Sprites Multiplexing problem

[sandruzzo]

I'm trying a classic Multiplexing sprites, by changing pointers into copperlist, but I'm getting some dirty pixel when sprites are displayed. My copperlist:

dc.w $3c01,$fffe ; copper wait
dc.w $0128,$0000 ; sprites pointers
dc.w $012a,$0000
dc.w $012c,$0000
dc.w $012e,$0000
dc.w $0150,$0000 ; sprxpos - sprxctlr
dc.w $0152,$0000
dc.w $0158,$0000
dc.w $015a,$0000

dc.w $4c01,$fffe ; copper wait
dc.w $0128,$0000 ; sprites pointers
dc.w $012a,$0000
dc.w $012c,$0000
dc.w $012e,$0000
dc.w $0150,$0000 ; sprxpos - sprxctlr
dc.w $0152,$0000
dc.w $0158,$0000
dc.w $015a,$0000

Do you have ever seen this problem?

[roondar]

My first guess is that it looks like the Sprites are either also displaying the Sprite control words (meaning, the Sprite control words are not just set by you in the Copperlist, they're also part of the Sprite data you're pointing too) or the Sprite pointers are off by one line each. If this either turns out to be the problem, both should be fixable. The first by removing the control words from the Sprite data, the second by increasing the pointer values by 4.

[sandruzzo]

@roondar

If I get rid of the first wait, all will be fine. Strange... I'll try to get rid of control word from sprites' pointers

[sandruzzo]

By getting rid of controls' words it works. Strange, since without coppers' waits all its ok. Learning never end!

[roondar]

Originally Posted by sandruzzo

By getting rid of controls' words it works. Strange, since without coppers' waits all its ok. Learning never end!

If you get rid of the Copper waits, the Sprite DMA will read the Sprite Control words itself. Basically, when multiplexing, you either need to set the Sprite Control words manually (usually using the Copper) and not have them in the Sprite data or have them in the Sprite data and not set them manually.

Combining both will lead to problems, as setting the control words manually using the Copper means the Sprite hardware will interpret the data it reads from memory as image data instead of control words.

[Photon]

Amiga sprite behavior is special. I wrote an article to detail exactly how to treat them. It's the results of many hours of testing and should explain completely how to program sprites in both modes and what to expect.