On 08/11/2015 00:43, Alex Tweedly wrote:
Actually, you should shorten the maths - makes it a bit more efficient
function getArea pPts
if line 1 of pPts <> line -1 of pPts then return 0
put 0 into tArea
put empty into oldL
repeat for each line L in pPts
if oldL is not empty then
-- put item 1 of L - item 1 of oldL into dx
-- put item 2 of oldL + (item 2 of L - item 2 of oldL)
/ 2 into avgY
-- put dx * avgY into thisArea
-- add thisArea to tArea
add (item 1 of L - item 1 of oldL) * ( item 2 of oldL + item 2
of L) / 2 to tArea
end if
put L into oldL
end repeat
return abs(tArea)
end getArea
Hi Alex,
It seems to me that this algorithm assumes that the polygon is convex,
and it will add area that should be subtracted if the polygon isn't
convex. Am I correct? Is there any way to include a test for convexity?
Peter
--
Dr Peter Brett <[email protected]>
LiveCode Open Source Team
LiveCode on reddit: https://reddit.com/r/livecode
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