Friday, February 11, 2005

Autopilot

It's true that sometimes when you are blocked on a problem you just have to leave it aside for a while to look at it from a new perspective.

Yesterday I spent much of the night fixing the tile decryption for the RISE10 chip, which is used by Raiden Fighters 2. With the experience gained on the earlier version of the chip this was much easier, and I could fix most of the problems reasonably quickly. However, there was one bit in one layer that just didn't want to work.

The algorithm, now that it's understood, is really clean and simple, following intuitive patterns, but that bit didn't fit - to partially decrypt it, I had to use the wrong bits from the tile code, and pick a carry from the wrong bit of the encrypted data. It just didn't make sense.

I decided to leave it alone for the night, but literally a few seconds after turning off the monitor and going to bed, the obvious answer came to me: that bit had to belong to a different plane! I must have been fetching the encrypted data from the wrong place. And indeed, this morning I checked, and bit 16 of the source data was used twice, while bit 15 was not used at all. Fixing that was all that was needed to completely fix the tile graphics.



There aren't many screenshots that I can take because the driver also has problems selecting the tile bank (this is an emulation problem not related to the encryption). Plus of course, sprites are still not decrypted correctly.

I still have to decide what to do next - I could either look at the RISE11 encryption, used by Raiden Fighters Jet, which will be a bit more work than the others because the current driver only decrypts two of the six planes (for the other games, the decryption was already very close). However, now that I have a good understanding of the algorithm it shouldn't take long to do it, even starting from scratch.

The other thing I could do is fix the tile banking problems in Raiden Fighters 2. I haven't looked at the driver yet, it might be something simple.

25 comments:

Jakesh said...

Wonderfull ...

Anonymous said...

One word AWESOME !!!

I believe many MAMErs are pleased to see progress for those games, at least the SHMUPS fans.

Good luck Nicola.

Anonymous said...

Jakesh of Kallus 2? Wicked...

- Stiletto

Anonymous said...

You are the MAN!
Congrats on your work so far.
I can't wait to see what else you got under your sleeve.
Thanks a million!
Keep up the great work.
-Jackie

Alessandro said...

Nicola, you're great!!

Alessandro said...

Nicola, you're great!!

Anonymous said...

GRAZIE Nicola per avermi fatto sognare ad occhi aperti, nn immagini quanto mi renda felice vedere i progressi fatti nelle ultime releases, cioè da quando 6 ritornato più attivo che mai. Non mollare mai e per nessun motivo al mondo.. non esistono termini per definire ciò che hai inventato. GRAZIE!!!

PS: in bocca al lupo per l'SPI.

Anonymous said...

I cannot see the screenshots...

Anonymous said...

Good work!!!
I'm so excited to see nice seibu games running on my PC in time.
Thank you , Nicola

- Mame pan in korea -

Raiden99 said...

Tell us the truth Nicola .... You come from another world, isn't it;)
It's really incredible to see how fast you progress and improve what seemt to be unreasonable and impossible. once again thanks a lot, and good luck for next steps .... i think a lot of people is counting on you ;)

Anonymous said...

CONGRATULATIONS !!!
And good luck.

Anonymous said...

Wow!!! dreams come true!!

May I beg you give a look on the decoding the great igs game "bee storm" and "kov2" If you had some interests!!!

Anonymous said...

Wow!!! dreams come true!!

May I beg you give a look on the decoding the great igs game "bee storm" and "kov2" If you had some interests!!!

Anonymous said...

The IGS games have unemulated protection, and ElSemi is currently looking at it.

Anonymous said...

Not to mention IGS still sell KOV2 as new so it won't even be considered.

Anonymous said...

well done nicola keep up the good work. you will please a lot of people fixin the raidens and viper phase 1.pitty we cant clone you a few times and the whole back catalogue will be sorted.

Anonymous said...

wonderfull,congrats on you work so far.
is anyone working on (sega st-v)will the games eve run faster.

there is another game i personally will love to see pleyable is (osman_1996 by mitchell)
is anyone working on that game.

thank you nicola. gods bless you

_whitefang_

Anonymous said...

wonderfull,congrats on you work so far.
is anyone working on (sega st-v)will the games eve run faster.

there is another game i personally will love to see pleyable is (osman_1996 by mitchell)
is anyone working on that game.

thank you nicola. gods bless you

_whitefang_

Ali Baba said...

yes, indeed it is awesome.
however; what fascinates me more is the sum of knowledge and experience people like Nicola and the other MAMEDevs have.
it must be fun in it's very greatest degree possible working with mame.
word is; i envy you Nicola, but at the same time i feel proud just knowing someone like you and MAMEDevs exist.
Good luck till the end.

Anonymous said...

You are the best Nicola.
Thanks for all your hard work on the Seibu games and now we all can play them soon on MAME.

I hope when all is said and done with Seibu that you can work on IGS games and make BEE STORM:DODONPACHI 2 to work.
again thanks so much for all your hard work and congrats.

Anonymous said...

im fan raiden fighter ;)congratulation Nicola nice job and nice fx ;)
good luck!!!! ^^

kemosabe said...

Really amazing work you've been doing all these years!!
What is even more amazing is that only very recently you've let us know a little (or a lot) more about yourself, and what you're up to lately.
As you can see, everyone appreciates your effort, but don't stress yourself too much!

'Live long and prosper' ;)

A big thank you from an eternal fan of yours and the whole MAME 'apostles' team :) !

Anonymous said...

Great work Nicola! Ever planned to looked at the Irem107 games? I reckon someone said it had an encryption issue too

Anonymous said...

Awesome work Nicola!

Can't wait to see it in action :D

Thanks

-Guus

Anonymous said...

Thank you so much for your hard work, there are many of us who can't wait for the opportunity to try out the seibu games!