Polygon geometry - any suggestions?

[R. Hillen]

Hello David,

I use the following function (sorry, but I forgot, who created it)

function ptInPoly p, pts
   put false into inside
   put item 1 of p into xt
   put item 2 of p into yt
   put item 1 of line 1 of pts into xOld
   put item 2 of line 1 of pts into yOld
   repeat with i = 2 to the number of lines in pts
     put item 1 of line i of pts into xNew
     put item 2 of line i of pts into yNew
     if (xNew > xOld) then --flip
       put xOld into x1
       put xNew into x2
       put yOld into y1
       put yNew into y2
     else
       put xNew into x1
       put xOld into x2
       put yNew into y1
       put yOld into y2
     end if
     if (xNew < xt) = (xt <= xOld) and  ((yt-y1)*(x2-x1)) < ((y2- 
y1)*(xt-x1)) then put not inside into inside
     put xNew into xOld
     put yNew into yOld
   end repeat
   return inside
end ptInPoly



> From: "David Bovill" <david at openpartnership.net>
> Subject: Polygon geometry - any suggestions?
> ..
> I am working with maps and geo-tagging media files - as part of this  
> I need
> to work out if a point is within an area - simplest case a polygon,  
> but this
> could be a simple volume - that is a polygon extruded to the ground.
>

Richard