Path: utzoo!mnetor!uunet!yale!wallman-george
From: wallman-george@CS.YALE.EDU (Natuerlich!)
Newsgroups: comp.sys.atari.8bit
Subject: Re: 3D on the 8 bits
Message-ID: <28438@yale-celray.yale.UUCP>
Date: 4 May 88 21:30:30 GMT
References: <8805020833.aa01825@ARDEC-3.ARDEC.ARPA>
Sender: root@yale.UUCP
Reply-To: wallman-george@CS.YALE.EDU (Natuerlich!)
Organization: Natuerlich!'s Software Vault #5 -- Location Yale
Lines: 32
Keywords: VBI BASIC doesn't mix
Summary: easy

In article <8805020833.aa01825@ARDEC-3.ARDEC.ARPA> ekijak@ARDEC.ARPA ("Edmund S. Kijak", IMD-SIAS) writes:
>Perhaps as wallman-george@yale... points out, something has to be done to 
>'shut-off' shadowing of memory locations pointing to the display list.  I haven't
>figured out how to do it though (or if it is even possible).  Maybe it works
>on the XE machines.

Nothing easier than that. Just circumvent the usual OS routine. As usual
I don't have my Atari sitting here "at work" but this should work (in
BASIC).

POKE 54286,0
POKE 546,PEEK(548)
POKE 547,PEEK(549)
POKE 54268,192

OK what I think this will do is preempt the immediate VBI by using
the deferred VBI that doesn't do the shadowing and usually does
nothing. 54286 is NMIEN that turns VBIs and DLIs on and off.

Watch out. Lots of stuff will not work anymore with shadowing disabled
such as  'comfortable typing' SETCOLOR commands etc. If you use 
BASIC pure in the first place, you won't get very far. Better write a
little VBI that does the work.
DISCLAIMER: the statements were done w/o consulting either my indis-
pensable Mapping the Atari book, nor by trying it out on a computer.
But I am confident that above statements are true.

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