Strategies for 1 pixel vertical scrolling on 9918 VDP (MSX 1)

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By igor.d.monteiro

Supporter (4)

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15-10-2020, 01:07

maybe you could use white tiles, like clouds to fill some of the combat screen.

By albs_br

Master (184)

albs_br's picture

09-01-2021, 01:54

albs_br wrote:

Hi guys, I'm working on Pacific 2 (...)

I was looking the code of Pacific and... what a shame. It's a tremendous mess and ugly, and all kinds of bad practices.
Very poor knowledge on the machine / assembly language + running for schedule. Sad

My current code is thousand times better (I hope). But rewrite this old code base is a big effort. Not sure if worth it.

By Chilly Willy

Supporter (16)

Chilly Willy's picture

10-01-2021, 04:07

albs_br wrote:
albs_br wrote:

Hi guys, I'm working on Pacific 2 (...)

I was looking the code of Pacific and... what a shame. It's a tremendous mess and ugly, and all kinds of bad practices.
Very poor knowledge on the machine / assembly language + running for schedule. Sad

My current code is thousand times better (I hope). But rewrite this old code base is a big effort. Not sure if worth it.

Where do you find the code for these things?
Seriously, I have been looking for a solid and fast 8 way scrolling with screen wrap.
I even tried to hire an experienced programmer to code it for me and the guy first said it was a breeze then never got back to me.

I have a 64x64 grid of 8x8 tiles that all I wanted was scrolling in any direction and the screen wraps around.
I do not care if it is slow or choppy but I need code and I will pay if there is none online for free.
double buffer and my machine does not have a hardware scroll register. In z80 assembly language.

BTW, I downloaded the 8 way scroll from earlier posts and it doesn't work the way I am looking for.

By ARTRAG

Enlighted (6462)

ARTRAG's picture

10-01-2021, 11:05

Choppy is fine? Go for tile based scrolling. It is trivial to implement and if the 64x64 map is in rom it will work eve on colecovision. If you want 8 way fine scrolling, you have to live with plenty of limitations and, I may be wrong, but the complexity would rise beyond the level of your skills

By Chilly Willy

Supporter (16)

Chilly Willy's picture

10-01-2021, 15:30

ARTRAG wrote:

Choppy is fine? Go for tile based scrolling. It is trivial to implement and if the 64x64 map is in rom it will work eve on colecovision. If you want 8 way fine scrolling, you have to live with plenty of limitations and, I may be wrong, but the complexity would rise beyond the level of your skills

I have a scroll routine in 8 directions which works so well I have to slow it down.
It is the wrapping part that eludes me because no matter how I work it the pointers are off.

I really try to be nice about these things.
I ask, I beg and I often try to hire someone with a larger set of programing skills because like any other computer business you have team members come together to work on a project.
I am a graphics man and even have to hire someone for music.
You would think that someone would jump at the opportunity to get paid just to write a computer routine.
Maybe it's just me.

By syn

Paragon (2003)

syn's picture

10-01-2021, 21:58

Chilly Willy come talk at https://qchat.rizon.net/?channels=msxdev we might be able to help out.

By santiontanon

Paragon (1138)

santiontanon's picture

11-01-2021, 03:12

Hi Chilly Willy, I remember you asked last week about a similar wrapping thing in this thread https://www.msx.org/forum/msx-talk/development/scroll-with-screen-wrap. A solution was posted there, is that what you were looking for?

By Chilly Willy

Supporter (16)

Chilly Willy's picture

11-01-2021, 17:37

santiontanon wrote:

Hi Chilly Willy, I remember you asked last week about a similar wrapping thing in this thread https://www.msx.org/forum/msx-talk/development/scroll-with-screen-wrap. A solution was posted there, is that what you were looking for?

Yes, thank you.
Now I am moving onto a larger aspect of my game.
Which is sort of like Hunt the Wumpus where the screen scrolls.
I don't care about the choppiness because they are 8x8 tiles moving but no matter what I have tried what moves to the right the screen shifts down to the next row. If I go left the screen moves up one row.
If I move up the data at the bottom does not go back to the beginning and shows memory garbage.
Same if I go down.

Scrolling works. I just can not get the wrap part working.
It is too large to tell me how and I either need code or pay someone to write the routine for me.

By ARTRAG

Enlighted (6462)

ARTRAG's picture

11-01-2021, 22:38

The simplest solution is to repeat a fraction of the map wide as the screen window at the right and at the bottom of your map. If your map is 64x64 and your screen window is 24x24, repeat the first 24 columns after the 64th in the map and the first 24 lines after the 64th line. The map will be 88x88 and you will be able to move your screen windows in a 64x64 area as it was wrapping.

By santiontanon

Paragon (1138)

santiontanon's picture

12-01-2021, 04:15

Exactly, using what ARTRAG suggests, you avoid having to do anything fancy on the code side. It's the same idea as "doubling" the snake pattern trick in the other thread, but applied to the 2-dimensional scrolling.

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