special graphics or maximum color/resolution

[TXG/MNX]

Hello,

 

On the 8-bit Atari there are several new graphic modes that mixes scanlines, dli's etc to create more colors and high resolution.

Are there also capabilities like this on the 7800 or are we bound to a few colors ?

 

Would like to hear what people have managed to make on 7800 so resolution and color (maybe a link to the pictures)

[TXG/MNX]

I was reading some more about Maria.

 

It should support dli but the display list pointer is only read at the start of the screen so it cannot be changed in a DLI correct ?

 

Secondly Maria can switch between 320 and 160 mode with dli is that correct ?

Edited September 15, 2014 by TXG/MNX

[Synthpopalooza]

I had wondered if a Super IRG type mode (switching font sets every screen redraw) could be done to increase the color resolution in 160B mode. You'd need to do checkerboarding on the characters to make the colors blend better but maybe it could be done. You'd basically get about 10 colors per character and somewhere about 40 colors onscreen at once, approximately.

[Synthpopalooza]

And also, if you do switch between 320B and 160B every scanline, can you then also use a PAL blending technique? Your vertical resolution would be cut in half, but maybe the pixels would blend to make extra colors?

[+Trebor]

The "New Graphics Mode 160C" is pretty impressive.

[TXG/MNX]

That 160C looks awesome I hope this will be available in 7800basic (soon) :-)

[Rybags]

DLI is only allowed at the start of a zone AFAIK. It's not really feasible to change the DList pointer during an active screen due to how they're constructed and how they work.

For each zone, the DList entries are read every scanline since there can be a fair number of them, ie generally one per object, bunch of text or scrolling area of background graphics.

 

As for the technique of PAL mixing to get the extra colours, that's something that the TV is doing for us, the machine in use needs to be able to provide some relatively dark colours and a good range of non-coloured luma on the other lines and that's a strong point of the 7800.

Moreso than the computer in many ways since 16 lumas choices are there for any mode and the use of more colours per scanline is somewhat more flexible.

 

But depending on how you generate these extra colours you might need to reload palette entries on a per-scanline basis. That's a potential falling down point, especially given that if you have lots of graphics going on, Maria can steal most of the cycles that might otherwise be available for the CPU.

On the computer it's fairly easy to know how many cycles you'll have but on the 7800 it can be highly variable, so you'd have to put constraints on how much graphical stuff you're doing if you need cycles available to do colour register changes.

[+Trebor]

Looking at was done originally, these are a few impressive in-game examples:

 

 

Unfortunately, many when the see/read about the Atari 7800, often they typically (only) come across the usual Dig Dug, Ms. Pac-Man, Centipede, captures. While great games in themselves, they hardly scratch the surface of what the 7800 can display. The above snapshots start to showcase the system's graphical abilities better.

 

Furthermore, it's even better when Alien Brigade, Basketbrawl, Midnight Mutants, and Ninja Golf are seen in action.

[EricBall]

Note: while the A8/5200 & 7800 use similar terms e.g. "display list", they are used in very different ways. See https://sites.google.com/site/atari7800wiki/atari-5200

 

The 7800 has a 25 entry LUT from a 256 color palette. Depending upon the graphics mode, a sprite may be 1 bpp (1 color + BG), 2 bpp (3 or 4 colors + BG) or 4bpp (12 colors + BG). In addition various strategies which take advantage of the way a TV processes the video signal may be used to create additional "artifact" colors. (e.g. Tower Toppler)

[+Trebor]

Would like to hear what people have managed to make on 7800 so resolution and color (maybe a link to the pictures)

 

Bentley Bear's Crystal Quest is absolutely gorgeous, flicker-free, and includes parallax scrolling on many levels with no graphical assistance. It is strictly all Maria. Here's a couple of captures for each of the first three levels:

 

 

To fully appreciate the programming genius of Bob/PacManPlus, the awesome graphics of PAC-MAN-RED, and not to neglect the beautifully assembled music from Synthpopalooza, you really need to watch it in action.