displaying multiplexed sprites using the copper

[jotd]

I'm trying to do a dynamic star field using copper and 1 multiplexed sprite (with WAIT statements)

ATM I'm not even able to display ONE sprite

Part of copperlist:

 0000048c: 01ba 0f00            ;  COLOR29 := 0x0f00
 00000490: 01bc 00f0            ;  COLOR30 := 0x00f0
 00000494: 01be 0f00            ;  COLOR31 := 0x0f00
 00000498: 0178 9072            ;  SPR7POS := 0x9072
 0000049c: 017a a000            ;  SPR7CTL := 0xa000
 000004a0: 017c f0f0            ;  SPR7DATA := 0xf0f0
 000004a4: 017e 0ff0            ;  SPR7DATB := 0x0ff0

setting bright colors for last color registers, using sprite 7, setting at X=100, Y=100 (computer pos/ctl set in registers) then random pattern (dots in line) in data/datb.

And nothing is displayed except sprite artefacts after a while.

Can someone help? (sprite dma is on, and I'm familiar with the SPRPT way of displaying a sprite in the copperlist, but that doesn't multiplex)

[ross]

Hi jotd, you mean that on the same line you also have a sprite where the data for DATA and B are fetched by the DMA and displayed in a x-position early than 100?

Then you have to make sure that the wait with the copper is in a later position in order to re-fill the sprite registers in an appropriate time.

Otherwise you risk not displaying anything or wrong parts.

[a/b]

If this is like an old skool effect where you have stars moving horizontally, then you only set the sprite pointer and colors, and the rest is done by sprite dma while you manually (cpu) adjust sprite positions in multiplexed sprite data (each part is 1 line tall): pos/ctrl, 1 line data, pos/ctrl, 1 line data, ... pos/ctrl, 1 line data, 0, 0.
Or if you go manual mode, you only load data once (each star is the same?) and then multiplex pos/ctrl with copper while sprite dma is *off* (you mentioned you have it on).
If I correctly understand what you are trying to achieve...

[jotd]

while sprite dma is *off*

that's the important part that I was doing wrong Yes, I want to do a stars effect. Not moving, just blinking. ATM I'm just trying to do a static stars effect. One dot, varying color, varying x and y

Now sprite dma is off (DMACON 03C0) but still nothing displayed

 00000490: 017c f0f0            ;  SPR7DATA := 0xf0f0
 00000494: 017e 0ff0            ;  SPR7DATB := 0x0ff0
 00000498: 01ba 0f00            ;  COLOR29 := 0x0f00
 0000049c: 01bc 00f0            ;  COLOR30 := 0x00f0

 000004a0: 01be 0f00            ;  COLOR31 := 0x0f00
 000004a4: 0178 9072            ;  SPR7POS := 0x9072
 000004a8: 017a a000            ;  SPR7CTL := 0xa000

[a/b]

Do you have any bitplanes enabled? Sprites won't show unless you have at least one, or write to bplXdat in each rasterline to enable them.

[ross]

Problem here is that SPR7CTL disarm the sprite.
Reverse the write and make SPR7DATA as the last in line.
(plus what a/b said)

[jotd]

yeah, getting better now I have colored bars because sprite data should be zeroed the line after probably. thanks a lot!

[ross]

Originally Posted by jotd

..I have colored bars because sprite data should be zeroed..

Yep, zero it, disarm it or ..multiplex it as you like
(if you don't do it, every time the x position is reached on each line the sprite is re-displayed, hence the bar; Denise know nothing about the y position and so repeats the DATA/B over and over)

[jotd]

by trial and error I will reach the required effect now. got a nive colored ladder already