Offset is inversed on symetrical objects (Problem with Curve's Normal ?)

[Anonymous]

Hi all,

I've a problem with defining an Offset for a curve.

I start from a curve I imported from an SVG file.

I then create a mirror symetry curve from the first one.

If I select the first curve and ask for an Offset of, say, 2 mm, the offset is on the outside of the curve.

If I select the second curve, and ask for the same Offset of 2 mm, the offset is on the inside of the curve.

Is this normal ?

Then, if I join the 2 curves (without the Offset) into one object, and ask for an Offset of the curve, depending if I click on the left or right initial curve, and ask for a 2mm Offset, the offset is inside or outside of the object.

If now I create a simple object, like a circle, and ask for an offset of 2 mm, the resulting circle is on the outside, as expected.

It looks like the "Normal" of one of the 2 curves (the mirrored one) is reversed.

Is my analysis correct ?

If yes, how can I reverse the Normal ?  Couldn't find the answer.

Thanks a lot

[jeff_strater · Accepted solution]

yes, this is expected behavior.  The offset direction is related to curve direction (a curve doesn't really have a "normal"), and when you mirror a curve its direction will get affected.  There is no way to "reverse" a curve's direction.  The solution is to just negate the offset value of the mirrored curves to get the offset going to the correct side.

[Anonymous]

Thanks for your quick and clear explanation.