Why rotating 3-point arc in a list generates a complementary arc?

王晓哲 shared this question 6 months ago
Answered

If a 3-point arc is put in a list and the list is rotated, then the result arc will be a complementary arc. But if the 3-point arc is rotated alone, the result is fine.

It's very confusing to me. Any suggestions?

Demostration is in the attachement.

Comments (6)

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The relevant difference between c and d is not in the type of command used but in the direction of rotation.

All elements of a list always have the same properties. The direction of rotation must therefore always be the same and is set (or assumed) to "counterclockwise" for all elements.

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What should I do to properly rotate a 3-point arc in a list? Would you show me an example please?

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2

in your example:

c: CircumcircularArc(C, B, A)

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If the direction of the arc is dynamic (not known at the time of programming), then you can make a copy of arc whose direction of rotation is always the same (for example counterclockwise and without complementary the arc).

important principle for the conversion:

instead of the original points (A,B,C) which define the arc (c) the points Point(c,0), Point(c,0.5), Point(c,1) are used (working with the pathparameter, where the direction is known)

See attachment.

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rounding error in Text2

corrected in version 2

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I see. Thanks a lot!

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