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-   -   What is Sliced Ham? (http://eab.abime.net/showthread.php?t=100716)

Retro1234 02 February 2020 19:08

What is Sliced Ham?
 
What is Sliced Ham and how does it work? and any examples?

Steril707 02 February 2020 19:25

You take some ham and a knife, and then you slice it... :D

Retro1234 02 February 2020 19:28

:lol I knew this would heppen :banghead

Rotareneg 02 February 2020 19:32

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.

Retro1234 02 February 2020 19:34

Quote:

Originally Posted by Rotareneg (Post 1376003)
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?

Rotareneg 02 February 2020 19:44

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.

Retro1234 02 February 2020 19:55

Thanks for your explaination:great

PeterK 02 February 2020 20:18

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

Retro1234 02 February 2020 20:37

Quote:

Originally Posted by PeterK (Post 1376013)
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?

jotd 02 February 2020 21:45

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...)

Retro1234 02 February 2020 22:08

Thanks for your reply.

maybe the repeating background of a Dual Playfield might work?

Viceroy 02 February 2020 22:22

Quote:

Originally Posted by Retro1234 (Post 1376000)
:lol I knew this would heppen :banghead

Haha!

Rotareneg 02 February 2020 22:37

Dual playfield and HAM are mutually exclusive.

coder76 02 February 2020 23:09

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.

Retro1234 03 February 2020 00:02

Quote:

Originally Posted by Rotareneg (Post 1376046)
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

Retro1234 03 February 2020 00:09

Quote:

Originally Posted by coder76 (Post 1376051)
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.

bwldrbst 03 February 2020 13:48

Quote:

Originally Posted by Retro1234 (Post 1376068)
Intresting to know, people are always asking how it was done.

Someone should have told the people making Space Quest IV!

Steril707 03 February 2020 13:50

Quote:

Originally Posted by Retro1234 (Post 1376066)
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.

Retro1234 03 February 2020 15:29

Quote:

Originally Posted by Steril707 (Post 1376168)
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?

jizmo 03 February 2020 17:04

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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