BOSS-X Half clock colour changes

[flashjazzcat]

I've been tinkering with Boss-X and I'm wondering how on earth the half colour clock foreground colour change is accomplished when mousing over an icon on the desktop. I'm assuming the colour is achieved with a sprite overlay (?), but there are shapes with diagonal borders drawn in hi-res mode, apparently filled with colour, and surely a sprite can't be less than a full colour clock wide. I don't play games so presumably I've missed out on some marvellous programming technique? Can anyone explain to me how it's done?

Edited February 23, 2009 by flashjazzcat

[Mathy]

Hello Flashjazzcat

 

Try contacting atarixle, he wrote BOSS-X and sometimes visits AtariAge. Maybe if you send him a private message, he'll respond sooner. Including the word "BOSS-X" in the title of this thread might work too.

 

greetings

 

Mathy

 

PS you can also do a search for BOSS-X or atarixle via Google. IIRC Mirko has his own site.

[flashjazzcat]

Try contacting atarixle, he wrote BOSS-X and sometimes visits AtariAge. Maybe if you send him a private message, he'll respond sooner. Including the word "BOSS-X" in the title of this thread might work too.

 

...

 

PS you can also do a search for BOSS-X or atarixle via Google. IIRC Mirko has his own site.

Thanks, I'll do that. I assumed the technique wasn't specific to BOSS-X, but if it is, I'll try and get the info from the horse's mouth so to speak.

[Irgendwer]

I don't play games so presumably I've missed out on some marvellous programming technique? Can anyone explain to me how it's done?

 

I think it's an 'optical illusion'. There is still a full colour clock but since the luma is lower you cannot recognize (very well) the chroma artefact.

Just like the yellow text in the crises image: http://atari.fandal.cz/detail.php?files_id=5223.

 

If you mean something else, please support a screen shot.

 

CU

Irgendwer

[+MrFish]

I've been tinkering with Boss-X and I'm wondering how on earth the half colour clock foreground colour change is accomplished when mousing over an icon on the desktop. I'm assuming the colour is achieved with a sprite overlay (?), but there are shapes with diagonal borders drawn in hi-res mode, apparently filled with colour, and surely a sprite can't be less than a full colour clock wide. I don't play games so presumably I've missed out on some marvellous programming technique? Can anyone explain to me how it's done?

 

In hi-res mode, the overlay will take on the luminosity of the hi-res pixels underneath it. So, a single color-clock pixel overlayed on two half color-clock pixels of different luminosities will appear as two half color-clock pixels of different luminosities with the color value of the overlay.

 

The result can be very effective, especially when the hi-res luminosities have sharply contrasting values (ie: black & white).

 

Image Example:

 

Image Example Zoomed:

 

You can see that the overlay is hard to detect in the region where it lies over the black background. This is because the overlay color is displayed here at it's lowest luminosity, which causes it to blend in the with the black background surrounding it. Therefore it appears as if your overlay has half color-clock resolution.

Edited February 24, 2009 by MrFish

[flashjazzcat]

I think it's an 'optical illusion'. There is still a full colour clock but since the luma is lower you cannot recognize (very well) the chroma artefact.

 

In hi-res mode, the overlay will take on the luminosity of the hi-res pixels underneath it. So, a single color-clock pixel overlayed on two half color-clock pixels of different luminosities will appear as two half color-clock pixels of different luminosities with the color value of the overlay.

 

The result can be very effective, especially when the hi-res luminosities have sharply contrasting values (ie: black & white).

 

...

 

You can see that the overlay is hard to detect in the region where it lies over the black background. This is because the overlay color is displayed here at it's lowest luminosity, which causes it to blend in the with the black background surrounding it. Therefore it appears as if your overlay has half color-clock resolution.

That's exactly what it is. I should have done a screenshot and blown it up in the first place. I couldn't see how the stepping of the sprite and the hi-res pixels would line up, but sure enough, they do:

 

 

Only on very close inspection can you detect the different colours in the low luminosity areas. This example relies on the icon's black border. It still looks very cool, though. Mystery solved; thank you!

Edited February 24, 2009 by flashjazzcat