transforming from screen to object coordinates

[Brent L. Bates AAD/TAB MS361 x42854]

   If I understand you correctly, I just started doing that recently.
Below is some sample FORTRAN:

      ...

      integer*4 tranmatrix,xmice4,xwinlen,xwinorg,ymice4,ywinlen,ywinorg
      real scaleyz,xo,xoff,xtekscale,yo,yoff,ytekscale,zmin,zoom

      ...

      call getori(xwinorg,ywinorg)
      call getsiz(xwinlen,ywinlen)

      ...

      tranmatrix=genobj()
      call makeob(tranmatrix)
         call viewpo(0,xwinlen,0,ywinlen)
         call ortho(0.,xtekscale,0.,ytekscale,-.1,.1)
         call lookat(0.0,0.0,.1,0.0,0.0,0.0,0.0)
         call transl(xtekscale/2.0,ytekscale/2.0,0.0)
         call scale(zoom,zoom,1.0)
         call transl(-xtekscale/2.0,-ytekscale/2.0,0.0)
         call transl(xoff,yoff,0.0)
         call scale(scaleyz,scaleyz,1.0)
         call transl(0.0,-zmin,0.0)
      call closeo

      ...

      xmice4=getval(mousex)-xwinorg
      ymice4=getval(mousey)-ywinorg
      if(xmice4.lt.0) then
         xmice4=0
      else if(xmice4.gt.xwinlen) then
         xmice4=xwinlen
      endif
      if(ymice4.lt.0) then
         ymice4=0
      else if(ymice4.gt.ywinlen) then
         ymice4=ywinlen
      endif
      call mapw2(tranmatrix,xmice4,ymice4,xo,yo)

   xo and yo are the 2d world coordinates
   I hope this is what you are looking for.
--

	Brent L. Bates
	NASA-Langley Research Center
	M.S. 361
	Hampton, Virginia  23665-5225
	(804) 864-2854
	E-mail: blbates at aero4.larc.nasa.gov or blbates at aero2.larc.nasa.gov