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New Game Port on the way


Heaven/TQA

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ok... TMR and I had some ideas years ago... but i was stucked with Beyond Evil (and still i am) so time went by...but i have thought after XXL is doing some nice conversions from spectrum I thought why not trying it with games which are not in our library...

 

so i do not tell more about it...and it's an early stage but It's definitly doable as the screenshots show... they are still messy and lack of colour but thats why there are no custom routines running right now... so it's pure game code running from other machine... ;)

post-528-1200234165_thumb.png

post-528-1200234171_thumb.png

Edited by Heaven/TQA
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ok... TMR and I had some ideas years ago... but i was stucked with Beyond Evil (and still i am) so time went by...but i have thought after XXL is doing some nice conversions from spectrum I thought why not trying it with games which are not in our library...

 

so i do not tell more about it...and it's an early stage but It's definitly doable as the screenshots show... they are still messy and lack of colour but thats why there are no custom routines running right now... so it's pure game code running from other machine... ;)

Great work Heaven. We too have been working hard on a similar project as you know ;)
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ok... TMR and I had some ideas years ago...

 

Years ago? Oh come on, back end of 2007 more like. =-) i did make a vague start on re-sourcing MetaLlamas as well, but you've got further than i did... still, there's loads of mileage in porting VIC games i reckon.

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ok...he really wrote a simple but addictive game... here it is... ;) first WIP... it crashes after you loose one life but that's because it depends on some VIC-stuff...

 

the game speed is not adjusted...

 

the zip contains the vic-20 original.

 

2 questions...

 

a) how does the game show normal font mixed with font? must be something with the 2nd font in rom... as the game shows the internal font in the copyright line etc... together with the custom font

b) how is the delay done with the raster bar effect at the title screen? haven't found the delay but could be that $9004 is different to $d40b...

 

and any ideas regarding the colour ram simulation?

mets.zip

post-528-1200236569_thumb.png

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The VIC scanline counter is single-line resolution - bit 7 of $9003 gives the lsb.

 

From http://www.geocities.com/rmelick/6561.txt

 

If you have redesigned most of the characters in your custom character set,

displaying understandable messages can be a problem.

One solution to this makes use of the fact that the VIC chip sees addresses

differently to the rest of the computer. If you place the custom character

set at 7168-7679, then printing RVSON within a string will cause the VIC chip

to access the unreversed character set in ROM when printing that string.

The reasons for this are as follows:

The VIC chip can only access 16384 bytes, which it sees as a contiguous

block from 0 to 16383. To it the location of the custom character set is

15360. Since RVS ON sets the high bit of a character's screen code, all

reversed characters have screen codes of 128 up. To access a character with

code 128 the VIC chip goes to location 15360 + ( 128 * 8 ) = 16384. Since the

VIC chip cannot access 16384 the address "overflows" and wraps around to 0,

which the VIC chip sees as the address of the start of character ROM. This

just happens to be the location of the unreversed straight forward, every

day representations.

Edited by Rybags
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Thanks Rybags... it's seems that Jeff did...I was wondering how he has mixed the standard vic font together with his custom one... thank good he hasnt used all of them so we can fit into the 64 chars of mode 6... next will be adding some colour...

 

the good thing is that Jeff used always the same "put char" routine for each printing on screen (text, sprites, llama etc) so this might be a good point to patch... ;)

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Colour RAM = a little tricky.

 

VIC screen is only 500 bytes or so, but still a loop which OR'd an entire Gr. 1 screen to set each character's colour would be CPU intensive.

 

Additionally, tricky if you're using GR. 1 to simulate the VIC-20 screen since you're limited to 64 characters.

 

PMG underlays could work, but then you'd need to redefine the character sets to have "background" colour as foreground such that it has priority.

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Another possibility is to do the thing in 40 column multicolour, but then would need a reworking of character defn's.

 

And, you're still effectively stuck on 64 characters as you'd have to "double up".

 

Not to mention that the game code would also require some major reworking.

Edited by Rybags
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at the moment its mode 6 with 22 bytes per line (thank god for antic) but i will go for overscan... this might work but if not seen on all TVs we can adjust the game code as Jeff has right boundary check there for nearly everything... (cmp #$16 = 22 for xpos).

Edited by Heaven/TQA
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small update...colours more or less in place but it could be that i missed some hit collission patches so please play it and tell me if you have a feeling that sometimes your shots go through spiders... thats an indication that i missed to patch a compare or the desired table...

 

best is to play it in atari800win PAL at around 80% which should be the original vic speed of the game. good would be if you compare the vic game in winvice against to see some differences...

 

thanks!

 

ps. good progress so far... :D i started yesterday reading source code and today the atari code... not bad :D

pss. START for starting the game, OPTION (will be changed to SELECT of course) to select the starting level (1-31)

mets.zip

post-528-1200257941_thumb.png

Edited by Heaven/TQA
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thanks!

 

but now its getting more tricky... ;) i love the flashy gfx of the vic original and i am not sure how i can get that over... but we will see... i started to implement real patches which means that i do not only exchange values in the original code (like $d40b with $9004 f.e.) but rewrite part of the code...

 

and the sound fx are great as well in this masterpiece so again i have to see how this works out with the pokey... the sound routines do take quite some space so i do not believe i simply can exchange the sound channels but who knows?

 

attachted screenshots of the vic 20 original just in case you do not know the original. (taken with winvice and PAL filter on)

post-528-1200263489_thumb.png

post-528-1200263494_thumb.png

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VIC just has 3 sound channels with 7 bits of frequency control each, covering a sperate range of frequencies per channel.

 

Translate that via tables for POKEY - use 2 voices in 8 bit and 3rd voice in 16 bit mode.

 

Should be reasonably easy, at the cost of 512 bytes of table data.

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VIC just has 3 sound channels with 7 bits of frequency control each, covering a sperate range of frequencies per channel.

 

And the white noise channel...

 

Maybe a bit off-topic....but maybe you know how the music of 'Robotic Liberation' was done? The instruments sound very much like Pokey distortions (polycounters). Doesn't the VIC20 support only squarewaves + noise? Or did they use a kind of softsynth?

 

 

here's a video of Robotic Liberation:

Edited by Analogue Multiplexer
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