# Slicing a potato

• posted
Hi,
I've got a potato-like 3D shape that was reconstructed from some
anatomical images. I need to cut it into slices (ultimately so that I
can assign different properties to different slices). What makes sense
to me is to create a series of thin hexahedra (such that every other
slice is represented), and intersect this with the potato to obtain
half the slices. Then subtract those slices from the potato to get the
other half. Does that sound like a reasonable way to do it?
Assuming an affirmative answer to that question, would someone be able
to quickly rattle off the command to create a solid hexahedron from
eight coordinates?
Thanks,
• posted
What's a "3d shape"? A solid? A mesh? A surface?
• posted
A solid.
Actually it starts as a bunch of triangles, and I convert it to a solid, so if a mesh or surface will make it easier, it can be that as well.
• posted
Why not make a few copies in place, use another solid, carefully placed, and then subtract, and repeat?
• posted
How about just using the "Slice" command? Orient the UCS to the plane you would like to slice, draw a circle at each elevation you need a slice, then slice away.
Slice >> Object (select a circle) >> Both (to retain both halves)
• posted
Can you tell I don't do a lot of 3D solid work? ; )
• posted
Thanks! Even easier than I had expected.
• posted
Heh Heh
• posted
You're welcome
• posted
I perhaps spoke too soon. I am not familiar with all that AutoCAD is doing with the SLICE command. I have 100 planes defined in the same coordinate system as my potato. My first effort was to make a lot of slice commands using those same coordinates, e.g.,
slice all
3points -20,121.103,294.725 -20,61.8016,303.852 20,61.8016,303.852 Both slice all
3points -20,120.746,292.407 -20,61.446,301.542 20,61.446,301.542 Both slice all
3points -20,120.387,290.072 -20,61.0879,299.219 20,61.0879,299.219 Both
But this doesn't seem to produce the desired result. The first several are correct, and then it falls apart. From documentation I guessed that AutoCAD is changing the UCS on me. So I inserted a "ucs world" before each "slice" commmand. This doesn't solve all the problems either.
(I've plotted the planes in Matlab, by the way, so they're in the right place.)
• posted
If you have Dynamics UCS's turned on (the DYN button), AutoCAD will try to set itself to the UCS of whatever surface the cursor is over. Maybe you need to be sure DYN is turned off... just a thought.
-Bill
==========
• posted
Thanks, I will try that. I work at a computer in the library (I am a grad student), so it would be helpful to have a number of options to try. Are there any other things that might be messing with the UCS?
(And just to confirm, am I correct in thinking that the SLICE command accepts coordinates in UCS?)
• posted
Are all the slices parallel with each other?
• posted
Slice accepts coordinates in the current UCS, whatever that happens to be. Pay attention to the prompts: if you are feeding three points to the routine, be sure to specify the "3point" option in your (command) statement. Otherwise, the last point might be getting interpreted as a the reply to the "Select side to keep" prompt.
Note that AutoCAD 2008 (and maybe 2007? I forget) defaults to a two-point vertical slice in the current UCS unless you specify the "3point" option.
Good hunting!
-Bill
=========