TheGameCreators - CodeBase - Distance Between A Point and a Line

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Category: Math / Physics

Version: 1.0

Information

Uploaded: 29th Feb 2004 17:55

Modified: 1st Jan 1970 01:00

Author: TDBoy

Summary

Set of Functions That Will Find The Shortest Distance Between a Point in 2D Space and A Line Segement.

Full Description

DarkBASIC Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

`*************************************************

`Distance From A Point To A Line

`*************************************************

`Written By:     Kyle Barrett

`Math Help From: http://astronomy.swin.edu.au/~pbourke/geometry/

`*********************

` Additional Info

`---------------------

` This code will find the shortest distance from a point to a line

`segement. Keep in mind that this code wont work if you are trying

`to find the distance from a point to a line or ray, just a line

`segement, as that is all I needed it for.

` Thanks to Paul Bourke and his website for sample C source code

`and extensive maths help.

` Questions? Comments? Improvements? E-mail me at RallySpeedX@Hotmail.com

Sync On

`First and Last Points of Our Line

X2# = 100.0

Y2# = 100.0

X1# = 300.0

Y1# = 257.0

`Clear the Screen

CLS

`Draw Our Line

Line X1#,Y1#,X2#,Y2#

`Our Point. For Demo's Sake, We'll Use The Mouse Pointer

X3# = MOUSEX()

Y3# = MOUSEY()

`Lets Find The Distance

D# = PointLineDistance(X1#,Y1#,X2#,Y2#,X3#,Y3#)

TEXT 20,20,str$(D#)

Sync

Loop

Function Dis(x1#,y1#,x2#,y2#)

VX# = X2# - X1#

VY# = Y2# - Y1#

V# = SQRT(VX#^2 + VY#^2)

Endfunction V#

Function PointLineDistance(x1#,y1#,x2#,y2#,x3#,y3#)

`First We Have To Find The Length Of The Line

LineMag# = Dis(x2#,y2#,x1#,y1#)

Text 20,35,"LineMag: " + str$(LineMag#)

`U# Is A Percentage. Its The Percent Of The Line That Can Be Added To The Line To Find The Intersection

U# = (((x3# - x1#) * (x2# - x1#)) + ((y3# - y1#) * (y2# - y1#))) / LineMag#^2

Text 20,50,"U: " + str$(U#)

`Lets Find The Intersection (Or The Closest Point On The Line To The Point)

IntersectionX# = X1# + U# * ( X2# - X1#)

IntersectionY# = Y1# + U# * ( Y2# - Y1#)

`This Section of Code Is Incase The Second Point Is Less Than The First Point.

`Normally, It Would Cause A Lot Of Problems, But We Solved Them

If X2# > X1#

If IntersectionX# > X2# then IntersectionX# = X2#

If IntersectionX# < X1# then IntersectionX# = X1#

Endif

If X2# < X1#

If IntersectionX# < X2# then IntersectionX# = X2#

If IntersectionX# > X1# then IntersectionX# = X1#

Endif

If Y2# > Y1#

If IntersectionY# > Y2# then IntersectionY# = Y2#

If IntersectionY# < Y1# then IntersectionY# = Y1#

Endif

If Y2# < Y1#

If IntersectionY# < Y2# then IntersectionY# = Y2#

If IntersectionY# > Y1# then IntersectionY# = Y1#

Endif

Text 20,65,"InterX: " + str$(IntersectionX#) + "  InterY: " + str$(IntersectionY#)

`Draw Our Intersecting Line. It Should Form A Right Angle With Our Original Line

Line IntersectionX#,IntersectionY#,X3#,Y3#

`Get Our Distance From The Point To The Line

Distance# = Dis(IntersectionX#,IntersectionY#,X3#,Y3#)

Endfunction Distance#

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Author Name:	TDBoy
CodeBase Entries:	1

CodeBase - Distance Between A Point and a Line

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