Chibi Akumas Episode 2: Confrontation! [game for CPC then MSX2]

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Por Grauw

Ascended (10605)

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26-09-2017, 10:37

DarkSchneider: from the previous posts, I doubt keith56 would be inclined to use the BIOS for graphics/PSG Big smile.

Por DarkSchneider

Paladin (944)

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26-09-2017, 10:37

Coming from CPC (a closed system) I suppose is natural. Also I don't remember if the blitter BIOS functions would be on SUBROM so the use could be more complex.

Por ARTRAG

Enlighted (6846)

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26-09-2017, 17:16

I would avoid bios as the black plague any time you need to maximize the throughput of audio and video.
The sole exceptions are disk and memory management, but in msxdos 64kb of ram are already paged in and disk has its own calls.

Por PingPong

Prophet (3898)

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26-09-2017, 19:48

IMHO: vdp with ports.
the msx2 vdp blitter is not known as a speedy gonzales, plus you have the overhead of a z80 @3.5mhz+m1 cycle. And in screen 5, you have two options:

Hw sprites: fast, but limited, 8 on a single scanline display , 32 on screen. Limited multicolor support.
Sw sprites: the blitter is not the amiga blitter, especially when using logical copy operations. It can be accelerated a bit by entirely disabling sprites display.

Plus msx2 screen5 is nice, but it is almost twice the amount of vram to manage, compared to CPC.
So do not waste time in bios that adds the overhead of interslot calls.

Por Grauw

Ascended (10605)

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26-09-2017, 20:10

As for hardware sprites;

Yes you can show only 8, but if they are only 2 pixels high (bullets), that may not be an issue (if you sort them bottom-to-top the priority system will only omit the lower lines). Hit9918 showed a demo of this once. And the 32 sprites limit can be overcome by multiplexing the SAT. Since there is only 1 bullet shape and 1 colour, there are no SPT and SCT management shenanigans which simplifies things to just updating the SAT coordinates. Advantage: these writes are linear, which suits the indirect I/O well.

Biggest hurdle would be to sort the sprites to make them end up in the correct SAT in bottom-up order (one bubble sort pass / frame depending on movement speed), and to have some cycling scheme for flickering if there’s more than 8 on a line, although the latter might be optional.

And use double buffered software sprites for the characters / background.

Not sure if that’d be good enough for this game, but it may be an interesting approach to consider.

p.s. So, screen 6 game? Wink

Por PingPong

Prophet (3898)

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26-09-2017, 23:00

screeen 3

Por keith56

Master (162)

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31-10-2017, 04:27

If everyone doesn't mind I'll take this opportunity to plug the CPC version of my game, and update you all on how the MSX port is going!

Episode 2 is now out for CPC: get it if you want at http://www.chibiakumas.com/ep2/
or please watch the youtube trailer:http://www.youtube.com/watch?v=-WoYu7u97us

Of course I'll be porting Episode 1 to MSX first - and will follow with Episode 2 later!
There's a bit of info on the MSX version at the official page here: http://www.chibiakumas.com/msx/
but its' a bit out of date, so I'll give you the latest!

I'm pretty happy I've got my head around the MSX2 hardware to the extent I need to, and I've not come across anything that I see as a problem which will stop me!

I've noticed the MSX2 VDP is slower than I could have hoped - I will use every dirty trick I can work out to get around it (I have a few ideas), but I have decided to make a V9990 version as well - so people with V9990 GPU will probably get much nicer backgrounds and more speed!

I'm now into the phase of breaking down the CPC version, and rewriting it bit by bit to work on the MSX - I have no idea how long it will take,but once that's done, I then need to rewrite and retest each level's code!

My testcode, and the early build of my multiplatform sprite editor are available on the download page:
http://www.chibiakumas.com/ep2/download/
in the AkuMagic toolkit - They are totally not finished, so use for educational purposes only - or don't use at all!

Por Grauw

Ascended (10605)

Imagen del Grauw

31-10-2017, 10:32

Congrats!

And cool that you will be making a V9990 version! It’s really nice hardware (and soon on CPC too! Big smile).

As for performance, the strengths of the V9938 are sprites, screen splits, the palette, parallel processing with the command engine, and hardware scroll (esp. V9958), while random bitmap access is not its greatest strength Smile. Playing to those strengths may give better results.

Another thing worth mentioning is, you can skip a byte while writing to VRAM by reading. May be handy.

Por erpirao

Paragon (1264)

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04-12-2017, 19:27

Hello.. A really full-paniac-bullet game in pleasure hearts by m-kai
Pleasure hearts in msx2

Por TomH

Champion (327)

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04-12-2017, 22:03

Grauw wrote:

p.s. The MSX ISR doesn’t touch shadow registers, so you are free to use them any way you like. Also, mind that the MSX Z80 is slower than the CPC’s because it runs at 3.58 MHz and has an M1 wait on every instruction (see 2nd column here).

This thread having been revived anyway: I would expect the Z80 in the MSX to compete effectively with that in the CPC, probably even be a shade faster, because the CPC holds WAIT for three cycles in every four, effectively rounding all machine cycles up to the next multiple of four. Given that normal read and write machine cycles are three clock cycles, it's sort of like the opposite of the MSX's WAIT strategy: the M1 machine cycle is its expected length and [almost] all the other machine cycles are a clock cycle longer than usual. People throw about an effective clock rate of 3.3Mhz but that's just an estimate somebody made once based on an average mix of instructions. It's merely a rule of thumb.

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