288 x 224 resolution

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robpearmain
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288 x 224 resolution

Post by robpearmain » Sun Apr 08, 2018 1:50 pm

Just out of interest

The Spectrum has a resolution of 256 x 192
Early arcade games used a resolution of 288 x 224, so an additional 32 pixels on each axis, I assume this took in some of the border area?

Is it possible to get the same resolution on the next?
Rob Pearmain
Bipboi (Zx Spectrum 48k), Harry Hedgehog (ZX Spectrum [1K]), Luna C (PC), Turbotoons (PC)

ZX Spectrum 48k, +, 128k, Next (board)

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SevenFFF
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Re: 288 x 224 resolution

Post by SevenFFF » Sun Apr 08, 2018 2:25 pm

You can put sprites in the border, but not the ULA screen or the layer 2 screen. The border is indeed 32 pixels in every direction, so the basic configuration is there for what you're proposing.

The sprites are limited to 12 on any given pixel line, with a maximum of 64 active at once. It would be possible to completely fill the side borders using 56 of the sprites without needing any redefinition, with spot effects using the remaining 8 sprites in the top and bottom borders.

If you used the raster interrupt on different lines, to redefine sprites multiple times every frame, you could put the maximum of 12 sprites in the top and bottom borders. 12x16 is only 192 pixels wide though, still leaving you with a shortfall of 192 pixel columns in the top and bottom borders. Depending on the game design, this still might work if the playfield was more sparsely populated - score in the top border, status in the bottom border, or something similar.

You can also redefine the border palette colour with a repeating copper program, so the shortfall regions could even have variable colours. I think it would be blocky like Atari 2600 playfield sprites though, not individually addressable for each pixel.

The bookkeeping necessary to do this would be not inconsiderable, but I can see it working for some game designs.

The game I'm working on uses some of these techniques to display to display score and status in the top and bottom borders. It's not 288 x 224, but it expands the play area by a useful amount, and makes it a little closer to original arcade version.
Robin Verhagen-Guest
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robpearmain
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Re: 288 x 224 resolution

Post by robpearmain » Sun Apr 08, 2018 11:59 pm

Thanks for the detailed explanation.

Also, a clipping window could be set up for sprites over border to allow clean wrap around the screen etc (e.g Pac-Man)

So in theory a full classic 80’s video game experience at the native resolution is possible with some clever sprite work, shame there wasn’t a mode implemented out of the box
Rob Pearmain
Bipboi (Zx Spectrum 48k), Harry Hedgehog (ZX Spectrum [1K]), Luna C (PC), Turbotoons (PC)

ZX Spectrum 48k, +, 128k, Next (board)

PiyoTaro
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Re: 288 x 224 resolution

Post by PiyoTaro » Mon Apr 09, 2018 5:00 pm

In the actual game table the CRT is placed vertically. If the function "can display screen by tilting it by 90 degrees" or "can make it possible to customize the scanning direction of the screen" is installed, it seems that the wish of "porting an arcade style game with the same image" can be fulfilled.

By the way, the resolution of Layer 2 extended screen of ZX SpectrumNEXT is 256*192 dots which is the same as MSX etc.
I thought that character fonts looked oblong looking bad, I wanted a resolution of 320*224 dots used in many game consoles such as PCEngine and SegaMegaDrive.
But, since Layer 2 was implemented as a bitmap-based graphic function rather than a tile-based like other game consoles, my opinion of increasing the resolution is to "waste valuable memory" here And it was done.

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