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Creating two colored players

colors graphics 2600

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#1 raross1980 OFFLINE  

raross1980

    Combat Commando

  • 7 posts

Posted Sat Aug 18, 2018 8:07 PM

How would I to make any character in any A2600 game a two colored character? Like Pac-Man being orange and black, and the Mrs. Red and blue. 

 

What code do I need to alter to accomplish this?  Is it the same way in other games as well?



#2 Nukey Shay OFFLINE  

Nukey Shay

    Sheik Yerbouti

  • 21,857 posts
  • Location:The land of Gorch

Posted Sun Aug 19, 2018 2:36 AM

There are a few ways...combining a sprite with one of the other objects (player, missile, or ball), altering the color of the player on each scanline, or flickering the color & sprite shape to be different on alternate frames.

 

Due to kernel timing (or lack of), the last one is probably the easiest to accomplish as you don't need to change the display kernel at all...just checking if the frame counter is odd or even and then adjusting the sprite pointer and color accordingly before the display is even rendered.  Of course, you'd still need to free some romspace to hold the the alternate sprite shapes and color.  So the word "easiest" is still highly dependant on how familiar you are with working on disassembled games.

 

On that note, there is one way which only requires 3 bytes of spare romspace.  Works best for any non-bankswitched 2k or 4k game which does not already flicker the sprite.  It involves doubling the rom to be two copies pasted back-to-back.  At some point of the program which is executed on every frame, hack in a JMP (for 2k games doubled to 4k), or bankswitch hotspot trigger (for 4k games doubled to 8k) to point to the other copy, and visa-versa for the code in the alternate copy.  During execution, the game will be rapidly switching between the two copies on alternate frames...so any of the sprite shapes or colors (and even playfield data) can differ between the two copies.







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