title: Normalized uv for shaderModifiers .fragment attached to SCNGeometry (SCNPlane)
body: <p>seems quite difficult for me to get this info so I will ask here directly.</p>
  <p><strong>Q:</strong> How do I get the correct normalized UV when dealing with shaderModifiers .fragment attached to a geometry in a SCNNode?</p>
  <p><strong>More info:</strong>
  SCNGeometry is SCNPlane and I want to make it half black, half white.</p>
  <p><em>The below all return wrong positions</em></p>
  <pre><code>float2 uv = _surface.diffuseTexcoord
  if ( uv.x &gt; 0 ) { color = white;} else { color = black;}
  </code></pre>
  <pre><code>float2 uv = _surface.diffuseTexcoord
  if ( uv.x &gt; 0.5 ) { color = white;} else { color = black;}
  </code></pre>
  <pre><code>float2 uv = -1.0+2.0*_surface.diffuseTexcoord;
  if ( uv.x &gt; 0 ) { color = white;} else { color = black;}
  </code></pre>
  <pre><code>float2 uv = _surface.diffuseTexcoord;
  if ( uv.x &gt; scn_node.boundingBox[0].x  &amp;&amp; uv.x &lt; (scn_node.boundingBox[1].x / 2 ) ) { color = white;} else { color = black;}
  </code></pre>
  <pre><code>float2 uv = -1.0+2.0*_surface.diffuseTexcoord;
  if ( uv.x &gt; scn_node.boundingBox[0].x  &amp;&amp; uv.x &lt; (scn_node.boundingBox[1].x / 2 ) ) { color = white;} else { color = black;}
  </code></pre>
  <p><strong>EDIT:</strong></p>
  <p>&quot;How you are using the color variable?&quot;
  _output.color = color;</p>
  <p><strong>UPDATE:</strong></p>
  <p>Removing</p>
  <pre><code>myMaterial.diffuse.contentsTransform = SCNMatrix4MakeScale(value1, value2 , 1)
  </code></pre>
  <p>did the trick.</p>
  <p><strong>Applying 1/value1 and 1/value2 to uv will bring me back to the normalized value?</strong></p>
  <p><strong>Also what is the normalized value for us in shaderModifiers? -1/+1 or 0/+1 ?</strong></p>