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Author Topic: Converting old Ocean games (Read 2136 times)

Offline elmer

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Re: Converting old Ocean games
« Reply #15 on: 2020.April.05. 21:32:36 »
Congratulations to Geco for doing such an excellent job on the Short Circuit conversion! :ds_icon_cheesygrin:

Renegade is going to be a much more difficult job to convert because I apparently only have a part of the source code archived.

Having said which, it is easy (for me) to see the progression/improvements in the code over the three games, and they were definitely built one on top of the other.

For my own part, I have been exploring and disasssembling the Gryzor game in the emulator, and have already started re-writing some of the routines to be a bit more efficient on the Enterprise because of both the screen layout, and the availability of 128KB of memory. :-)




Offline elmer

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Re: Converting old Ocean games
« Reply #16 on: 2020.April.05. 22:38:36 »
From a developer view: most important difference at EP64/EP128 not just the memory size. At EP64 all memory are video memory, where the CPU accesses are delayed by the Nick chip. The extra 64K in EP128 or any other memory expansion runs at full speed. Like the Amiga Chip RAM and Fast RAM :-)
...
Another problem the different system memory map at EXOS 2.0 and 2.1+ versions. But if you programming on the right way, allocate memory from EXOS, don't using direct system memory addresses, then the program will run on any Enterprise configuration.
...
But for a developing EP64 are ok, and optionaly any memory expansion if needed more or faster RAM.

It's not hard to write code so that it uses the EXOS interfaces, so that's not going to be a problem.

But I am going to have to add some extra RAM to my EP64 because I'm going to need the extra space of a 128KB machine to do some optimizations to the code, add scrolling, and perhaps fit in some extra graphics.

The added speed of the faster RAM will also help, and may even allow me to draw a bigger screen than on the Amstrad.


The price of an EP128 these days seems far too high for my comfort, so I jumped on one of the Egyptian EP64 imports that have recently turned up on eBay.

The serial number is 71370, so I'm hoping that any of the hardware problems were fixed in a machine that was manufactured that late.

Anyway, I'm afraid that I won't even be able to see the output from the computer (and verify the EXOS version) until I make an RGB-to-BNC cable, because I don't have a PAL TV.

The Enterprise has arrived, and is as asolutely beautiful as I remember!

I already have a modern 9V-DC center-negative PSU that I can use to power the system, so that side of things is OK.

But I still have to make an RGB cable before turning the computer on and finding out what EXOS version is inside.


If you name the maker and model of your monitor we can aid you to make the video cable. If it has BNC connectors it is a professional one, sometimes they need Sync on Green or other strange ways to input the Sync signal.

I have a Panasonic BT-H1390Y, which can either use sync-on-green, or a separate composite-sync signal.

I also have a LCD TV/Monitor that can accept 15KHz TV signals through the VGA connector.

I'm not sure what the next step is to make/buy a cable that will work.

I have found a company in Spain that sells an Enterprise RGB-to-SCART cable, does anyone have any experience with that cable?
« Last Edit: 2020.April.06. 05:46:39 by elmer »

Online gflorez

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Re: Converting old Ocean games
« Reply #17 on: 2020.April.06. 03:28:23 »
The cable from Retrocables makes perfectly its function, although the EP plug will need some tailoring to enter completely on the EP strange socket. I have one of these and it works good for a LCD TV with Scart connector.

If your LCD TV/Monitor doesn't have a Scart connector....  

You need to make a cable yourself....

One good new is that your two monitors directly accept the Enterprise RGB signals(Scart needs some additional resistors). And other one is that  our computer delivers both composite sync and split syncs signals apart from the RGB colour signals.

The CRT will give you the more accurate "classic" feelings of scan-lines and colours, but less pixel-perfect than the LCD. 13'' screen seems too little for today standards, but on the contrary it is enough retro..... Amazing professional specs in that jewel.

The VGA cable on 15KHz can be seen apparently like a good solution, but it depends a lot on the maker to be or not compatible with all the screen modes that an Enterprise could deliver. Of course the Interlaced mode is discarded, and some very high line modes(like for example the presentation screen of the new Short Circuit game), will be shown cut.  

Other drawback of multi-sync monitors is that they tend to show false colours for Pal, the palette they use is not so wide as the original. But even so, maybe it suits to you.

Resolutions and colours were the main attractive of the EP computer on its days, but also its stereo capabilities and, if your monitors don't have integrated amplifier and speakers you will need to use a pair of space-wasting external ones.....

To finish, the aspect ratio of the monitor is also important, because the EP was build on the 4:3 past era, and you probably don't want to see forever a flattened image or these ugly black strips at the sides on a 16:9 monitor.

For the Enterprise I better would recommend you to buy a cheap 4:3 second-hand LCD Stereo TV with Scart if your LCD TV lacks the connector or stereo sound. 15'' is enough, but 4:3 LCD TVs were manufactured even on 17'' or 19''.

If you still prefer the CRT monitor or the VGA multi-sync, I can make you a cable.
« Last Edit: 2020.April.06. 03:31:30 by gflorez »

Offline geco

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Re: Converting old Ocean games
« Reply #18 on: 2020.April.06. 08:17:00 »
Congratulations to Geco for doing such an excellent job on the Short Circuit conversion! :ds_icon_cheesygrin:
Thank you very much :)

For my own part, I have been exploring and disasssembling the Gryzor game in the emulator, and have already started re-writing some of the routines to be a bit more efficient on the Enterprise because of both the screen layout, and the availability of 128KB of memory. :-)
Cool, i am waiting the result :), Gryzor with scrolling, and probably with other new features :)
I use DZ80 for disassembling, the emulator is also very good, just the output is not so friendly if source is planned make from it, probably there are much better tools which can give more help to create source from binary ex IDA ( personally i do not like it :D ).

Offline elmer

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Re: Converting old Ocean games
« Reply #19 on: 2020.April.12. 21:55:47 »
For the Enterprise I better would recommend you to buy a cheap 4:3 second-hand LCD Stereo TV with Scart if your LCD TV lacks the connector or stereo sound. 15'' is enough, but 4:3 LCD TVs were manufactured even on 17'' or 19''.

I live in the USA these days, and TVs here never had either SCART nor any other type of RGB connector here, so nothing is available second-hand ... and most wouldn't display 50Hz 625-line signals anyway.


The CRT will give you the more accurate "classic" feelings of scan-lines and colours, but less pixel-perfect than the LCD. 13'' screen seems too little for today standards, but on the contrary it is enough retro..... Amazing professional specs in that jewel.

Yes, I got very, very lucky finding that monitor locally many years ago.

I think that it is the best option that I have for using with the Enterprise, especially since seeing the true colours and aspect-ratio is important for doing any development work on the computer.


If you still prefer the CRT monitor or the VGA multi-sync, I can make you a cable.

Thank you for the offer, I really appreciate it!

Honestly, I'd much rather buy a cable from someone like you who obviously loves and cares about the Enterprise, and who is actively involved in this forum, rather than some company that I have never heard of in Spain.  I'll send you a PM.

Offline elmer

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Re: Converting old Ocean games
« Reply #20 on: 2020.April.12. 22:11:44 »
I have extracted the main maps from Gryzor. It is funny to think that this is probably the first time in over 30 years that they have been in an editable format!  :cool:

Here's the first level in the original Amstrad colours ...




I've been working on coming up with a set of Enterprise colours that will make the game look both nicer, and more like the original arcade game.

Here is my favorite set of colors so far. The palette is still ordered in the original Amstrad order, and has not been remapped for the Enterprise with its colours 8..15 coming from the FIXBIAS setting.

First is the original Amstrad screen, and then the Enterprise screen.

This currently uses 17 colours instead of 16, but I am hoping that a raster-split will be possible to make it work.







Offline geco

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Re: Converting old Ocean games
« Reply #21 on: 2020.April.12. 22:41:48 »
Looks cool, raster split should work if any of colours are not used on any part of the screen, hopefully fixbias will not cause any problem :)
I like the new colours :)

Offline SlashNet

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Re: Converting old Ocean games
« Reply #22 on: 2020.April.12. 23:24:26 »
In EP palette enemies looks more visible. It's better.

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Re: Converting old Ocean games
« Reply #23 on: 2020.April.13. 10:54:55 »
I have extracted the main maps from Gryzor.
I can see so much water in these pictures. Now I know why they are called OCEAN games. :D
100 SOUND SOURCE 3,STYLE 16,LEFT 16,RIGHT 64,SYNC 2
110 SOUND SOURCE 2,STYLE 128,PITCH 25.2,SYNC 2
120 SOUND PITCH 25,SYNC 2
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Offline elmer

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Re: Converting old Ocean games
« Reply #24 on: 2020.April.17. 00:41:07 »
I can see so much water in these pictures. Now I know why they are called OCEAN games. :D

Hahaha ... good joke! :lol: 

But in this case, I think that you have to blame Konami for putting all of that water in the original arcade game ...




In EP palette enemies looks more visible. It's better.

Thanks, that is definitely one of the important goals in picking the Enterprise colours to use. :cool:


Looks cool, raster split should work if any of colours are not used on any part of the screen, hopefully fixbias will not cause any problem :)
I like the new colours :)

I'm still investigating to see whether a raster split will be useful in adding another colour or two.

The re-coloured Enterprise screen grab that I posted earlier is using a FIXBIAS-compliant set of colours, but I'm only finding a way to use at-most 6 out of the 8 colours for any of the FIXBIAS values that I've tried.

If I can't find an easy raster split, then I'll have to change some of the sprites so that they use one or both of the unused colours in the FIXBIAS set.

In order to see what that might look like, I've extracted the rest of Mark's graphics from the Amstrad game.

For anyone interested in seeing the whole set, so that you can get a visual idea of how things were put together decades ago, I'm attaching a zip file.

Offline geco

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Re: Converting old Ocean games
« Reply #25 on: 2020.April.17. 08:57:03 »
I have mostly problem with the pink, or light purple :D , and with the orange if i use bias 1fh , in this case i use color 249 as orange :D , and pink/light purple for faces, the sprites look as bit drunken guys :D
By the original picture the water and sky border could be an ideal split, but on the CPC screen as i see the blues are used at the top too.

Offline elmer

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Re: Converting old Ocean games
« Reply #26 on: 2020.April.20. 05:35:40 »
hopefully fixbias will not cause any problem :)

I have mostly problem with the pink, or light purple :D , and with the orange if i use bias 1fh , in this case i use color 249 as orange :D , and pink/light purple for faces, the sprites look as bit drunken guys :D

Hmmm, yes FIXBIAS can be quite challenging to work with! :shock:

I guess that a FIXBIAS of either 00h or 1Fh are the obvious values to use when converting Amstrad games, but I *really* don't like either of those settings. The pink and purple colours seem like they are practically unusable.


I have spent the last few days working on the Gryzor loading screen, trying to get more comfortable with the different FIXBIAS values, and also editing the screen so that there are only 8-or-less unique non-FIXBIAS colours on each line of the screen.

Once I had results that seemed to look OK, then I figured out where to put some raster splits to add a few extra colours to the screen.

Here's the result (with 24 colours displayed), together with the Amstrad original for comparison.

Please note ... I'm not an artist, so this is about the best that I can do! ;-)

« Last Edit: 2020.April.20. 21:40:34 by elmer »

Offline Dr.OG

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Re: Converting old Ocean games
« Reply #27 on: 2020.April.20. 05:48:50 »
Looks really nice, better than the original!
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Offline geco

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Re: Converting old Ocean games
« Reply #28 on: 2020.April.20. 08:15:19 »
I guess that a FIXBIAS of either 00h or 1Fh are the obvious values to use when converting Amstrad games, but I *really* don't like either of those settings. The pink and purple colours seem like they are practically unusable.
Yes, purple, and pink (color 5) really unusable, if i remember well it was useful in one or 2 games, but we have to live with it :D

I have spent the last few days working on the Gryzor loading screen, trying to get more comfortable with the different FIXBIAS values, and also editing the screen so that there are only 8-or-less unique non-FIXBIAS colours on each line of the screen.

Once I had results that seemed to look OK, then I figured out where to put some raster splits to add a few extra colours to the screen.

Here's the result (with 24 colours displayed), together with the Amstrad original for comparison.

Please note ... I'm not an artist, so this is about the best that I can do! ;-)
You could be an artist too :), the new picture is amazing,, color shades just perfect.
How many splits did you use on the screen?
Probably EPimgconv can help to find places of raster split also, by checking the generated LPT and it's colour definitions.

Offline elmer

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Re: Converting old Ocean games
« Reply #29 on: 2020.April.20. 09:38:38 »
How many splits did you use on the screen?

Thank you for the kind words! :)

If you right-click the image and save it, then you can open it up in an editor like ProMotion or Grafx2 and see where the raster splits are.

There are 4 different areas in the Enterprise image, and each uses a different 16-colour palette of the main 256-colour image (0-15, 16-31, 32-47, ...).

That's how we created game graphics in the 16-bit era for the PC Engine/MegaDrive/SNES.

To see the different screen areas, just alter colour 0, 16, 32, 48, etc and you will see the area of the screen that is used by that palette.

Encoding the screen in that way makes it both easy to edit, and easy to process it into an LPT and graphic data.