Which circle command or procedure for tan through and centre?

Hi,
V5
see attached.
I am at a loss to know how to draw a circle with centre on line as shown, tangent to line as shown and through point as shown.
Please indicate procedure step by step.

I have tried for 20 mins, time I got the white flag out !

There is no tan through centre command so no doubt its a combination of a tool and another not so obvious control.

I also would love to see a site where all sorts of circle and curve tasks are presented with step by step solutions. Very useful to us all in fact.

e.g I am forever pondering on how to end a curve I have drawn to be tangent on a circle.

To have a sort of crib sheet we can run to online showing such in a list of challenges down the screen and answers would be great. e.g. my task shown visually, click it and a video plays. Somewhere where contributors could post an image and a jing video. McNeel start it off and populate it with some. …or Mcneel create it, believe you me it would get many visits !

what circle tool.3dm (30.1 KB)
Cheers

Steve

not sure if there’s a command that will help out with this.
but…

Hi Jeff,…and McNeel
Looks like we need a tan through centre tool doesnt it !
Geometrical mind there Jeff better than mine. Now who else would have sussed that ?

Are we limited to what circle commands we have by the size of the commands box when circle tool dragged out from tools menu or can some kind soul at McNeel add such a tool in ?

Otherwise a code etc…I recall drawing an icon for a tool to go with a code Pascal created many yrs ago to orient a shape perp to path , where I needed many for a sweep.

Such for this would be good as a temporary thing until maybe a V5 update, or V6 adds it in.

Are such additions the task of updates or a waiting game until V6 ?

Cheers

Steve

[quote=“Steve1, post:3, topic:16341, full:true”]
Hi Jeff,…and McNeel
Looks like we need a tan through centre tool doesnt it !
Geometrical mind there Jeff better than mine. Now who else would have sussed that ?[/quote]

well, the way i showed it is probably more complex than what is happening… that being- a perpendicular line from the required tangent side to the centerpoint needs to be the same length as a line to the through point…

[quote]
Are we limited to what circle commands we have by the size of the commands box when circle tool dragged out from tools menu or can some kind soul at McNeel add such a tool in ?[/quote]

i think the required addition would be one that allows for a sliding centerpoint (in a similar way as how the sliding tangent points work)… you’d have to be able to constraint the centerpoint to a line first, then do the tangent edge which also slides… then click the through point or radius…

as is now, whenever you click a centerpoint in any of the arc/circle commands, that’s where the centerpoint is…

A cool mind sometimes sees things differently :smile:when the task grounded my progress, I tried all ways but thought of that.
yes sliding tan, sliding centre, pick point.

This is do-able as a tool.

Wish someone can add it in, whos kind hearted and capable at Mcneel ? :smile:
Steve

Another way to construct the circle.
what circle tool DC1.3dm (54.3 KB)

Hi, David,
Cheers
what were the steps though ?

It looks like the one line is equi angle from the other two but I cannot get angle dim to measure the upper angle, only the lower, why I dont know.

Jeff…I had success with the method first two I had to do, however see attached, from then on the others all missed by a small amount, yet I see the logic in the method.
see this in the file attached

Circle tan point centre method misses line.3dm (28.3 KB)

Steve

there’s no intersection at the centerpoint… the perpendicular line is just missing the cpoint line. (instead of drawing the 2nd perpendicular line, you could just move the first one down… it’s the same angle and will extend past the centerline ensuring an intersection)

david’s method is drawing a line perpendicular to the centerpoint_line… then extending the tangent line… then bisecting the angle formed by those two.

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Correct.

Any circle is perpendicular to any line which passes through the circle center. So a circle will be tangent to a line perpendicular to a line passing through the center of the circle.

The center of a circle is on a line bisecting two lines each tangent to the circle.

Now for a tougher problem. I don’t know if it has a direct solution.

Find the circle with:

  • Center on a line
  • Tangent to another line
  • Passes through a point not on either of the two lines

Example with circle attached. Circle Two.3dm (48.8 KB)

Edit: This problem is equivalent to finding the circle passing through two points and tangent to a line.

this problem does not always have a solution.

By giving the tangent line and center point line, actually we constrain the radius of the circle equal to the perpendicular length between those lines, which is mandatory if a tangent relation is asked.

and the given points distance to the center point line can be greater than the radius of the circle, which leads to no solution for every occasion.

Agree that for finite length center line and tangent line there may not always be a solution.

The example I gave has a solution; turn on the Circle layer to see it.

If the center line and tangent line are extended to infinite length, then there is a solution except for the degenerate case of the center line and tangent line being parallel and the distance from the point to center being greater than the distance between the lines.

that one might be a little easier since you can use rhino’s Circle-> Tangent option…



• run _Circle
• choose the Tangent option and click on the tangent line
• choose the Point option and click on the end of the mirrored line
• choose the Point option and click on the original point

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there won’t be a solution if the rotated line (in the method i showed) goes past the tangent line… for example, this one doesn’t have a solution:

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Excellent solution!

Very nice. That also covers the two parallel line situation I described above as not having a solution.

Glad to see this has sparked of similar quests.

Does the forum have a repository for where such visual tasks and fixes or not, can reside, in a more obvious location for users to access ?

I am all for ensuring easy access to such visual methods. Other Forums have Stickys or pinned posts for threads with ‘meaty’ content of a particular theme.

Steve

Different things are important to different people… You personally can bookmark the post so that you can recall it.

–Mitch