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Topic: How to check if a point is inside a polygon? (Read 1540 times) |
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knudvaneeden
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Posts: 32
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How to check if a point is inside a polygon?
« Thread started on: Jan 9th, 2014, 03:44am » |
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Hi,
How to check if a point is inside a polygon?
http://goo.gl/T6vhHS
with friendly greetings,
Knud van Eeden
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knudvaneeden
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Posts: 32
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Re: How to check if a point is inside a polygon?
« Reply #2 on: Jan 9th, 2014, 08:09am » |
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Would it be possible to show a simplest example in BBC Basic using that API
PtInRegion()?
Thanks
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admin
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Posts: 1145
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Re: How to check if a point is inside a polygon?
« Reply #3 on: Jan 9th, 2014, 09:17am » |
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on Jan 9th, 2014, 08:09am, knudvaneeden wrote:| Would it be possible to show a simplest example in BBC Basic using that API PtInRegion()? |
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Here's a simple program which changes the shape of the mouse pointer depending on whether it is inside or outside the polygon:
Code: DIM Poly{(4) x%, y%}
DATA 650, 680, 440, 470, 800, 230, 1300, 640, 930, 600
FOR I% = 0 TO 4
READ Poly{(I%)}.x%, Poly{(I%)}.y%
NEXT
MOVE Poly{(0)}.x%, Poly{(0)}.y%
FOR I% = 1 TO 4
DRAW Poly{(I%)}.x%, Poly{(I%)}.y%
NEXT
DRAW Poly{(0)}.x%, Poly{(0)}.y%
SYS "CreatePolygonRgn", Poly{(0)}, DIM(Poly{()},1)+1, 1 TO hrgn%
REPEAT
MOUSE X%, Y%, B%
SYS "PtInRegion", hrgn%, X%, Y% TO inside%
IF inside% MOUSE ON 137 ELSE MOUSE ON 0
WAIT 1
UNTIL FALSE
Another use of the function can be found in the Rosetta Code example Honeycombs:
http://rosettacode.org/wiki/Honeycombs#BBC_BASIC
Richard.
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