TheGameCreators - CodeBase - LineIntersect() and Parallel()

Category: Math / Physics

Version: 1.0

Information

Uploaded: 7th Feb 2005 15:27

Modified: 1st Jan 1970 01:00

Author: mathkid

Summary

LineIntersect() - Analytic geometry function that calculates the intersection point of two lines given a starting point and an x- and y-component of the slope for each line. Parallel() - Determines whether two lines are parallel.

Full Description

Analytic geometry function that calculates the intersection point of two lines given a starting point and an x- and y-component of the slope for each line. The additional Parallel function at the bottom is used to determine whether the two lines are parallel and have no intersection point.

DarkBASIC Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

Function LineIntersectX(X1#,Y1#,V1X#,V1Y#,X2#,Y2#,V2X#,V2Y#)

If V1X#=0 and V2X#=0

set cursor 0,0

print "ERROR: TWO UNDEFINED SLOPES PUT INTO LINEINTERSECT FUNCTION"

loop

Endif

`ONLY USE THIS FUNCTION AFTER USING PARALLEL() TO BE SURE THAT THE LINES ARE NOT PARALLEL

`check to see if slopes are undefined

If V1X#<>0

If V2X#<>0

`lines are not vertical and not parallel

M1#=V1Y#/V1X#

M2#=V2Y#/V2X#

`intersection point (analytic geometry)

X3#=M1#*X1#-M2#*X2#

X3#=X3#+Y2#-Y1#

X3#=X3#/(M1#-M2#)

Y3#=M1#*(X3#-X1#)+Y1#

Else

`can't be both zero, since they aren't parallel

`V2X# line is vertical

M1#=V1Y#/V1X#

`X of intersection is the same since the second line is vertical

X3#=X2#

`Y of intersection

Y3#=M1#*(X2#-X1#)+Y1#

Endif

Else

`V1X# line is vertical

M2#=V2Y#/V2X#

`X of intersection is the same since the first line is vertical

X3#=X1#

`Y of intersection

Y3#=M2#*(X1#-X2#)+Y2#

Endif

Endfunction X3#

Function LineIntersectY(X1#,Y1#,V1X#,V1Y#,X2#,Y2#,V2X#,V2Y#)

`ONLY USE THIS FUNCTION AFTER USING PARALLEL() TO BE SURE THAT THE LINES ARE NOT PARALLEL

`check to see if slopes are undefined

If V1X#<>0

If V2X#<>0

`lines are not vertical and not parallel

M1#=V1Y#/V1X#

M2#=V2Y#/V2X#

`intersection point (analytic geometry)

X3#=M1#*X1#-M2#*X2#

X3#=X3#+Y2#-Y1#

X3#=X3#/(M1#-M2#)

Y3#=M1#*(X3#-X1#)+Y1#

Else

`can't be both zero, since they aren't parallel

`V2X# line is vertical

M1#=V1Y#/V1X#

`X of intersection is the same since the second line is vertical

X3#=X2#

`Y of intersection

Y3#=M1#*(X2#-X1#)+Y1#

Endif

Else

`V1X# line is vertical

M2#=V2Y#/V2X#

`X of intersection is the same since the first line is vertical

X3#=X1#

`Y of intersection

Y3#=M2#*(X1#-X2#)+Y2#

Endif

Endfunction Y3#

Function Parallel(V1X#,V1Y#,V2X#,V2Y#)

`lines are not parallel

parallel=0

`...or they are

`both lines vertical

If V1X#=0 and V2X#=0

parallel=1

Else

`both lines not vertical

If V1X#<>0 and V2X#<>0

M1#=V1Y#/V1X#

M2#=V2Y#/V2X#

If M1#=M2# then parallel=1

Else

`one line vertical (not parallel)

Endif

Endfunction parallel

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Author Name:	mathkid
CodeBase Entries:	1

CodeBase - LineIntersect() and Parallel()

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