GS_get_cat_at_xy

diff gsdrape.c gsdrape.bak  - region clipping not working
(see cont. example in germany location testdata)
Inconsistent error - depends on view res, maybe check I3d init.
or num points returned. 
I think fixed now.

did a bunch of DIFFUSE -> AD changes for trial

shininess not working
OK - working now - will be different from SG3d due to infinite light.

--------------------------------
NVIZ color bug:
  see /BUGS
  -> small z-scaled elevations are displayed dark.
  - problem in lat/long databases, too

Helena wrote:
>applied with the opengl function glNormal found in gsd_prim.c. I suspect       
>that there is a problem with how the normal vectors are calculated and         
>normalized. With a large Z range the normal XY values span -1 to 1, and        
>the normal Z values span 0 -1. With lat / long data and data with a low        
>Z range, the normal Z (temp[Z]) component is not normalized to the 0-1         
>range but rather a small component of it.                                      
                                                                                
You are right that there is a problem with normals for surfaces with values     
<0-1>- I have already reported it, it seems that it is also causing parts of    
the surface to disapear for larger values of z for higher resolution/higher     
zscale case. Bill fixed it for the SGI-GL version - if the GL version           
is available it would be good to compare them. I will check with Bill,          
but I would like him to finish the legends first.              

--------------------------------
The trans.c file should be removed and any calls to the functions in that
file should be replaced with appropriate OpenGL calls. All the functionality
in trans.c can be achieved with OpenGL.

--------------------------------
This library needs a general overhaul. There are many places which have
empty functions containing only return statements, as well as several comments
that say /* You can do better than this */ which indicates areas for
improvements.
