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Thanks for accepting my challenge and to have kindly updated this demo.
STF digisound is nothing more than the Hextracker driver at work at 10 KHz with 4 voices, full volume and pitch control and 3 YM volume registers for virtual DAC.
Use real HW or SainT to test it as Steem and Hatari currently have problems with the disk drive loading timing on STF and everything gets slower.
To admins, please set the platform to ST and STE. Thanks. |
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added on the 2013-05-24
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This brings back some 21 years old memories !!!
Thanks ! |
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added on the 2013-05-24
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As an Atari ST pioneer, i like demos on Amiga OCS that show some optimzed code AND really take advantage of the available hardware.
Add a nice soundtrack and some cool efects and you get a great demo.
Thanks. |
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added on the 2013-04-11
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For those that might be interested, there is some info here:
http://www.atari-forum.com/viewtopic.php?f=28&t=21123 |
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added on the 2013-01-27
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Hi !
I do not know if it works on STE, because i don't have one, but it works on STeem 3.2 that is an STE emulator as well as on a STF.
Anyway, this screen was built in October 2004 as a challenge that i did to myself to do a fullscreen version of my MOD replay mixer.
On top of that, the program would have to use the biggest scope possible on ST low res (416 pixels wide in fullscreen).
This means that the replay frequency would have to be 416*50 = 20800 Hz.
To be able to do that you need to have 4 updates to the sound chip every 3 lines.
As every VBL you have 313 lines, if you have 4 updates every 3 lines, you get 313*4/3 = 417.333 .
In fact, you have a sound chip update every 384 cycles.
If you mix that with the precise needs to maintain the fullscreen, with 6 sync switches every 512 cycles, may be you will understand the coding mess this represents.
I included this to Sommarhack 2011 just for fun as this screen would have no chance to go anywhere.
There are no appealing effects to keep the viewer interest after 20 seconds, no great graphics, no big design to have a nice multipart changing demo.
Sorry, this is again only a tech screen with some good quality sound for STF and a piece of crazy coding.
This has always been the way i enjoyed the ST: try do build things that would seem impossible at first.
Bye,
Paulo. |
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added on the 2011-07-04
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The Spectrum 512 Scrollshow demo refered above, from 08/02/1989, can now be fetched here in a disk image file:
http://www.atari-forum.com/viewtopic.php?f=28&t=21123 |
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added on the 2011-06-23
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Source code available here:
http://www.atari-forum.com/viewtopic.php?f=68&t=9527&p=188067#p188067 |
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added on the 2011-06-20
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Thanks Leonard !
You can now try a 3D STNICCC 2000 like STF demo but WITH digi-sound ! :) |
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added on the 2011-06-07
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Hi britelite !
The problem is not the emulator.
In fact your code does not set the image refresh rate (50/60Hz).
So if you start your machine in NTSC/60 Hz as Steem does, you will get this small bug.
You can check that on a real ST as well.
This also means that you have plenty of CPU time left and that all screen can run at 60 Hz except that twister. Probably in some cases, when you are updating the frame buffer, your screen base address switch that is probably located at the VBL has already occured and so you are clearing at the wrong address ...
There is also a minor graphic bug on the first girl screen pic: 2 small blue lines at the top.
But don't worry these are details.
Again, congratulations. |
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added on the 2011-06-07
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Nice effects !
A pity we get an sudden end.
Also there is a little bug with the greetings twister: some data that should be erased is not when moving up ... |
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added on the 2011-06-06
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Just forgot to add that that i still have time on the STE code path so you could have 2x176 dots instead of 2x144 dots but there is no physical pixel space without overlapping both stereo scopes or having more than 1 dot sometimes for some of the horizontal pixels and that would not look nice.
I guess sometime you have to leave some unused CPU time ... :) |
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added on the 2011-05-11
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Actually, my first ever demo on the ST is from 08/02/1989 and is a small multipart demo called The Spectrum 512 Scrollshow.
That program is refered by Manikin in Maggie 02 disk while reviewing the Overscan Demos release.
I have never produced a disk image of it as it uses a very special disk format as the original Overscan Demos did and it also uses a costum way to remove the top border and so i am not sure it even works with current emulators.
Who knows, if one day i have time i will do the code updates required to handle 11 512 bytes sectors on the first side instead of 5 times 1024 bytes + one time 512 bytes that is a much safer format. |
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added on the 2011-05-11
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Hi !
This is only a small tech screen to show the possibilities of Hextracker.
Not much free area for graphics but some specific STF / STE graphics could have been included for the scope part.
Now, you can costumize the colors by hacking the .TOS program file:
- at offset $0E70 you can change the Scope beam color;
- at offsets $105A/5E/62/66/6A/6E/72/76/7A/7E/82/86, you can change the 12 individual V.U. colors;
Color format is $0RGB with R, G and B from 0 to 7 for STF and 0 to F for STE.
Enjoy,
Paulo. |
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added on the 2011-05-10
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| Files updated due to bus error during video init on some Atari ST/Fs. |
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added on the 2011-04-28
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Hi !
For those that might be interested, any future possible corrections / updates will be announced / included here:
http://www.atari-forum.com/viewtopic.php?f=28&t=20760
Enjoy,
Paulo |
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added on the 2011-04-14
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This is just for those who still do not know about this demo and MOD player allowing Protracker MOD replay at 50KHz for most of the MODs on a simple Atari STF with 1MB.
The player can be found by not booting the disk.
Enjoy it. |
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added on the 2005-05-01
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Rulez for the time it was done: this product was released by me in 1990:
the 14/05/1990 to be exact as it appears in the scroller. If you don't belive me, check the edition 2 of Maggie. An STE left border updated version was released the 25/07/2004.
In 1990, there was not much like this.
Use real HW, last SainT or last STEem.
If you can't fetch the file, send me a mail:
ljbk@clix.pt or ljbk@oniduo.pt . |
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added on the 2005-04-01
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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. |
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added on the 2005-02-19
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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 ... |
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added on the 2005-02-19
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