Graphics Modes 9 and 11 question

[TGB1718]

If I open a screen in graphics mode 11 and after plotting/drawing and switch to graphics mode 9 by changing GPRIOR

high 3 bits it doesn't look quite right, if I do it the other way start in graphic mode 9 and switch to 11 again doesn't

look right (see screen shots) I know I'm setting the bits right as if I switch back to the original mode everything

is fine. Am I missing something or is this switch not possible (in theory it should be)

 

OK

NOT OK

 

OK

 

NOT OK

 

[phaeron]

This is due to the different default for the background color in GR.11. Most modes use $00 for COLBK, but GR.11 uses $06, because in that mode the background luma value is used to set playfield luma for non-zero pixels. However, $06 is bad for GR.9 because in that mode the background luma gets ORed into all of the pixels, which screws up the grayscale ramp if non-zero. Thus, if you're changing GPRIOR manually without reopening the screen you need to change COLOR4 to match the new mode.

 

[TGB1718]

Thanks @phaeron I was thinking it had something to do with COLBK but couldn't find the info I was looking for, I'll see if

I can "tweak" the code a bit to correct for the difference

[thorfdbg]

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

[TGB1718]

Fix was easy thanks to @phaeron , I was already using a custom display list and screen memory, so the

switch routine just closes the screen, re-opens in the "other" mode, then I just reset the variables pointing

to my DL and screen, as it was not cleared, it's all still there and looking good.

 

Thanks again

[+Stephen]

2 hours ago, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

I don't recall much notable content using GTIA mode 11.  Most of the GTIA modes were underused, but it's tough to do things in that quad pixel mode.

[ivop]

Also note that in graphics 10 the background color is not $02C8/$D01A, but $02C0/$D012.

 

Edited February 4, 2022 by ivop
fix

[+MrFish]

I really wish Atari had gone with Antic D sized pixels for the GTIA modes -- instead of the weird flat and wide pixels. It would have been so much more useful. Same number of pixels/bytes...

 

[phaeron]

1 hour ago, MrFish said:

I really wish Atari had gone with Antic D sized pixels for the GTIA modes -- instead of the weird flat and wide pixels. It would have been so much more useful. Same number of pixels/bytes...

 

There's not enough bandwidth in the AN0-2 bus between ANTIC and GTIA, which can only send 3 bits per color clock. Line buffering and duplication is done by ANTIC, but the decoded data is still sent in full to GTIA for each scanline.

 

[FifthPlayer]

6 hours ago, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

I believe the EA game "Murder on the Zinderneuf" uses this mode to draw the playfield, a vertically-scrolling floorplan of the interior of the airship.

[+MrFish]

1 hour ago, phaeron said:

There's not enough bandwidth in the AN0-2 bus between ANTIC and GTIA, which can only send 3 bits per color clock. Line buffering and duplication is done by ANTIC, but the decoded data is still sent in full to GTIA for each scanline.

I figured there might be some technical reason for it. I guess nobody would deliberately use pixels like those. So, it's more down to squeezing everything possible out of the design limitations, for which I'm grateful. The modes have their uses, just less so because of the pixel dimensions.

 

[+MrFish]

11 minutes ago, FifthPlayer said:

I believe the EA game "Murder on the Zinderneuf" uses this mode to draw the playfield, a vertically-scrolling floorplan of the interior of the airship.

And quite dull-looking as a result.

 

[Rybags]

Fairly sure I've seen a few games use the colour only mode - but for small region background patterns that don't really participate in the gameplay.

 

[Heaven/TQA]

15 hours ago, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

Predator like visuals. Toyed with it in my Voxel engine.

[Rybags]

Not forgetting the colour only mode is also a vital part of APAC and similar interleaved modes though generally not so much use in games but plenty in still pics and demos.

[zzip]

17 hours ago, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

Murder on the Zinderneuf?  Or is that Graphics 10?

Graphics 11 is kind of useless though,  unless you interpolate it with another mode, or rapidly flip screens with a different mode to give the impression of high color.

 

One issue if it you have a monochrome screen, you cannot see a difference between the colors in Gr 11.

[thorfdbg]

17 hours ago, phaeron said:

 

There's not enough bandwidth in the AN0-2 bus between ANTIC and GTIA, which can only send 3 bits per color clock. Line buffering and duplication is done by ANTIC, but the decoded data is still sent in full to GTIA for each scanline.

 

While certainly highly hypothetical, GTIA could have had a line buffer of 64 bytes, and store there every other line, allowing square pixels. Of course, this would require a much different and much more complicated design of GTIA. Instead, GTIA was a rather small patch-up job of CTIA.

[Rybags]

An extra bit on the AN bus would probably have been sufficient.  Then get rid of some of the superfluous Antic modes and add some with higher bit width.

e.g. 16 colours in 160 pixel width - it would have about the same DMA pattern as the first mode line of hires text modes except on every scanline.

Then the extra likely addition for GTIA would be more colour registers.

 

Or at the least they could have enhanced Gr. 9 - instead of repeating registers used on the higher pixel values, a half brightness mode on pixel values >=8 could have been done.

[+Adam+]

On 2/3/2022 at 10:04 PM, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable?

"Murder on the Zinderneuf" (1983) was already mentioned.

 

One of "AtariBlast!" levels uses that mode:

 

 

I created the title logo in "Assembloids XE" game in GR.11:

 

[Irgendwer]

On 2/3/2022 at 10:04 PM, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable?

Ultra Tetris

[emkay]

On 2/3/2022 at 10:04 PM, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable? The 16 luma value modes is handy for creating smooth shades, and the 9 colors mode is also quite handy - see Koronis Rift.

Some features still miss their very usage. 

Imagine some game , like Final Assault, using Gr. 11 for some "infrared" view...

 

 

[+MrFish]

On 2/8/2022 at 1:57 PM, Irgendwer said:

Ultra Tetris

The mode usually looks better when a higher luminance -- like this -- is used.

 

[pps]

On 2/3/2022 at 10:04 PM, thorfdbg said:

Has the 16 hue mode (graphics 11) actually been used for anything valuable?

I made some intros with scroller that has mode 11 as background. Latest one is this: >>colored fx<<

[+Philsan]

 

[Rybags]

Maybe it should have been called "Gunfight at the Old Koronis Corral"