is it possible to use multiplexed sprite to display/scroll this image?

[jotd]

This is a background pic with 3 colors, not repeating





Can I multiplex X number of sprites to create a fake background layer?


Or do I have to blit / use dual playfield, knowing that there's another scrolling layer (3 different parallax layers)

[roondar]

Well, I'd say it depends on the number of active bitplanes. If it's 4 or less, you can create a Sprite based background that has no repeating patterns in it by reloading Sprite DATA/DATB and the position with the Copper. If it's 5 bitplanes or over, it's going to be much harder, if not impossible (though it may still be possible if you are clever about how you reload the Sprites - if some of the Sprites stay the same, you might be able to make it fit).

I've done this for a 4 bitplane screen in one of my Amiga Tech examples, found here: https://powerprograms.nl/amiga/spr-layer.html

However, the effect is quite costly so if most of the background is the same colour as it seems to be in your example, make sure to not do that for those lines

Of course, if you limit yourself to a 128 pixel wide pattern, it becomes much easier.

[Codetapper]

First of all, I would redraw that slightly, as almost all of the bottom part is a single colour, and if you stripped out that extra dark blue bit hanging down, you'd be down to 256x48 rather than probably have a layer that's more like 256x128.

In one of my projects, I was able to switch the top part of my display to 16 colour mode (most of it is in 32 colours) which gave me enough DMA time to do the panel at the top completely with sprites. So it really depends how many colours you're using for the display.

Even if you failed to make a complete sprite layer, you could always do a combination by using sprites as much as you can, maybe reposition some of them, and do a blit for the small part you couldn't get done with sprites alone.

The other thing I would consider is simplifying the pattern above so that it does repeat. Assuming your game scrolls and you lose the 8th sprite, you could still make a 7 sprite wide background layer and repeat it with a few copperlist moves. If you have enough memory, you could precalculate all necessary combinations (a la Risky Woods) and then wouldn't even have to scroll it.

Basically it all just depends on how many colours you're using, how much spare memory you have, if you have all 8 sprites available or just a few, how much spare DMA time you have etc etc.

[Codetapper]

Assuming this is for a Moon Patrol conversion, if you look at the graphics, the back blue mountains layer hardly interacts with the green hills layer anyway - those 2 could share the same layer, switching from blue mountains at the top and then becoming the green layer underneath.

There'd only be a tiny part with some random blue pixels that could be done with a few random sprites to fake the entire thing being 2 independent layers. There's literally no need for a full sprite layer imho. Fake it until you make it!

[jotd]

Yes, I was considering Moon Patrol and I don't care about the solution as long as it works.

I would like to use dual playfield if number of colors is enough, even if sprites can be used to add more colors too. In which case not using sprites for mountains would be better.

Anyway, funny how a simple 1982 game is a challenge for ECS or even AGA amiga!