Neat sprite trick

[+SpiceWare]

The Care Bears in the prototype are fat, but detailed.

 

In checking out the prototype, Laura Nikolich used 2 copies of P0 with P1 lined up between the copies. While P1 is being displayed, she switches P0 to reflected mode.

 

 LDX #$08
 LDA ($90),y; left/right of Care Bear
LOOP:
 STA WSYNC
 STA GRP0
 LDA ($96),y; Color for center of Care Bear(note the nose on the pink bear and the ears on the yellow bear)
 STA COLUP1
 LDA ($92),y; center of Care Bear
 STA GRP1
 JMP ($0085) (precalced to jump to one of the following NOPs)
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 NOP
 STX REFP0; P1 is being drawn, so flip P0 for the right side of the bear.
 INY
 LDA ($94),y; color for left/right of Care Bear (not use in the prototype)
 STA COLUP0
 LDA #$00
 STA REFP0; done drawing second P0 so flip back for next scanline
 LDA ($90),y; left/right of Care Bear
 BPL LOOP; if bit 7 of CareBear graphic is on then we're done drawing the bear.

Edited April 11, 2007 by SpiceWare

[+SpiceWare]

Oops - I meant to post this in Atari 2600 Programming, can a moderator move it for me?

[supercat]

In checking out the prototype, Laura Nikolich used 2 copies of P0 with P1 lined up between the copies. While P1 is being displayed, she switches P0 to reflected mode.

 

Strawberry Shortcake probably does the same thing, but with the bonus of writing the color registers as well.

[+SpiceWare]

This one writes all the color registers too - it's only noticeable on the nose of one bear and the ears of the other.

[Cybergoth]

That's pretty cool stuff.

 

Seawolf is doing a variant that is writing three different shapes instead of just reflecting left and right. P0 and P1 share the same color though. It also does the delaying jump outside the kernel, so instead of just NOPing time away it displays the torpedos