Line lengths.

[SoLo2]

  Hello!

  I am new to the Amiga World!
  Testing a little assembler I
  got to this code, that sets the
  screen I will be using.
  So, it seems like it _must_ be
  reinitialized at each screen refresh,
  true?
  That means that it can be initialized
  in the copper list, or otherwise in a
  separate routine,
  that writes directly to the registers.

  The problem arises when changing
  the "diwstrt" and "diwstop" registers.
  If I try using horizontal (x) start and
  end coordinates that are more to the
  left, for example $xx51 and $xx91,
  (this would start,stop at 079,145+256)
  then the effective visible line shrinks
  from 320 down to 272. The virtual line
  seems to remain the correct 320, but
  you   see   I set the modulo registers
  ($0108, $010a) to zero, to not have a
  bigger, virtual line...

  Why? who knows?

 
CopperList
  dc.w    $0100,$1200 ;bplcon0 set 1 plane, color
  dc.w    $0108,$0000 ;bpl1mod offset to next line
  dc.w    $010a,$0000 ;bpl2mod offset to next line
  dc.w    $008e,$3081 ;diwstrt start coords 048,129
  dc.w    $0090,$30c1 ;diwstop stop coords  304,449
  ; 320 (normal) visible line width
  dc.w    $0092,$0038 ;ddfstrt L margin normal (horz)
  dc.w    $0094,$00d0 ;ddfstop R margin normal (horz)
  ; to point to bitplane 1
  dc.w    $00e0       ;bitplane0 hi
hi0
  dc.w    $0000
  dc.w    $00e2       ;bitplane1 lo
lo0
  dc.w    $0000
  dc.w    $0182,$0ff0 ;color01



  I am using excellent UAE-0.8.21
  emulator under Linux. Great!

  SoLo2

[Lando]

SoLo2 wrote:

  Hello!

  I am new to the Amiga World!
  Testing a little assembler I
  got to this code, that sets the
  screen I will be using.
  So, it seems like it _must_ be
  reinitialized at each screen refresh,
  true?
  That means that it can be initialized
  in the copper list, or otherwise in a
  separate routine,
  that writes directly to the registers.

Welcome to amiga.org!

Of course the hw registers don't _have_ to be reinitialised at each refresh - you can set them just once and they will stay that way until you change them.

It's just handy to have them in the copperlist.

  The problem arises when changing
  the "diwstrt" and "diwstop" registers.
  If I try using horizontal (x) start and
  end coordinates that are more to the
  left, for example $xx51 and $xx91,
  (this would start,stop at 079,145+256)
  then the effective visible line shrinks
  from 320 down to 272. The virtual line
  seems to remain the correct 320, but
  you   see   I set the modulo registers
  ($0108, $010a) to zero, to not have a
  bigger, virtual line...

  Why? who knows?

 
CopperList
  dc.w    $0100,$1200 ;bplcon0 set 1 plane, color
  dc.w    $0108,$0000 ;bpl1mod offset to next line
  dc.w    $010a,$0000 ;bpl2mod offset to next line
  dc.w    $008e,$3081 ;diwstrt start coords 048,129
  dc.w    $0090,$30c1 ;diwstop stop coords  304,449
  ; 320 (normal) visible line width
  dc.w    $0092,$0038 ;ddfstrt L margin normal (horz)
  dc.w    $0094,$00d0 ;ddfstop R margin normal (horz)
  ; to point to bitplane 1
  dc.w    $00e0       ;bitplane0 hi
hi0
  dc.w    $0000
  dc.w    $00e2       ;bitplane1 lo
lo0
  dc.w    $0000
  dc.w    $0182,$0ff0 ;color01



  I am using excellent UAE-0.8.21
  emulator under Linux. Great!

  SoLo2

I really have no clue.  Why are you messing with diwstrt and diwstop anyway?  I never understood them and didn't really try to - just found values that worked and used those same values for ever - dc.w $8e,$2c81,$90,$2cc1 - centred for every (Pal) TV or monitor I tried.

Just thinking about this makes me remember how much fun Amiga coding used to be.  I suddenly want to buy another A1200 and write a parallax starfield with a sine-scroller and glenz-vectors.

I never had anywhere near so much fun coding on XBox, GC, PS2, or DC. (PS1 was cool to code on also.)

[uncharted]

Lando wrote:
(PS1 was cool to code on also.)

It was such a shame Sony dropped the Net Yaroze, there was some cool stuff produced with it.  I remember one really unique game involving a time traveling snail.

[Louis Dias]

Lando wrote:

I never had anywhere near so much fun coding on XBox, GC, PS2, or DC. (PS1 was cool to code on also.)

You used to code for consoles?  Professionally or homebrew?

[SoLo2]

  Hello!


  Interesting is, to be able to have a
  virtual line length of at least double
  length the physical line length:
  physical=320, virtual=640 (lo-res);
  physical=640, virtual=1280 (hi-res)
  This is the best for horizontal scrolling.

  The physical screen (or line length) is
  the part of a very large screen (the virtual)
  shown to the player.
  Consequently, the virtual screen is "like"
  an extension of the physical, that makes it
  much larger.
  In fact only double as large.
  The virtual is more like an super screen
  that "contains" the visible screen.

  The physical part acts like a window that
  moves over the total screen width.
  It is incremented pixel by pixel, and then
  Word by Word (16 pixels), by de/incrementing
  registers $DFF102 BPLCON1 and $DFF0E0 to
  $DFF0F6 BPL?PTH/L, until a whole physical
  screen width has been scrolled.
  At this point the physical window position
  jumps back to the beginning, by resetting
  the screen base addresses BPL?PTH/L.

  In this example we increment by 2 pixels,
  to make the drawing shorter:

================== frames
|physical########| 0,1
==================
|#physical#######| 2,3
==================
|##physical######| 4,5
==================
|###physical#####| 6,7
==================
|####physical####| 8,9
==================
|#####physical###| a,b
==================
|######physical##| c,d
==================
|#######physical#| e,f
==================
|########physical| 0,1
==================

  flip both window parts
  and we are at the start:

==================
|physical########| 0,1
==================



  Always after scrolling 1 whole Word, the
  program has to fill 1 Word column at the
  new border of the screen, and 1 Word column
  in the just disappeared border of the screen.
  This column painted at the disappeared border
  is a column of a whole screen "to come"
  (in the future of the scrolling).
  This is an "amortized" way to cope with the
  big jump, when the physical is resetted to
  the beginning of the virtual screen.
  This way we avoid a frame that takes longer
  to paint, because it has to refill the whole
  window with "tiles".


  The question is:
  Is it possible to have such a big virtual
  screen with Amiga's hardware?


  SoLo2

[Hyperspeed]

I doubt there was much on the Net Yaroze that the CD32/SX32 couldn't manage.

We neglect our hidden heritage!

[Lando]

Hyperspeed wrote:
I doubt there was much on the Net Yaroze that the CD32/SX32 couldn't manage.

We neglect our hidden heritage!

The PlayStation 1 was way more powerful even than a CD32/SX32 Combo.  The CD32 lacked 3D hardware (Akiko doesn't really count).  Something like Ridge Racer Type 4 or Resident Evil 3 still couldn't be done to the PS1 standard on a 060 equipped A4000 without at least a 3D card. The minimum spec for the conversion of Wipeout 2097 (the only PS1 conversion I know of for the Amiga) was a PowerPC accellerator and 3D graphics card   and even then the framerate wasn't as high as the PS1.

I never actually used a Yaroze when I first started PS1 programming - I started on a standard chipped grey PS1 connected to a PC via an Action replay cartridge and a parallel cable.

lou_dias wrote:

Lando wrote:

I never had anywhere near so much fun coding on XBox, GC, PS2, or DC. (PS1 was cool to code on also.)

You used to code for consoles?  Professionally or homebrew?

First homebrew, then professionally over 5 years.  I worked on about 6 published games for the major consoles.  Homebrew is more fun - there is so much pressure when you're working to deadlines and a 7-days a week, 16 hours a day schedule when you're nearing the end of a project or coming up to a big show like E3 where you have to show a demo.  But still nothing beats walking into a game store and seeing the end result on the shelf.

[Hyperspeed]

I know all that...

The CD32 came out in 1993 and the Playstation 1 was 1996. Even for those 3 years the PS1 was proportionally way more powerful.

However, if you put an SX32 into the CD32 and play a few Amiga scene demos then you won't see anything on the Yaroze home brewed that could match the quality of the 3D in the Amiga demos.

I have been calling on other threads for a cheap PPC/3D GPU to be made for the classic Amigas but for some reason hardware developers are too geeked up with crappy mediator-style pass-thru boards for defunct PCI cards and the USB stuff.

I wish someone would give us some meaty gaming hardware. The Phase5 PPC boards were not slender enough to be cheap and gamer friendly, they fussed about too much with SCSI, SIMM slots etc.

As for programming homebrew, I hear there are cults that program for the Dreamcast (and it's Visual Memory card) and the Atari Jaguar!

:-)