I've gotten the slice information into the fragment programs. Here are two examples of red planes which correspond to the sagital slice on the right. (And yes, I need to put a red rectangle around the 2D slice) These 2 images show the red blade with high and low opacities. The low opacity slice lets you see a bit of the cross section in the volume. I think I will add a "slicerr" opacity tool to the interface for controlling this. 
 
 
 
 
Should this be a wireframe instead of a solid plane? Hmmm. I'll put up screenshots of one with a wireframe fiducial for comparison. 
 
Also, the launcher is more or less working now. I waffled some on how much control the launcher app should have over the other programs. Should the launcher spawn and kill the other apps? Or should each program be responsible for terminating itself and launching the next application? Anyway, I think I have a handle on it now.