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Re: [canvas-developers] Re: Text placement by angle

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  • Richard Heyes
    ... The translate method however needs coords to move to. I think it s just some trig I need. And to get said trig working. Unfortunately the JS Math.sin
    Message 1 of 6 , Sep 28, 2008
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      > Hm, I'm not sure why you need an arc() -- note that arc() doesn't
      > actually draw anything, it just adds an arc to the current path.
      > drawText ignores the current path (or should!). What you want is
      > something like:

      The translate method however needs coords to move to. I think it's
      just some trig I need. And to get said trig working. Unfortunately the
      JS Math.sin function comes out differently tro my calculator.

      To recap, I'm trying to get horizontal text (ie readable) text at a
      point but only knowing the angle in relation of the hypotenuse, and
      the length of said line. So the equation would be:

      Opposite = Math.sin(45) * 100

      Where 100 is the radius of the circle I'm drawing (for example) and 45
      is 45 degrees. I've just got to get it working... :-/

      --
      Richard Heyes

      HTML5 Graphing for FF, Chrome, Opera and Safari:
      http://www.phpguru.org/RGraph
    • Matt Westcott
      ... [...] ... Javascript s trig functions work in radians, not degrees (as do most other programming languages and libraries). To convert from degrees to
      Message 2 of 6 , Sep 28, 2008
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        --- In canvas-developers@yahoogroups.com, "Richard Heyes"
        <richard.heyes@...> wrote:
        >
        > Unfortunately the
        > JS Math.sin function comes out differently tro my calculator
        [...]
        > Opposite = Math.sin(45) * 100
        >
        > Where 100 is the radius of the circle I'm drawing (for example) and 45
        > is 45 degrees. I've just got to get it working... :-/

        Javascript's trig functions work in radians, not degrees (as do most
        other programming languages and libraries). To convert from degrees to
        radians, multiply by Math.PI/180 (e.g. Math.sin(45 * Math.PI/180) in
        this case). More generally though, for this sort of thing it helps to
        get into the habit of 'thinking' in radians and using them
        consistently across your application rather than having to convert
        between radians and degrees...

        - Matt
      • Richard Heyes
        ... Ah, that explains a lot... :-) ... Well it s a public API, and people recognise degrees. Most probably don t even know what a radian is (radioactive?), so
        Message 3 of 6 , Sep 29, 2008
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          > Javascript's trig functions work in radians, not degrees

          Ah, that explains a lot... :-)

          > (as do most
          > other programming languages and libraries). To convert from degrees to
          > radians, multiply by Math.PI/180 (e.g. Math.sin(45 * Math.PI/180) in
          > this case). More generally though, for this sort of thing it helps to
          > get into the habit of 'thinking' in radians and using them
          > consistently across your application rather than having to convert
          > between radians and degrees...

          Well it's a public API, and people recognise degrees. Most probably
          don't even know what a radian is (radioactive?), so for said API, I
          think I'll have to stick with convertiong to radians.

          >
          > - Matt
          >
          >



          --
          Richard Heyes

          HTML5 Graphing for FF, Chrome, Opera and Safari:
          http://www.phpguru.org/RGraph
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