Petition to fix sprites on Valis on MSX2.

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Par JohnHassink

Ambassador (5468)

Portrait de JohnHassink

03-12-2012, 19:46

I really like the idea! But I've understood that 'transferring' from screen 2 to screen 4 is very hard, and that these screen modes aren't as similar (behind the screens, lol) as they seem. Sad
Anyway, I'd love an excuse to re-arrange the soundtrack to PSG+FM. Wink

Par PingPong

Prophet (3555)

Portrait de PingPong

03-12-2012, 22:52

JohnHassink wrote:

I really like the idea! But I've understood that 'transferring' from screen 2 to screen 4 is very hard, and that these screen modes aren't as similar (behind the screens, lol) as they seem. Sad
Anyway, I'd love an excuse to re-arrange the soundtrack to PSG+FM. Wink

if there is time one can try.

most games have this kind of code to write VRAM

outi
outi
outi
outi

it is necessary to replace this routine with a little more complicated where the out of the third byte is replaced with 0. then a similar loop should be used to fill vram. for each sprite.
If there is time.....

Par Manuel

Ascended (16975)

Portrait de Manuel

03-12-2012, 23:12

john, I also made that mistake ones, it's actulaly "behind the scenes" Smile

Par JohnHassink

Ambassador (5468)

Portrait de JohnHassink

04-12-2012, 01:05

Manuel wrote:

john, I also made that mistake ones, it's actulaly "behind the scenes" Smile

Thanks, I know, it was a play on that. Smile

Par anonymous

incognito ergo sum (118)

Portrait de anonymous

04-12-2012, 01:10

But it's true, right? That sc2 and sc4 aren't so exchangeable as the similarities would make you presume.

Par Huey

Prophet (2654)

Portrait de Huey

04-12-2012, 08:47

Well there are some degrees. Appart from the sprites they are pretty much the same.

As Pingpong suggested it isn't too hard to replace SAT updates to be screen4 compatible. Maybe it gives slowdown due to the extra colordata you need to write.

But adding sprite rotation (or an other flickerng routine)and upgrading the sprites (more colors) takes some dedication.
Adding smooth scroll is pretty much like rewriting the game engine as all movements are 8 pixels.

Par MäSäXi

Paragon (1884)

Portrait de MäSäXi

04-12-2012, 12:26

As you are talking about patching it to work in Screen 4, what about making a hack which just changes the colour of enemy sprites and does nothing else? Game still stays in Screen 2 and sprites are easier to see.

Par PingPong

Prophet (3555)

Portrait de PingPong

04-12-2012, 19:27

Huey wrote:

But adding sprite rotation (or an other flickerng routine)and upgrading the sprites (more colors) takes some dedication.

Yes,but is does not take extra cpu time. That's because every game i'm aware of, does always a full blit of the entire sat at every frame, despite the game uses or not sprite rotation.
Plus, a more primitive form of sprite rotation (that is the same used in most games) can be done by replicating the SAT 4 times. Every frame you write to a different SAT address, and every SAT have pre-rotated sprite color attributes by 8 sprites entry, so the z80 only write the 128bytes part of the SAT, because colors are fixed and already prerotated. However this can only work if you do not change to often sprites colors. In some games this can be done, because enemies are linked to sprite priority planes so their colors are also fixed or they change rarely

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