Too bad the 7800 never got a port of Rainbow Islands

[miker]

But, but... BombJack is still at its demo stage. So it's not a game, no?

 

😜

 

 

[+Defender_2600]

4 hours ago, Eagle said:

But Maria's bottleneck is access to the video memory. Fixed bank at $C000-$FFFF it's Big problem.

Therefore, if you want to create a game with heavy use of gfx, you need a new mapper.

That's why TailChao did Souper for Rikki&Vikki, Reveng did Bankswitch for Petscii Robots, Activision for Double Dragon and I did mine.

160B uses a lot of ROM and hardly anyone uses the above mappers.

 

 

" The display for 7800 petscii robots doesn't rely on any mapper tricks - the tile engine can run on a supergame cart no problem, but it would just have access to half as many tile graphics. That's not enough to implement the petscii game, but certainly enough to run a game with the same 160b tile type display. Supergame or even a flat 48k would even be enough to recreate any one particular petscii robots screenshot. It's just the arbitrary combinations of the 256 24x24 tiles that demanded the new mapper."

 

 

Edited June 10, 2023 by Defender_2600

[Eagle]

Yes. Petscii robots don't use Holey DMA, so no need special banking for Maria.

Probably just need lots of rom for graphics. That's why they used halt trick.

[Synthpopalooza]

As a matter of interest, here is an attempt I did on the Atari XL, using a flicker trick called super IRG.  It allows 14 colors, 9 per palette.  This is also achievable on 7800 as well.  The effect will look better on ntsc than pal.  On 7800 you can have 8 palettes in 160A, and using flicker, 9 color per palette plus BG color.  160B allowing about 90 colors per palette over 2 palettes, although you have to be careful not to blend more than 2 luma steps apart.

 

The image was converted from Amiga version

 

 

 

[KrunchyTC]

Because I'm a dummy. Someone who is very familiar with how color works on these old machines, how does color work on the 7800?  What does "25 colors per scanline" mean? How many does mean can be drawn on the entire screen at once? Also curious to know what palette swapping is. 

[Synthpopalooza]

Here's a link to a topic on font swapping:

 

 

The idea is, you store two character fonts in memory, and change the character pointer every cycle.  By using checkerboard dithering, you can blend colors.  160A will get you 9 colors plus BG per palette, with 8 palettes, 160B is 91 colors per palette, using two palettes, and 320B is 9 colors per palette, 2 palettes available, although this requires turning on kangaroo mode.  In theory 320D allows 3 colors plus BG when interlaced (same as 320B) but with the lower 320A DMA cost, again needing kangaroo mode turned on.  However, I have been unable to get any results that don't wash out the letters.

 

In addition, better results are had if you blend the colors within one or two steps of each other.  The effect looks better in ntsc than pal.

Edited June 16, 2023 by Synthpopalooza

[Synthpopalooza]

In the basic modes:

 

160A:  3 color + BG, 8 palettes

160B:  12 color + BG, 2 palettes

 

320A: 1 color plus BG, 8 palettes

320B: 3 colors plus BG, 2 palettes.  bitpair 00 and 01 cannot coexist in the same nybble without turning off transparency (kangaroo mode)

 

320C:  is similar to 320B except every two pixels gets their color from the same palette

320D:  odd numbered pixels get BG + 00, even numbered gets 01 + 02.  00 and 01 cannot be in the same nybble unless you turn on kangaroo.  It incurs same D

 

My 320D interlace experiment involved swapping palette registers as well as the character pointer.  The 4 color interlace happens on vertical lines.  It will look bad on a standard CRT because of hi resolution artifacting.

[KrunchyTC]

I'm starting to understand, pretty cool.

Edited June 16, 2023 by KrunchyTC

[+Defender_2600]

1 hour ago, Synthpopalooza said:

 

320B: 3 colors plus BG, 2 palettes.  bitpair 00 and 01 cannot coexist in the same nybble without turning off transparency (kangaroo mode)

 

320C:  is similar to 320B except every two pixels gets their color from the same palette

 

 

320C  4 colors from two palettes + BG

 

320B  3 colors from two palettes + BG

 

320C and 320B have different restrictions regarding pixel placement but in many cases you can get better results with 320C and you can still use 320C + 320A (for example you can use 320A - 1 bpp for a starry background, consuming less cycles).
 

Edited June 16, 2023 by Defender_2600