ljbk information 20 glöps
- general:
- level: user
- personal:
- intro Atari ST panic by Paulo Simoes [web]
- Regarding Sync's screen in the Sowatt Demo, please note that their wave is a simple ellipse and that the sprites never "touch" each other ...
TCB's wave is also very simple.
Regarding who invented what, i don't know, i just look at the screens result and try to figure out how it is done without looking inside ...
What i can tell you is that this mixer is 100% mine and that it dates from 1991.
Regarding 1990 versus 2005: i just say that the hardware is still the same so are its limits.
As i was suprised to find this here, you can imagine that i am not too worried if people don't like it: i made this screen for my own pleasure and i released it so that i can share with others.
Anyone is free to like it or not, but at least it has to be juged fairly.
Old school or not, i would like so see more Atari ST suff being done, to prove that this platform is not dead.
Bye the way, Keops, i enjoy your demos, especially the Virtual Escape. - isokadded on the 2005-02-19 15:02:35
- intro Atari ST panic by Paulo Simoes [web]
- As the author, i vote against, of course :) .
If you have problems in running this on your ST hardware, try the 1 byte updated version, you can find at Atari-Legend. This is caused by the different ST MMUs that control the top border openning. Both versions work fine on my 1985 ST.
Now some details about this screen.
First of all, this is a technical screen and not a nicely designed demo so it does not surprise me that you don't like the design, the colors, the "old-school" look ...
It was build in response to a challenge from Leonard (read more at Atari-Forum).
But, Keops, as this is piss easy to do, i will expect to see your next total fullscreen, featuring a 3 minute MOD with 8 voices at 15.6KHz with full frequency and volume control with a 1Meg STF (without ripping my code), that will blow up this screen to the garbadge can ... It can be a 4 voices 31.2KHz if you prefer ...
Now for those who don't know:
- the background is achieved by changing 8 colors at every scan line, that allows to move/dist any 8 pixel wide bitmap of any size: this was used a lot by ULM under the name of "playfield technique". It takes a minimum of 80 cycles per scan line + some small control code that leads to 15% of the CPU
- so in fact the background consists of 40 groups of 8 monochrome vertical lines
- any fullscreen needs sync switches at every scan line and forces the remaing code to fit between those sync switches => 9% of the CPU is used for this
- the sprite(s) follow(s) a predefined wave of 4096 positions (80 seconds of movement at 50Hz). There is no trick with the wave, it can be any one. At every frame, one sprite is drawn with mask and one sprite is cleared with mask and background. The sprite is NOT pre-shifted due to the 1MB constraint. This takes about 6% of the CPU
- the 8 voices 15.6 KHz mixer with full frequency and volume control takes the remaining 70% of the CPU
As final words, it is ok that you don't like this screen, as for me the important thing was the pleasure it gave me in building it, but try to do it first before you say it is not that impressive technically ... - sucksadded on the 2005-02-19 12:49:17
account created on the 2005-02-19 10:50:59