To process a faces to a 2d or to a 3d model
Copy and then flatten one 3d model to a 2d model with scale tool
draw rectangle on back plain, useing the move tool, move the left corner, by left click and hold buttom of mouse while dragging the rectangle to front plain, above the flatten 3d high spot. Then turn on xray and make a face to 2d model.
Now return face to 3d model with push-pull and paste in place 3d model or vector push-pull witch tranfer flatten 3d detail to 2d model.
Right click and used context intersect face to model
Cut off ends of the pull face or the 2d rectangle edges.
delete 3d flatten model
Answer
You now made a 2d face or a 3d face suface via 1-6
Now for terrain lines,
Answer:
draw rectangle on ground plain, use move tool to front left corner, left click hold buttom of mouse while pressing the control key. Now drag the
rectangle to top plain. type in the indext input box type /20 enter
right click and used context intersect face to model
Cut the 2d rectangle plains edges.