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From: blaho@hpfcdq.HP.COM (Bruce Blaho)
Newsgroups: comp.sys.hp
Subject: Re: Reading Z-buffer Memory on the HP Turbo SRX
Message-ID: <350011@hpfcdq.HP.COM>
Date: 12 Oct 89 13:34:10 GMT
References: <9028@batcomputer.tn.cornell.edu>
Organization: Hewlett-Packard - Fort Collins, CO
Lines: 24

>Is it possible to directly read the contents of the z-buffer on the
>HP Turbo SRX?  I know that the z-buffer memory can be read, 8 bits at a 
>time, using bank_switch(3G) and block_read(3G).  Unfortunately, these
>routines are fairly slow.  
>
>I'd really like the z-buffer analog to the frame buffer's R_GET_FRAME_BUFFER 
>gescape.  (As briefly outlined in the HP 98731 device driver manual, the 
>R_GET_FRAME_BUFFER gescape returns the starting address of the frame buffer, 
>allowing all 24 bits of the frame buffer to be read at one time).
>
>Many thanks,
>Tim (toc@wisdom.graphics.cornell.edu)
>----------

Tim,

You  should  be able to use the same  method  to read the  zbuffer.  The
zbuffer  will be mapped into the same address  space as the frame buffer
when you  have  selected  it with  bank_switch.  Use the  same  starting
address you got from R_GET_FRAME_BUFFER.

Bruce Blaho
  HP Workstation Group
  Graphics Technology Division, Software Lab