Ancient knowledge for free! (sort of)

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By Pat

Expert (67)

Pat's picture

03-04-2006, 11:28

Next: Which techniques did you use for the copy protections?

I'm aware of the cartridge with ARC (not that I ever saw that game, (different subject though))
And the codes printed in orange on red paper with Black Cyclon (iirc): Did you use some cyclic codes for that?

By parallax

Expert (85)

parallax's picture

03-04-2006, 11:34

What do you mean by cyclic codes? Well, of course, there is a relation between the input and the output of the code, so the game could check correctness. It was not a random table, if that's what you mean.

By Pat

Expert (67)

Pat's picture

03-04-2006, 11:44

Oei, I types 'cyclic codes' without thinking really hard what that means, naah, What I meant was if there was some sort of system behind it, that calcalutes if the code was correct, and not a big loop-up table. (ok, pretty evident)

But back to the point, what type of calculation did you use (if you remember). Maybe some modulo , shifting , polynomials, ala CRCs or something else? ( modulo polynomials etc (haha, never used that after I got my grade for that subject)). I hope this is clear.

By parallax

Expert (85)

parallax's picture

03-04-2006, 11:49

It involves shifting, modulo, exclusive-or, and some constants. It doesn't need anything more fancy because if you hack it (as was done) you would cripple the detection mechanism. I can't imagine anybody trying to reverse-engineer the code function, it wouldn't make sense.

By ricbit

Champion (438)

ricbit's picture

04-04-2006, 06:15

I bought a second-hand Akin some years ago, to me it is THE best european game for MSX2. However, I found the ending was very strange. Was it by design, or did you lack time/resources to make more stages?

By parallax

Expert (85)

parallax's picture

04-04-2006, 09:33

Thanks Smile
It was by design (the way the story went) but there was definitely time pressure, so the ending should have been more elaborate. Furthermore, I sometimes spent too much time trying to make things perfect at some point, leaving less time for the other points (e.g. the ending). You can explain this as perfectionism or simply bad planning... I would approach things slightly different now.

By Manuel

Ascended (18246)

Manuel's picture

04-04-2006, 12:55

ricbit - did you see the Core Dump promo then?

By ricbit

Champion (438)

ricbit's picture

04-04-2006, 21:28

Thanks for the explanation parallax. I remember thinking, when I saw Metroid Fusion for the GBA, "oh my god, this metroid game is almost as fun as akin" Smile (I had never played any metroid before Akin, so I was biased)

Manuel, I don't count promos when choosing a best game. But Core Dump would surely surpass Akin if it was finished.

By Sonic_aka_T

Enlighted (4130)

Sonic_aka_T's picture

05-04-2006, 18:46

I always wondered if in Akin the one-color areas are drawn using one big fill, or just doing filled 8x8 cells instead of the 8x8 copy. Also, are (small) sprites copied with one big copy, or are they also plotted as cells?

By parallax

Expert (85)

parallax's picture

05-04-2006, 22:57

One colour areas are done using copies as well, the engine doesn't scan for this. However, as only the edge blocks of these areas need to be constructed, it is not a big deal. I can image that I could have scanned for that as well, but it occurs only very seldom, so maybe testing for it might even be relatively expensive on average. In Core Dump the black bars between the camera windows are fills though Wink

Sprites are plotted as cells, and they have to be, because cells are re-used among animation frames. Say you have a tank with turning wheels, then each animation frame has largely the same set of cells (blocks) except for the wheels. In particular, the big spider thing in Akin shares many blocks between its animation frames. So in general, big copies are not an option, as this would mean that the sprites take up much more VRAM (as lots of unnecessary information is copied throughout the animation frames)

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