hardware textmode 40x40 example

[Heaven/TQA]

as fox & jaskier described this new mode i wrote this little demo... it displays the main-screen of the new theta music composer 2.0 written by jaskier at the moment. i ripped the text 40x40 mode parts out of the published source just for myself to test this new mode. i insert random colours to see how tricky the timing is. i haven't tested the code on real machine yet but in 800win it runs fine...

 

for educational proposes attachted the source as well...

 

interesting that after more than 20 years nobody used this technique and (again) the guys from taquart made it possible... esp. fox & jaskier.

40x40.zip

[Schmutzpuppe]

Cool thing, you can put a lot of information on screen using this mode (and it is still readable)

[pps]

Looks not bad... But where is the trick?

 

There are no upper and lower borders. What´s else to do?

I can´t see it yet.

 

Have to look into the source tomorrow...

 

btw I countet "only" 39 lines :-)

[Heaven/TQA]

the trick is to cut scanlines with vscrol register so a charline is just 6 instead of 8 scanlines... please have in mind that this is not highres mode it's pure graphics 0...

 

haven't count lines on my own but 240 scanlines divided through 8x6 font = 40 lines...

 

still do not know what else can be done with this method...

[classics]

Very nice!

 

On my NTSC TV the top 2 lines and the bottom line are off the screen.

 

How do you handle the lower 2 lines of each GR.0 drawing if you change the font after 6 lines?

[Heaven/TQA]

jaskier is the expert. but how i understood is that with some clever DLI you can fool antic to fetch the new data of the next char line with triggering vscrol register. and with altering 2 fonts you can compensate the missing of the 2 scanlines...

 

more info here

 

http://www.s-direktnet.de/homepages/k_nadj...dj/mode9++.html and

here http://www.atariage.com/forums/viewtopic.p...=43159&start=25

 

on NTSC you have to leave out some lines... if you check the source code than you'll see how simple this mode is (but clever... )

[classics]

Ok I will look at the sources.. It seemed like there was too little source there for such a neat trick but I see now what you are talking about.

[Jaskier]

haven't count lines on my own but 240 scanlines divided through 8x6 font = 40 lines...

Heaven: remember that you cannot draw full 240 lines. The screen is 240 lines high but if you put something on the 240'th line (anything except empty scan line) you get synchronization error (strange flickering of screen etc.). So I have choosen to draw only 39 text lines.

 

classics: in another topic (about RMT if I remember correctly) I've explained everything (I think) about 8x6 text mode. And one more think: You said that on NTSC you see all except 2 top and 1 bottom line. Is it means that you can still use TMC on NTSC machine?

[Cybernoid]

The 40x40 example is very interesting. I wonder what this method would look like applying it to Antic modes 4 and 5. This could be used for character mapped background graphics for a game, for example. You sacrifice 2 lines per character, but you can fit more on the screen.

 

Also, is this really more than 40 characters wide, since you are using wide playfield?

[Heaven/TQA]

cyber, i dont see why it should not work with antic 4... just exchange the dlist in the source from antic 2 into antic 4... and as these modes are similar (from antic point of view) i dont see any problem but i have to admit that i havent checked it yet...

 

regarding overscan i am not sure as the timing seems to be critical for the vrscol setting on a rasterline... but can easily checked with the supplied source code as well...just set antic into "cinemascope"

[Irgendwer]

cyber, i dont see why it should not work with antic 4... just exchange the dlist in the source from antic 2 into antic 4... and as these modes are similar (from antic point of view) i dont see any problem but i have to admit that i havent checked it yet...

 

Does anybody have checked this until now? If this would work, then the Atari is also able to put out

pictures with a more flexible 5th colour handling!

(When using the inverse mode you automatically colour an 8 times high block - with this trick you could toggle

in every line the inverse mode!)

Sounds to me as this would be a great G2F enhancement.

 

CU

Irgendwer

[Rybags]

You should be able to do it in Mode 4 just fine.

 

I'm using a slightly different technique to get 1 pixel high Mode 4 lines - only problem is the RAM usage goes up quite a bit.

 

For G2F type pics - sure it would be a good enhancement, although I don't know if it supports it. Also, you get a bit less time to do colour changes - and there's a pretty tight window where you have to plug the VSCROL value in.

 

Also, if you went for 4 pixel high chrs in a G2F type situation, you could do so without using too much extra RAM. You need the character cells, so that would double - say from 960 to 1920 if going from a 40x24 8 pixel to 40x48 4 pixel situation.

 

But, you can use the CHACT register to give upside down characters - so you could have each alternate row of characters using the top and bottom half of the character set.

[Heaven/TQA]

Tebe is the G2F master.