rem                            P_2Ln.CDL


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


rem        Intersection of two Lines


clear
acc = 0.0001
rem     accの値は許容誤差値です

:start
	getent "Select First Line",enttype
	on (@key + 3) goto exit,start, start,
	if (enttype!=2)
		goto start

	x1 = @fltdat[0]
	y1 = @fltdat[1]
	z1 = @fltdat[2]
	x2 = @fltdat[3]
	y2 = @fltdat[4]
	z2 = @fltdat[5]
	
	f1 = x2 - x1
	g1 = y2 - y1
	h1 = z2 - z1
rem     ***********************************************************************
rem     first line
rem     x = x1 + f1 * t
rem     y = y1 + g1 * t
rem     z = z1 + h1 * t
rem     ***********************************************************************

:second
	getent "Select Second Line",enttype
	on (@key + 3) goto exit, start, second, 
	if (enttype!=2)
		goto second

	x3 = @fltdat[0]
	y3 = @fltdat[1]
	z3 = @fltdat[2]
	x4 = @fltdat[3]
	y4 = @fltdat[4]
	z4 = @fltdat[5]
	
	f2 = x4 - x3
	g2 = y4 - y3
	h2 = z4 - z3
rem     ***********************************************************************
rem     2nd line
rem     x = x3 + f2 * s
rem     y = y3 + g2 * s
rem     z = z3 + h2 * s
rem     

rem     x1 + f1 * t = x3 + f2 * s
rem     y1 + g1 * t = y3 + g2 * s
rem     z1 + h1 * t = z3 + h2 * s
rem     Solve t

rem     ***********************************************************************

	fg = f1 * g2 - f2 * g1
	gh = g1 * h2 - g2 * h1
	hf = h1 * f2 - h2 * f1


	if (abs(fg)>acc)
		goto case1
	if (abs(gh)>acc)
		goto case2
	if (abs(hf)>acc)
		goto case3

	pause "Line is Parallel"
	redraw
	goto start

:case1
	t = (-f2 * (y3-y1) + g2 * (x3-x1))/fg
	goto next1
:case2
	t = (-g2 * (z3-z1) + h2 * (y3-y1))/gh
	goto next1
:case3
	t = (-h2 * (x3-x1) + f2 * (z3-z1))/hf

rem     ***********************************************************************
rem     Dist between Lines
rem     Dist = abs(bunshi) / bunbo
rem
rem              | x3 - x1    y3 - y1   z3 - z1 |
rem     bunshi = |    f1         g1        h1   |
rem              |    f2         g2        h2   |
rem
rem     bunbo = sqrt(fg*fg + gh*gh + hf*hf)
rem
rem     fg = f1*g2 - f2*g1 , gh = g1*h2 - g2*h1 , hf = h1*f2 - h2*f1
rem     ***********************************************************************
:next1
	bunshi = abs((x3-x1) * gh + (y3-y1) * hf + (z3-z1) * fg)
	if ( bunshi < acc)
		goto next2
	pause "No Intersection!"
	redraw
	goto start


:next2
	x = x1 + f1 * t
	y = y1 + g1 * t
	z = z1 + h1 * t

	point x, y, z,

	pause "Intersection Point( %.5f , %.5f , %.5f )", x, y, z
	redraw
	goto start
:exit