How to scroll on Atari?

[Ecernosoft]

Hello.

 

 

I'm trying not to overpopulate the forum but unfortunately C&A is my first Atari 8bit game, so I will have questions. 

 

How can I scroll on Atari 8bit?

Before you say "Dude. Use HSCROL and change the Display list" Yes, I know. But then we get into the screen wrap part.

I'm using ANTIC 4 here for lots of color, but it also requires lots of memory and lots of DMA. 

I plan to use ANTIC 6 for the final boss zone so that it looks unique though!

 

But then I got to the Screen wrap part. Oh dear. 

So, how do I handle this? Do I need to do the afwul C64 way and move all of memory myself, or can I do it the NES/7800 way and use "screen wrapping"?

Basically how that works is I have a tilemap (I'm using the atari 7800 as an example here) and it's bigger than the screen. Say, 32*12 characters of 8*16 pixels.

When I scroll, I move the table (duh) and when I reach the end, I start writing to the beginning of the table and when I do pass the end, what's "After" the end shows the beginning.

If that makes any sense. 

 

I'm trying to take a break from the 7800 area since..... reasons, don't ask.  And also the 7800 is...... the 7800. I want at least an ICT game on the big 3 atari systems!

 

Thanks guys. 

[+DjayBee]

Check this terrific tutorial by PlayerMissile.com

https://playermissile.com/scrolling_tutorial/index.html

 

... and, no you do not have to move memory.

Most of the time you can do all the magic in the display list.

Edited December 29, 2022 by DjayBee

[tebe]

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll.asm

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll_2.asm

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll_3.asm

[Ecernosoft]

3 hours ago, tebe said:

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll.asm

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll_2.asm

https://github.com/tebe6502/Mad-Assembler/blob/master/examples/hscroll_3.asm

dasm please?

I use DASM, not mads......

Thats ok though.

I'll take a look since I convert whenever I need to, thanks!

 

Edit: yeah I need DASM please. Sorry. Also, I can't understand whatever language the person who wrote this used. I'll still try my best to interpret it.

Edited December 29, 2022 by Ecernosoft

[Ecernosoft]

3 hours ago, DjayBee said:

Check this terrific tutorial by PlayerMissile.com

https://playermissile.com/scrolling_tutorial/index.html

 

... and, no you do not have to move memory.

Most of the time you can do all the magic in the display list.

Thanks!

[TGB1718]

I wrote a sideways scroller bitd but never finished the game, what I found was the ends of the "Wide Screen"

are the same, can't remember how much overlap was needed, but if you get it right it's as smooth as silk.

 

As said before, it's all done with the display list, you just have to be careful when designing the width of

the scroll area to insert the LMS instructions so it steps cleanly over 4K boundaries 

[Ecernosoft]

4 hours ago, TGB1718 said:

I wrote a sideways scroller bitd but never finished the game, what I found was the ends of the "Wide Screen"

are the same, can't remember how much overlap was needed, but if you get it right it's as smooth as silk.

 

As said before, it's all done with the display list, you just have to be careful when designing the width of

the scroll area to insert the LMS instructions so it steps cleanly over 4K boundaries 

Do you have the code?

 

 

[TGB1718]

13 hours ago, Ecernosoft said:

Do you have the code?

Unfortunately not, was on a bunch of disks that failed over the years before I got an SIO2PC to make disk images,

I've looked at the disks I saved, but it's not there, shame really as I lost tons of other game software and graphics

I was writing.

[Ecernosoft]

20 hours ago, TGB1718 said:

I wrote a sideways scroller bitd but never finished the game, what I found was the ends of the "Wide Screen"

are the same, can't remember how much overlap was needed, but if you get it right it's as smooth as silk.

 

As said before, it's all done with the display list, you just have to be careful when designing the width of

the scroll area to insert the LMS instructions so it steps cleanly over 4K boundaries 

I kind of thought I could use the 4k boundary to "wrap" to the beginning again. 🤔

[scitari]

In addition to what others have mentioned, I have a how-to posted on the Atari Projects website:

 

Learn to Implement Horizontal Scrolling in BASIC on Atari 8-Bit Computers (30-60 mins) – Atari Projects

 

Learn to Implement Vertical Scrolling in BASIC on Atari 8-Bit Computers (30-60 mins) – Atari Projects

 

Hope this helps!