rem        ********************* 3PTCONIC.CDL ***********************

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

rem        Conic with 3 points
rem        **************   Procedure   *************************
rem        1. Define view for Conic (Do not forget)
rem        2. Select 3 points
rem        3. Create conic through 3 points



clear
defopt = 2
acc = 0.00001

:start
getpos "Indicate 1st Point",defopt

on (@key + 3) goto exit, start,
defopt=@key
wx1 = @xworld
wy1 = @yworld
wz1 = @zworld

:second
getpos "Indicate 2nd Point",defopt

on (@key + 3) goto exit, start, second, 
defopt=@key
wx2 = @xworld
wy2 = @yworld
wz2 = @zworld

:third
getpos "Indicate 3rd Point",defopt
on (@key + 3) goto exit, second, third, 

defopt=@key
wx3 = @xworld
wy3 = @yworld
wz3 = @zworld

call xfwv,wx1,wy1,wz1,vx1,vy1,vz1
call xfwv,wx2,wy2,wz2,vx2,vy2,vz2
call xfwv,wx3,wy3,wz3,vx3,vy3,vz3

det = vx1 * vx2 * (vx1 - vx2) + vx2 * vx3 * (vx2 - vx3) + vx3 * vx1 * (vx3 - vx1)
f1 = vx1 - vx2
g1 = vy1 - vy2
f2 = vx2 - vx3
g2 = vy2 - vy3

if (abs(det)>acc)
	goto next1
	
pause "Position is not correctiPress Return Key)"
goto start

:next1
if (abs(vy1-vy2)>acc || abs(vy2-vy3)>acc)
	goto next2
pause "Position is not correctiPress Return Key)"
goto start

:next2
if (abs(f1-f2)>acc || abs(g1-g2)>acc)
	goto next3

pause "Position is not correctiPress Return Key)"
goto start

:next3
a=((vy1-vy2)*(vx2-vx3)-(vy2-vy3)*(vx1-vx2))/(vx1-vx2)/(vx2-vx3)/(vx3-vx1)
d=-(vy1-vy2)/(vx1-vx2)-(vx1+vx2)*a
f=-(vx1*vx1*a+vx1*d+vy1)
b = 0
c = 0
e = 1
conic a, b, c, d, e, f, vx1, vy1, vx3, vy3, vz1

goto start
:exit