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-   -   OCS/ECS Playfields - blitting objects using colours 16-31? (http://eab.abime.net/showthread.php?t=94487)

Marle 03 October 2018 10:16

OCS/ECS Playfields - blitting objects using colours 16-31?

Wasn't sure which to post this in but as I'll be working on this in Blitz, we'll go with here, also not sure how to title this so we'll also go with what I have :D

So I want to create dual playfields and I can work with the copper and 3bpp per bitplane happily for the foreground and background art. But when it comes to enemy design, using the foreground's colours will be, a shame to say the least, but I'm guessing if instead of using sprites, any blits to the foreground bitmap are limited to the 3bpp.

Is there any way that you can blit 'somehow' with the shape using the unused colour registers 16-31?

I think I know the answer (no :))

Otherwise I was going to somehow make use of attached sprites, but they are limiting, especially when I wanted to create a 32px wide character with attached sprites (that's 2 of my attached 4 gone!), and then multiplex the use of the last 2.

It's the only way I can think of doing this, and I really want to make this OCS/ECS compatible.


dodke 03 October 2018 10:39

I'm also guessing the answer is no. I think common in dual playfield games is to use attached sprites for a colourful main character, maybe the rest for some other little bits like bullets or similar. Then enemies would be 7 colours in the foreground playfield.

Do you absolutely need to use dual playfields? at least without them you'll have more options for having more than 3 bitplanes for things.

Or maybe try to work with non-attached sprites. Few colour sure but at least they can stand out from the background.

Marle 03 October 2018 11:35

I think I do need it in order to get the nice open world (potentially anyway) parallax look that I am going for. I think it can work, it just needs some clever thought given to how to place enemies on screen, 2 per platform doesn't seem to be a huge limitation for what I had in mind, as I can use the enemy fire to be blitted objects that use the foreground 7 colours (as one of those will be transparent).

Using fewer colours for the enemy sprites might be on idea, but 3 colours is really damn difficult to design with, although who knows maybe I can make it work :)

Zener 03 October 2018 11:48

If you use dual playfield you will be limited to 8 colors per playfield (16 on aga). 3 bitplanes (4 on aga) per playfield.

This games uses dualplayfield in blitz, one playfield for background, one for enemies

Marle 03 October 2018 12:18

That's cool! Is that an AGA example? In my head the background is just the background, the foreground will be the platforms, and foreground objects in general, then sprites for player and enemies, to overcome the 3bpp limit on the foreground layer if I was to blit objects. And then I can blit enemy fire using the limits of the foreground colour with a bit of luck, as those don't need to be so detailed.

Daedalus 03 October 2018 12:46

If it's dual playfield and isn't using sprites, then it would be AGA alright - there are more than 8 colours in the foreground (enemies) that I can see. Unfortunately, as others have said, you're limited to colours 8-15 for the second playfield on OCS and ECS.

Instead of using a dual playfield display, have you thought about using buffered blits for the top layer of objects? It should be doable to remove and reblit a reasonable number of items to give a parallax effect without losing speed, and that would give you access to all 32 colours. Queued blits might be a bit faster if you keep a separate copy of the background imagery around to restore under the blits. If you have a lot of platform area or enemies to blit, this might not be fast enough however...

Marle 03 October 2018 19:19

I have thought of that but I think given this will hopefully eventually 8 way scroll there might be too much to blit for the foreground for the basic 7MHz ECS/OCS Amiga. But I will see how far I can get with the basics of 3bpp dual playfields and sprites and then if that doesn't work, we'll go from there!

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