code: @Override
  	public double getAttributeAsDbl(int semantics, int offset, int ordinate) {
  		if (offset < 0 || offset >= m_pointCount)
  			throw new IndexOutOfBoundsException();
  
  		int ncomps = VertexDescription.getComponentCount(semantics);
  		if (ordinate >= ncomps)
  			throw new IndexOutOfBoundsException();
  
  		_verifyAllStreams();
  		int attributeIndex = m_description.getAttributeIndex(semantics);
  		// TODO check if statement
  		if (attributeIndex >= 0)// && m_vertexAttributes[attributeIndex] !=
  								// null) {
  		{
  			return m_vertexAttributes[attributeIndex].readAsDbl(offset * ncomps
  					+ ordinate);
  		}
  		return VertexDescription.getDefaultValue(semantics);
  	}
docs: Checked vs. Jan 11, 2011