rem                            L_2LN.CDL


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


rem        Intersection between 2 planes



clear
dspflg = 1
acc = 0.00001

:start
getplane "Select First Plane", dspflg

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

getplane "Select Second Plane", dspflg

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

f = b1 * c2 - b2 * c1
g = c1 * a2 - c2 * a1
h = a1 * b2 - a2 * b1
bunbo = f * f + g * g + h * h

if (bunbo>acc)
	goto next
pause "Two Planes Are Parallel (Press Return)"
goto start

:next
f = f / sqrt(bunbo)
g = g / sqrt(bunbo)
h = h / sqrt(bunbo)

dc = d1 * c2 - d2 * c1
db = d1 * b2 - d2 * b1
da = d1 * a2 - d2 * a1

x0 = (g * dc - h * db) / bunbo
y0 = (h * da - f * dc) / bunbo
z0 = (f * db - g * da) / bunbo

vx1 = @xmax
vy1 = @ymax
vx2 = @xmin
vy2 = @ymin
dist = sqrt((vx1 - vx2) * (vx1 - vx2) + (vy1 - vy2) * (vy1 - vy2))
vx = (vx1 + vx2) / 2.0
vy = (vy1 + vy2) / 2.0
call xfvw, vx, vy, 0, wx, wy, wz

t = (f * (wx - x0) + g * (wy - y0) + h * (wz - z0)) / bunbo

x0 = x0 + f * t
y0 = y0 + g * t
z0 = z0 + h * t

x1 = x0 + f * dist /2.0
y1 = y0 + g * dist /2.0
z1 = z0 + h * dist /2.0

x2 = x0 - f * dist /2.0
y2 = y0 - g * dist /2.0
z2 = z0 - h * dist /2.0


line x1, y1, z1, x2, y2, z2
redraw
goto start
:exit