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Old 14th June 2017, 04:18 PM   #1
jleslie
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Default Problems with boolean subtract, or removing materal

I keep having problems with this. with simple 3d objects there isn't a problem. but
if you make a polygon, or try and boolean -> subtract a couple of times, the program starts to fail.

Here is a simple demonstration. I've made a trapezoidal extrusion, and I want to remove that shape from a simple cube. boolean -> subtract does weird things.

Any suggestions?
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Old 17th June 2017, 04:25 PM   #2
Andy
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Default Re: Problems with boolean subtract, or removing materal

There are a number of things wrong with the trapezium shape. There are internal surfaces inside the object and the normals are all over the place. You can check this by settings the surfaces to single sided (1S) and switching on display normals.

I made a new shape by copying the end of the shape into a single polygon (a quick rough copy) and extruding it.

In this image (from left to right), you can see your original shape, the new end, the extruded shape, the two objects positioned before selecting the box and the shape, the result of the boolean subtract. I'll attach the model.
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Old 17th June 2017, 04:27 PM   #3
Andy
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Default Re: Problems with boolean subtract, or removing materal

in this case, it would have been easier and quicker to create a polygon which represented the end of the final shape and then extrude that
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Old 17th June 2017, 05:00 PM   #4
jleslie
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Default Re: Problems with boolean subtract, or removing materal

Quote:
Originally Posted by Andy View Post
in this case, it would have been easier and quicker to create a polygon which represented the end of the final shape and then extrude that
Thanks for the answer. I'll keep your ideas in mind.
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Old 17th June 2017, 05:16 PM   #5
jleslie
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Default Re: Problems with boolean subtract, or removing materal

" You can check this by settings the surfaces to single sided (1S)" I'm not sure what you mean by this, how do you do it?


I understand the normals thing, and I guess to boolean subtract, I have to have the knife surfaces all set to the outside.
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