title: maya api vs python commands: vertex normals
body: <p>I'm trying to extract the vertex normal of a mesh object at a particular vertex. I've noticed that I get different results when using the python API instead of the maya python commands.</p>
  
  <p><strong>Python commands (gives me the result i want)</strong>:</p>
  
  <pre><code>cmds.polyNormalPerVertex("&lt;myshapename&gt;.vtx[523]", q=True,normalXYZ=True)
  </code></pre>
  
  <p><strong>The maya python API call (gives me a different result)</strong>:</p>
  
  <pre><code># empty selection list
  selectionList = om.MSelectionList()
  selectionList.add(&lt;myshapename&gt;)
  
  # create empty dag path object
  dagPath = selectionList.getDagPath(0)
  
  # get mesh 
  mesh = om.MFnTransform(dagPath)
  
  # get vertex normal
  mesh.getVertexNormal(523, False, space=om.MSpace.kWorld)
  </code></pre>
  
  <p>I noticed this discrepancy when trying to extract normals on an object whose vertices are on the seam border with another object. The normals have been averaged in maya using <code>Normals &gt; Average Normals</code> from the <code>Polygons</code> menu set.</p>
  
  <p>I know it's difficult without an example object, but I'm hoping somebody has seen this problem before.</p>
  
  <p>Can anyone provide a possible explanation for this discrepancy?</p>