Answer to a question no one asked
James Hurley
jhurley at infostations.com
Thu Jan 6 10:40:10 EST 2005
What is the perpendicular distance between a point and a line?
Application for which there is no redeeming social value:
Create a line graphic "line" and an oval graphic "circle"
Put the following script into a transparent radio button
and then drag that button.
local myName, p2,p3
on mouseDown
put the name of me into myName
put the points of grc "line" into tPoints
put line 1 of tPoints into p2
put line 2 of tPoints into p3
end mouseDown
on mouseUP
put "" into myName
end mouseUP
on mouseLeave
mouseUP
end mouseLeave
on mouseMove u,v
if myName is "" then exit mouseMove
set the loc of me to u,v
put u,v into p1
put abs(perpDist(p1,p2,p3)) into tRadius
set the loc of grc "circle" to u,v
set the width of grc "circle" to 2*tRadius
set the height of grc "circle" to 2*tRadius
end mouseMove
function perpDist p1,p2,p3
--Returns the perpendicular distance
--between point p1 and the line with
--end points p2 and p3
put item 1 of p1 into x1
put item 2 of p1 into y1
put item 1 of p2 into x2
put item 2 of p2 into y2
put item 1 of p3 into x3
put item 2 of p3 into y3
if x3-x2 is 0 then
return (x1-x2)
else
put (y3-y2)/(x3-x2) into m -- The slope
return (m*(x1-x2)-(y1-Y2))/sqrt(1+m*m)
end if
end perpDist
Jim
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