Asteroids emulator - other games possible?

[Synthpopalooza]

I was playing around with the Asteroids emulator today, and I had a thought ... color vector games in hi-res on the Atari. Maybe it's possible to emulate Tempest?

 

I came up with a technique (thanks to a look at popmilo's code for 4x4 160x196 mode) to display color vector graphics in 320x192 hires.

 

It works by alternating mode E and F and shifting the screen up and down a scanline every VBLANK, this makes a color hi res screen but without extra memory usage.

 

I did a conversion of a tempest screen, it's rough but it shows the idea is possible. You only get 4 colors here. You could also use mode 10 for the colors but it would make more artifacting.

 

tempest.obx

[Keatah]

Cool. I would think that processing all this artifacting would be too much. Graphics mode will need to be more native to the target hardware.

[Rybags]

VBXE would be a more logical choice for the colour vector games albeit the result being much smaller target audience.

 

CPU line draws in VBXE modes can be much quicker due to 1> no DMA loss since Antic/GTIA graphics can be turned off, 2> pixels are byte addressable so less calculations and no bitshift/mask ops needed for draws, 3> in cases of small vector objects like text/bullets it might be possible to offload to the blitter.

 

Traditional Atari - yes, the modal change would become a bit more of an overhead. Asteroids works well to the extent it does thanks to original being 1024 wide which divides down evenly to the 256 res that narrow mode gives.

 

Using flicker modes - multiple problems, 1> these emulated games don't run at 50/60 FPS to begin with thanks to the already fairly large overhead of translating graphics renders, 2> in a mixed E/F situation you're effectively needing to draw 2 lines instead of 1. That alone amounts to a slowdown of nearly 50%

 

Possibly some compromise. Maybe a single screen interleaved mode with E/F and the line draw could be altered to either do point at single colour or multicolour depending if it's an even or odd scanline. Still some slowdown but not near as much as drawing twice.

 

The other thing - out of the question to do any CPU dependant graphics modes, too much slowdown.

 

As well, using an interleaved E/F without CPU tricks, we don't get very much of a colour boost. PF2 would need to be left as Black/background which only leaves PF0 / PF1 for colour enhancement.

So effectively we get 2 "enhanced" colours with the 3rd one being lines with blank pixels.

[kiwilove]

Although I think this is beyond the capabilities of the Atari 5200 (and 400/800 etc computers) - I do wonder about a Wobble 3D game, whether it could be possible?

If you look at the various Wobble 3d photos and graphics around - you'll see what I am getting at.

http://s.mlkshk.com/r/E21O

This is Van Gogh's Starry night in this mode...

 

Maybe something done in 8? frames will achieve this effect --- but can you play a game in it?

 

Harvey

[Keatah]

If the machine has the capability to draw 8 frames of the game for each iteration, why not?