I was looking to implement Half angle slicing but
due to some problems I was unable to get the results.
see the image below. The problems included how to
update the OpenGL blending order front to back
and back to front for the light and eye buffers.
Once this was sorted, I was still not getting the same
output as was shown in the paper by Joe Kniss.
So just today I noticed I was not clearing the eye
and light buffers doing so removed the bugs. Finally,
I managed to get it working. Compare the above images
to this one.