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Old 13 January 2020, 18:28   #41
Foebane
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Quote:
Originally Posted by malko View Post
^ I may be wrong, but isn't it what ross has done on the Ziriax - Ultimate Edition's cracktro ?
I saw that cracktro here:
[ Show youtube player ]

And it immediately reminded me of this:
[ Show youtube player ]

Exactly the same principles used, just take 2 or 3 sprites and split them all the way down to move across the screen at random speeds, off the left and reappear on the right. Relatively simple to do on the Atari 8-bit, but REALLY simple on the Amiga with the Copper.

It just goes to show the similarity in the two hardware chipsets.
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Old 13 January 2020, 18:54   #42
ross
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Originally Posted by Foebane View Post
.. but REALLY simple on the Amiga with the Copper.
Copper?
I've not touched it for this effect
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Old 13 January 2020, 20:40   #43
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One positive thing about Amiga sprites is that they are available with HAM.

Still, the limited support means this is hard to take advantage of.

With slightly better sprite support a nice vertical scroller using a HAM background would have looked nice.
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Old 13 January 2020, 21:03   #44
Foebane
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Originally Posted by mc6809e View Post
One positive thing about Amiga sprites is that they are available with HAM.

Still, the limited support means this is hard to take advantage of.

With slightly better sprite support a nice vertical scroller using a HAM background would have looked nice.
I described in my opening post how sprites are used for text scrollers and captions with HAM effects, but yes, games are very impractical with HAM.
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Old 13 January 2020, 21:27   #45
DanScott
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Quote:
Originally Posted by ross View Post
Copper?
I've not touched it for this effect
my first thought too

https://www.pouet.net/prod.php?which=12454
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Old 13 January 2020, 21:48   #46
Steril707
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Neither does the starfield in the Inviyya titlescreen...
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Old 13 January 2020, 22:06   #47
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Originally Posted by DanScott View Post
my first thought too


The damned spaceship uses 4 sprites!
Not resorting to copper usage, in a 256y screen I can use max 256/2*3=384 sprites (I've a light overscan, so lost sprite7).

But probably I've more layers and subpixels usage
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Old 13 January 2020, 22:45   #48
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How do you split up a few sprites as I've shown above without the Copper then? The same principle as the Warhawk game on the Atari?
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Old 13 January 2020, 23:00   #49
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Originally Posted by Foebane View Post
How do you split up a few sprites as I've shown above without the Copper then? The same principle as the Warhawk game on the Atari?
Sprites on Amiga uses sprite_list in memory.
Position on screen is not defined, like on C64, setting custom registers by CPU (well, actually you can also do it).

On Amiga sprites DMA fetches position/dimension/features from this list, then start fetch real data on the same line it need to visualize.
At end, DMA reload position for a new sprite (or NULL if you want to stop it).

From this you can understand that if you display a sprite in a line then reload the position in the next, then display a new sprite in the next line, you can use the same sprite (1 line high) 128 times on a 256 lines screen.

And this not using any copper trick
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Old 13 January 2020, 23:40   #50
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okay, but you have to busy wait with VPOSR with the CPU right?
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Old 13 January 2020, 23:47   #51
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okay, but you have to busy wait with VPOSR with the CPU right?
Not if you double buffer the sprite_list.
Then simply switch with copper at VB time (or double buffer also the copper_list).

Moreover Copper pointers are buffered so you can set it when you want during frame.
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Old 14 January 2020, 01:21   #52
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okay, but you have to busy wait with VPOSR with the CPU right?
The CIAs provide resources for syncing the CPU with the display. That and cycle counting can allow the CPU to write to chip registers at specific times relative to the beam. There is potential with this for using the copper to drive the blitter while the CPU does what the copper normally does.

I really believe that Jay Miner expected Amiga programmers at times to use the CPU in a way like that done with the Atari 2600. The availability of sprites' manual mode further supports this.

Again, the implementation of the sprites was a little flubbed.

If a programmer is really careful, a MOVEM.L might be useful with manual mode.
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Old 14 January 2020, 15:54   #53
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This thread is really interesting to read. When I started reading on Sprites on Amiga, I thought, that they are so clumsy and ineffective that I wonder why one would use them at all, especially when compared with the C64. But now that I read this thread, I revised my opinion and think that they have more potential than I initially thought, when I had just read the docs.
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Old 15 January 2020, 20:19   #54
Photon
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Quote:
Originally Posted by Foebane View Post
Oh, I know, I consider my topic title fully DEBUNKED. Now if only a Moderator would change the topic title accordingly...
All in good spirit. Comparing the whole (games) can give rise to unfounded generalisms, but a technical comparison might reveal the details. It really was the best sprite chip on the market. Sometimes we forget that.

Quote:
Originally Posted by Foebane View Post
No, and Atari sprites could only be stretched out on the X-axis. C64 could do both X- and Y- axes, which makes them even better.
I'm pretty sure nobody would tolerate halfres sprites on Amiga, let alone call them better. Vertical stretching is possible, but with all the RAM in the Amiga you'd rather have them fullres (i.e. just 'tall') to begin with.

Quote:
Originally Posted by roondar View Post
I'd like to point out that this is not fully accurate. The Archimedes does in fact have a single hardware sprite: 32 pixels wide and just like the Amiga of "any height".

Looking at the specs, I'd personally guess the intention of this hardware sprite is to be used as a mouse pointer or similar.
Yes, PC graphics cards at the time had 1 sprite dedicated to a pointer. You explained your reply well, though, so I understand what you mean - my mention of it was to point out that Amiga's main competitors weren't anywhere close, and only a few consoles that came out after Amiga had more sprites, in the time window before the era of mostly 3D games.
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