Rotate until intersection with circle / given distance to point

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yetanotheruser
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Rotate until intersection with circle / given distance to point

Post by yetanotheruser » Thu May 24, 2018 7:53 pm

I have a complex issue that's best explained by this image:
Image
1) I want to rotate the blue curve counter-clockwise until it's upper end hits the circle. Unfortunately on rotation there only seems to be tangential snapping, which leads to this:
Image
Zoom in:
Image
Well, obviously tangential snapping gives an intersection, but not the intersection of the real end of the blue curve with the circle. However this was the best I could get - how to make it better, really making the end of the blue curve hit the circle?

2) I consider the circle as a construction utility. Actually I want to rotate the blue curve counter-clockwise until it's upper end is 200 mm (=radius of circle) away from the upper end of the red line. Is this maybe somehow directly possible / are there alternatives to the way I tried in (1) ?

Thanks for any help on this :D

Update: Attached dxf file.
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circle_sample.dxf
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andrew
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Re: Rotate until intersection with circle / given distance to point

Post by andrew » Thu May 24, 2018 8:11 pm

Create a circle with center at lower end of blue curve (or whatever the center of rotation is) and its circle line through the upper end of blue curve. The intersection between that circle and the yellow circle is your target point for the upper end of the blue curve (use Modify > Align Reference Points or Modify > Rotate with angle entered by mouse cursor).

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Husky
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Re: Rotate until intersection with circle / given distance to point

Post by Husky » Thu May 24, 2018 8:42 pm

yetanotheruser wrote:
Thu May 24, 2018 7:53 pm
1) I want to rotate the blue curve counter-clockwise until it's upper end hits the circle.
What is the center of that rotation?
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andrew
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Re: Rotate until intersection with circle / given distance to point

Post by andrew » Thu May 24, 2018 8:49 pm

Based on the screenshots I'd assume the center of rotation is the lower end point of the blue curve. Just a guess.

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Husky
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Re: Rotate until intersection with circle / given distance to point

Post by Husky » Thu May 24, 2018 9:06 pm

andrew wrote:
Thu May 24, 2018 8:49 pm
Based on the screenshots I'd assume the center of rotation is the lower end point of the blue curve. Just a guess.
Understood - then your solution will work just fine. :lol:
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If a thread is considered as "solved" please change the title of the first post to "[solved] Title..."

yetanotheruser
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Re: Rotate until intersection with circle / given distance to point

Post by yetanotheruser » Thu May 24, 2018 9:31 pm

Indeed center of rotation is the lower end point of the blue curve.
Using a second circle works great:
Image
with hairlines:
Image
but now comes the interesting thing: when zooming in and zooming in and ... it ends up like this:
Image
I guess this is a display bug though.

Attached circle_sample_2.dxf, just zoom in very often on the intersection circle - curve.
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circle_sample_2.dxf
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andrew
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Re: Rotate until intersection with circle / given distance to point

Post by andrew » Thu May 24, 2018 9:39 pm

Circles are never 100% accurate.

You can adjust the arc precision under
Edit > Application Preferences > Graphics View > Appearance > Minimum angle step for rendering arcs

The tradeoff to display precision is performance. Definitely not a bug though.

yetanotheruser
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Re: Rotate until intersection with circle / given distance to point

Post by yetanotheruser » Thu May 24, 2018 9:43 pm

very interesting to know, thanks :D

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