Points of Regular Polygon
Randy Hengst
iowahengst at mac.com
Tue Nov 29 16:43:45 EST 2016
Well, this was fun. I write a question, go teach class, and come back to a very interesting conversation.
Thanks all.
be well,
randy
www.classroomFocusedSoftware.com
> On Nov 29, 2016, at 1:24 PM, hh <hh at hyperhh.de> wrote:
>
> I should have better used the wording
> "graphic of type" than "graphic of style"
> because we can
> set the style of grc 1 to "polygon"
> for example (the function again, just for the completeness here):
>
> on mouseUp
> if there is no grc "poly" then create grc "poly"
> set style of grc "poly" to "polygon"
> -- 7 vertices, 1 vertix at 12 o'clock, radius 42, loc (100,100)
> set points of grc "poly" to regularPoints(7,42,100,100)
> set foreColor of grc "poly" to "0,128,128" -- teal
> set lineSize of grc "poly" to 2
> end mouseUp
>
> -- N is the number of vertices
> -- x0,y0 is the center of the polygon
> -- r is the radius of the polygon
> -- b is the angle of rotation in degrees
> -- (positive b turns clockwise, negative b turns ccw)
> function regularPoints n,r,x0,y0,b
> put 2*pi/n into cn
> -- n vertices --> n+1 points if 'closed' polygon
> -- usually done by setting last=first
> -- This is here true as sin(0)=sin(2*pi) and cos(0)=cos(2*pi)
> put empty into pts
> if b=0 or b is empty then
> ## compute unrotated n+1 vertices of the n-sided regular polygon
> repeat with j=0 to n
> put CR & (round(r*sin(j*cn)+x0),round(-r*cos(j*cn)+y0)) after pts
> end repeat
> else
> ## compute *rotated* n+1 vertices of the n-sided regular polygon
> put sin(pi*b/180) into s; put cos(pi*b/180) into c
> repeat with j=0 to n
> put round( r*sin(j*cn)) into sx; put round(-r*cos(j*cn)) into sy
> put CR & ( (round(x0+c*sx-s*sy),round(y0+c*sy+s*sx)) ) after pts
> end repeat
> end if
> return char 2 to -1 of pts
> end regularPoints
>
>
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