variable height extrusion or trim or...

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 From:  bisenberger
4771.1 
Hi,
I have a surface that I want to extrude or trim (or something) to a variable height. The image indicates a surface and a curve of varying height. Is there a way to extrude the surface (or trim the extrude) so that it's height matches the height of the curve.



It looks like offsetting the curve comes close to doing what I need, but with the shape of the curve the offset becomes disjointed.
Bill

EDITED: 7 Dec 2011 by BISENBERGER


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 From:  coi (MARCO)
4771.2 In reply to 4771.1 
Hi,

you could use the Sweep-command and use that special height curve as a scaling rail.







cheers,
Marco

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 From:  bisenberger
4771.3 In reply to 4771.2 
Thanks Marco!
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 From:  SteveMacc (STEVEH)
4771.4 
Why not use extrude with snap?
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 From:  Michael Gibson
4771.5 In reply to 4771.1 
Hi Bill, so because your extrusion object has a kind of 2-sided path nature to it, you can use Sweep with a scaling rail like Marco mentions.

But also a common way to get a modified height extrude is to do a regular extrusion first and then slice the top of the extrusion off with the boolean difference command. Usually you would do the cut with a 2D side profile curve as the cutting object, but in your case here the different heights along each station that you want does not correspond to just one 2D side profile, so instead of cutting with a 2D side profile curve you would have to build a cutting surface. In your case here you could use sweep along height curve (with the ends extended slightly) like this:





That needs to extend far enough to all sides to divide the extrusion into 2 pieces.

Then you do the extrusion to make one blocky solid with a uniform height:



Run boolean difference and pick the variable height surface as the cutting object, that will divide the extrusion into 2 pieces:



Delete the piece you don't want to keep:




So with this method you focus more directly on modeling the variable height capping piece itself and it becomes part of your final model after it slices off the extrusion.

- Michael

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 From:  bisenberger
4771.6 In reply to 4771.5 
Hi Michael,
I figured there would be more than one way to do this and seeing them is very helpful.
Thanks,
Bill
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 From:  bisenberger
4771.7 
The two different methods have different results. With Marco's method the upper surface is flatter (the result I'm after in this instance). With Michael's method it looks like the sweep is banking making the upper surface more sloped. While not giving the result I'm after in this instance I can see it's utility for others.

Thanks for the help Marco and Michael,
Bill
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