Test for "within graphic"?

[Jim Hurley]

>
>Message: 4
>Date: Wed, 24 Mar 2004 09:35:58 -0600
>From: "Ken Ray" <kray at sonsothunder.com>
>Subject: RE: Test for "within graphic"?
>To: "'How to use Revolution'" <use-revolution at lists.runrev.com>
>Message-ID: <033f01c411b5$b77509b0$6601a8c0 at precision340>
>Content-Type: text/plain;	charset="US-ASCII"
>
>Yes - use the within() function:
>
>   if within(grc "Polygon","100,125") then
>     -- etc.
>   end if
>
>HTH,
>
>Ken Ray
>Sons of Thunder Software
>Email: kray at sonsothunder.com
>Web Site: http://www.sonsothunder.com/
>

Ken,

I was unaware of this use of "within" It opens up new possibilities 
for a question that came up  some time ago on the list, namely that 
of detecting a collision between two polygons.

For example the following beeps when two polygons intersect:

local myName

on mouseUP
   put "" into myName
end mouseUP

on mouseDown
   put the name of me into myName
end mouseDown

on mouseMove x,y
   if myname is empty then exit mouseMove
   set the loc of me to x,y
   put the points of grc "myPoly1" into myPolyPoints1
   put the points of grc "myPoly2" into myPolyPoints2
   repeat for each line tPoint in myPolyPoints1
     if   within(grc "myPoly2",tPoint)  then beep
     --The following line doesn't work
     --if tPoint is within the rect of grc "myPoly2" then beep
   end repeat
   repeat for each line tPoint in myPolyPoints2
     if within(grc "myPoly1",tPoint) then beep
   end repeat
end mouseMove

Notice that

     If tPoint is within the rect of grc  "myPoly"

is not the same as

    if within(grc "myPoly,tPoint)

although the docs says they should be.

I confess this is a bit confusing, since "put the rect of grc 
"myPoly" yields the four rectangular points defining the rect of 
"myPoly," and not the set of points which define the vertices.

Jim