Re: Calculate points in an arc
For the points below, from an online calculator it seems that the centre
of the circle lies at 58.0263,-870.1806, but I expect, because the
points are almost on a straight line, that there could be considerable
error in that calculation. The perpendicular bisectors of the first two
and last two of your trio of points, (which determines the centre) will
be almost parallel, and a small error in the location of one of your
points will significantly alter their crossing point.
On 16/04/2022 20:21, Jan Öhman via Discuss wrote:
Thanks!
Tried to analyze the answer (but, do not see how it will solve my desire)
I have 3 points that I want "a line" through to create the 2D object.
Points
x1=10, y1=49.25
x2=55,5, y2=50,5
x3=101, y3=49,5
58.0263,-870.1806 is correct for the center, which gives a radius of
920.68. If I needed this circle in OpenSCAD, I'd draw it around the origin
and then translate it to the center. But if all that is needed is the arc
along the three points, then, as noted, it's so close to a straight line as
to make no difference in most situations.
Google sheet here:
https://docs.google.com/spreadsheets/d/1L8g1SgyPrhca6UjL12qHet5ves57tPzsFqiLlw5JA8M/edit?usp=sharing
On Sat, Apr 16, 2022 at 4:42 PM Raymond West raywest@raywest.com wrote:
For the points below, from an online calculator it seems that the centre
of the circle lies at 58.0263,-870.1806, but I expect, because the
points are almost on a straight line, that there could be considerable
error in that calculation. The perpendicular bisectors of the first two
and last two of your trio of points, (which determines the centre) will
be almost parallel, and a small error in the location of one of your
points will significantly alter their crossing point.
On 16/04/2022 20:21, Jan Öhman via Discuss wrote:
Thanks!
Tried to analyze the answer (but, do not see how it will solve my desire)
I have 3 points that I want "a line" through to create the 2D object.
Points
x1=10, y1=49.25
x2=55,5, y2=50,5
x3=101, y3=49,5
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On 18/04/2022 03:06, Father Horton wrote:
58.0263,-870.1806 is correct for the center, which gives a radius of
920.68. If I needed this circle in OpenSCAD, I'd draw it around the
origin and then translate it to the center. But if all that is needed
is the arc along the three points, then, as noted, it's so close to a
straight line as to make no difference in most situations.
Google sheet here:
https://docs.google.com/spreadsheets/d/1L8g1SgyPrhca6UjL12qHet5ves57tPzsFqiLlw5JA8M/edit?usp=sharing
On Sat, Apr 16, 2022 at 4:42 PM Raymond West raywest@raywest.com wrote:
For the points below, from an online calculator it seems that the
centre
of the circle lies at 58.0263,-870.1806, but I expect, because the
points are almost on a straight line, that there could be
considerable
error in that calculation. The perpendicular bisectors of the
first two
and last two of your trio of points, (which determines the centre)
will
be almost parallel, and a small error in the location of one of your
points will significantly alter their crossing point.
On 16/04/2022 20:21, Jan Öhman via Discuss wrote:
Thanks!
Tried to analyze the answer (but, do not see how it will solve
my desire)
I have 3 points that I want "a line" through to create the 2D
object.
Points
x1=10, y1=49.25
x2=55,5, y2=50,5
x3=101, y3=49,5
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To unsubscribe send an email to discuss-leave@lists.openscad.org
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To unsubscribe send an email todiscuss-leave@lists.openscad.org
apologies for previous post, hit the wrong button!
If the arc is required for the surface of a cam, say, and only the
curve between the first and last points are required, (a straight line
being unsuitable) then I would simply intersect the circle with the
appropriately sized translated square.
On 18/04/2022 03:06, Father Horton wrote:
58.0263,-870.1806 is correct for the center, which gives a radius of
920.68. If I needed this circle in OpenSCAD, I'd draw it around the
origin and then translate it to the center. But if all that is needed
is the arc along the three points, then, as noted, it's so close to a
straight line as to make no difference in most situations.
Google sheet here:
https://docs.google.com/spreadsheets/d/1L8g1SgyPrhca6UjL12qHet5ves57tPzsFqiLlw5JA8M/edit?usp=sharing
On Sat, Apr 16, 2022 at 4:42 PM Raymond West raywest@raywest.com wrote:
For the points below, from an online calculator it seems that the
centre....
That would be a lot simpler than all the trig I thought of doing!
On Mon, Apr 18, 2022 at 5:30 AM Raymond West raywest@raywest.com wrote:
apologies for previous post, hit the wrong button!
If the arc is required for the surface of a cam, say, and only the curve
between the first and last points are required, (a straight line being
unsuitable) then I would simply intersect the circle with the appropriately
sized square