[bb] Yet Another Line Intersect Function by Andy_A [ 1+ years ago ]

[BlitzBot]

Title : Yet Another Line Intersect Function
Author : Andy_A
Posted : 1+ years ago

Description : Hopefully this function is easier to understand and has a simple usage demo.

Instructions:
Press a key to generate a new pair of random line segments.
Press [ESC] to exit.

Code :

Code (blitzbasic) Select Expand

;Lines Intersect Function
;   By: Andy Amaya
; Date: Nov 07, 2006

AppTitle "Line Intersection Function by Andy_A"

Graphics 800,600,32,2
SetBuffer BackBuffer()

Global intersectX%, intersectY%
SeedRnd MilliSecs()

While KeyHit(1) = 0
Cls
x1 = Rand(0,799) : y1 = Rand(60,599)
x2 = Rand(0,799) : y2 = Rand(60,599)
Line(x1,y1, x2,y2)

x3 = Rand(0,799) : y3 = Rand(60,599)
x4 = Rand(0,799) : y4 = Rand(60,599)
Line(x3,y3, x4,y4)

result = linesIntersect(x1,y1,x2,y2,x3,y3,x4,y4)

Text 0,0,"Result= "+result
If result = True
Text(10,20,"Intersection Coords")
Text(10,40,"   X="+ Str(intersectX) +" , Y="+Str(intersectY))
Color 255,0,0
Oval intersectX-3, intersectY-3, 7, 7, True
Color 255,255,255
Else
Text(10,20,"No Intersection")
End If

Flip
WaitKey()
Wend

End

;Source: http://Local.wasp.uwa.edu.au/~pbourke/geometry/lineline2d/
;Intersection point of two lines
;(2 dimensions)
Function linesIntersect(x1%,y1%, x2%,y2%, x3%,y3%, x4%,y4%)

numeratorA#  = (x4-x3)*(y1-y3)-(y4-y3)*(x1-x3)
numeratorB#  = (x2-x1)*(y1-y3)-(y2-y1)*(x1-x3)
denominator# = (y4-y3)*(x2-x1)-(x4-x3)*(y2-y1)

If denominator = 0.0 Then
; Text(10,20,"No intersection")
; If numeratorA = 0.0 And numeratorB = 0.0 And denominator = 0.0 Then
; Text(10,40,"Lines are coincident")
; Else
; Text(10,40,"Lines are parallel")
; End If
Return False
Else
Ua# = numeratorA/denominator
Ub# = numeratorB/denominator
range1% = Ua >= 0.0 And Ua <= 1.0
range2% = Ub >= 0.0 And Ub <= 1.0
If range1 And range2 Then
intersectX% = Floor(x1 + Ua*(x2-x1)+.5)
intersectY% = Floor(y1 + Ua*(y2-y1)+.5)
Return True
Else
; Text(10,20,"No intersection")
Return False
End If
    End If
End Function

Comments :


RemiD(Posted 6 months ago)

 @Andy>>thanks for sharing !