quad strips bugs ?

[M. J. Cole]

In article <9104280445.AA10669 at karron.med.nyu.edu>, Dan Karron at UCBVAX.BERKELEY.EDU writes:
> 
> I am trying to use the bgnqstrip and endqstrip commands to draw
> filled squares.
> 
> I keep getting a figure that looks like it is starting at the
> local origin, then drawing my square, then returns to the origin.
> 
> I have worked around it by using the polygon functions, but
> I was wondering if this was a known problem. My data is good because
> I get the expected results from the poly calls. 
>

Two possible problems:  
  1) qstrips require a different vertex ordering than polygons. 
     For polygon: 1--2      For quadrilateral: 1--3
                  |  |                         |  |
                  0--3                         0--2  
     Quoting from page 2-27 of the Graphics Library Programming Guide: 
	"Note that the vertex order required by quad strips 
	 matches the order required for `equivalent' triangle 
	 meshes."

  2) If you are using lighting on a Personal Iris DO NOT USE triangle meshes
     or quadrilateral strips (weird things will happen).  This has been
     a "known bug" for so long, I wonder why they don't put a notice in
     the manuals. :-)

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Mary J. Cole        ARCO Oil & Gas Company 
mjcole at arco.com     2300 W. Plano Parkway; PRC-D3239; 
(214)754-6857       Plano, TX 75075 
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I'm continually AMAZED at th'breathtaking effects of WIND EROSION!! -ZIPPY
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