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Apple II games ideal candidates for some conversions?

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Games like Dino Eggs use hires, 280x192 - 6 color screens. 

 

So doing a "straight forward" port might be challenging to pull off.

 

 

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Edited by shoestring

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On 11/3/2019 at 3:29 AM, www.atarimania.com said:

That would be fantastic. Of course, the coders would need to be convinced about the enterprise first :)

 

BTW, I really like the 4 am cracks. Maybe a number of titles are not doable because of the double hi-res or other things but there are many neat titles in the collection: https://archive.org/details/apple_ii_library_4am

I've been following 4am's exploits for some time now.  :)  I like his cracking work as well as the WOZ preservation work.  Lots of goodies have been turning up there.  :D

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On 10/31/2019 at 12:10 PM, playermissile said:

Sorry for the confusion. Bit 7 counting from zero, so bits 0 - 6 are graphics and bit 7 selects the palette.

 

To confuse things even further, what bit 7 really does is, if it's set, is to cause a one-half pixel shift for the pixels in this byte. Apple II hi-res graphics is drawn on a 560x192 grid where each pixel in the 280x192 normal resolution takes two horizontal grid spaces, so bits 0 - 6 determine 14 grid spaces representing 7 pixels. Setting bit 7 moves the pixels one grid space to the right, i.e. half a pixel. This generates the different "palette" by creating different artifacting colors.

 

It's even more complicated than that, so here's a really great description of hi-res graphics:

 

https://www.xtof.info/blog/?p=768

The way I understand it,  Apple II uses artifacting for color, similar to 320x192 mode on the A8.   But while A8 would gain two extra colors from artifacting (usually red/blue),  Apple used the extra bit to chose between "red/blue" or "green/purple",  meaning Apple 2 hi-res screens would have up to 6 colors on them that could be placed with different color placement restrictions than A8.   This could make ports to A8 tricky, either lose the colors, use a different mode to mimick it,  use DLIs or PM placements to compensate

Edited by zzip

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Here's a very early Dino Eggs WIP I just started a couple of weeks ago. Disassembled original code and working with source derived from that.

 

Yes it needs quite a lot of work!

 

 But essentially the Atari is running the Apple II code in an 130xe config. I'm using xbios to load all the original images from the Apple II straight into the available memory banks. At least the bottom row is showing up correctly, looks as though I'm on the right track in terms of using a lookup table to mimic the Apple IIs weird display layout.

 

 

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Spent a couple of hours on it tonight and it's looking slightly better albeit many bugs. Rather than doing them by hand, the bit patterns in the tiles are now horizontally flipped during initialisation. Haven't implemented any DLIs yet, so excuse the jerkiness.

 

Have some ideas to deal with the vertical stripes in all the graphics.

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