1 files changed, 11 insertions, 1 deletions

diff --git a/js/helper-classes/3D/StageLine.js b/js/helper-classes/3D/StageLine.js
index d6eea478..b869fb17 100755
--- a/js/helper-classes/3D/StageLine.js
+++ b/js/helper-classes/3D/StageLine.js
@@ -246,8 +246,17 @@ var StageLine = exports.StageLine = Object.create(Object.prototype, {
                 if (s0 != s1)
                 {
                     var t = Math.abs(d0)/( Math.abs(d0) + Math.abs(d1) );
-                    if (t == 0)
+                                        if (MathUtils.fpSign(t) === 0)
                     {
+                                                // the first point of the line is on the (infinite) extension of a side of the boundary.
+                                                // Make sure the point (pt0) is within the range of the polygon edge
+                                                var vt0 = vecUtils.vecSubtract(3, pt0, bp0),
+                                                        vt1 = vecUtils.vecSubtract(3, bp1, pt0);
+                                                var dt0 = vecUtils.vecDot(3, vec, vt0),
+                                                        dt1 = vecUtils.vecDot(3, vec, vt1);
+                                                var st0 = MathUtils.fpSign(dt0),  st1 = MathUtils.fpSign(dt1);
+                                                if ((st0 >= 0) && (st1 >= 0))
+                                                {
                         if (s1 > 0) // entering the material from the beginning of the line that is to be drawn
                         {
                             // see if the start point of the line is at a corner of the bounded plane
@@ -291,6 +300,7 @@ var StageLine = exports.StageLine = Object.create(Object.prototype, {
                             }
                         }
                     }
+                                        }
                     else if ( (MathUtils.fpSign(t) > 0) && (MathUtils.fpCmp(t,1.0) <= 0))
                     {
                         // get the point where the line crosses the edge of the element plane