rem                            P_3PL.CDL


rem        Copy Right by International Technology Transfer Corp.
rem        revision 1.0-7/30/99   

rem        Intersection of 3 Planes



clear
dspflg = 1
acc = 0.00001

:start
getplane "Select First Plane ", dspflg

on (@key + 3) goto exit, start,
a1 = @fltdat[10]
b1 = @fltdat[11]
c1 = @fltdat[12]
d1 = @fltdat[13]

:second
getplane "Select Second Plane", dspflg

on (@key + 3) goto exit, start, second,
a2 = @fltdat[10]
b2 = @fltdat[11]
c2 = @fltdat[12]
d2 = @fltdat[13]

:third
getplane "Select Third Plane", dspflg

on (@key + 3) goto exit, second, third,
a3 = @fltdat[10]
b3 = @fltdat[11]
c3 = @fltdat[12]
d3 = @fltdat[13]

ab = a2 * b3 - a3 * b2
bc = b2 * c3 - b3 * c2
ca = a3 * c2 - a2 * c3
bunbo = a1 * bc + b1 * ca + c1 * ab
if (abs(bunbo)>acc)
	goto next
pause "At Least Two Planes are Parallel (Press Return)"
redraw
goto start

:next
da = d2 * a3 - d3 * a2
db = d2 * b3 - d3 * b2
dc = d2 * c3 - d3 * c2
x = (b1 * dc - c1 * db - d1 * bc) / bunbo
y = (- a1 * dc + c1 * da -d1 * ca ) / bunbo
z = (a1 * db - b1 * da - d1 * ab) / bunbo
point x, y, z

redraw
goto start
:exit