Drawing arcs with ESTK ...

[K.Daube]

Dear friends,

Next step after lines and polylines: I want to draw arcs (with a constant radius) and encounter a similar problem as with the lines in the different quadrants.

The blue lines are what I want to achieve. The outer three are correct, their starting angle is ≥ 0. The inner ones have starting angles -90, -60 and -30 degrees, which converted to 270, 300 and 330 respectively - because negative values are not allowed (they are interpreted as 0).

I do not see how to force the Arc object to draw what I want. Drawing with UI is not easier: To get the desired angles is quite simple, but to get the arc in correct position after rotation …

It seems that I need a comparable approach to the Line function (a multitude of transformations).

#target framemaker
main();
function main () {
var j, oDoc, oFrame, x0, y0, r, th0, thf, aArcs = [];
    CM = 1857713, PT = 65536, DEGREE = 65536, pi = Math.PI;
  oDoc = app.ActiveDoc;
  oFrame = oDoc.FirstSelectedGraphicInDoc;
  if (!oFrame.ObjectValid()) {
    Alert("Select an anchored frame and try again.", Constants.FF_ALERT_CONTINUE_WARN);
    return;
  }
  for (j= 0; j < 6; j++) {                       // FM-coordinate systemin cm
    r = 2 + j*0.5;                               //  2, 2.5, 3.0, ...
    th0 = -90 + j* 30;                           // -30, 0, 30, ...
    thf = th0 + 90;
    aArcs = DrawArc(oDoc, oFrame, 5, 5, r, th0, thf);
    aArcs.BorderWidth = 0.05*CM;
    aArcs.Color = oDoc.GetNamedColor("Magenta");
    aArcs.HeadArrow = 1;                      // default arrows
  }
} //--- end main
function DrawArc(oDoc, oFrame, x0, y0, r, th0, thf) { // === Draw an arc ==========================
// Arguments  x0/y0  coordinates of center point [CM] FM coord system
//            r      radius of circular arc
//            th0    Angle (degrees) of start-point
//            thf    Angle (degrees) of end-point
// Returns    object (e.g. for grouping)
var oArc, th1, 
    CM = 1857713, PT = 65536, DEGREE = 65536, pi = Math.PI;
  oArc = oDoc.NewArc(oFrame);
  oArc.Width = r * CM;
  oArc.Height= r * CM;                            // let's start with a square 90° arc
  oArc.LocX = x0 * CM;
  oArc.LocY = (y0 - r) * CM;
  if (th0 < 0) {th0 = th0 + 360;}
  oArc.Theta  = th0 * DEGREE;
  oArc.DTheta = (th0 - thf)* DEGREE;
  oArc.Theta  = th0 * DEGREE;
  oArc.DTheta = (thf - th0)* DEGREE;
  return oArc;
} //--- end DrawArc

[K.Daube]

Modifying line 42 to

  if (th0 < 0) {
    th0 = th0 + 360;
    thf = thf + 360;
  }

did the trick at least for this set of angles...

[K.Daube · Accepted solution]

Well, after much fiddling around and expeiments with various angles etc. I have this insight:

• Angle is the rotation angle relative to the original object
• Theta and DTheta exist only for object Arc
• Trying to work in a mathematical/geometrical space for drawing requires some transformation.
• The solution I found is documented in https://daube.ch/zz_tests/FM-graphics.pdf see page 29 of current issue

But:

There is a very strange thing with rotation. Any object rotated (by UI or by script) reflect the rotation in property Ange - but not so for Line. This object always displays 0 for the rotation angle!

See the experiment describe on pages 30-31 of the mentioned pdf.