what should i write next?

reminisce about bbc micro & electron games like chuckie egg, repton, elite & exile

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tricky
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Re: what should i write next?

Postby tricky » Sat Apr 23, 2016 2:44 pm

I've never played wizard of war.
I played Astro fighter in the early eighties, but I don't remember liking it that much.
I did play pacland a bit bitd, but it is another that would need 1 pixel scrolling in mode 1 at 50fps.
Original game, if I had a creative cell in my brain that wasn't hardware or coding related, or could be less fixated by 50 fps,I would go back and finish Jeltron.
I'll have a think...

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Re: what should i write next?

Postby Arcadian » Sun Apr 24, 2016 6:30 pm

Another vote for 1942 ... !

This probably is the game I'd most like to see on the Beeb next!!
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Re: what should i write next?

Postby tricky » Sun Apr 24, 2016 10:31 pm

I think I got about this far last time, then got sidetracked with a level editor and trying to write a generic vertical scroller game framework.
The real 1942 has lots of planes and some really big ones; the home ports have few planes.
How faithful do you think it would have to be?
The CPC has a very low framerate and few frames of animation, while the c64 version is too fast.
I think I will revisit the level editor and vertical scrolling framework to convert them to mode 1 and probably grab some code from rally-x.

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Re: what should i write next?

Postby oss003 » Mon Apr 25, 2016 6:24 am

The CPC version has little variences in background. The ZX Spectrum version looks a lot better even if there are only 2 colours.

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Re: what should i write next?

Postby tricky » Mon Apr 25, 2016 11:53 am

That looks better than either the c64 or the CPC, although although, maybe a little sluggish.

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Re: what should i write next?

Postby MatthewThompson » Mon Apr 25, 2016 7:10 pm

Is it not possible to rip the graphics from other machines versions of the game and then transfer them to the BBC ? for example somebody recently did a conversion of BBC E Type to the Atari and it looks identical so they must of got the graphics from the BBC version.

Just a suggestion, but how about helping finish off some of the Retro Software WIP projects? be great to see them finished, failing that how about a BBC version of Exorcist (from C16) and Perils Of Willy (Vic 20)?

Forgot to say, 1942 would be most welcome too.

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Re: what should i write next?

Postby Arcadian » Mon Apr 25, 2016 7:33 pm

If you went with 1942, would you consider making a Master 128 the host platform from the off (if you deemed that to be beneficial)?
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Re: what should i write next?

Postby tricky » Mon Apr 25, 2016 8:54 pm

Arcadian, Master128, I'm OK with sideways RAM, as at least 10 of my beebs have it, but all that shadow shenanigans!
I do have a beeb with watford shadow RAM, but I'm not sure about using it for gfx (I know that is what it's for).
I do support shadow RAM for sampled speech in AstroBlaster on the beeb, b+ and master, although I only have beebem to suggest that it works (iirc).
MatthewThompson, what, like Jeltron :roll:
I'm fine with ripping the gfx out of other versions :shock: it's the attack/movement patterns that take the time.
I haven't really done anything (except faff around with Rally-X) on the beeb since Frogger.

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Re: what should i write next?

Postby jbnbeeb » Mon Apr 25, 2016 9:10 pm

I vote 1942. If I can manage master 128 shadow ram for double buffer, you definitely could and take it to new heights :-D
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Re: what should i write next?

Postby flibble » Mon Apr 25, 2016 10:52 pm

If you're really desperate for something to do, you could write for me a 16x16 masked sprite plotting routine over a tiled 16x16 background.

FFlegend1.png
(3.38 KiB) Not downloaded yet


Then I can get on and write the BBCs first JRPG :D

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Re: what should i write next?

Postby tricky » Tue Apr 26, 2016 11:19 am

Does it have to scroll, if so, in what directions and at what granularity?
The vertical scroller demo I put up http://www.retrosoftware.co.uk/forum/viewtopic.php?f=19&t=925&hilit=+vertical+scrolling#p6949 with a map editor does this, but vertically and the map is 1x16 screens of 4x4 tiles of 4x4 characters where each character is 4x4 pixels (mode 5 with vertical doubling). The player is 8x16 (or maybe x15 or x17) as it was for more 5.

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Re: what should i write next?

Postby flibble » Tue Apr 26, 2016 1:40 pm

Actually it doesn't have to scroll at all. The sprites move over the background, when the reach an edge (say the left edge) it would draw a new background (room) with the character sprite on the right edge. Similar-ish to the beeb game robotron.

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Re: what should i write next?

Postby tricky » Tue Apr 26, 2016 2:09 pm

I forgot the interesting bit, what is on screen at any one time is 16x16 quarter tiles of what would be 16x16 mode 1 or 4 pixels iirc and it is this but that is used to do the redrawing ;)
Iirc, the ship is drawn using any non zero pixels as a mask, so as long as you don't need to draw masks that are different to the sprite (for shadows etc), you don't need any extra storage. RichTW uses a more optimised version of the same thing for some of his stuff.

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Re: what should i write next?

Postby MatthewThompson » Tue Apr 26, 2016 3:36 pm

tricky wrote:Arcadian, Master128, I'm OK with sideways RAM, as at least 10 of my beebs have it, but all that shadow shenanigans!
I do have a beeb with watford shadow RAM, but I'm not sure about using it for gfx (I know that is what it's for).
I do support shadow RAM for sampled speech in AstroBlaster on the beeb, b+ and master, although I only have beebem to suggest that it works (iirc).
MatthewThompson, what, like Jeltron :roll:.


I didn't realise you were involved with Jeltron, but not that one specifically (be good though) but I was thinking of Treasure Island and Bombjack maybe. I loved Treasure Island on the C16 and be great to play it on the BBC .

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Re: what should i write next?

Postby JonC » Tue Apr 26, 2016 5:40 pm

Tricky, if you're still taking suggestions, a better version of Battlestation: Harbinger for the beeb would be good :)

The PC version only has 4 races to fight, but I bet that can be improved on!
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Re: what should i write next?

Postby tricky » Tue Apr 26, 2016 6:33 pm

Battlestation: Harbinger,
Well, at least the space station has a familiar docking port :lol:
Were you thinking something like starship command?
EDIT: also, really needs a mouse!

Jeltron,
Gil (Jaysmith/Johnson-Smith) and I wrote it back in the 80s, we got it far enough to be signed with Tynesoft, but then uni/work/shrinking market got in the way and we never finished it. Gil is in games, but has an incredibly busy social life in Canada, so I doubt he will even come back to it.

BombJack,
I was thinking of doing it a few years ago, but then I spotted that someone had started one - I think they popped up a little while ago, but no new bits since.

Treasure Island,
is not my sort of game; disposable swords with dodgy gfx aside!

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Re: what should i write next?

Postby JonC » Tue Apr 26, 2016 6:48 pm

tricky wrote:Battlestation: Harbinger,
Well, at least the space station has a familiar docking port :lol:
Were you thinking something like starship command?
EDIT: also, really needs a mouse!

Similar to Starship Command could work if your 'fleet' were AI controlled, could be done without a mouse too.
The benefit over starship command is that all the ships weapons can be changed (power ups maybe) as you progress, whereas *ship command only changed your ship icon IIRC. :lol:
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Re: what should i write next?

Postby sydney » Tue Apr 26, 2016 7:17 pm

I've thought about starting a FTL type of game a couple of times but never got further than thinking about it!

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Re: what should i write next?

Postby SimonSideburns » Mon May 02, 2016 5:23 pm

I've always been surprised there was never a version of the arcade game Gauntlet made for the BBC Micro, so I would say that could work really well.

Ok, the resolution/colours may be awkward to achieve, but there are unofficial/custom screen MODEs that provide 16 colours in a resolution similar to MODE 6, so that would provide more space for code, and it's no hardship to load each level from floppy (much better than waiting for a cassette tape), but a tape version wouldn't be so bad either.
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Re: what should i write next?

Postby paulb » Mon May 02, 2016 7:20 pm

SimonSideburns wrote:I've always been surprised there was never a version of the arcade game Gauntlet made for the BBC Micro, so I would say that could work really well.

Ok, the resolution/colours may be awkward to achieve, but there are unofficial/custom screen MODEs that provide 16 colours in a resolution similar to MODE 6, so that would provide more space for code, and it's no hardship to load each level from floppy (much better than waiting for a cassette tape), but a tape version wouldn't be so bad either.


Where are these custom modes? :shock:

With Gauntlet, you just have to do better than the other microcomputers of the era, really. From this comparison of Spectrum, Amstrad, C64, NES and Master System, ignoring the latter two for their late-mover advantage, the Amstrad version would be the one to beat, but none of them are really that graphically advanced. (Ignore the usual "C64 is best" self-justification in the comments... or just ignore the comments: it's YouTube, after all!)

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Re: what should i write next?

Postby RobC » Mon May 02, 2016 7:56 pm

paulb wrote:Where are these custom modes? :shock:

With Gauntlet, you just have to do better than the other microcomputers of the era, really. From this comparison of Spectrum, Amstrad, C64, NES and Master System, ignoring the latter two for their late-mover advantage, the Amstrad version would be the one to beat, but none of them are really that graphically advanced. (Ignore the usual "C64 is best" self-justification in the comments... or just ignore the comments: it's YouTube, after all!)

The 6845 can be programmed to create modes that are smaller (or larger) than the standard modes. Creating a smaller mode saves memory and another useful trick is to make a mode that is 64 bytes wide (rather than say 80 bytes in mode 2) as this makes for simpler sprite plotting calculations.

The Amstrad CPC also uses the 6845 and so the Beeb can match it for resolution - Gauntlet appears to be using the equivalent of mode 2. However, the CPC has a greater range of colours and can display 16 real colours rather than the Beeb's 8 + 8 flashing colours.

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Re: what should i write next?

Postby paulb » Mon May 02, 2016 8:33 pm

RobC wrote:
paulb wrote:Where are these custom modes? :shock:

With Gauntlet, you just have to do better than the other microcomputers of the era, really. From this comparison of Spectrum, Amstrad, C64, NES and Master System, ignoring the latter two for their late-mover advantage, the Amstrad version would be the one to beat, but none of them are really that graphically advanced. (Ignore the usual "C64 is best" self-justification in the comments... or just ignore the comments: it's YouTube, after all!)

The 6845 can be programmed to create modes that are smaller (or larger) than the standard modes. Creating a smaller mode saves memory and another useful trick is to make a mode that is 64 bytes wide (rather than say 80 bytes in mode 2) as this makes for simpler sprite plotting calculations.


Oh, I've seen various weird modes, as well as the usual stretching and blanking done by games. But I've never seen one with 16 proper colours as a mere custom mode: that is supposed to require one of those Chameleon palette extender things, unless rapid palette-switching is what was meant.

RobC wrote:The Amstrad CPC also uses the 6845 and so the Beeb can match it for resolution - Gauntlet appears to be using the equivalent of mode 2. However, the CPC has a greater range of colours and can display 16 real colours rather than the Beeb's 8 + 8 flashing colours.


Yes, the CPC had the benefit of "learning" from the Beeb's design and apparently supported more than just the eight possible on/off RGB combinations. However, the CPC only had 200 pixel lines according to Wikipedia, although Beeb games tend to stretch the screen to get fewer lines, anyway.

Still, I don't think 16 colours would really be required, anyway.

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Re: what should i write next?

Postby tricky » Mon May 02, 2016 8:45 pm

Sorry, you had a complete conversation while I was typing, but let's not waste it ;)

I did consider gauntlet, even started a compressor for the maps.
I played it in the arcades a bit, but playing it on mame, it just isn't the same with free continue and I'm not sure how to resolve that.
The problem with the 8-10K 16 colour (8!) is that the pixels are 4 mode 1 pixels wide, so any kind of definition would be lost.
btw, custom gfx modes are very easy on the beeb if you leave BASIC behind, just choose your pixel width and colour count, width in bytes and height in pixels and off you go (well, there is a bit of simple add/subtract/divide by a small power of two).
I usually prefer 256x256 mode 1 which requires 16K, is a close match to arcade games, which were usually 256x224 or 224x256 and gives 2 pages across the screen so add &200 to get to the next char row.
The Circus/Acrobat-TV and RipCord emulators I wrote, used mode 4 (256x256) as the originals were monochrome with horizontal translucent coloured plastic stuck to the screen (colour is fairly easy to add in full width horizontal strips). Sprint was 512x256 mode 0, as the original was 512 wide to give better resolution to depict the rotating cars.
Sorry, got a bit sidetracked there ;)

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Re: what should i write next?

Postby tricky » Mon May 02, 2016 8:47 pm

The flashing was a real waste on the beeb, I'm sure with a big of thought they could have done something cheap and dirty and come up with a few more colours, even if it was only provide 2 or 3 levels of green!

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Re: what should i write next?

Postby RobC » Mon May 02, 2016 9:26 pm

paulb wrote:Oh, I've seen various weird modes, as well as the usual stretching and blanking done by games. But I've never seen one with 16 proper colours as a mere custom mode: that is supposed to require one of those Chameleon palette extender things, unless rapid palette-switching is what was meant.

Ah right - sorry if I misunderstood. I've actually built a Chameleon and have written a demo where it shows 15 colours on screen at once (I kept one colour the same to hide the palette switch mid-frame).
tricky wrote:The flashing was a real waste on the beeb, I'm sure with a big of thought they could have done something cheap and dirty and come up with a few more colours, even if it was only provide 2 or 3 levels of green!

Yes, although I do remember being really impressed with the Beeb's graphics compared to those on my ZX81. Acorn could have done better with later machines - the Wild Vision PaletteMate came out in 1989-ish and gave 16 genuine colours from a palette of4096...

I've got a plan to use a CPLD and a RAMDAC to recreate something like a PaletteMate -just need the time to build one!

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Re: what should i write next?

Postby 1024MAK » Tue May 03, 2016 6:36 am

CPC464 & CPC6128: A colour palette of 27 colours was supported. Underlying the CPC's video output was the Motorola 6845 address generator. This chip was connected to a pixel generator that supported 4 bpp, 2 bpp and 1 bpp output (bits per pixel). The address generator was clocked at a constant rate so the 4 bpp display generated half as many pixels as the 2 bpp and a quarter as many as the 1 bpp. The ROM featured three built-in display resolutions but many others could be achieved by reprogramming the 6845.

The standard video modes were:
Mode 0: 160×200 pixels with 16 colours (4 bpp)
Mode 1: 320×200 pixels with 4 colours (2 bpp)
Mode 2: 640×200 pixels with 2 colours (1 bpp)

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Re: what should i write next?

Postby 1024MAK » Tue May 03, 2016 9:09 am

tricky wrote:The flashing was a real waste on the beeb, I'm sure with a big of thought they could have done something cheap and dirty and come up with a few more colours, even if it was only provide 2 or 3 levels of green!

Flashing was a complete waste of time on any computer IMHO. Even worse on the Beeb, as the actual flash control rate is done by the OS (software) flipping a bit in the video processor/ULA.
As the original video processor was a ULA made by Ferranti, it would have been possible to replace the flash control with the circuitry required for more than eight colours. Sinclair found a way to have three level voltage outputs on some of the ULA output pins in the ZX Spectrum's ULA for example. In the case of video, it would be output high, half voltage and output low. Giving three values per each video (Red, Green & Blue) line.

If the palette was extended:

Code: Select all

1 = full output voltage
½ = half voltage output
0 = zero output

 #  R G B
 0  0 0 0 = black
 1  0 0 ½ = dark blue
 2  0 0 1 = bright blue
 3  0 ½ 0 = dark green
 4  0 ½ ½ = cyan
 5  0 ½ 1 = sky blue
 6  0 1 0 = bright green
 7  0 1 ½ = sea green
 8  0 1 1 = bright cyan
 9  ½ 0 0 = dark red
10  ½ 0 ½ = dark magenta
11  ½ 0 1 = mauve
12  ½ ½ 0 = dark yellow / mustard
13  ½ ½ ½ = grey
14  ½ ½ 1 = pastel blue
15  ½ 1 0 = lime green
16  ½ 1 ½ = pastel green
17  ½ 1 1 = pastel cyan
18  1 0 0 = bright red
19  1 0 ½ = purple
20  1 0 1 = bright magenta
21  1 ½ 0 = orange
22  1 ½ ½ = pink
23  1 ½ 1 = light pink
24  1 1 0 = bright yellow
25  1 1 ½ = pastel yellow
26  1 1 1 = bright white

Of course, this would have made the video processor/ULA far more complex. And the colour encoder circuitry for the UHF video circuit would have had to been redesigned to cope with three voltage level RGB signals.

Alternatively instead the flash bit could have been a bright bit. This would have exited the ULA as a single digital output in place of the (almost) useless invert input pin. Then that could be mixed into the RGB outputs without any problems at all (I have not looked at how easy or not it could have been used in the UHF circuitry).

The colours then would be:

Code: Select all

# is just a reference number
nn is the sum of the 4 bit nybble
h,r,g,b are the ULA  output pin, h=the bright pin, r,g,b are the colour channels.
R,G,B are the video channel levels:
1 = full output voltage
½ = half voltage output
0 = zero output

 # nn  h r g b  R G B
       < pin > 
 0  0  0 0 0 0  0 0 0 = black
 1  1  0 0 0 1  0 0 ½ = dark blue
 2  9  1 0 0 1  0 0 1 = bright blue
 3  2  0 0 1 0  0 ½ 0 = dark green
 4  3  0 0 1 1  0 ½ ½ = cyan
 5  A  1 0 1 0  0 1 0 = bright green
 6  B  1 0 1 1  0 1 1 = bright cyan
 7  4  0 1 0 0  ½ 0 0 = dark red
 8  5  0 1 0 1  ½ 0 ½ = dark magenta
 9  6  0 1 1 0  ½ ½ 0 = dark yellow / mustard
10  7  0 1 1 1  ½ ½ ½ = grey
11  C  1 1 0 0  1 0 0 = bright red
12  D  1 1 0 1  1 0 1 = bright magenta
13  E  1 1 1 0  1 1 0 = bright yellow
14  F  1 1 1 1  1 1 1 = bright white

Note: all the colour names/descriptions given above (both lists) are guides, the actual displayed colour will of course vary depending on the actual voltage levels in the colour circuitry and on the settings/adjustments on the display device/monitor.

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Re: what should i write next?

Postby MatthewThompson » Tue May 03, 2016 12:05 pm

SimonSideburns wrote:I've always been surprised there was never a version of the arcade game Gauntlet made for the BBC Micro, so I would say that could work really well..


There's White Magic by The 4th Dimension which whilst not a direct Gauntlet clone, comes pretty close and is clearly inspired by it.

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Re: what should i write next?

Postby ThomasHarte » Tue May 03, 2016 12:38 pm

The CPC has another trick up its sleeve though: linear scan lines. Through rerouting of the address lines. Being officially a 4Mhz system (albeit with contended memory, so the CPU sees some wait states if it accesses memory inopportunely), probably the pixel clock ends up being much the same as the BBC too? So pixels are the same physical size on screen?

MatthewThompson wrote:There's White Magic by The 4th Dimension which whilst not a direct Gauntlet clone, comes pretty close and is clearly inspired by it.


Dunjunz is also unashamedly on the Gauntlet spectrum.

1024MAK wrote:Alternatively instead the flash bit could have been a bright bit. This would have exited the ULA as a single digital output in place of the (almost) useless invert input pin. Then that could be mixed into the RGB outputs without any problems at all (I have not looked at how easy or not it could have been used in the UHF circuitry)


Pretty easy I think as luminance and chrominance are handled in a cleanly separated fashion until the very last moment, and I understand the UHF box accepts anything composite. It's purely analogue. At least, if my memory of the very familiar UM1233 being in my Electron is correct.

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Re: what should i write next?

Postby fwibbler » Tue May 10, 2016 6:42 pm

Much as I like Paradroid for the Archimedes, I still prefer Quazatron for the ZX Spectrum (I may have mentioned this before :roll: ). An updated and more colourful version of this would be nice.

1942 (or 1943) would be nice too as we don't really have anything like that on the Beeb.
Lightforce for the Beeb? (With the speccy version as inspiration as the Amstrad and C64 vesions were horrid)

A Mode 1 version of Dig Dug would be nice, but I don't know how you could get around the lack of colour in that Mode.
Also, the game would need to behave like the arcade version, unlike The Mine which just totally doesn't!

Cheers!


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