._strokeAngle;
+};
 
-    this.setStrokeColor = function (c) {
-        this._strokeColor = c; this._isDirty = true;
-    };
+BrushStroke.prototype.getStrokeStyle = function () {
+    return this._strokeStyle;
+};
 
-    this.setFillColor = function(c){
-        return;
-    }; //NO-OP for now as we have no fill region
+BrushStroke.prototype.setStrokeStyle = function (s) {
+    this._strokeStyle = s;
+};
 
-    this.setSecondStrokeColor = function(c){
-        this._secondStrokeColor=c; this._isDirty = true;
+BrushStroke.prototype.setWidth = function (newW) {
+    if (newW<1) {
+        newW=1; //clamp minimum width to 1
     }
 
-    this.setStrokeHardness = function(h){
-        if (this._strokeHardness!==h){
-            this._strokeHardness=h;
-            this._isDirty = true;
-        }
-    }
-    this.getStrokeHardness = function(){
-        return this._strokeHardness;
+    //scale the contents of this subpath to lie within this width
+    //determine the scale factor by comparing with the old width
+    var oldWidth = this._BBoxMax[0]-this._BBoxMin[0];
+    if (oldWidth<1) {
+        oldWidth=1;
     }
 
-    this.setDoSmoothing = function(s){
-        if (this._strokeDoSmoothing!==s) {
-            this._strokeDoSmoothing = s;
-            this._isDirty = true;
-        }
+    var scaleX = newW/oldWidth;
+    if (scaleX===1) {
+        return; //no need to do anything
     }
 
-    this.getDoSmoothing = function(){
-        return this._strokeDoSmoothing;
-    }
+    //scale the local point positions such that the width of the bbox is the newW
+    var origX = this._BBoxMin[0];
+    var numPoints = this._LocalPoints.length;
+    for (var i=0;i<numPoints;i++){
+        //compute the distance from the bboxMin
+        var oldW = this._LocalPoints[i][0] - origX;
+        this._LocalPoints[i] = [(origX + oldW*scaleX),this._LocalPoints[i][1],this._LocalPoints[i][2]];
 
-    this.setSmoothingAmount = function(a){
-        if (this._strokeAmountSmoothing!==a) {
-            this._strokeAmountSmoothing = a;
-            this._isDirty = true;
-        }
+        oldW = this._OrigLocalPoints[i][0] - origX;
+        this._OrigLocalPoints[i] = [(origX + oldW*scaleX),this._OrigLocalPoints[i][1],this._OrigLocalPoints[i][2]];
     }
+    this._isDirty = true;
+};
 
-    this.getSmoothingAmount = function(){
-        return this._strokeAmountSmoothing;
+BrushStroke.prototype.setHeight = function (newH) {
+    if (newH<1) {
+        newH=1; //clamp minimum width to 1
     }
 
-    this.setStrokeUseCalligraphic = function(c){
-        if (this._strokeUseCalligraphic!==c){
-            this._strokeUseCalligraphic = c;
-            this._isDirty = true;
-        }
+    //scale the contents of this subpath to lie within this height
+    //determine the scale factor by comparing with the old height
+    var oldHeight = this._BBoxMax[1]-this._BBoxMin[1];
+    if (oldHeight<1) {
+        oldHeight=1;
     }
 
-    this.setStrokeAngle = function(a){
-        if (this._strokeAngle!==a){
-            this._strokeAngle = a;
-            this._isDirty = true;
-        };
+    var scaleY = newH/oldHeight;
+    if (scaleY===1) {
+        return; //no need to do anything
     }
 
-    this.getStrokeUseCalligraphic = function(){
-        return this._strokeUseCalligraphic;
-    }
+    //scale the local point positions such that the width of the bbox is the newW
+    var origY = this._BBoxMin[1];
+    var numPoints = this._LocalPoints.length;
+    for (var i=0;i<numPoints;i++){
+        //compute the distance from the bboxMin
+        var oldH = this._LocalPoints[i][1] - origY;
+        this._LocalPoints[i] = [this._LocalPoints[i][0],(origY + oldH*scaleY),this._LocalPoints[i][2]];
 
-    this.getStrokeAngle = function(){
-        return this._strokeAngle;
+        oldH = this._OrigLocalPoints[i][1] - origY;
+        this._OrigLocalPoints[i] = [this._OrigLocalPoints[i][0],(origY + oldH*scaleY),this._OrigLocalPoints[i][2]];
     }
+    this._isDirty = true;
+};
 
-    this.getStrokeStyle = function () {
-        return this._strokeStyle;
-    };
-
-    this.setStrokeStyle = function (s) {
-        this._strokeStyle = s;
-    };
-
-    this.setWidth = function (newW) {
-        if (newW<1) {
-            newW=1; //clamp minimum width to 1
-        }
-
-        //scale the contents of this subpath to lie within this width
-        //determine the scale factor by comparing with the old width
-        var oldWidth = this._BBoxMax[0]-this._BBoxMin[0];
-        if (oldWidth<1) {
-            oldWidth=1;
-        }
-
-        var scaleX = newW/oldWidth;
-        if (scaleX===1) {
-            return; //no need to do anything
-        }
-
-        //scale the local point positions such that the width of the bbox is the newW
-        var origX = this._BBoxMin[0];
-        var numPoints = this._LocalPoints.length;
-        for (var i=0;i<numPoints;i++){
-            //compute the distance from the bboxMin
-            var oldW = this._LocalPoints[i][0] - origX;
-            this._LocalPoints[i] = [(origX + oldW*scaleX),this._LocalPoints[i][1],this._LocalPoints[i][2]];
-
-            oldW = this._OrigLocalPoints[i][0] - origX;
-            this._OrigLocalPoints[i] = [(origX + oldW*scaleX),this._OrigLocalPoints[i][1],this._OrigLocalPoints[i][2]];
-        }
-        this._isDirty = true;
-    };
-
-    this.setHeight = function (newH) {
-        if (newH<1) {
-            newH=1; //clamp minimum width to 1
-        }
-
-        //scale the contents of this subpath to lie within this height
-        //determine the scale factor by comparing with the old height
-        var oldHeight = this._BBoxMax[1]-this._BBoxMin[1];
-        if (oldHeight<1) {
-            oldHeight=1;
-        }
+BrushStroke.prototype.getWidth = function() {
+    if (this._isDirty){
+        this.update();
+    }
+    return this._BBoxMax[0]-this._BBoxMin[0];
+};
 
-        var scaleY = newH/oldHeight;
-        if (scaleY===1) {
-            return; //no need to do anything
+BrushStroke.prototype.getHeight = function() {
+    if (this._isDirty){
+        this.update();
+    }
+    return this._BBoxMax[1]-this._BBoxMin[1];
+};
+
+//remove all the points
+BrushStroke.prototype.clear = function () {
+    this._Points = [];
+    this._OrigLocalPoints    = [];
+    this._isDirty=true;
+    this._isInit = false;
+};
+
+BrushStroke.prototype._addSamples = function() {
+    //**** add samples to the long sections of the path --- Catmull-Rom spline interpolation *****
+    // instead of the following, may use 4-point subdivision iterations over continuous regions of 'long' segments
+    // look at http://www.gvu.gatech.edu/~jarek/Split&Tweak/ for formula
+
+    var numPoints = this._Points.length;
+    var numInsertedPoints = 0;
+    var newSampledPoints = [];
+    var threshold = this._MAX_SAMPLE_DISTANCE_THRESHOLD;//this determines whether a segment between two sample too long
+    var prevPt = this._Points[0];
+    newSampledPoints.push(this._Points[0]);
+    for (var i=1;i<numPoints;i++) {
+        var pt = this._Points[i];
+        var diff = [pt[0]-prevPt[0], pt[1]-prevPt[1]];
+        var distance = Math.sqrt(diff[0]*diff[0]+diff[1]*diff[1]);
+        if (distance>threshold){
+            //build the control polygon for the Catmull-Rom spline (prev. 2 points and next 2 points)
+            var prev = (i===1) ? i-1 : i-2;
+            var next = (i===numPoints-1) ? i : i+1;
+            var ctrlPts = [this._Points[prev], this._Points[i-1], this._Points[i], this._Points[next]];
+            //insert points along the prev. to current point
+            var numNewPoints = Math.floor(distance/threshold);
+            for (var j=0;j<numNewPoints;j++){
+                var param = (j+1)/(numNewPoints+1);
+                var newpt = this._CatmullRomSplineInterpolate(ctrlPts, param);
+                newSampledPoints.push(newpt);
+                numInsertedPoints++;
+            }
         }
+        newSampledPoints.push(pt);
+        prevPt=pt;
 
-        //scale the local point positions such that the width of the bbox is the newW
-        var origY = this._BBoxMin[1];
-        var numPoints = this._LocalPoints.length;
-        for (var i=0;i<numPoints;i++){
-            //compute the distance from the bboxMin
-            var oldH = this._LocalPoints[i][1] - origY;
-            this._LocalPoints[i] = [this._LocalPoints[i][0],(origY + oldH*scaleY),this._LocalPoints[i][2]];
-
-            oldH = this._OrigLocalPoints[i][1] - origY;
-            this._OrigLocalPoints[i] = [this._OrigLocalPoints[i][0],(origY + oldH*scaleY),this._OrigLocalPoints[i][2]];
+        //end this function if the numPoints has gone above the max. size specified
+        if (numPoints> this._MAX_ALLOWED_SAMPLES){
+            console.log("leaving the resampling because numPoints is greater than limit:"+this._MAX_ALLOWED_SAMPLES);
+            break;
         }
-        this._isDirty = true;
-    };
+    }
+    this._Points = newSampledPoints.slice(0);
+    newSampledPoints = [];
+};
 
-    this.getWidth = function() {
-        if (this._isDirty){
-            this.update();
-        }
-        return this._BBoxMax[0]-this._BBoxMin[0];
-    };
+BrushStroke.prototype.init = function(){
+    if (!this._isInit){
+        // **** add samples to the _Points in stageworld space ****
+        this._addSamples();
 
-    this.getHeight = function() {
-        if (this._isDirty){
-            this.update();
-        }
-        return this._BBoxMax[1]-this._BBoxMin[1];
-    };
+        // **** compute the 2D (canvas space) coord. of the _Points  ****
+        this._buildLocalCoordFromStageWorldCoord();
 
-    //remove all the points
-    this.clear = function () {
-        this._Points = [];
-        this._OrigLocalPoints    = [];
-        this._isDirty=true;
-        this._isInit = false;
-    };
+        // **** turn off the init. flag ****
+        this._isInit = true;
+        this._isDirty= true;
+    }
 
-    this._addSamples = function() {
-        //**** add samples to the long sections of the path --- Catmull-Rom spline interpolation *****
-        // instead of the following, may use 4-point subdivision iterations over continuous regions of 'long' segments
-        // look at http://www.gvu.gatech.edu/~jarek/Split&Tweak/ for formula
-
-        var numPoints = this._Points.length;
-        var numInsertedPoints = 0;
-        var newSampledPoints = [];
-        var threshold = this._MAX_SAMPLE_DISTANCE_THRESHOLD;//this determines whether a segment between two sample too long
-        var prevPt = this._Points[0];
-        newSampledPoints.push(this._Points[0]);
-        for (var i=1;i<numPoints;i++) {
-            var pt = this._Points[i];
-            var diff = [pt[0]-prevPt[0], pt[1]-prevPt[1]];
-            var distance = Math.sqrt(diff[0]*diff[0]+diff[1]*diff[1]);
-            if (distance>threshold){
-                //build the control polygon for the Catmull-Rom spline (prev. 2 points and next 2 points)
-                var prev = (i===1) ? i-1 : i-2;
-                var next = (i===numPoints-1) ? i : i+1;
-                var ctrlPts = [this._Points[prev], this._Points[i-1], this._Points[i], this._Points[next]];
-                //insert points along the prev. to current point
-                var numNewPoints = Math.floor(distance/threshold);
-                for (var j=0;j<numNewPoints;j++){
-                    var param = (j+1)/(numNewPoints+1);
-                    var newpt = this._CatmullRomSplineInterpolate(ctrlPts, param);
-                    newSampledPoints.push(newpt);
-                    numInsertedPoints++;
-                }
+    // **** update the current brush stroke ****
+    // smoothing, re-compute bounding box, etc.
+    this.update();
+};
+
+BrushStroke.prototype._unprojectPt = function(pt, pespectiveDist){
+    var retPt = pt.slice(0);
+    if (MathUtils.fpCmp(pespectiveDist,-pt[2]) !== 0){
+        z = pt[2]*pespectiveDist/(pespectiveDist + pt[2]);
+        var x = pt[0]*(pespectiveDist - z)/pespectiveDist,
+            y = pt[1]*(pespectiveDist - z)/pespectiveDist;
+        retPt[0] = x;  retPt[1] = y;  retPt[2] = z;
+    }
+    return retPt;
+};
+
+BrushStroke.prototype._buildLocalCoordFromStageWorldCoord = function() {
+    var stage = ViewUtils.getStage();
+    var stageOffset = ViewUtils.getElementOffset(stage);
+    ViewUtils.setViewportObj(stage);
+
+    var numPoints = this._Points.length;
+    var i;
+
+    // ***** compute center of bbox based on stage world coords *****
+    var bboxMin = [Infinity, Infinity, Infinity];
+    var bboxMax = [-Infinity, -Infinity, -Infinity];
+    for (i=0;i<numPoints;i++){
+        var pt = this._Points[i];
+        for (var d = 0; d < 3; d++) {
+            if (bboxMin[d] > pt[d]) {
+                bboxMin[d] = pt[d];
             }
-            newSampledPoints.push(pt);
-            prevPt=pt;
-
-            //end this function if the numPoints has gone above the max. size specified
-            if (numPoints> this._MAX_ALLOWED_SAMPLES){
-                console.log("leaving the resampling because numPoints is greater than limit:"+this._MAX_ALLOWED_SAMPLES);
-                break;
+            if (bboxMax[d] < pt[d]) {
+                bboxMax[d] = pt[d];
             }
         }
-        this._Points = newSampledPoints.slice(0);
-        newSampledPoints = [];
-    };
+    }
+    //save the center of the bbox for later use (while constructing the canvas)
+    this._stageWorldCenter = VecUtils.vecInterpolate(3, bboxMin, bboxMax, 0.5);
+
+    // ***** center the input stageworld data about the center of the bbox *****
+    this._LocalPoints = [];
+    for (i=0;i<numPoints;i++){
+        var localPoint = [this._Points[i][0],this._Points[i][1],this._Points[i][2]];
+        localPoint[0]-= this._stageWorldCenter[0];
+        localPoint[1]-= this._stageWorldCenter[1];
+
+        // ***** unproject all the centered points and convert them to 2D (plane space)*****
+        // (undo the projection step performed by the browser)
+        //localPoint = this._unprojectPt(localPoint, 1400); //todo get the perspective distance from the canvas
+        localPoint = MathUtils.transformPoint(localPoint, this._planeMatInv);
+
+        //add to the list of local points
+        this._LocalPoints.push(localPoint);
+    }
 
-    this.init = function(){
-        if (!this._isInit){
-            // **** add samples to the _Points in stageworld space ****
-            this._addSamples();
+    // ***** compute width, height, and midpoint position (in stage world position) of the canvas
+    this._updateBoundingBox(); //compute the bbox to obtain the width and height used below
+    var halfwidth = 0.5*(this._BBoxMax[0]-this._BBoxMin[0]);
+    var halfheight = 0.5*(this._BBoxMax[1]-this._BBoxMin[1]);
+    this._OrigLocalPoints    = [];
+    for (i=0;i<numPoints;i++) {
+        this._LocalPoints[i][0]+= halfwidth;
+        this._LocalPoints[i][1]+= halfheight;
+
+        //store the original points
+        this._OrigLocalPoints.push([this._LocalPoints[i][0],this._LocalPoints[i][1],this._LocalPoints[i][2]]);
+    }
+    //update the bbox with the same adjustment as was made for the local points above
+    this._BBoxMax[0]+= halfwidth;this._BBoxMin[0]+= halfwidth;
+    this._BBoxMax[1]+= halfheight;this._BBoxMin[1]+= halfheight;
+};
 
-            // **** compute the 2D (canvas space) coord. of the _Points  ****
-            this._buildLocalCoordFromStageWorldCoord();
+BrushStroke.prototype.update = function() {
+    if (this._isDirty){
+        // **** do smoothing if necessary ****
+        this._doSmoothing();
 
-            // **** turn off the init. flag ****
-            this._isInit = true;
-            this._isDirty= true;
-        }
+        // **** recompute the bounding box ****
+        this._updateBoundingBox();
 
-        // **** update the current brush stroke ****
-        // smoothing, re-compute bounding box, etc.
-        this.update();
-    };
+        // **** offset the local coords to account for the change in bbox ****
+        this._offsetLocalCoord(-this._BBoxMin[0], -this._BBoxMin[1]);
 
-    this._unprojectPt = function(pt, pespectiveDist){
-        var retPt = pt.slice(0);
-        if (MathUtils.fpCmp(pespectiveDist,-pt[2]) !== 0){
-            z = pt[2]*pespectiveDist/(pespectiveDist + pt[2]);
-            var x = pt[0]*(pespectiveDist - z)/pespectiveDist,
-                y = pt[1]*(pespectiveDist - z)/pespectiveDist;
-            retPt[0] = x;  retPt[1] = y;  retPt[2] = z;
-        }
-        return retPt;
-    };
-
-    this._buildLocalCoordFromStageWorldCoord = function() {
-        var stage = ViewUtils.getStage();
-        var stageOffset = ViewUtils.getElementOffset(stage);
-        ViewUtils.setViewportObj(stage);
-
-        var numPoints = this._Points.length;
-        var i;
+        // **** turn off the dirty flag ****
+        this._isDirty = false;
+    }
+};
 
-        // ***** compute center of bbox based on stage world coords *****
-        var bboxMin = [Infinity, Infinity, Infinity];
-        var bboxMax = [-Infinity, -Infinity, -Infinity];
-        for (i=0;i<numPoints;i++){
-            var pt = this._Points[i];
+BrushStroke.prototype._offsetLocalCoord = function(deltaW, deltaH){
+    var numPoints = this._LocalPoints.length;
+    for (var i=0;i<numPoints;i++) {
+        this._LocalPoints[i][0]+= deltaW;
+        this._LocalPoints[i][1]+= deltaH;
+    }
+};
+
+//I had to write this function to do a deep copy because I think slice(0) creates a copy by reference
+BrushStroke.prototype._copyCoordinates3D = function(srcCoord, destCoord){
+    var i=0;
+    var numPoints = srcCoord.length;
+    for (i=0;i<numPoints;i++){
+        destCoord[i] = [srcCoord[i][0],srcCoord[i][1],srcCoord[i][2]];
+    }
+};
+BrushStroke.prototype._doSmoothing = function() {
+    var numPoints = this._LocalPoints.length;
+    if (this._strokeDoSmoothing && numPoints>1) {
+        this._copyCoordinates3D(this._OrigLocalPoints   , this._LocalPoints);
+        //iterations of Laplacian smoothing (setting the points to the average of their neighbors)
+        var numLaplacianIterations = this._strokeAmountSmoothing;
+        for (var n=0;n<numLaplacianIterations;n++){
+            var newPoints = this._LocalPoints.slice(0); //I think this performs a copy by reference, which would make the following a SOR step
+            for (var i=1;i<numPoints-1;i++) {
+                var avgPos = [  0.5*(this._LocalPoints[i-1][0] + this._LocalPoints[i+1][0]),
+                                0.5*(this._LocalPoints[i-1][1] + this._LocalPoints[i+1][1]),
+                                0.5*(this._LocalPoints[i-1][2] + this._LocalPoints[i+1][2])] ;
+                newPoints[i] = avgPos;
+            }
+            this._LocalPoints = newPoints.slice(0);
+        }
+    }
+};
+
+BrushStroke.prototype._updateBoundingBox = function() {
+    // *** compute the bounding box *********
+    var points = this._LocalPoints;
+    var numPoints = points.length;
+
+    this._BBoxMin = [Infinity, Infinity, Infinity];
+    this._BBoxMax = [-Infinity, -Infinity, -Infinity];
+    if (numPoints === 0) {
+        this._BBoxMin = [0, 0, 0];
+        this._BBoxMax = [0, 0, 0];
+    } else {
+        for (var i=0;i<numPoints;i++){
+            var pt = points[i];
             for (var d = 0; d < 3; d++) {
-                if (bboxMin[d] > pt[d]) {
-                    bboxMin[d] = pt[d];
+                if (this._BBoxMin[d] > pt[d]) {
+                    this._BBoxMin[d] = pt[d];
                 }
-                if (bboxMax[d] < pt[d]) {
-                    bboxMax[d] = pt[d];
+                if (this._BBoxMax[d] < pt[d]) {
+                    this._BBoxMax[d] = pt[d];
                 }
-            }
-        }
-        //save the center of the bbox for later use (while constructing the canvas)
-        this._stageWorldCenter = VecUtils.vecInterpolate(3, bboxMin, bboxMax, 0.5);
-
-        // ***** center the input stageworld data about the center of the bbox *****
-        this._LocalPoints = [];
-        for (i=0;i<numPoints;i++){
-            var localPoint = [this._Points[i][0],this._Points[i][1],this._Points[i][2]];
-            localPoint[0]-= this._stageWorldCenter[0];
-            localPoint[1]-= this._stageWorldCenter[1];
-
-            // ***** unproject all the centered points and convert them to 2D (plane space)*****
-            // (undo the projection step performed by the browser)
-            //localPoint = this._unprojectPt(localPoint, 1400); //todo get the perspective distance from the canvas
-            localPoint = MathUtils.transformPoint(localPoint, this._planeMatInv);
-
-            //add to the list of local points
-            this._LocalPoints.push(localPoint);
+            }//for every dimension d from 0 to 2
         }
+    }
 
-        // ***** compute width, height, and midpoint position (in stage world position) of the canvas
-        this._updateBoundingBox(); //compute the bbox to obtain the width and height used below
-        var halfwidth = 0.5*(this._BBoxMax[0]-this._BBoxMin[0]);
-        var halfheight = 0.5*(this._BBoxMax[1]-this._BBoxMin[1]);
-        this._OrigLocalPoints    = [];
-        for (i=0;i<numPoints;i++) {
-            this._LocalPoints[i][0]+= halfwidth;
-            this._LocalPoints[i][1]+= halfheight;
-
-            //store the original points
-            this._OrigLocalPoints.push([this._LocalPoints[i][0],this._LocalPoints[i][1],this._LocalPoints[i][2]]);
-        }
-        //update the bbox with the same adjustment as was made for the local points above
-        this._BBoxMax[0]+= halfwidth;this._BBoxMin[0]+= halfwidth;
-        this._BBoxMax[1]+= halfheight;this._BBoxMin[1]+= halfheight;
-    };
-    
-    this.update = function() {
-        if (this._isDirty){
-            // **** do smoothing if necessary ****
-            this._doSmoothing();
+    //increase the bbox given the stroke width and the angle (in case of calligraphic brush)
+    var bboxPadding = this._strokeWidth/2;
+    //todo TEMP!
+    //bboxPadding = 0; //for now, ignore the effect of stroke width on bounding box
+    //end todo TEMP
+    //if (this._strokeUseCalligraphic) {
+    //todo re-enable this if check once we are able to change the left and top of the brush canvas
+    if (false){
+        this._BBoxMin[0]-= bboxPadding*Math.cos(this._strokeAngle);
+        this._BBoxMin[1]-= bboxPadding*Math.sin(this._strokeAngle);
+        this._BBoxMax[0]+= bboxPadding*Math.cos(this._strokeAngle);
+        this._BBoxMax[1]+= bboxPadding*Math.sin(this._strokeAngle);
+    } else {
+        for (var d = 0; d < 3; d++) {
+            this._BBoxMin[d]-= bboxPadding;
+            this._BBoxMax[d]+= bboxPadding;
+        }//for every dimension d from 0 to 2
+    }
+};
+
+BrushStroke.prototype.buildBuffers = function () {
+    //return; //no need to do anything for now
+};//buildBuffers()
+
+//render
+//  specify how to render the subpath in Canvas2D
+BrushStroke.prototype.render = function () {
+    // get the world
+    var world = this.getWorld();
+    if (!world){
+        throw( "null world in brushstroke render" );
+    }
 
-            // **** recompute the bounding box ****
-            this._updateBoundingBox();
+    var numPoints = this.getNumPoints();
+    if (numPoints === 0) {
+        return; //nothing to do for empty paths
+    }
 
-            // **** offset the local coords to account for the change in bbox ****
-            this._offsetLocalCoord(-this._BBoxMin[0], -this._BBoxMin[1]);
+    if (this._isDirty){
+        this.update();
+    }
+    var bboxMin = this.getBBoxMin();
+    var bboxMax = this.getBBoxMax();
+    var bboxWidth = bboxMax[0] - bboxMin[0];
+    var bboxHeight = bboxMax[1] - bboxMin[1];
+
+    if (!this._canvas){
+        //set the canvas by querying the world
+        this._canvas = this.getWorld().getCanvas();
+    }
+    if (this._canvas) {
+        var newLeft = Math.round(this._stageWorldCenter[0] - 0.5 * bboxWidth);
+        var newTop = Math.round(this._stageWorldCenter[1] - 0.5 * bboxHeight);
+        //assign the new position, width, and height as the canvas dimensions through the canvas controller
+        //CanvasController.setProperty(this._canvas, "left", newLeft+"px");
+        //CanvasController.setProperty(this._canvas, "top", newTop+"px");
+
+        CanvasController.setProperty(this._canvas, "width", bboxWidth+"px");
+        CanvasController.setProperty(this._canvas, "height", bboxHeight+"px");
+        //this._canvas.elementModel.shapeModel.GLWorld.setViewportFromCanvas(this._canvas);
+    }
 
-            // **** turn off the dirty flag ****
-            this._isDirty = false;
-        }
-    };
 
-    this._offsetLocalCoord = function(deltaW, deltaH){
-        var numPoints = this._LocalPoints.length;
-        for (var i=0;i<numPoints;i++) {
-            this._LocalPoints[i][0]+= deltaW;
-            this._LocalPoints[i][1]+= deltaH;
-        }
-    };
+    //get the context
+    var ctx = world.get2DContext();
+    if (!ctx) {
+        throw ("null context in brushstroke render");
+    }
+    ctx.save();
+    ctx.clearRect(0, 0, bboxWidth, bboxHeight);
+    this.drawToContext(ctx, false);
+    ctx.restore();
+}; //this.render()
 
-    //I had to write this function to do a deep copy because I think slice(0) creates a copy by reference
-    this._copyCoordinates3D = function(srcCoord, destCoord){
-        var i=0;
-        var numPoints = srcCoord.length;
-        for (i=0;i<numPoints;i++){
-            destCoord[i] = [srcCoord[i][0],srcCoord[i][1],srcCoord[i][2]];
-        }
-    };
-    this._doSmoothing = function() {
-        var numPoints = this._LocalPoints.length;
-        if (this._strokeDoSmoothing && numPoints>1) {
-            this._copyCoordinates3D(this._OrigLocalPoints   , this._LocalPoints);
-            //iterations of Laplacian smoothing (setting the points to the average of their neighbors)
-            var numLaplacianIterations = this._strokeAmountSmoothing;
-            for (var n=0;n<numLaplacianIterations;n++){
-                var newPoints = this._LocalPoints.slice(0); //I think this performs a copy by reference, which would make the following a SOR step
-                for (var i=1;i<numPoints-1;i++) {
-                    var avgPos = [  0.5*(this._LocalPoints[i-1][0] + this._LocalPoints[i+1][0]),
-                                    0.5*(this._LocalPoints[i-1][1] + this._LocalPoints[i+1][1]),
-                                    0.5*(this._LocalPoints[i-1][2] + this._LocalPoints[i+1][2])] ;
-                    newPoints[i] = avgPos;
-                }
-                this._LocalPoints = newPoints.slice(0);
-            }
-        }
-    };
 
-    this._updateBoundingBox = function() {
-        // *** compute the bounding box *********
-        var points = this._LocalPoints;
-        var numPoints = points.length;
 
-        this._BBoxMin = [Infinity, Infinity, Infinity];
-        this._BBoxMax = [-Infinity, -Infinity, -Infinity];
-        if (numPoints === 0) {
-            this._BBoxMin = [0, 0, 0];
-            this._BBoxMax = [0, 0, 0];
-        } else {
-            for (var i=0;i<numPoints;i++){
-                var pt = points[i];
-                for (var d = 0; d < 3; d++) {
-                    if (this._BBoxMin[d] > pt[d]) {
-                        this._BBoxMin[d] = pt[d];
-                    }
-                    if (this._BBoxMax[d] < pt[d]) {
-                        this._BBoxMax[d] = pt[d];
-                    }
-                }//for every dimension d from 0 to 2
-            }
-        }
+//buildColor returns the fillStyle or strokeStyle for the Canvas 2D context
+BrushStroke.prototype.buildColor = function(ctx,          //the 2D rendering context (for creating gradients if necessary)
+                                          ipColor,      //color string, also encodes whether there's a gradient and of what type
+                                          w,            //width of the region of color
+                                          h,            //height of the region of color
+                                          lw,           //linewidth (i.e. stroke width/size)
+                                          alphaVal)     //alpha value for this color (usually computed by the rendering code separately)
+{
+    if (ipColor.gradientMode){
+        var position, gradient, cs, inset; //vars used in gradient calculations
+        inset = Math.ceil( lw ) - 0.5;
 
-        //increase the bbox given the stroke width and the angle (in case of calligraphic brush)
-        var bboxPadding = this._strokeWidth/2;
-        //todo TEMP!
-        //bboxPadding = 0; //for now, ignore the effect of stroke width on bounding box
-        //end todo TEMP
-        //if (this._strokeUseCalligraphic) {
-        //todo re-enable this if check once we are able to change the left and top of the brush canvas
-        if (false){
-            this._BBoxMin[0]-= bboxPadding*Math.cos(this._strokeAngle);
-            this._BBoxMin[1]-= bboxPadding*Math.sin(this._strokeAngle);
-            this._BBoxMax[0]+= bboxPadding*Math.cos(this._strokeAngle);
-            this._BBoxMax[1]+= bboxPadding*Math.sin(this._strokeAngle);
+        if(ipColor.gradientMode === "radial") {
+            var ww = w - 2*lw,  hh = h - 2*lw;
+            gradient = ctx.createRadialGradient(w*0.5, h*0.5, 0, w*0.5, h*0.5, Math.max(ww, hh)*0.5);
         } else {
-            for (var d = 0; d < 3; d++) {
-                this._BBoxMin[d]-= bboxPadding;
-                this._BBoxMax[d]+= bboxPadding;
-            }//for every dimension d from 0 to 2
+            gradient = ctx.createLinearGradient(inset, h*0.5, w-inset, h*0.5);
         }
-    };
+        var colors = ipColor.color;
 
-    this.buildBuffers = function () {
-        //return; //no need to do anything for now
-    };//buildBuffers()
-
-    //render
-    //  specify how to render the subpath in Canvas2D
-    this.render = function () {
-        // get the world
-        var world = this.getWorld();
-        if (!world){
-            throw( "null world in brushstroke render" );
-        }
-
-        var numPoints = this.getNumPoints();
-        if (numPoints === 0) {
-            return; //nothing to do for empty paths
-        }
-
-        if (this._isDirty){
-            this.update();
-        }
-        var bboxMin = this.getBBoxMin();
-        var bboxMax = this.getBBoxMax();
-        var bboxWidth = bboxMax[0] - bboxMin[0];
-        var bboxHeight = bboxMax[1] - bboxMin[1];
-
-        if (!this._canvas){
-            //set the canvas by querying the world
-            this._canvas = this.getWorld().getCanvas();
-        }
-        if (this._canvas) {
-            var newLeft = Math.round(this._stageWorldCenter[0] - 0.5 * bboxWidth);
-            var newTop = Math.round(this._stageWorldCenter[1] - 0.5 * bboxHeight);
-            //assign the new position, width, and height as the canvas dimensions through the canvas controller
-            //CanvasController.setProperty(this._canvas, "left", newLeft+"px");
-            //CanvasController.setProperty(this._canvas, "top", newTop+"px");
-
-            CanvasController.setProperty(this._canvas, "width", bboxWidth+"px");
-            CanvasController.setProperty(this._canvas, "height", bboxHeight+"px");
-            //this._canvas.elementModel.shapeModel.GLWorld.setViewportFromCanvas(this._canvas);
+        var len = colors.length;
+        for(n=0; n<len; n++) {
+            position = colors[n].position*0.01;
+            cs = colors[n].value;
+            gradient.addColorStop(position, "rgba(" + cs.r + "," + cs.g + "," + cs.b + "," + alphaVal + ")");
         }
+        return gradient;
+    } else {
+        var c = "rgba(" + 255*ipColor[0] + "," + 255*ipColor[1] + "," + 255*ipColor[2] + "," + alphaVal + ")";
+        return c;
+    }
+};
 
 
-        //get the context
-        var ctx = world.get2DContext();
-        if (!ctx) {
-            throw ("null context in brushstroke render");
-        }
-        ctx.save();
-        ctx.clearRect(0, 0, bboxWidth, bboxHeight);
-        this.drawToContext(ctx, false);
-        ctx.restore();
-    } //this.render()
-
-    this.drawToContext = function(ctx, drawStageWorldPts, stageWorldDeltaX, stageWorldDeltaY, stageWorldToScreenMat){
-        var points = this._LocalPoints;
-        if (drawStageWorldPts){ //this is usually true when we're drawing the brush stroke on the stage (no canvas yet)
-            points = this._Points;
-        }
-        var numPoints = points.length;
-        var tempP, p;
-        if (this._strokeUseCalligraphic) {
-            //build the stamp for the brush stroke
-            var t=0;
-            var numTraces = this._strokeWidth;
-            var halfNumTraces = numTraces*0.5;
-            var opaqueRegionHalfWidth = 0.5*this._strokeHardness*numTraces*0.01; //the 0.01 is to convert the strokeHardness from [0,100] to [0,1]
-            var maxTransparentRegionHalfWidth = halfNumTraces-opaqueRegionHalfWidth;
-
-            //todo this brush stamp should be created outside of this function
-            //build an angled (calligraphic) brush stamp
-            var deltaDisplacement = [Math.cos(this._strokeAngle),Math.sin(this._strokeAngle)];
-            deltaDisplacement = VecUtils.vecNormalize(2, deltaDisplacement, 1);
-            var startPos = [-halfNumTraces*deltaDisplacement[0],-halfNumTraces*deltaDisplacement[1]];
-
-            var brushStamp = [];
-            for (t=0;t<numTraces;t++){
-                var brushPt = [startPos[0]+t*deltaDisplacement[0], startPos[1]+t*deltaDisplacement[1]];
-                brushStamp.push(brushPt);
+BrushStroke.prototype.drawToContext = function(ctx, drawStageWorldPts, stageWorldDeltaX, stageWorldDeltaY, stageWorldToScreenMat){
+    var points = this._LocalPoints;
+    if (drawStageWorldPts){ //this is usually true when we're drawing the brush stroke on the stage (no canvas yet)
+        points = this._Points;
+    }
+    var numPoints = points.length;
+    var tempP, p, w, h;
+
+    var world = this.getWorld();
+    var useBuildColor = false;
+    if (world){
+        if (this._strokeColor.gradientMode){
+            useBuildColor = true;
+        }
+        //vars used for the gradient computation in buildColor
+        w = world.getViewportWidth();
+        h = world.getViewportHeight();
+    }
+    
+    if (this._strokeUseCalligraphic) {
+        //build the stamp for the brush stroke
+        var t=0;
+        var numTraces = this._strokeWidth;
+        var halfNumTraces = numTraces*0.5;
+        var opaqueRegionHalfWidth = 0.5*this._strokeHardness*numTraces*0.01; //the 0.01 is to convert the strokeHardness from [0,100] to [0,1]
+        var maxTransparentRegionHalfWidth = halfNumTraces-opaqueRegionHalfWidth;
+
+        //todo this brush stamp should be created outside of this function
+        //build an angled (calligraphic) brush stamp
+        var deltaDisplacement = [Math.cos(this._strokeAngle),Math.sin(this._strokeAngle)];
+        deltaDisplacement = VecUtils.vecNormalize(2, deltaDisplacement, 1);
+        var startPos = [-halfNumTraces*deltaDisplacement[0],-halfNumTraces*deltaDisplacement[1]];
+
+        var brushStamp = [];
+        for (t=0;t<numTraces;t++){
+            var brushPt = [startPos[0]+t*deltaDisplacement[0], startPos[1]+t*deltaDisplacement[1]];
+            brushStamp.push(brushPt);
+        }
+
+        ctx.lineJoin="bevel";
+        ctx.lineCap="butt";
+        ctx.globalCompositeOperation = 'source-over';
+        ctx.globalAlpha = this._strokeColor[3];
+
+        for (t=0;t<numTraces;t++){
+            var disp = [brushStamp[t][0], brushStamp[t][1]];
+            var alphaVal = 1.0;
+            var distFromOpaqueRegion = Math.abs(t-halfNumTraces) - opaqueRegionHalfWidth;
+            if (distFromOpaqueRegion>0) {
+                var transparencyFactor = distFromOpaqueRegion/maxTransparentRegionHalfWidth;
+                alphaVal = 1.0 - transparencyFactor;//(transparencyFactor*transparencyFactor);//the square term produces nonlinearly varying alpha values
+                alphaVal *= 0.5; //factor that accounts for lineWidth == 2
+            }
+            ctx.save();
+            if (t === (numTraces-1) || t === 0){
+                ctx.lineWidth = 1;
+            } else {
+                 //todo figure out the correct formula for the line width
+                ctx.lineWidth=2;
             }
 
-            ctx.lineJoin="bevel";
-            ctx.lineCap="butt";
-            ctx.globalCompositeOperation = 'source-over';
-            ctx.globalAlpha = this._strokeColor[3];
-
-            for (t=0;t<numTraces;t++){
-                var disp = [brushStamp[t][0], brushStamp[t][1]];
-                var alphaVal = 1.0;
-                var distFromOpaqueRegion = Math.abs(t-halfNumTraces) - opaqueRegionHalfWidth;
-                if (distFromOpaqueRegion>0) {
-                    var transparencyFactor = distFromOpaqueRegion/maxTransparentRegionHalfWidth;
-                    alphaVal = 1.0 - transparencyFactor;//(transparencyFactor*transparencyFactor);//the square term produces nonlinearly varying alpha values
-                    alphaVal *= 0.5; //factor that accounts for lineWidth == 2
-                }
-                ctx.save();
-                if (t === (numTraces-1) || t === 0){
-                    ctx.lineWidth = 1;
-                } else {
-                     //todo figure out the correct formula for the line width
-                    ctx.lineWidth=2;
-                }
+            if (!useBuildColor){
                 ctx.strokeStyle="rgba("+parseInt(255*this._strokeColor[0])+","+parseInt(255*this._strokeColor[1])+","+parseInt(255*this._strokeColor[2])+","+alphaVal+")";
-                //linearly interpolate between the two stroke colors
-                var currStrokeColor = VecUtils.vecInterpolate(4, this._strokeColor, this._secondStrokeColor, t/numTraces);
-                //ctx.strokeStyle="rgba("+parseInt(255*currStrokeColor[0])+","+parseInt(255*currStrokeColor[1])+","+parseInt(255*currStrokeColor[2])+","+alphaVal+")";
-                ctx.translate(disp[0],disp[1]);
-                ctx.beginPath();
+            } else {
+                ctx.strokeStyle = this.buildColor(ctx, this._strokeColor, w, h, this._strokeWidth, alphaVal);
+            }
+            //linearly interpolate between the two stroke colors
+            var currStrokeColor = VecUtils.vecInterpolate(4, this._strokeColor, this._secondStrokeColor, t/numTraces);
+            //ctx.strokeStyle="rgba("+parseInt(255*currStrokeColor[0])+","+parseInt(255*currStrokeColor[1])+","+parseInt(255*currStrokeColor[2])+","+alphaVal+")";
+            ctx.translate(disp[0],disp[1]);
+            ctx.beginPath();
+            if (drawStageWorldPts) {
+                tempP = points[0].slice(0);
+                tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
+                p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
+            } else {
+                p = points[0];
+            }
+            ctx.moveTo(p[0],p[1]);
+            for (var i=0;i<numPoints;i++){
                 if (drawStageWorldPts) {
-                    tempP = points[0].slice(0);
+                    tempP = points[i].slice(0);
                     tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
                     p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
                 } else {
-                    p = points[0];
+                    p = points[i];
                 }
-                ctx.moveTo(p[0],p[1]);
-                for (var i=0;i<numPoints;i++){
-                    if (drawStageWorldPts) {
-                        tempP = points[i].slice(0);
-                        tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
-                        p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
-                    } else {
-                        p = points[i];
-                    }
-                    ctx.lineTo(p[0],p[1]);
-                }
-                ctx.stroke();
-                ctx.restore();
+                ctx.lineTo(p[0],p[1]);
             }
-        } else {
-            ctx.globalCompositeOperation = 'lighter'; //we wish to add up the colors
-            ctx.globalAlpha = this._strokeColor[3];
-            ctx.lineCap = "round";
-            ctx.lineJoin="round";
-            var minStrokeWidth = (this._strokeHardness*this._strokeWidth)/100; //the hardness is the percentage of the stroke width that's fully opaque
-            var numlayers = 1 + Math.ceil((this._strokeWidth-minStrokeWidth)*0.5);
-            var alphaVal = 1.0/(numlayers); //this way the alpha at the first path will be 1
+            ctx.stroke();
+            ctx.restore();
+        }
+    } else {
+        ctx.globalCompositeOperation = 'lighter'; //we wish to add up the colors
+        ctx.globalAlpha = this._strokeColor[3];
+        ctx.lineCap = "round";
+        ctx.lineJoin="round";
+        var minStrokeWidth = (this._strokeHardness*this._strokeWidth)/100; //the hardness is the percentage of the stroke width that's fully opaque
+        var numlayers = 1 + Math.ceil((this._strokeWidth-minStrokeWidth)*0.5);
+        var alphaVal = 1.0/(numlayers); //this way the alpha at the first path will be 1
+
+        if (!useBuildColor){
             ctx.strokeStyle="rgba("+parseInt(255*this._strokeColor[0])+","+parseInt(255*this._strokeColor[1])+","+parseInt(255*this._strokeColor[2])+","+alphaVal+")";
-            for (var l=0;l<numlayers;l++){
-                ctx.beginPath();
+        } else {
+            ctx.strokeStyle = this.buildColor(ctx, this._strokeColor, w,h, this._strokeWidth, alphaVal);
+        }
+
+        for (var l=0;l<numlayers;l++){
+            ctx.beginPath();
+            if (drawStageWorldPts) {
+                tempP = points[0].slice(0);
+                tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
+                p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
+            } else {
+                p = points[0];
+            }
+            ctx.moveTo(p[0],p[1]);
+            if (numPoints===1){
+                //display a tiny segment as a single point
+               ctx.lineTo(p[0],p[1]+0.01);
+            }
+            for (var i=1;i<numPoints;i++){
                 if (drawStageWorldPts) {
-                    tempP = points[0].slice(0);
+                    tempP = points[i].slice(0);
                     tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
                     p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
                 } else {
-                    p = points[0];
-                }
-                ctx.moveTo(p[0],p[1]);
-                if (numPoints===1){
-                    //display a tiny segment as a single point
-                   ctx.lineTo(p[0],p[1]+0.01);
-                }
-                for (var i=1;i<numPoints;i++){
-                    if (drawStageWorldPts) {
-                        tempP = points[i].slice(0);
-                        tempP[0]+=stageWorldDeltaX; tempP[1]+=stageWorldDeltaY;
-                        p = MathUtils.transformAndDivideHomogeneousPoint(tempP, stageWorldToScreenMat);
-                    } else {
-                        p = points[i];
-                    }
-                    ctx.lineTo(p[0],p[1]);
+                    p = points[i];
                 }
-                ctx.lineWidth=2*l+minStrokeWidth;
-
-
-                //experiments with shadows
-                /*
-                ctx.shadowOffsetX = 10;
-                ctx.shadowOffsetY = 10;
-                ctx.shadowBlur    = 10;
-                ctx.shadowColor   = //"rgb("+parseInt(255*this._strokeColor[0])+","+parseInt(255*this._strokeColor[1])+","+parseInt(255*this._strokeColor[2])+")";
-                    "#FF6666";  //or use rgb(red, green, blue)
-                 */
-                ctx.stroke();
-            }//for every layer l
-        } //if there is no calligraphic stroke
-    }; //this.drawToCanvas()
-
-
-    this.exportJSON = function(){
-        var retObject= new Object();
-        //the type of this object
-        retObject.type = this.geomType();
-        retObject.geomType = retObject.type;
-
-        //the geometry for this object
-        retObject.localPoints = this._LocalPoints.slice(0);
-        this._copyCoordinates3D(this._LocalPoints, retObject.localPoints); //todo is this necessary in addition to the slice(0) above?
-        retObject.origLocalPoints = this._OrigLocalPoints.slice(0);
-        this._copyCoordinates3D(this._OrigLocalPoints, retObject.origLocalPoints); //todo <ditto>
-
-        retObject.stageWorldCenter = [this._stageWorldCenter[0],this._stageWorldCenter[1],this._stageWorldCenter[2]];
-        retObject.planeMat = this._planeMat;
-        retObject.planeMatInv = this._planeMatInv;
-        retObject.dragPlane = [this._dragPlane[0],this._dragPlane[1],this._dragPlane[2],this._dragPlane[3]];
-
-        //stroke appearance properties
-        retObject.strokeWidth = this._strokeWidth;
-        retObject.strokeColor = this._strokeColor;
-        retObject.strokeHardness = this._strokeHardness;
-        retObject.strokeUseCalligraphic = this._strokeUseCalligraphic;
-        retObject.strokeAngle = this._strokeAngle;
-
-        //stroke smoothing properties
-        retObject.strokeDoSmoothing = this._strokeDoSmoothing;
-        retObject.strokeAmountSmoothing = this._strokeAmountSmoothing;
-
-        return retObject;
-    };
-
-    this.importJSON = function(jo){
-        if (this.geomType()!== jo.geomType){
-            return;
-        } 
-        //the geometry for this object
-        this._LocalPoints = jo.localPoints.slice(0);
-        this._copyCoordinates3D(jo.localPoints, this._LocalPoints); //todo is this necessary in addition to the slice(0) above?
-        this._OrigLocalPoints = jo.origLocalPoints.slice(0);
-        this._copyCoordinates3D(jo.origLocalPoints, this._OrigLocalPoints); //todo <ditto>
-
-        this._stageWorldCenter = [jo.stageWorldCenter[0],jo.stageWorldCenter[1],jo.stageWorldCenter[2]];
-        this._planeMat = jo.planeMat;
-        this._planeMatInv = jo.planeMatInv;
-        this._dragPlane = [jo.dragPlane[0],jo.dragPlane[1],jo.dragPlane[2],jo.dragPlane[3]];
-
-        //stroke appearance properties
-        this._strokeWidth = jo.strokeWidth;
-        this._strokeColor = jo.strokeColor;
-        this._strokeHardness = jo.strokeHardness;
-        this._strokeUseCalligraphic = jo.strokeUseCalligraphic;
-        this._strokeAngle = jo.strokeAngle;
-
-        //stroke smoothing properties
-        this._strokeDoSmoothing = jo.strokeDoSmoothing;
-        this._strokeAmountSmoothing = jo.strokeAmountSmoothing;
-
-        this._isInit = true; //do not re-initialize this brush stroke
-        this._isDirty = true;  //force a re-computation of meta-geometry before rendering
-        this.update();      //after this, the stroke is ready to be rendered
-    };
-
-    this.collidesWithPoint = function (x, y, z) {
-        if (x < this._BBoxMin[0]) return false;
-        if (x > this._BBoxMax[0]) return false;
-        if (y < this._BBoxMin[1]) return false;
-        if (y > this._BBoxMax[1]) return false;
-        if (z < this._BBoxMin[2]) return false;
-        if (z > this._BBoxMax[2]) return false;
-
-        return true;
-    };
-
-    this.collidesWithPoint = function (x, y) {
-        if (x < this._BBoxMin[0]) return false;
-        if (x > this._BBoxMax[0]) return false;
-        if (y < this._BBoxMin[1]) return false;
-        if (y > this._BBoxMax[1]) return false;
-
-        return true;
-    };
-
-}; //function BrushStroke ...class definition
-
-BrushStroke.prototype = Object.create(GeomObj, {});
+                ctx.lineTo(p[0],p[1]);
+            }
+            ctx.lineWidth=2*l+minStrokeWidth;
+
+
+            //experiments with shadows
+            /*
+            ctx.shadowOffsetX = 10;
+            ctx.shadowOffsetY = 10;
+            ctx.shadowBlur    = 10;
+            ctx.shadowColor   = //"rgb("+parseInt(255*this._strokeColor[0])+","+parseInt(255*this._strokeColor[1])+","+parseInt(255*this._strokeColor[2])+")";
+                "#FF6666";  //or use rgb(red, green, blue)
+             */
+            ctx.stroke();
+        }//for every layer l
+    } //if there is no calligraphic stroke
+}; //this.drawToCanvas()
+
+
+BrushStroke.prototype.exportJSON = function(){
+    var retObject= new Object();
+    //the type of this object
+    retObject.type = this.geomType();
+    retObject.geomType = retObject.type;
+
+    //the geometry for this object
+    retObject.localPoints = this._LocalPoints.slice(0);
+    this._copyCoordinates3D(this._LocalPoints, retObject.localPoints); //todo is this necessary in addition to the slice(0) above?
+    retObject.origLocalPoints = this._OrigLocalPoints.slice(0);
+    this._copyCoordinates3D(this._OrigLocalPoints, retObject.origLocalPoints); //todo <ditto>
+
+    retObject.stageWorldCenter = [this._stageWorldCenter[0],this._stageWorldCenter[1],this._stageWorldCenter[2]];
+    retObject.planeMat = this._planeMat;
+    retObject.planeMatInv = this._planeMatInv;
+    retObject.dragPlane = [this._dragPlane[0],this._dragPlane[1],this._dragPlane[2],this._dragPlane[3]];
+
+    //stroke appearance properties
+    retObject.strokeWidth = this._strokeWidth;
+    retObject.strokeColor = this._strokeColor;
+    retObject.strokeHardness = this._strokeHardness;
+    retObject.strokeUseCalligraphic = this._strokeUseCalligraphic;
+    retObject.strokeAngle = this._strokeAngle;
+
+    //stroke smoothing properties
+    retObject.strokeDoSmoothing = this._strokeDoSmoothing;
+    retObject.strokeAmountSmoothing = this._strokeAmountSmoothing;
+
+    return retObject;
+};
+
+BrushStroke.prototype.importJSON = function(jo){
+    if (this.geomType()!== jo.geomType){
+        return;
+    }
+    //the geometry for this object
+    this._LocalPoints = jo.localPoints.slice(0);
+    this._copyCoordinates3D(jo.localPoints, this._LocalPoints); //todo is this necessary in addition to the slice(0) above?
+    this._OrigLocalPoints = jo.origLocalPoints.slice(0);
+    this._copyCoordinates3D(jo.origLocalPoints, this._OrigLocalPoints); //todo <ditto>
+
+    this._stageWorldCenter = [jo.stageWorldCenter[0],jo.stageWorldCenter[1],jo.stageWorldCenter[2]];
+    this._planeMat = jo.planeMat;
+    this._planeMatInv = jo.planeMatInv;
+    this._dragPlane = [jo.dragPlane[0],jo.dragPlane[1],jo.dragPlane[2],jo.dragPlane[3]];
+
+    //stroke appearance properties
+    this._strokeWidth = jo.strokeWidth;
+    this._strokeColor = jo.strokeColor;
+    this._strokeHardness = jo.strokeHardness;
+    this._strokeUseCalligraphic = jo.strokeUseCalligraphic;
+    this._strokeAngle = jo.strokeAngle;
+
+    //stroke smoothing properties
+    this._strokeDoSmoothing = jo.strokeDoSmoothing;
+    this._strokeAmountSmoothing = jo.strokeAmountSmoothing;
+
+    this._isInit = true; //do not re-initialize this brush stroke
+    this._isDirty = true;  //force a re-computation of meta-geometry before rendering
+    this.update();      //after this, the stroke is ready to be rendered
+};
+
+BrushStroke.prototype.collidesWithPoint = function (x, y, z) {
+    if (x < this._BBoxMin[0]) return false;
+    if (x > this._BBoxMax[0]) return false;
+    if (y < this._BBoxMin[1]) return false;
+    if (y > this._BBoxMax[1]) return false;
+    if (z < this._BBoxMin[2]) return false;
+    if (z > this._BBoxMax[2]) return false;
+
+    return true;
+};
+
+BrushStroke.prototype.collidesWithPoint = function (x, y) {
+    if (x < this._BBoxMin[0]) return false;
+    if (x > this._BBoxMax[0]) return false;
+    if (y < this._BBoxMin[1]) return false;
+    if (y > this._BBoxMax[1]) return false;
+
+    return true;
+};
 
 BrushStroke.prototype._CatmullRomSplineInterpolate = function(ctrlPts, t)
 {
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