Polygon Pick

Hi all

I have a polygon in 2D with (5, 6, 7...) points, and I need a function that tells me if a point (the mouse cursor) is inside this poly.

Any ideas?

Thanks in advance,
Banky

If you look at the collision stuff in brl.max2d, you may be able to work out how to use the system to collide arbitrary quads rather than just rectangles. Might have to add your own functions into the library though, unfortunately.

Here is one I made in Blitz3D which we use extensively in GEOM. It's Pretty Simple to convert to BMAX.

x & Y are the mouse co-ords

Function InsidePoly(p.Polygon,x#,y#)
	Local i, j
	Local bInPoly = 0
	Local xt1#,xt2#,yt1#,yt2#
	j = p\VertexCount - 1 
	For i = 0 To p\VertexCount - 1 
		xt1 = p\VertexX[j]
		xt2 = p\VertexX[i]
		yt1 = p\VertexY[j]
		yt2 = p\VertexY[i]
		If x < ( (xt1 - xt2) * (y - yt2) / (yt1 - yt2) + xt2 ) And ((yt2 <= y And y < yt1) Or (yt1 <= y And y < yt2)) Then  bInPoly = 1 - bInPoly
		j = i
	Next

	Return bInPoly

End Function

I don't know if this helps but here is a polygon collision routine I made a while back:
http://www.altitude-studios.com/blitzmax/Polygon%20Collision%20&%20Response.zip

Thank you, guys

Indiepath, your function works perfect!!!
Thank you very much, it's just what I need!

Nice one :D

If you want to make sure it's really fast do a quick distance check to see if you are near the poly, if not then ignore the insidepoly function.