topic Re: create clockwise arc in .NET Forum

create clockwise arc

jwe03 — Tue, 08 Jan 2019 18:51:20 GMT

How can I create a clockwise arc using .NET.

By default all arcs are drawn counter-clockwise. I need to draw them clockwise as well.

Re: create clockwise arc

_gile — Tue, 08 Jan 2019 19:37:22 GMT

Hi,

If you do not provide more details about the the input data uses to create the arc 'clockwise', I'm afraid nobody can really help you (from my part I can't).

Re: create clockwise arc

jwe03 — Tue, 08 Jan 2019 20:03:27 GMT

HI @_gile,

Basically what I'm trying to do is to convert all arcs in a polyline into segments which can have a maximum length (input by the user). The less this maximum length, the finer are the arcs cut (the more segments generated and the more vertices are added to the polyline).

So while trying the algorithm, i had a problem with arcs in the polyline which go clockwise. I got their start point, endpoint, radius and center (deriving them from the bulge) and then when i created the arc it was always created in the counter clockwise direction.

This is why i'm asking if this can be done and if yes, how?

Re: create clockwise arc

Alexander.Rivilis — Tue, 08 Jan 2019 21:56:33 GMT

@jwe03 написал (-а):

Hi

How can I create a clockwise arc using .NET.

By default all arcs are drawn counter-clockwise. I need to draw them clockwise as well.

You can not create clockwise arc, but you can change it normal (for example, from (0 0 1) to (0 0 -1)) and arc will be look as counter-clockwise if view direction is (0 0 1). This result can be achieved by mirroring the arc relative to the bisector of its central angle.

Re: create clockwise arc

fieldguy — Wed, 09 Jan 2019 02:34:40 GMT

assuming you have a CircularArc2d (ca), you can use the ca.GetLength method. When you create the arc, check that arc length is the same as the ca.getlength result. If it's not, you have to swap arc parameters (start pt, end pt, startangle, and endangle).