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[Atari7800] "Kangaroo" mode???


2 replies to this topic

#1 DEBRO OFFLINE  

DEBRO

    Stargunner

  • 1,862 posts
  • Location:Atlanta, GA

Posted Mon Aug 18, 2003 1:33 PM

In the development documents there is mention of a "Kangaroo" mode. What is this? I've looked at Kangaroo but don't quite understand what they mean. Am I missing something?

#2 jindroush OFFLINE  

jindroush

    Chopper Commander

  • 110 posts
  • Location:Czech Republic

Posted Mon Aug 18, 2003 4:46 PM

It just makes black non-transparent (if I recall that correctly).

I also don't understand what it has to do with Kangaroo game :?

#3 EricBall OFFLINE  

EricBall

    Dragonstomper

  • 711 posts
  • Location:Markham, Ontario, Canada

Posted Tue Aug 19, 2003 9:55 AM

(From the 7800 Software Guide:)

Bit 2 ($04) of CTRL enables "Kangaroo" mode which eliminates transparency, so that any pixel of color "0" will be background color, rather than transparent.

Most games will leave this off since it would result in rectangular sprites.

However, the 7800 Software Guide also mentions Kangaroo mode in relation to the 320 modes. The 320 modes have a quirk where transparency only works if the even/odd pair of 320 pixels are both color "0". Otherwise any pixel of color "0" will be background color, rather than transparent.

Note: Kangaroo and the 320 quirk is not yet implemented correctly in MESS. I have an update to the driver, but I haven't submitted it yet.




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