Intersection Precision

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Intersection Precision

Helmanfrow
This post was updated on .
Sometimes if I have trouble generating certain geometry in SketchUp so I turn to FreeCAD or LibreCAD and then export a DXF which I import into SketchUP.

Today I imported such a drawing from LibreCAD and noticed that in SketchUp some of the curves were not tangent to each other as I had intented. I re-examined the geometry in LibreCAD and discovered that the curves were, indeed, not lining up.

They looked okay at a magnification of 1/10 or 10/100, but when zoomed in to .001/.01, the lines did not intersect.

I tried to reconstruct the drawing using a number of different methods but each time the geometry failed at high magnification.

I've attached screenshots from some simplified sample geometry which exhibits the same issue.

In the the 10/100 shot the diagonal radius line appears to intersect perfectly with the edges of the square and circle, but when zoomed in we see that the line is in fact snapped to some other point in space, seemingly arbitrary.

Is this an expected behavior? Are there limits to the precision at certain scales?



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Re: Intersection Precision

LordOfBikes
Administrator
Welcome @Helmanfrow!

See https://forum.librecad.org/Bug-with-Line-and-Circle-Intersection-mismatch-on-snap-Intersection-tp5717031p5717032.html

Not sure, if my post applies to your issue. At nearly 45° the offset might not be so much.
You can simply check correctness by selecting or measuring the diagonal line. In the status bar you see the length of selected entities, so when the length of the diagonal equals the radius, the math is correct and the straight lines, including their intersection too.
Then just the circle is not drawn accurately, sadly nothing we can control in LibreCAD.

Armin
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