NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/programmer/5303

Internet Message Format | 1996-08-05 | 4.5 KB

Path: informatik.tu-muenchen.de!fischerj
From: [e-mail] (Juergen "Rally" Fischer)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: TMapping again!
Date: 12 Mar 1996 18:09:21 GMT
Organization: Technische Universitaet Muenchen, Germany
Distribution: world
Message-ID: <4i4ekh$[e-mail]>
References: <[e-mail]> <4h45g4$[e-mail]> <[e-mail]>
NNTP-Posting-Host: hphalle10.informatik.tu-muenchen.de
Originator: [e-mail]


In article <[e-mail]>, [e-mail] (Tim Boescke) writes:
|> Reply to Re: TMapping again! / 29.02.1996
|> by [e-mail] (Juergen Rally Fischer)
|> JF> In article <[e-mail]>, "Jyrki Saarinen" <[e-mail]> writes:
|> JF> |>
|> JF> |> >     A time ago I did an approach to this problem using a similar trick
|> JF> |> >     than my two-command mapper.
|> JF> |> >     (btw. actually this one WORKS .. I have tried it out)
|> JF> |> >
|> JF> |> >
|> JF> |> >         move.l  d3,d2           ;d3=d4=0000000000000XXXXXXXxxxxxxYYYYYY
|> JF> |> >         move    d0,d5           ;d0=a6=yyyyyyyy000000000000BBBBBBbbbbbb
|> JF> |> >         and.l   d6,d2           ;d6=   00000000000001111111000000111111
|> JF> |> >         and.b   d7,d5           ;d7=   xxxxxxxxxxxxxxxxxxxxxxxx11000000
|> JF> |> >         or      d5,d2
|> JF> |> >         move.b  (a4,d2.l),(a2)+ ;d2=   00000000000000xxxxxxbbbbbbyyyyyy
|> JF> |> >         add.l   a6,d0
|> JF> |> >         addx.l  d4,d3
|> JF> |> >
|> JF> |> >      This one is doing Texturemapping + gouraud shading with
|> JF> |> >      shadetable. (!!)
|> JF> |> >
|> JF> |> >      The Texture is 64x64 (6 bit) and the shading is 6 bit two. You
|> JF> |> >      will need a 256k combined Texture/Shading table.
|> JF> |>
|> JF> |> Hmm. Not nice in a game for example where several textures
|> JF> |> are needed. But a nice idea anyway!
|>
|>     YOu can use this code with several textures. For example you could
|>     split up the shading range. For example B=0-31 is textere one and
|>     B=32-63 is Texture two.. etc. or use 32x32 textures...
|>
|> JF> nice ? Cooooooool!
|> JF> Cool idea to pack the shading value into the texture adress!
|>
|>     Thanks ;)
|>
|> JF> The example does too much instructions :) but allows more general
|> JF> mem usage.
|> JF>
|> JF> What about this...
|> JF>
|> JF>  add.l  a2,d2          0...00BBBbbbbbbbbbbbbbbbb
|> JF>  add.l  a3,d1          x...xxxxxYYYYYYYYyyyyyyyy
|> JF>  addx.l d3,d0          0...0000000000000XXXXXXXX
|> JF>  move.l d2,d6
|> JF>  move.w d1,d6
|> JF>  move.b d0,d6
|> JF>  move.b 0(a0,d6.l),(a1)+
|> JF>
|> JF> 20 cycles gouraud mapping :)
|> JF>
|> JF> 8 shadingsteps are 512k, not too much even for a A1200 game imho
|> JF> (well, people tell me they aim for higher machines anyway,
|> JF> so the mem consumption can't be considered so bad ;)
|>
|>     Welll. of course this is two cycles faster, but it takes twice the
|>     memory and 8 shading steps are simply not enough ;)

why twice the mem ?

it can do also 16 steps, just like yours.
n colors shaded textures, needing 2^(n-1) times more mem, just like yours :)


|>
|> JF> I would really think about using this routine, it's really LOT quicker.
|> JF> You can put multiple textures into a given 64k range btw. but those can't
|> JF> be "repeart-mapped" uh "multiplexed" ? how you call it if x gets 256 and then
|> JF> _plop_, 0 again on the left side ? Is this called bump-mapping ? :D
|>
|>     wrap-around textures ?? Well erhm.. Bump-mapping is a bit different.

not knowing what it is I can imagine it is a bit different, though the ":D" ;)
so what is bump-mapping ?

wrap-around: imagine you scan over the border of a 256x256 texture.
pointer will be in same texture again, beacuse it's all "anded" to 64k.
you can have multiple times the same texture in one polygon this way.

when using the 256x256 space for storting multiple textures (4 times
128x128 etc) you loose "wrap-around" :) Is the word silly ? what you'd use
for it ?


|>     (hehe found a nice and fast innerloop for that, too. ;) )
|>
|> --
|>     +--------------------------------------------------------------------+
|>     |      -  [e-mail] - Tim Boescke - AZURE /atw.bzr    |
|>     +---------------------------------<AMIGA,PC,C64,PLUS/4,VCS2600>------+
------------------------------------------------------------------------
   [e-mail] (Juergen "Rally" Fischer)   =:)