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PostPosted: Mon Dec 14, 2015 9:33 pm 
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psycopathicteen wrote:
Does the m92 have sizes from 16x16 to 64x64 in multiples of 16x16? Then that is a waste.

Yup, (16, 32, 48, or 64) x (16, 32, 48, or 64), so it's like the Genesis except with 16x16 tiles.

psycopathicteen wrote:
The only thing it helps is ROM size, because it takes up 8 cells instead of 9 cells, but arcade games typically went crazy with ROM sizes anyway.

There's still plenty of blank space. It kind of boggles my mind how stingy they were for space on this little explosion when they have the large 128x128 one, and it has over twice the frames of a regular 64x64 one because the 64x64 sized explosions for the most part run at 30fps, and the large 128x128 has explosions spawn within one frame of each other, and the game runs at 60fps. (Unlike Metal Slug...)

I know a bunch of random things about this game, like the last level has unused graphics on the tilemap in places where they are never visible, and it's obvious that the game was originally supposed to be four player at some point evidenced by the fact that there are graphics that say "3P" and "4P" (and match the "1P" and "2P" graphics perfectly) and palettes are loaded during the levels right after the 1 and 2 player palettes that are set up the same (in that the skin color is the same and in the right place) but that some things are recolored (the armor is yellow for what I assume would be 3P and green for 4P based on the order they're in palette ram.) It seems that this decision must have been fairly last minute. (I'm not sure how they expected to run the game with four people when it runs poorly enough with two...)

I have a serious problem... :oops:


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PostPosted: Tue Dec 15, 2015 3:49 pm 
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It's not how many pixels a picture generator is actually sending; it's how many it could be sending throughout the 52.148 microsecond active scanline period.

Oh of course, this makes perfect sense. So it would be possible to get square pixels with many different resolution (up to a maximum), it's just that the range of pixels that makes it sensible in regard to overscan is somewhat limited, right ?

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So let me sum up: You won't go wrong if you simulate a Mega Play.

Yeah but it appears a little recent (1991 and onwards) although based on SMD hardware from 1988.


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PostPosted: Tue Dec 15, 2015 5:39 pm 
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Bregalad wrote:
although based on SMD hardware from 1988.

Exactly. Home console hardware was often a bit weaker too. (One of the main advantages with arcade hardware seemed to be the amount of ram.) In fact, I'd even beef it up a bit by increasing the color palette to either 256 or 512 colors, and making the color depth 12 bit. The Irem M72 (R-Type I and II arcade hardware) built in 1987 has 512 colors and actually 15 bit color, although the CPS1 from the same time which was more powerful in about every way used 12 bit color. Is there some sort of weird correlation with hardware from 1987 and 384 pixel wide displays?


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PostPosted: Tue Dec 15, 2015 5:57 pm 
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Espozo wrote:
The Irem M72 (R-Type I and II arcade hardware) built in 1987 has 512 colors and actually 15 bit color, although the CPS1 from the same time which was more powerful in about every way used 12 bit color. Is there some sort of weird correlation with hardware from 1987 and 384 pixel wide displays?

Perhaps 1987 is when CPU clock speeds hit 8 MHz. The video chip often shares a crystal with the CPU, and a plausible picture width for an 8 MHz dot clock on a 15.7 kHz horizontal frequency is 384 pixels.


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PostPosted: Wed Dec 16, 2015 3:59 am 
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Bregalad wrote:
I'm surprised. I'd expect 320px horizontally to yield square pixels, as 240 * 4:3 = 320. Guess I was wrong.

That'd make the assumption the screen is 4:3 in the first place.

Bregalad wrote:
If I ever do what I mention in the title I'll probably use 256x224 in order to convert it easily from the NES, but I could also use 384x224 and scale everything horizontally times 1.5 (my 32x32 metatiles would become 48x32).

If you were to treat 320×224 like it was 4:3, then 384×224 would be its 16:10 counterpart.

tepples wrote:
And in theory, there's nothing wrong with 40x32 pixel metatiles on a Genesis VDP.

They're usually 64×32, just that only a portion is shown. (possible sizes are 32×32, 64×32, 128×32, 32×64, 64×64 and 32×128 - if you wonder about the missing combinations, they don't work because they'd need over 8KB per table =P)


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PostPosted: Wed Dec 16, 2015 4:54 am 
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Sik wrote:
They're usually 64×32, just that only a portion is shown. (possible sizes are 32×32, 64×32, 128×32, 32×64, 64×64 and 32×128 - if you wonder about the missing combinations, they don't work because they'd need over 8KB per table =P)

Are you talking about tile maps? The comment you replied to was about metatiles. :wink:

The idea is that a 320-pixel wide screen will show as many 40x32-pixel metatiles as a 256-pixel wide screen will show 32x32-pixel metatiles. If I understood it correctly.


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PostPosted: Wed Dec 16, 2015 7:37 am 
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Sik wrote:
tepples wrote:
And in theory, there's nothing wrong with 40x32 pixel metatiles on a Genesis VDP.

They're usually 64×32, just that only a portion is shown.

If you haven't come across the term "metatiles" before, it refers to a level being built out of (nearly) square pieces. A "40x32 pixel metatile" is 5 tiles wide and 4 tiles tall, so you can fit 8 of them across and 7 of them down in the visible portion of a Genesis background.


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PostPosted: Wed Dec 16, 2015 12:26 pm 
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The idea is that a 320-pixel wide screen will show as many 40x32-pixel metatiles as a 256-pixel wide screen will show 32x32-pixel metatiles. If I understood it correctly.

Yes, you understood correctly. If I want to have the same game but a higher resolution I have the choice between :

a) Alter game levels so that each screen is more metatiles

or

b) Adapt the graphics so that each metatile is larger in pixel

(or both at once, why not).


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PostPosted: Wed Dec 16, 2015 8:10 pm 
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tepples wrote:
If you haven't come across the term "metatiles" before, it refers to a level being built out of (nearly) square pieces. A "40x32 pixel metatile" is 5 tiles wide and 4 tiles tall, so you can fit 8 of them across and 7 of them down in the visible portion of a Genesis background.

Ugh, the problem with those is that the term used literally depends on the developer. (there's a reason why the 8×8 bitmaps are called "cells" or "characters" in official documentation and never "tiles") I guess I confused it with NES-style nametables.

And point stands even moreso though. Just use 32×32 (4×4 cells) metatiles and then you have a screen that's 10×7 metatiles large. I'd avoid using 40×32 (5×4 cells) metatiles because 1) width not being a power of two means extra calculations (dunno how bad it really is but it does end up requiring more verbose code) and 2) now you risk metatiles not aligning with the background plane boundaries which means much more complex code to account for crossing them.


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PostPosted: Wed Dec 16, 2015 10:49 pm 
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Sik wrote:
Bregalad wrote:
I'm surprised. I'd expect 320px horizontally to yield square pixels, as 240 * 4:3 = 320. Guess I was wrong.

That'd make the assumption the screen is 4:3 in the first place.

Sometimes the picture doesn't even fit the shape of the screen perfectly anyway. I've played Pocky and Rocky on my girlfriend's TV, and I noticed some blank space on the left and right sides of the screen.


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PostPosted: Thu Mar 02, 2017 6:53 am 
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So after some thoughts, I wrote down the graphical requirements of it if I was to convert my game to "pseudo-arcade" as well as the NES port. The major limitation is that I'd like the levels to be the same but the graphics to be more colorful and slightly better in the arcade. So if I could pick up any graphic chips, I'd pick one of the following options :

  • 16x16 sprites (with possibility of pairing them up to create metasprties), at least 64 of them. Possibly choice between different sizes, 16x16 being the most common. Either 4BP with single palette (SMS-like) or 3BP with multiple palettes.
  • Maybe support for larger sprites such as 16x24, 24x16. Or even 32x32 or 40x40 in order to simulate a background (was such a thing was common in arcade games ?), then 128 sprites and multiple palettes are required.
  • Either 256x192 resolution - (same as NES but with the status bar overlaid over the playfield instead of being separate (hence the lower graphical resolution).
  • Or 320x240 resolution - meta-tiles will be scaled up by 25% to be 40x40px instead of 32x32px like in the NES version. This means the background needs to be either be made of 40x40px tiles (weird) or metatiles are made out of 5x5 tiles of 8x8px. Also this requires all 240 lines to be shown - no NTSC overscan !
  • I could even consider using 256x240 resolution and either scale tiles only vertically or have the status bar separate like in the NES version, but for some reason that's not the preferred option.
  • In all cases 2 background layers, the main one below sprites either 4BP with single palette or 3BP with multiple palettes, bidirectional scrollable. The second one above sprites for text and the status bar only, 2BP with multiple palettes or 3BP with single palette. Perhaps one of those could be simulated with sprites instead.

In a 1st place everything will be "emulated" but if this ever becomes popular I could try and build hardware specifically for that game !


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PostPosted: Thu Mar 02, 2017 2:40 pm 
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Prototyping the game on modern computer is possible. I have prototyped Attribute Zone on QBASIC, although the different grid size resulted in a bit different game (40x25 on PC and 30x26 on Famicom). But that is on DOS. You could also do with more modern programs such as using SDL and/or OpenGL (a fragment program could be written to make something similar to the NES name table, and then use a vertex program and fragment program together for sprites).

Espozo wrote:
Anyway, about hardware from about the time period, this is about what I think of: (although I'm not even sure if such a machine exists)

320 x 224 pixel resolution
2 BG layers
512 x 512 pixel tilemaps
8 x 8 BG tiles
128 sprites
16 x 16 sized sprites
320 sprite pixels per scanline? (maybe more)
512 palette entries (256 colors or BGs, 256 colors for sprites)
12 bit color
4bpp graphics for everything
I have not heard of such thing like that, but most of the systems I know of are less capable than that (so is the original PC, which in text mode you could not even alter the graphics for the tiles). A design I have made (but not implemented) has the following capabilities (compare to above):
  • 320x240 pixels
  • One BG layer
  • BG tiles have a width of 8 pixels, and a height of whatever you want
  • Up to 40 sprites per scanline (it can read only 40 sprites from the memory for sprite info, because it reads one for each background tile)
  • Sprites are 8x8 or 8x16 (can use both on one screen) (you can also stretch them vertically, but all sprites on a scanline have to use the same stretching)
  • 32 palette entries (16 for playfield, 16 for sprites; in some modes you can even use sprite palettes for playfield too)
  • If you are scrolling, the size of the entire map can be whatever size you want
  • Four planes (one page of memory stores one row of eight pixels of one plane for all 256 characters; other than that the order of the pages is up to you)

_________________
.


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PostPosted: Thu Mar 02, 2017 3:57 pm 
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Espozo wrote:
Anyway, about hardware from about the time period, this is about what I think of: (although I'm not even sure if such a machine exists)

320 x 224 pixel resolution
2 BG layers
512 x 512 pixel tilemaps
8 x 8 BG tiles
128 sprites
16 x 16 sized sprites
320 sprite pixels per scanline? (maybe more)
512 palette entries (256 colors or BGs, 256 colors for sprites)
12 bit color
4bpp graphics for everything


That's really close to the Genesis, aside from the palette entries and color depth.


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