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From: BurrMan
So you have the tangent point on red line you want (the 1.75)?
Off the top of my head, the "easiest" would be to draw 2 curves, split at the tangent. (Tangency maintained by the first 2 pick points of a cotrol point curve)
I am away and on my phone. CN explore curve tools when i get home...
From: Psygorn (DRILLBIT)
Hello dear,
I don't have the Tangent point yet! I want to find it! :)
I have the red line (1.75 millimetres away from the main axis) and start and end point of the 3_Points curve at 2.16 & 2.50 respectively then I want to be sure that the 3 points curve ( blue curve) is tangent to the red line!
From: Frenchy Pilou (PILOU)
When you say Curve 3 Points, you mean Arc 3 Points ?
Because if it's a curve you have an infinity of solutions!
From: Jfs (PAQUICINNO)
Hi Psygorn, may be you can do it the (not so) hard way with 3pt circle ?
Attachments:
Untitled.mp4
From: Psygorn (DRILLBIT)
Sorry my bad! yes you are right I mean Arc 3 points. :-)
From: Psygorn (DRILLBIT)
Your method sounds promising, However, I have to check it thoroughly. ( I mean I want to check if it yields true tangent point) needless to say it sounds promising.
One thing that made me suspicious about it is that when I zoom in I see two different crossing! ( I mean when I zoom in it seems the curve crosses the red line at two different points which means this method does not show the true tangent point)
I checked it using Trim method and it seems your method is correct way of finding the tangent point!
From: Michael Gibson
Hi Psygorn so if you do mean "Arc through 3 points", 3 non-collinear points already fully defines a single unique arc and so there isn't any way to set up a tangent additionally there.
I'm not sure that there is a built in tool in MoI currently that will generate a circle by tangent and 2 points on the circle. It can be calculated with this method:
https://www.emathzone.com/tutorials/geometry/equation-of-a-circle-given-two-points-and-tangent-line.html
- Michael
From: ed (EDDYF)
I'll be the first to say I'm not good at geometry. May be a simpler way.
This does seem to match your blue curve. Coincidence? Will it work in all cases? Don't know :)
Draw two small half circles (magenta)
Draw straight line to ends of circles (green)
Select both circles and Blend [Tangent G1, Bulge = 1] (cyan)
Pilou find apex trick (orange lines)
Draw Perp to Perp line from Blend apex to green line (black)
Draw 3-point arc from top to bottom of green line while snapping the center to the intersection of the black & red lines (blue)
Ed Ferguson
From: Frenchy Pilou (PILOU)
Perfect maybe...
So my little trick can help! :)
A curious problem who can have some solutions! :)
A perfect headache!
PS Alas your method don't work :( Big zoom shows 2 crossing curves!
Or i miss the verification...
Little half circles are well on the same line than the green one ?
From: Michael Gibson
The Circle tangent command can do circle tangent to 2 curves through a point, or tangent to 3 curves, but not tangent to one curve through 2 points like you want in this case.
- Michael
From: Michael Gibson
Hi Psygorn,
re:
> So, in MOI 3D, when you already have a line how could you draw a curve tangent to that line, quick and fast?
Circle Diameter can make a circle tangent to a line quick and fast, the problem is that you want not just a tangent circle quick and fast but also passing through 2 points.
- Michael
From: Frenchy Pilou (PILOU)
OK I believe i have found! :) Half only ! :( so...on the track!
And with my Apex trick! ;)
Just draw a little red arc circle 3 points! :)
Resists half to the big zoom! :)
Damned! It's good just on upper part! :(
https://moiscript.weebly.com/uploads/3/9/3/8/3938813/resist.3dm
From: Frenchy Pilou (PILOU)
What a fight!
With a little red, a big black, intersection with the 2 Apex on the green Vertical
quasi perfect but...the black arc is not totally under the green one always on the bottom part at atomic zoom size! :(
From: Frenchy Pilou (PILOU)
An another simple and quasi perfect but...
From: Frenchy Pilou (PILOU)
Another one quasi perfect! But...
(crossing to perpendicular)
From: Michael Gibson
Some geometric solutions at:
https://www.quora.com/How-do-you-construct-a-circle-passing-through-2-points-outside-line-L-and-tangent-to-line-L
- Michael
From: ed (EDDYF)
Pilou -
I zoomed in to the microscopic level on my model and indeed it's not tangent. Then I tried the Jfs (PAQUICINNO) method in his video (which I think is the better solution), and it also was not tangent. Of course these are visual checks.
I don't know the mathematical solution, or even if displayed curves are 100% visually accurate when zoomed in that far.
Practically speaking, the error I saw when zoomed in that far is below the resolution on my micrometer :)
But it would be nice to verify what the precise solution is.
Update - I see Michael has linked to a solution above. Who wants to test it? :)
Ed Ferguson
From: Michael Gibson
From
https://www.quora.com/How-do-you-construct-a-circle-passing-through-2-points-outside-line-L-and-tangent-to-line-L?share=1
I think this one is the easiest:
Create circle/arc 3 pts through points A, B, P.
- Michael
Image Attachments:
tan_pt_pt1.jpg
tan_pt_pt2.jpg
tan_pt_pt3.jpg
tan_pt_pt4.jpg
tan_pt_pt5.jpg
tan_pt_pt_solution.png
From: blowlamp
Here's a video I made that demonstrates a reasonable way to make the tangent.
https://vimeo.com/545453177
Martin.
From: ed (EDDYF)
Nice solution Martin!
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