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Please help me understand how ARCTO is drawn.

Posted: Tue Sep 13, 2011 12:16 pm
by applegrew
I have the following code.

Code: Select all

startshape BL
 
path BL {
    MOVETO {x 0 y 0}
    2* [r 90]
     ARCTO {
       x 1
       y 0
       r 1
     }
  STROKE{}
}
When drawn the second curve is not really a circle, but looks skewed. Isn't this supposed to draw a perfect circle, or am I missing something?

Re: Please help me understand how ARCTO is drawn.

Posted: Tue Sep 13, 2011 5:47 pm
by MtnViewJohn

Code: Select all

startshape BL

path BL {
    MOVETO {x 1 y 0}
    4* [r 90]
     ARCTO {
       x 0
       y 1
       r 1
     }
  CLOSEPOLY {}
  STROKE {}
}

Re: Please help me understand how ARCTO is drawn.

Posted: Tue Sep 13, 2011 10:21 pm
by applegrew
MtnViewJohn wrote:

Code: Select all

startshape BL

path BL {
    MOVETO {x 1 y 0}
    4* [r 90]
     ARCTO {
       x 0
       y 1
       r 1
     }
  CLOSEPOLY {}
  STROKE {}
}
@MtnViewJohn Can you please make me understand why this is drawing a skewed arc in my case? The reason I ask is that I am trying to understand who is drawing correctly - my program (http://cink.applegrew.com), or ContextFree.

Please see the attached screenshots.

Re: Please help me understand how ARCTO is drawn.

Posted: Tue Sep 13, 2011 10:37 pm
by MtnViewJohn
Your CInk program is correct. Context Free isn't even drawing a true arc. If you manually unroll the loop:

Code: Select all

startshape BL

path BL {
    MOVETO {x 0 y 0}
    //2* [r 90]
     ARCTO {
       x 1
       y 0
       r 1
     }
     ARCTO {
       x 0
       y 1
       r 1
     }
  STROKE{}
}
You get the same result as CInk. When I try this on Context Free 3 I get the correct result. Clearly there is a bug in ARCTO rotation in Context Free 2.

Re: Please help me understand how ARCTO is drawn.

Posted: Wed Sep 14, 2011 12:33 am
by applegrew
@MtnViewJohn

Oh I never noticed the version 3. When are you planning to release that?

Re: Please help me understand how ARCTO is drawn.

Posted: Wed Sep 14, 2011 4:35 pm
by MtnViewJohn
I'm working on the last feature right now: user-defined functions. Then I will put out a beta release. You can get an alpha release with most of the features right now.

Re: Please help me understand how ARCTO is drawn.

Posted: Wed Sep 14, 2011 8:23 pm
by applegrew
Good to know.