Author Topic: Draw two arcs  (Read 3673 times)

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Fabricio28

  • Swamp Rat
  • Posts: 670
Draw two arcs
« on: April 04, 2024, 07:57:20 AM »
Hello everyone!
How are you?

Can I draw that arcs (yellow)?

File example attached.

Thanks

dexus

  • Bull Frog
  • Posts: 232
Re: Draw two arcs
« Reply #1 on: April 04, 2024, 08:55:50 AM »
You can start here: https://www.cadtutor.net/forum/topic/71940-extend-line-with-a-line-tangent-to-it/
It finds the start point of your arc and the direction, but not the endpoint.

Finding the endpoint that is tangent to the other circle might get a little more tricky. Maybe someone has a full solution for this.

Ingpro

  • Mosquito
  • Posts: 8
Re: Draw two arcs
« Reply #2 on: April 05, 2024, 05:39:52 AM »
Can I draw that arcs (yellow)?
If the radius of the yellow arc is known, that you can build an arc by choosing the type:
"Start-End-Radius".
Or, from the extreme points of the blue arc, build circles with the radius of the yellow arnc, so you get the center of the yellow arc, from the center, you can draw a circle and then crop it.

Fabricio28

  • Swamp Rat
  • Posts: 670
Re: Draw two arcs
« Reply #3 on: April 05, 2024, 08:12:48 AM »
You can start here: https://www.cadtutor.net/forum/topic/71940-extend-line-with-a-line-tangent-to-it/
It finds the start point of your arc and the direction, but not the endpoint.

Finding the endpoint that is tangent to the other circle might get a little more tricky. Maybe someone has a full solution for this.

Thank you! I'll take look on that code.

Fabricio28

  • Swamp Rat
  • Posts: 670
Re: Draw two arcs
« Reply #4 on: April 05, 2024, 08:21:22 AM »
Can I draw that arcs (yellow)?
If the radius of the yellow arc is known, that you can build an arc by choosing the type:
"Start-End-Radius".
Or, from the extreme points of the blue arc, build circles with the radius of the yellow arnc, so you get the center of the yellow arc, from the center, you can draw a circle and then crop it.

No my friend, the yellow arc is unknown. I'd like to learn the best way to draw that arcs.
 Thank in advance

Bryco

  • Water Moccasin
  • Posts: 1883
Re: Draw two arcs
« Reply #5 on: April 08, 2024, 03:01:20 PM »
The old school way is to draw a ray from the center of each arc to the arc endpoint then use the intersection as the center of the new arc

dexus

  • Bull Frog
  • Posts: 232
Re: Draw two arcs
« Reply #6 on: April 09, 2024, 03:03:57 AM »
You can try this approach:
  • Draw a line perpendicular to the derivative of the first line where you want the arc to cut through. Point c in the image below
  • Mirror the arc over that perpendicular line
  • Following commands:
    • "circle"
    • "3p"
    • "tan"
    • select first arc (a)
    • "tan"
    • select mirrored arc (b)
    • select point c
  • Trim all the parts that you don't want and the construction lines from step 1 and 2
« Last Edit: April 09, 2024, 04:34:29 AM by dexus »

dexus

  • Bull Frog
  • Posts: 232
Re: Draw two arcs
« Reply #7 on: April 09, 2024, 03:23:24 AM »
I just noticed that in the previous image, if you draw:
a circle from the center of arc a, through point c.
a circle from the center of arc b, through point c.
it intersects at c, but it also intersects at the center of the arc you are looking for.


Actually, this doesn't always work, only in the example I was trying.
The center of the circle follows a parabola and you must find the value where x matches the start point of the curve.
I have no idea how to deal with parabolas though.
« Last Edit: April 09, 2024, 11:11:51 AM by dexus »

Fabricio28

  • Swamp Rat
  • Posts: 670
Re: Draw two arcs
« Reply #8 on: April 10, 2024, 10:44:55 AM »
The old school way is to draw a ray from the center of each arc to the arc endpoint then use the intersection as the center of the new arc

Hello friend
How are you?

Thanks for replay

But I have only road 1 and 2 (blue lines). And I'd like to result like a yellow lines.
Any advise?

Fabricio

danAllen

  • Newt
  • Posts: 135
Re: Draw two arcs
« Reply #9 on: April 10, 2024, 10:50:15 AM »
The yellow lines seem to be made of three parts, either 2 arcs & a line, or 3 arcs of varying radii. You'll need to provide more geometric rules that define the constraints.