code: public void addAttribute(int semantics) {
  		_touch();
  		if (m_description.hasAttribute(semantics))
  			return;
  		
  		VertexDescription newvd = VertexDescriptionDesignerImpl.getMergedVertexDescription(m_description, semantics);
  		_assignVertexDescriptionImpl(newvd);
  	}
docs: Adds a new attribute to the Geometry.
  
  @param semantics The VertexDescription.Semantics to add.