how to plot coordinates from a file the has been drawn on a cad system


Say someone draws a cube
on a cad system like unigraphics which uses open GL to render 3d models and wire frames its a drawing API that is used to design.
I`m wanting to know is there any way that I can load the the design (file) and some how
figure out the xyz coordinates of the cube in inches .

What I`m tring to do is load the cube and and some how figure out the cube size in inches
and have a ball go around the inside of the cube

its about loading meshes from files.
find the filespec, there it is described.
else look for export-formats in the cad-program, there will be for sure an option to save as .3ds for example, for wich you can find tons of infos on the web…

its not opengl-related, its file-loading wich does not affect drawing it…