Congrats! You have found a bug vintage 1990, in Vis5D code
that we ported from C to Java for VisAD. Probably the oldest
bug fixed yet for VisAD. It lingered so long because it was
masked by the behavior of graphics libraries (as you noted,
it only manifest with recent versions of Java3D), and by the
general wierdness of transparency.
The fix is in the *.jar files at: