mouse within oval filled area

James Hurley jhurley0305 at sbcglobal.net
Sun Nov 13 01:01:57 EST 2011


Hugh,

Would this help? The script below will draw a polygon that looks like an ellipse with a start and stop angle.

The trouble with the start angle and the arcangle in RR is that they are not polar angles but are related in a complex way:

arcAngle = arctangent( b/a * tangent(polarangle)

(Don't ask.)

And then use a mousewithin handler for the "oval" grc--actually a polygon


local a,b

on mouseUp
   put 10 into tStartAngle -- Or whatever
   put 250 into tEndAngle -- Or whatever
   put 200 into a --Semi major axis
   put 100 into b -- Semi minor axis
   put 300 into x0 -- The origin
   put 250 into y0 -- The origin
   put x0,y0 & cr into tPoints
   --Construct the points for the ellipse
   repeat with i = tStartANgle to tEndANgle
      put  r(i) into tR
      put round ( x0 + r(i) * cos(i*pi/180)), round(y0+r(i) * sin(i*pi/180)) into temp
      put temp & cr after tPoints
   end repeat

   put x0,y0 after tPoints
   --Construct the graphic
   if there is no grc "oval" then create grc "oval"
   set the style of grc "oval" to "polygon"
   set the opaque of grc "oval" to true
   set the points of grc "oval" to tPoints
end mouseUp


function r tA --Radial distance to the ellipse as afunction of the angle
   put (cos(tA*pi/180))^2 / (a*a) + (sin(tA*pi/180))^2 / (b*b) into temp
   return 1/sqrt(temp)
end r

> Has anyone worked out how to test if the mouseLoc is within the filled area
> of an oval graphic (defined by startAngle and arcAngle)? I was thinking
> polar coordinates, but this assumes a circle and a fixed radius which is not
> necessarily the case. A btter math brain than mine is needed!
> 
> Hugh Senior
> FLCo




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