Intersection of lines - GameCreators Forum

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Manson

21

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Joined: 20th Oct 2002

Location: Denmark

Posted: 8th Nov 2002 02:30

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Does anybody have a function for checking if 2 lines cross each other?

Not where they intersect, just if they do,,,

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Easily Confused

21

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Joined: 22nd Oct 2002

Location: U.K. Earth. (turn right at Venus)

Posted: 8th Nov 2002 05:24

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Hope this works

+ Code Snippet

Function LineCross(x1,y1,x2,y2,x3,y3,x4,y4)
  rem --- x1,y1 = start position of line 1     x2,y2 = end position of line 1
  rem --- x3,y3 = start position of line 2     x4,y4 = end position of line 2

  rem --- will return 1 if lines cross over

  d# = (y4-y3)*(x2-x1) - (x4-x3)*(y2-y1)
  ua# =((x4-x3)*(y1-y3) - (y4-y3)*(x1-x3)) / d#
  ub# =((x2-x1)*(y1-y3) - (y2-y1)*(x1-x3)) / d#
  if (ua# > 0.0) and (ua# <= 1.0) and (ub# > 0.0) and (ub# <= 1.0) then exitfunction 1
endfunction 0

"Earth is the cradle of humanity,
but one cannot live in a cradle forever"
Konstantin E. Tsiolkovsky (1911)

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Easily Confused

21

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Joined: 22nd Oct 2002

Location: U.K. Earth. (turn right at Venus)

Posted: 8th Nov 2002 16:51

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Perhaps that last line should be:

if (ua# >= 0.0) and (ua# <= 1.0) and (ub# >= 0.0) and (ub# <= 1.0) then exitfunction 1

"Earth is the cradle of humanity,
but one cannot live in a cradle forever"
Konstantin E. Tsiolkovsky (1911)

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Manson

21

Years of Service

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Joined: 20th Oct 2002

Location: Denmark

Posted: 8th Nov 2002 20:37

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Thanks!
I'll check it out!
BTW: I'll use it to create a function to draw polygon-objects of triangles,,, With the possiblity of 'holes' or 'islands' inside them.
Primeraly for use as floors/ceilings in FPS games,,,
You want a copy when it's done?

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DarkBASIC Discussion / Intersection of lines