Cylinder entirely changing in composition after becoming a negative

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#1

I’ve been trying to union a negative piece onto another piece, but I keep getting an issue with the negative piece not being precisely the same size. Both the objects are cylinder. Upon turning one of the cylinders negative in order to union both of them, this cylinder changes slightly in shape. Not only is the size different, but it seems like the overall proportions of the cylinder also change.

I’ve looked around the DevForum to see if anybody else was experiencing this issue, but I stumbled across one post which had the same issue, yet, unsolved. However, there was a reply stating that changing the orientaion of both the original cylinder and negative one to “0,0,0” would fix it. I attempted that as well, but it ended in failure. (Unless I’m doing it wrong, which I doubt)

Here is video displaying the issue:

Here are some screenshots of the size, before and after, however, changing the size of the negative part into the same one as the original one proves to no avail

BEFORE:

1
1284×554 20.7 KB

AFTER:

2
2282×552 19.8 KB

If anyone could follow up with a solution or possible fix, that would be great. If you have experienced this issue in the past, please tell me any alternatives you have used to get around the problem. Thanks in advance. - null

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#2

Select the white cylinder only and press union, then union it to the negative green part.

2 Likes
#3

Unions sort of lose precision when they are made, likely due to technical/optimization contraints. I come across this most when unioning large spheres and cylinders together, since they take up alot of triangles.

The workaround is to either retry unioning it a few times, manually create a mesh, or by simply unioning within these constraints.

By the last point, I mean for example in your case: it looks like youre trying to trim off a cylinder extruding from the ground. Instead of using a cylinder of same diameter to trim it, increase it’s diameter or use a large square that can cover more than how far out your base cylinder extends so that no matter how much it loses precision, it will still negate the whole thing.