Slicing a potato

What's a "3d shape"? A solid? A mesh? A surface?

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.

Adam

Why not make a few copies in place, use another solid, carefully placed, and then subtract, and repeat?

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)

Can you tell I don't do a lot of 3D solid work? ; )

Thanks! Even easier than I had expected.

Adam

Heh Heh

You're welcome

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.)

Any help appreciated, Adam

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

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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?)

Thanks, Adam

Are all the slices parallel with each other?

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

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Adam Baker wrote:

Some of them are close, but I doubt any of them are actually parallel. They're normals of an L-shaped spline (a curved L). None of them intersect within the volume.

Adam