NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/programmer/3255

Internet Message Format | 1996-08-05 | 2.7 KB

Path: informatik.tu-muenchen.de!fischerj
From: [e-mail] (Juergen "Rally" Fischer)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: 90 degree rotation
Date: 9 Feb 1996 15:37:51 GMT
Organization: Technische Universitaet Muenchen, Germany
Distribution: world
Message-ID: <4ffpof$[e-mail]>
References: <[e-mail]> <4fev39$[e-mail]>
NNTP-Posting-Host: hphalle5.informatik.tu-muenchen.de
Originator: [e-mail]


In article <4fev39$[e-mail]>, [e-mail] (Stephan Schaem) writes:
|> Organization: Teleport - Portland's Public Access [phone]
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|>
|> Irmen de Jong ([e-mail]) wrote:
|> : Regarding texturemapping (doom like):
|> : Wouldn't it be wise to write the walls in a 90 degree rotated fashion?
|> : I mean, not vertically, but horizontally. It might then be possible to write
|> : whole longs at once, which is much faster than writing single bytes.

on 020/030 writing .l is hardly usefull, only into chipmem.

but then, the rerotating of the pic will cost more than
anything...

|>
|>  Much faster, the following is basic wall tmaping?
|>
|>  REPEAT 16
|>  move.b    (a0,d0.w),(a1)
|>  addx.l    d1,d0
|>  adda.l    a2,a1
|>  ENDR

yep, a wallmapper.

|>
|>  Even if you trandform this to write long (Would be slower) how do you
|>  handle your chunky buffer? Do you tmap 1 line and c2p it?

nooo. only c2p complete screen after render.

|>
|> : Is 90 degree rotation in the C2P phase easy to do? Or do I miss something
|> : here?
|>
|>  In your c2p loop you want to read 32bit from your chunky buffer and
|>  write 32bit to chipram... You do this when the chunky buffer is
|>  rendered, not a few pixels at a time.
|>  But lets say you just wrote a Vline of 32pixel on the stack, now
|>  if you c2p this you will only write 1 pixel Hline in the chunky
|>  buffer. So 8*32*1 read+And+Or+write. What you want really is
|>  8 write... So this would be more then 64 time slower....
|>
|> : I recall that the "PicCon" program can save 90 degree rotated chunky
|> : textures. What other use might this have?
|>
|>  You would use rotated tmap for walls only.... because you step verticaly
|>  in your display buffer, and horizontaly in your texture buffer.(Just
|>  a speedup for the inner mapping loop)

ah yes that's it: you go the horizontal way in _source_ for
adressing reasons.

|>
|>  Stephan
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   [e-mail] (Juergen "Rally" Fischer)   =:)