I would like the volume renderer to render the label map that I am working on, but it renders something different. I am in the process of editing. I went into the volume renderer and selected the label map that I am working on, but what is rendered looks to me like the base line volume, which I have not selected. What the volume rendering should be rendering are the ventricles. See attached image.
http://wiki.slicer.org/slicerWiki/index.php/Documentation/4.1/Training#Slicer4_Neurosurgical_Planning_Tutorial
Follow the tutorial until you split the merge volume and are editing the ventricles. At that point switch to volume rendering to render the volume containing the ventricles. Sometimes (not consistently) the wrong volume is rendered. See attached screenshot. Even though the label volume has been selected, the gray scale volume is rendered.