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-   -   Different resolutions on the same screen (http://eab.abime.net/showthread.php?t=75157)

whitebird 19 September 2014 18:16

Different resolutions on the same screen
 
Hello,

It is often said in technical articles that the Amiga can display different resolutions on the same screen.

What does it really mean?

First half of the screen can be of one resolution and second half of another resolution?

tero 19 September 2014 19:53

On Amiga you can have, for example, Hires/Interlaced Workbench and a Paint programm on a lowres screen, and then drag the screen as shown in this Video:
http://www.youtube.com/watch?feature...&v=ka0HwsfNURw

The Vid is from Aros, but it's similar to Amiga. But works only with native OCS/ECS/AGA screens.

EDIT:Found a better Video on real amiga, the boing ball demo:
http://www.youtube.com/watch?v=qwFbWkr71wA

modern_hermit 19 September 2014 21:00

And this is possible because Amiga can wait for a specified by the programmer electronic beam vertical and horizontal position and then start feeding the monitor with data in a different way .
By the way , has some experienced Amiga assembler programmer tried a crazy idea to display an interlaced screen in the middle of a low resolution one ? I mean an interlaced picture surrounded in all four directions by a low resolution one .

whitebird 19 September 2014 23:29

One thing that would never be emulated by winuae as it relies on the Amiga video controller...

modern_hermit, your idea should be possible only if the resolution boundaries can be setup on a per-pixel basis.

tero 20 September 2014 00:09

Quote:

Originally Posted by whitebird (Post 976688)
One thing that would never be emulated by winuae as it relies on the Amiga video controller...

It does work in winuae.

whitebird 20 September 2014 00:42

OK, don't know exactly how it works but I suppose it's something like the pixels beeing larger on the low resolution portions of the screen (software duplication), but the native resolution is the same everywhere on the screen. On the Amiga it is really a different resolution as the pixel clock may be changed on the fly even at the middle of a screen.

Under Winuae, it's same as zooming a picture, it seems like the resolution gets lower and lower but the native resolution is unchanged.

Z3k 20 September 2014 11:15

This ancient inro from Quartex shows the "magic" quite well. In the upper side you see a bouncing bar over the lo-res logo that reveal the hi-res version of the same.
You better download it and watch in Uae.

Toni Wilen 20 September 2014 11:33

It is impossible to have interlace and non-lace at the same time, PAL/NTSC display technology won't allow it. Scanline vertical position selection (odd or even) selection is simply done by checking timing of vertical blank pulse.

Mrs Beanbag 21 September 2014 02:51

lowres and hires on same scanline should be possible though, right? but i don't think i've ever seen it done

Vot 21 September 2014 06:06

Doesn't disposable hero do mixed resolutions in the menu / title screen

Jope 21 September 2014 08:25

The resolutions you'd expect are there when you mix interlace and non-interlace, but the entire signal will be interlaced if an interlaced screen is visible, then flips to progressive if only noninterlaced screens are visible.

Get some monitor that doesn't deinterlace the signal, open some intuition screens and try dragging them around.

Toni Wilen 21 September 2014 10:18

Quote:

Originally Posted by Vot (Post 976906)
Doesn't disposable hero do mixed resolutions in the menu / title screen

Quote:

Originally Posted by Mrs Beanbag (Post 976889)
lowres and hires on same scanline should be possible though, right? but i don't think i've ever seen it done

Disposable Hero title screen and demo Innovation 2 (or Innovation part 2) by Axxis are 2 most common programs that mix lores and hires horizontally.

Resolution is simply a pixel clock value ("width" of pixel) and with copper resolution change timing is easy. Tricky part is to not have "borders" around switch point (to hide graphics garbage, Denise and Agnus gets "out of sync" until next complete bitplane "block").


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