NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/programmer/3254

Internet Message Format | 1996-08-05 | 3.0 KB

Path: informatik.tu-muenchen.de!fischerj
From: [e-mail] (Juergen "Rally" Fischer)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Fastest way to clear a Window?
Date: 9 Feb 1996 15:23:48 GMT
Organization: Technische Universitaet Muenchen, Germany
Distribution: world
Message-ID: <4ffou4$[e-mail]>
References: <4fck5b$[e-mail]> <4fcush$[e-mail]>
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In article <4fcush$[e-mail]>, [e-mail] (Andreas Malerz) writes:
|> Organization: Rheinische Friedrich-Wilhelms-Universit"at Bonn, Institut
|> Lines: 30
|> Message-ID: <4fcush$[e-mail]>
|> References: <4fck5b$[e-mail]>
|> NNTP-Posting-Host: malve.informatik.uni-bonn.de
|> X-Newsreader: TIN [version 1.2 PL2]
|>
|> Dave Jackson ([e-mail]) wrote:
|> : I'm writing a 3d graphics viewer thingy using intuition windows.  What I
|> : want to know is, what is the fastest way of clearing a window?  At the
|> : moment I'm using SetRast() but there must be a faster way.  I'm using a
|> : custom screen, so I could make it draw lines on a single bitplane and
|> : then just clear that one plane, but the RKM:Libraries has nothing on how
|> : to clear one plane...  help!

sorry don't know, but why do you want to clear a window quick ?
do you intend to clear and then draw ?

this might flicker...

I'd build the 3d object in mem. IF a point averagely is overwritten
more than about 2 times, rendering to fastmem and then copying to
a chipmem bitmap is faster.
When done, copy the bitmap into the window with blitbitmaprastport().

Don't know about the 1-plane problem, though...

|>
|> : TIA
|> : Dave Jackson
|>
|> Depending on your processor, you can try to do it with the CPU itself.
|> The fastest way I know is the following:
|>
|>   Save all registers on STACK
|>   Save STACK-Pointer somewhere else
|>
|>   Clear all registers
|>   Put the Address of your bitplane in one Adressregister
|>   Copy the registers to your plane with "movem"
|>   Do the last step as often as necessary.
|>
|>   Restore STACK-Pointer
|>   Restore all registers.
|>
|> This solution is systemfriendly and on a fast processor faster than the
|> blitter.

a) it is not systemfriendly, as you must turn off interrupt
   if sp doesn't point to enough free space.

b) Forgett all that movem crap unless you're not on a A500.
   on A1200, this is the loop you can't beat:

clear:
   move.l d0,(a0)+
   dbra d7,clear

This runs 8cycles/longword on A1200 and you won't get it faster
(The dbra doesn't disturb, "free cycles" on 020+).

BTW this method might not be useful for clearing windows...

|>
|>     Best greetings,
|>         Andy.
------------------------------------------------------------------------
   [e-mail] (Juergen "Rally" Fischer)   =:)