I did a project where I placed many simple house models on a hillside for a design scheme and development approval. However it was ridiculous that I couldn't show the houses at their correct elevation and also have a plan view showing the internal layouts (walls) because the global cutplane was either above or below many of the houses. Dermot posted a NG question and in conversing with him he provided me with the answer to this dilemma. I was very excited because I had even had a response from one of the ACA team who said it couldn't be done. I'm sure I was misunderstood because this situation would occur on many campus, hospital or school projects but I was told it was not a common situation and wouldn't be addressed. I wanted an option to be able to override the Global Cut Plane with the x-ref's CP which would assume the walls are sitting at 0 and would cut correctly for plan view. (I was using the PN).
However, the solution was much simpler, thanks Dermot.
I simply overrode the Standard Wall Style cut plane (I have no style overrides to my various wall styles because they are set up to display ByMaterial and follow the std wall style).
(Any specialist styles like cabinets, eave, kerbing, built with a wall style already have their own CP override in the style.)
The effect of this surprised me! With a wall style using the Global Cut Plane, when you raise the wall it will disappear when it is no longer 'cut'. However, override the wall style CP and you can raise or lower a wall as you like and the wall will display perfectly. (It will cut each wall based on the it's cut plane and THAT wall's baseline). I was very surprised and excited that it was so simple. Whilst it obviously overrides the cutplane, it's not obvious that it also overrides the baseline that the CP height is taken from. So why doesn't the OOTB standard style have it's own cutplane. I can't see any advantage to use the global cutplane. If you work with straight single or 2 storey construction this problem won't be obvious to you but as soon as you do a split level it becomes a problem to get a mezzanine to display correctly. With the new cleanup rules introduced in v2009 it's easy to create the 2 floors at their own 0 and still have the walls cleanup.
So now I can have units at varying heights and each one will assume it's own cutplane at the right height according to it's own floor level. This behaviour will occur whether I am using the PN and /or x-ref's or it's in the same file. I've been wanting to work with multi storey in a one file approach for years and this tip was a key to allowing me to make this happen easily - thanks again Dermot.
It used to be hard to get a high window to display. You had to override the style display rep to raise the cutplane. Unfortunately overriding a cutplane will require to cut that wall (style) off from it's parent wall style and it will no longer respond to style adjustments made to the parent. In ACA2009+ you can have the baseline at various heights and it will still clean up so maybe instead of overriding the cutplane, it might be an option to raise/lower the baseline and adjust the bottom and top of the wall instead (as long as you have this blog tip in place!).