Drawing an arc thru 3 intersection pts
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I have tried this numerous times using the arc tool but I cannot get the arc to pass through all three points. Is there a another method?
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Because Arcs in SUp are really segmented polygons only certain configurations of radius and 3 arbitrary points etc can guarantee intersections.
You can up the number of segments in an Arc whilst making it - e.g. typing 360s will give it 360 sides ! or later in Entity Info - Arc with non-coplanar faces are no editable later - e.g. parts of a cylinder: this will give good but not perfect results.
To ensure that your Arc has vertices at three given points mark/draw the points, let's call them p1, p2 and p3.
Draw a well segmented 3pt Arc with its ends at p1 and p2 and another 3rd point that's approximating to the radius - immediately then change the Arc's radius to what's required using Entity Info - that Arcs ends remain where they are.
Repeat for the other Arc from p2 to p3 at the same radius.
You now have an Arced shape of a constant radius that has nodes at 3 defined points... -
Tricky tip
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Jean, is there an advantage to using your way versus just using the arc tool? When I snap Point A first, Point B second and Point C for the bulge, SU gives me the identical arc that you calculated(except for the number of arc segments). I'm just asking because I always enjoy your clever way of working in SU, but this one seems like it could be simpler
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The arc I was attempting to create is very big arc. First establish a baseline, erect a perpendicular line on the end to the right. Call it FP. Then, erect a second perpendicular line from the FP to the left a distance of 182 feet and call it AP. Then erect a third perpendicular line from the FP to the left a distance of 63 feet 11-3/4 inches, call it dead flat. You should have now have one base line and 3 perpendicular lines. Mark off a distance from the base line at the dead flat of 24 feet. At the FP mark off a distance of 26 feet and mark off a distance at the AP of 26 feet 3 inches. Now construct an arc through the 3 distance pts you just established. Just so you know the apex or bottom of the arc will pass below the baseline, which is ok, what I want is for the arc to pass through the 3 pts. I set my arc segments to 1000.
I'll have to give jean's idea a try.
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Hi D12dozr, hi folks.
@d12dozr said:
Jean, is there an advantage to using your way versus just using the arc tool? When I snap Point A first, Point B second and Point C for the bulge, SU gives me the identical arc that you calculated(except for the number of arc segments). I'm just asking because I always enjoy your clever way of working in SU, but this one seems like it could be simpler
No, in my example, the two arcs are quite similar, my mistake, so it looks like the bulge can be snapped to the center point.
Try it with inequally spaced points and you will see that the bulge cannot be snapped rigth on the center point.
Just ideas.
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Thanks, Jean
That makes perfect sense now.
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