o3d-webgl: Fixes picking edge case where two components of the world ray are both 0.

samples/o3d-webgl/primitive.js

 /*
  * Copyright 2010, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 507 matching lines @@
     var v0 = (t00 * x -
         (m10 * m22 - m12 * m20) * y +
         (m10 * m21 - m11 * m20) * z) / d;
     var v1 = (-t10 * x +
         (m00 * m22 - m02 * m20) * y -
         (m00 * m21 - m01 * m20) * z) / d;
     var v2 = (t20 * x -
         (m00 * m12 - m02 * m10) * y +
         (m00 * m11 - m01 * m10) * z) / d;
 
-    if (v0 > 0 && v1 > 0 && v2 > 0) {
+    if (v0 >= 0 && v1 >= 0 && v2 >= 0 && (v0 + v1 + v2 > 0)) {
       // Rescale by the one-norm to find the intersection of the transformed.
       // ray with the unit triangle.
       var one_norm = v0 + v1 + v2;
       v0 /= one_norm;
       v1 /= one_norm;
       v2 /= one_norm;
       // Multiply m to get back to the original triangle.
       var px = m00 * v0 + m10 * v1 + m20 * v2;
       var py = m01 * v0 + m11 * v1 + m21 * v2;
       var pz = m02 * v0 + m12 * v1 + m22 * v2;
@@ skipping 42 matching lines @@
     }
     points.push(p);
   }
 
   o3d.BoundingBox.fitBoxToPoints_(points, this.boundingBox);
   return this.boundingBox;
 };