are you trying to solve for the volume of the illustration?
There is a script for Adobe illustrator for length of path and area.
How would you solve it otherwise with vector illustrations?
Are you doing this in Illustrator CC? Let me know so I can move it if necessary.
Yes I am using CC
The only way I've been able to think of so far is work out the area of the shape in units^2 and then create overlay a rectangle and slowly reduce the area of the shape until I get a roughly accurate area that is equivalent to the percentage I require.
However I am struggling to work out the area of a shape in illustrator to begin with...
I also am unsure on how to use scripts... so it's going well!!
Can you show us? Post screen shots of what you have and what the resulting images should be.
You can find the area by:
var area = app.activeDocument.pathItems.area;
if you after a graph a bit like this, then thats not hard if they are boxes.
but if the shapes are free form it would be harder...
if at 50% you just took 50% of the height, then that would be ok.
if you want to shade 50% of the area it would be much harder.
and would involve a lot of trial and error in the script slowing it down.