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Old 02 February 2020, 19:08   #1
Retro1234
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What is Sliced Ham?

What is Sliced Ham and how does it work? and any examples?
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Old 02 February 2020, 19:25   #2
Steril707
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You take some ham and a knife, and then you slice it...
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Old 02 February 2020, 19:28   #3
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I knew this would heppen
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Old 02 February 2020, 19:32   #4
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Instead of using a single 16 color palette for the whole screen, it loads a new palette for each scanline, which can help reduce HAM artifacts, depending on the image.

There is also the similar dynamic high-res which also loads a new palette per scan line, but in high-res mode instead of HAM.

Digiview 4.0 supported them, not sure what else.
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Old 02 February 2020, 19:34   #5
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Quote:
Originally Posted by Rotareneg View Post
Instead of using a single 16 color palette for the whole screen, it loads a new palette for each scanline, which can help reduce HAM artifacts quite a bit, depending on the image.

There is also the similar dynamic high-res which loads a new palette per scan line too, but in high-res mode instead of HAM.

Digiview 4.0 supported them, not sure what else.
Thanks for your reply

was it slow? and was it CPU intensive?
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Old 02 February 2020, 19:44   #6
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I think they typically used the Copper to load the new palette, so it wasn't specifically CPU intensive, but unless you have some fast RAM the CPU isn't going to be doing much as there's little DMA time left.

Apparently the original version of SHAM only changed the palette every other line, leaving more time for the CPU.
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Old 02 February 2020, 19:55   #7
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Thanks for your explaination

Last edited by Retro1234; 03 February 2020 at 17:45.
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Old 02 February 2020, 20:18   #8
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If you would like to play with S-HAM, dynamic Hires or PCHG there is HamLabPlus 2.10 at the FTP site of the user LoadWB (amiga.org):

https://forum.amiga.org/index.php?PH...7399#msg267399

ftp://nexus.polaris.net/pub/forager/Amiga
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Old 02 February 2020, 20:37   #9
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Quote:
Originally Posted by PeterK View Post
If you would like to play with S-HAM, dynamic Hires or PCHG there is HamLabPlus 2.10 at the FTP site of the user LoadWB (amiga.org):

https://forum.amiga.org/index.php?PH...7399#msg267399

ftp://nexus.polaris.net/pub/forager/Amiga
Thanks I was more wondering about it's use in games?
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Old 02 February 2020, 21:45   #10
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I suppose that palette had to be computed specifically for each line, so it was good for static images, but not for games (HAM itself had the same issue).

Unless you want to paste a background image and use only sprites for all characters.

Games already use various copper effects to change the palette (copper rainbows, palette change between playfield and status bar...)
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Old 02 February 2020, 22:08   #11
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Thanks for your reply.

maybe the repeating background of a Dual Playfield might work?
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Old 02 February 2020, 22:22   #12
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I knew this would heppen
Haha!
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Old 02 February 2020, 22:37   #13
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Dual playfield and HAM are mutually exclusive.
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Old 02 February 2020, 23:09   #14
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It's of course also possible to use normal bitplane mode or extra halfbright (EHB), and then change palette on every scanline, but leave a set of colors unchanged; that way you can also move around blitter objects without distorting their colors when moving object horizontally or vertically.

The sliced EHB mode certainly works better for games than sliced HAM.

Sliced EHB technique was used by the game Universe. It changes only first 16 colors on a scanline basis and leaves the other 16 colors untouched for objects, and these colors are also used by sprites. It seems that not that many colors are changed per scaline (probably 2-8), as the game is said to have only 256 colors in all, so the copper doesn't also slow down CPU access to chip ram completely. But this mode is probably not suitable for fast action games on OCS.
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Old 03 February 2020, 00:02   #15
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Originally Posted by Rotareneg View Post
Dual playfield and HAM are mutually exclusive.
I was thinking of some kind of Copper Rainbow that could be more than one colour per scanline, sorry.

the guy Kev G did more than one Rainbow Side by Side and I think it worked with Dual
Playfield.
https://www.ultimateamiga.co.uk/index.php?topic=9300.0

Last edited by Retro1234; 03 February 2020 at 00:10.
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Old 03 February 2020, 00:09   #16
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Originally Posted by coder76 View Post
It's of course also possible to use normal bitplane mode or extra halfbright (EHB), and then change palette on every scanline, but leave a set of colors unchanged; that way you can also move around blitter objects without distorting their colors when moving object horizontally or vertically.

The sliced EHB mode certainly works better for games than sliced HAM.

Sliced EHB technique was used by the game Universe. It changes only first 16 colors on a scanline basis and leaves the other 16 colors untouched for objects, and these colors are also used by sprites. It seems that not that many colors are changed per scaline (probably 2-8), as the game is said to have only 256 colors in all, so the copper doesn't also slow down CPU access to chip ram completely. But this mode is probably not suitable for fast action games on OCS.
Intresting to know, people are always asking how it was done.
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Old 03 February 2020, 13:48   #17
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Intresting to know, people are always asking how it was done.
Someone should have told the people making Space Quest IV!
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Old 03 February 2020, 13:50   #18
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Quote:
Originally Posted by Retro1234 View Post
I was thinking of some kind of Copper Rainbow that could be more than one colour per scanline, sorry.

the guy Kev G did more than one Rainbow Side by Side and I think it worked with Dual
Playfield.
https://www.ultimateamiga.co.uk/index.php?topic=9300.0
Thats actually easy.
Just change the value for that color ($dff180) with the copper inbetween starts of lines.
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Old 03 February 2020, 15:29   #19
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Thats actually easy.
Just change the value for that color ($dff180) with the copper inbetween starts of lines.
How many colours can you have on a line like this?
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Old 03 February 2020, 17:04   #20
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It's a technique that was established relatively early on in Amiga history and there's no technical reason why it couldn't have been used in various title screens and background images in Amiga.

Probably the biggest reason for it not being used is similar that of Ham mode: it's really usable to art digitised with quality hardware from quality source or the end result is garbage.

Secondly, it would have given only a debatable step up in the quality compared to HAM as most of the players play their games thru tiny CRT sets anyway.

So, not worth the hassle, extra 3rd party software (for conversion) and the extra code.
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