From info-iris-request(+ at +)vmb.brl.mil Fri Jun 14 13:27:35 1991
Date: 14 Jun 91 14:55:43 GMT
From: Don Sosoka <eagle!monet.lerc.nasa.gov!xxdon %-% at %-% ucbvax.berkeley.edu>
Organization: NASA/Lewis Research Center, Cleveland
Subject: lighted, multi-colored polys
To: info-iris-: at :-BRL.MIL
Status: R

I know this should be an easy one and the answer must be docummented some-
where but I can't find it.  Please Help!

I want to draw smooth (GOURAUD) shaded lighted polygons starting with   
different colors at each vertex.  Assuming the lighting model is setup 
correct (which it seems to be), if I do something like

      call SHADEM (GOURAU)
      call BGNPOL
      do 10 i = 1,N
         vn(1) = XN(i)
         vn(2) = YN(i)
         vn(3) = ZN(i)
         call N3F (vn)
         icv(1) = IRED(i)
         icv(2) = IGREEN(i)
         icv(3) = IBLUE(i)
         call C3I (icv)
         v(1) = X(i)
         v(2) = Y(i)
         v(3) = Z(i)
         call V3F (v)
10    continue
      call ENDPOL

I get smooth shaded colored polygons but no lighting effects.  If I reverse the
order:

      call SHADEM (GOURAU)
      call BGNPOL
      do 10 i = 1,N
         icv(1) = IRED(i)
         icv(2) = IGREEN(i)
         icv(3) = IBLUE(i)
         call C3I (icv)
         vn(1) = XN(i)
         vn(2) = YN(i)
         vn(3) = ZN(i)
         call N3F (vn)
         v(1) = X(i)
         v(2) = Y(i)
         v(3) = Z(i)
         call V3F (v)
10    continue
      call ENDPOL

I get a nicely lit surface but all gray shaded.

What's the trick? (or am I way off base).

Thank's.