Reply To: Detecting Line Intersection

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Péter Baksa


There is a call (gosub) to “LineLineIntersection” in the 3D script. The input variables are set up before the call.

vx, vy is computed from two points (_intersectEdge[1] and _intersectEdge[2]) on the line, divided by the distance of the two points:

	! line 1
	vx1 = (_intersectEdge[2][1] - _intersectEdge[1][1]) / _intersectEdgeLength
	vy1 = (_intersectEdge[2][2] - _intersectEdge[1][2]) / _intersectEdgeLength

px, py is any point on the line:

	px1 = _intersectEdge[1][1]
	py1 = _intersectEdge[1][2]

This is done again for the second line:

	! line 2
	vx2 = (_intersectEdgeLeft[2][1] - _intersectEdgeLeft[1][1]) / _intersectEdgeLeftLength
	vy2 = (_intersectEdgeLeft[2][2] - _intersectEdgeLeft[1][2]) / _intersectEdgeLeftLength
	px2 = _intersectEdgeLeft[1][1]
	py2 = _intersectEdgeLeft[1][2]

The result intersection is ipx, ipy, when state = 1 (otherwise the lines are parallel):

	gosub "LineLineIntersection"	! returns ipx, ipy, state
	if state <> 0 then
		_intersectPtLeft[1] = ipx
		_intersectPtLeft[2] = ipy

Péter Baksa
Library Platform, Software Engineer