V9990 setpage

Supporter (6)

24-06-2022, 16:12

Hi everyone,

I'm trying develop a new game for V9990 (Prince of Persia), and trying to understand how it works.
The game is using B1 mode, 8 bits, 64 colors, and the game do some copy commands.
Basically it saves the background, blit the player, blit the columns that are in front of player and so on.
The "problem" is: The player blinks a little (sometimes). On V9938 we use "set page" to write on a not visible page and show another page, but on V9990 I only found a SetScrollY routine.
So, I tryied to use this tecnique (SetScrollY), it shows the correct page, but switching it 15 times per second, just after the vblank, sometimes the screen appears to be "rolling" (up and down some pixels).
Any sugestions?

I can upload two videos, one without page switch and one with.

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Van MsxKun

Paragon (1134)

24-06-2022, 19:05

Ritter wrote:

Any sugestions?

Just one. Try pattern mode

Van Ritter

Supporter (6)

24-06-2022, 19:11

Thanks for answer.
screen "rolling" on "setpage" was solved now, the problem was one non-optimized routine. Now executing SetScrollY exactly on vblank, the problem desapeared.

Van Maximilian Privrat

Rookie (22)

11-10-2022, 19:51

Great project! I hope it will be soon avaible! <3

Van Manel46

Paladin (674)

12-10-2022, 00:40

The scroll is instant. Scrolling in bitmap mode on the V9990 is equivalent to the MSX2 "setpage".

Van Manel46

Paladin (674)

12-10-2022, 09:36

It is not necessary to scroll the area that appears on the screen, for bitmap sprites.
What I do is after drawing the screen with tilset + map, I make a copy of it in another area of the vram, and then by means of copies from the saved screen, I cover the sprite before drawing it again in another position or with another image.