3DVIA Composer adds some new capabilities regarding cutting planes and vectorization. Take a look at the image on the left, and you should notice a few things.
The first thing you should notice is that I have two cutting planes turned on simultaneously.
Second, notice that there is capping on the end surfaces where the cutting planes interact with my target actors (in this case, just the outer housing is selected).
Finally, you can see that I have hatching in the vectorized graphic. This is also new in V6R2012.
These options are easily discoverable, and for the most part getting familiar with them is a matter of playing with the new settings available on the actors you already know and love. On the Technical Illustration panel there is nothing new you have to do; almost all of the settings reside with the individual actors.
One trick you will want to know about is how to regulate the capping color; it's not as intiutive as it is for the hatching and cutting line. That's because it's not set per each cutting plane actor, but rather at the top level of the cutting plane actor subtree. So select the Cutting planes item at the top, not the individual actors. The screencapture at left doesn't appear to show that I've selected the overall Cutting planes item but that's just a limitation of the screencap tool I used to grab the image -- I definitely had to click on the upper item to get all the capping color settings to show.
I've circled the relevant settings in red in this picture. Note that if you want to have a white cap color for a non-shadowed "line art only" effect, you will need to set the capping color specifically to white. Otherwise, it will show the part color on the end cap (turn that option off and set the color manually to white).