Found the answer.  Working with the floating point vertices you do a half
pixel offset in either direction for each triangle.  Pretty straight
forward.  However, I need a floating point equivalent to the S12_4 macro
used to cast and bit shift the integers for the Voodoo3 drawing routines.
Denis, can you help me with that?

This is functionally equivalent to drawing a 2 pixel wide rectangle with a
half pixel offset.

Thanks,
David Wood


-----Original Message-----
From: Denis Oliver Kropp [mailto:[EMAIL PROTECTED]] 
Sent: Friday, July 05, 2002 11:58 AM
To: Wood, David
Cc: Directfb-Dev ([EMAIL PROTECTED])
Subject: Re: [directfb-dev] Re: Accelerated Line Rendering Voodoo3

Quoting Wood, David ([EMAIL PROTECTED]):
>    I write the required three vertices for the 3d engine and set the Alpha
>    Mode flag.  But, when I write to the triangle command register it draws
>    nothing.  Weird.  Looks like you guys attempted to build an accelerated
>    alpha blended line drawing function but it doesn't work either.  Any
>    suggestions?

You need to draw two triangles for one line ;)
I looked at the Glide source and ran away...

-- 
Best regards,
  Denis Oliver Kropp

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| DirectFB - Hardware accelerated graphics |
| http://www.directfb.org/                 |
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