Retroceder: Re: Circle - 2 points and radius

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Retroceder: Re: Circle - 2 points and radius

gabriel
If you draw a perpendicular línea (construction) at both points where you want touch circle and línes, dont know if this would work.

"dxli [via LibreCAD]" <[hidden email]> wrote:

one way is to use command line:

for example:

you have the two points at (30, 0) and (60,0), and you want to draw a circle passing them with a radius of 50

1, set relative zero at (30, 0)
2, Draw->Circle-> Circle, Point
3, when prompted by: "Specify Center", activate command line (clicking on it, or by spacebar)
4, type in coordinates of center:  @50<acos(15/50)*180/pi
5, when prompted by: "specify radius", type in the coordinates: 30,0

if you points are not on a horizontal line, you have to add the angle to the polar coordinates in step 4.

Doing geometry construction is fine by construction lines. However, in LibreCAD you can get the benefits of our complex math parser.

<quote author="jmweaver41">
Hey, I'm a new user to CAD in general, so I'm not sure if I'm missing some functionality somewhere.  I typically do a lot of 2D drawing, and usually can use geometry to figure out a way to do what I want within the functionality that I know of.

Currently I'm trying to draw a circle, and the measurements I have are the radius, and I can figure out two points where it will intersect lines, although I don't think its orthagonal.

My question is, am I missing functionality to snap a circle with two points and the radius?  That should specify two possible circles, correct?  If not, is there an obvious workaround that I'm missing?

Thanks!


edit:  The best solution I've managed is to draw a circle with the correct radius through one of the points, then anchor a rotation from that point.  Going to play around and see if I can get the rotation to snap to the correct second point somehow.




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Re: Retroceder: Re: Circle - 2 points and radius

jmweaver41
Normally I use the perpendicular lines trick, and draw a circle tangent to those - my problem is that my circle isn't crossing at 90 degrees relative to the lines.  Basically its a triangle, I have the circle intersecting near a corner, so the center point is somewhere below and to the side.  I know the two points it will intersect the triangle at, and the radius of the arc between.



I think the command line version will work for me, I already know that I should be using it a lot more to simplify things, I just need to figure out the syntax and see if I can remember some of the math involved.  

Thanks for the help, I'll try it out now!
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Re: Retroceder: Re: Circle - 2 points and radius

gabriel
i found this maybe itll help youTangent_lines_to_circles

Soy Yo


On Wed, Apr 16, 2014 at 4:41 PM, jmweaver41 [via LibreCAD] <[hidden email]> wrote:
Normally I use the perpendicular lines trick, and draw a circle tangent to those - my problem is that my circle isn't crossing at 90 degrees relative to the lines.  Basically its a triangle, I have the circle intersecting near a corner, so the center point is somewhere below and to the side.  I know the two points it will intersect the triangle at, and the radius of the arc between.



I think the command line version will work for me, I already know that I should be using it a lot more to simplify things, I just need to figure out the syntax and see if I can remember some of the math involved.  

Thanks for the help, I'll try it out now!


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Re: Retroceder: Re: Circle - 2 points and radius

dxli
In reply to this post by gabriel
This feature is implemented in my branch:

https://github.com/dxli/LibreCAD/tree/dli

You may build from source to test.

We will decide whether to add this into the official repository.
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Re: Retroceder: Re: Circle - 2 points and radius

jmweaver41
Oh I'll definitely take a look at it, would be great to have it implemented!  (At least for what I do)
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Re: Retroceder: Re: Circle - 2 points and radius

dxli
After some code review, I have merged this feature to official repository, master branch, as this feature seems to be so basic, and should be there on day 1.

Please let me know, if you any any opinion on this implementation.
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Re: Retroceder: Re: Circle - 2 points and radius

dxli
In reply to this post by jmweaver41
a screenshot
screenshot