alpha and rib files on the NeXT.

[Dennis Roseman <roseman at dimension4.math.uiowa.edu>]

I am working on a NeXT and want to make an object transparent.

I know I can't see this in QuickRenderman, but my intention is to use  
prman.

The problem is that when I save to a .rib file in geomview, I loose  
transparency.

For example-- if I load dodec.off and give the command:

(merge-ap g1 appearance { material {alpha .2}})

then when I save it, the file reads in part:


***********

{ LIST # World list 

{ # dodec.off
  INST transform {
    0.31820917             0             0             0
             0    0.31820917             0             0
             0             0    0.31820917             0
             0             0             0             1

}
  geom {appearance {
  material {
	alpha 0.200000
  }
}
geom NOFF
20 12 30

1.214124 0 1.589309  0.607062 0 0.794654

***********

BUT the .rib file that I save looks in part like:

***********

# Interpreting Material  
**********************************************
TransformBegin
Identity    

TransformEnd
TransformBegin
ConcatTransform [1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1] 

TransformBegin
ConcatTransform [1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1] 

TransformBegin
Identity
ConcatTransform [1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1] 

AttributeBegin
Polygon
"P" [0.238383 -0.292916 -0.339734   0.24324 -0.274523 -0.352826    
0.215005 -0.290016 -0.359653] 

"Cs" [0.349303 0.888683 0.1   0.37636 0.876602 0.1   0.32891 0.897789  
0.1] 

"N" [-0.850033 0.040672 0.525157   -0.850033 0.040672 0.525157    
-0.850033 0.040672 0.525157] 

Polygon
"P" [0.319168 -0.24455 -0.327642   0.32438 -0.233358 -0.336446    
0.307418 -0.24095 -0.338892] 

"Cs" [0.491784 0.825064 0.1   0.501308 0.820811 0.1   0.483758  
0.828647 0.1] 

"N" [-0.783132 0.097824 0.614114   -0.783132 0.097824 0.614114    
-0.783132 0.097824 0.614114] 

    


**********

Note that there is no saving of the trasparency which should look  
like:
"Os"[ .2 .2 .2] 

for each triangle.  I've tested this out on some simple files--this  
addition does indeed make a polygon transparent.

So it seems to me there is a problem.

I know I can "fix this" with a simple awk program etc & probably will  
have to.

I know this has not been a problem with rib files in SGI machine--at  
least ones done a year ago.