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Trekiej 
Bit Plane Technology
Posted on 21-Jul-2018 4:25:18
#1 ]
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Joined: 17-Oct-2006
Posts: 890
From: Unknown

Hello.
Is Bit Plane Technology why the Amiga is good a Parallax Scrolling?
Also, do modern cards use Bit Plane Tech?
Thanks.

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NutsAboutAmiga 
Re: Bit Plane Technology
Posted on 21-Jul-2018 7:18:08
#2 ]
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Joined: 9-Jun-2004
Posts: 12795
From: Norway

@Trekiej

No, it’s the aid of co-processor that good at scrolling graphics, 3D graphics for example is lot better at Parallax Scrolling then 2D Bit Plane Technology ever was, the modern GPU vs the old blitter.

And about dual playfield's, it can easily be done by shifting and OR'ing two pixel maps on top of etch other, the process is pretty simple and if was done on some external logic it be just as efficient maybe even faster.

Last edited by NutsAboutAmiga on 21-Jul-2018 at 08:38 AM.

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kamelito 
Re: Bit Plane Technology
Posted on 21-Jul-2018 7:42:36
#3 ]
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Joined: 26-Jul-2004
Posts: 813
From: Unknown

@NutsAboutAmiga

Scrolling on the Amiga was about moving some bytes, not the all screen so it was more efficient.

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Hypex 
Re: Bit Plane Technology
Posted on 21-Jul-2018 8:19:47
#4 ]
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Joined: 6-May-2007
Posts: 11180
From: Greensborough, Australia

@Trekiej

It was said because of the planar format why the Amiga was good at parallax scrolling. However, I don't think the pixel format really has any bearing on this. Each playfield on the Amiga has it's own scroll offset. The main reason it was good at this was because it supported two separate screen layers super imposed on each other with the sprites.

But, because it was planar, it could fill in blocks on the edge incrementally until they came into view. Such as blitting 16x16 blocks at a time. The blitter was made for transferring images of different sizes onto a full screen bitmap .

Check out the specs of the Sharp X68000 here. It doesn't give enough technical details on pixel format but here it has different planes. Tilemap, bitmap and sprite planes. The bitmap can have one plane with 65536 colours with the full palette or four planes with 16 colours each from the selected palette. This implies the planes are in packed format. Or as we would call them chunky. (Yuck).

http://gaming.wikia.com/wiki/Sharp_X68000

So there is an example of parallax layers using a packmap. A horizontally packed bitmap you could say. Or chunkmap if you like but chunky or packed map isn't really a bitmap as the pixels are stored as whole values. Where as in a bitmap the pixels are split up into different bits per plane.

VGA supported bitplanes but only up to four planes. However it could arrange them differently. Where as the Amiga never was updated to support other pixel formats like packed pixels in a plane.

As to today, a bitmap formatted set of bitplanes wouldn't be in use. But there is pixel plane. Just one with packed pixel data like RGB. That they call a framebuffer.

Last edited by Hypex on 21-Jul-2018 at 08:25 AM.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 8:20:15
#5 ]
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Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@Trekiej

Quote:
Is Bit Plane Technology why the Amiga is good a Parallax Scrolling?

If what you refer to is foreground moving freely over background (like in Lionheart, Impossible Missions 2025, The Misadventures of Flink, Worms, to name a few) and similar effects, yes. Most of the times, the effect is obtained thanks to the Dual Playfield mode (which is based on the bitplanes). A few times, also sprites help (e.g. Jim Power has an additional layer made of sprites).
If you're thinking of depths effects similar to the plains in the background of Lionheart (again), the floor and ceiling in Apache, the floor in Elfmania, the key for that is the Copper.

Last edited by saimo on 21-Jul-2018 at 08:28 AM.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 8:25:47
#6 ]
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Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@Hypex

Quote:
It was said because of the planar format why the Amiga was good at parallax scrolling. However, I don't think the pixel format really has any bearing on this.

Wrong: it's precisely the fact that there are (mostly) indipendent planes that allows full screen parallax scrolling.

Quote:
Each playfield on the Amiga has it's own scroll offset. The main reason it was good at this was because it supported two separate screen layers super imposed on each other with the sprites.

The Dual Playfield mode is possible precisely thanks to the bitplanes, so again it's the fact that the graphics are based on bitplanes that makes parallax scrolling easy.
Also, the Dual Playfield mode is not the only way to obtain parallax scrolling (although definitely the most popular one).

Quote:
But, because it was planar, it could fill in blocks on the edge incrementally until they came into view. Such as blitting 16x16 blocks at a time.

Wrong: the kind of filling that you're talking about is possible thanks to the fact that it's possible to have "movable" rasters bigger than the display. It's here that bitplanes are irrevelant.

Last edited by saimo on 21-Jul-2018 at 08:27 AM.

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Hypex 
Re: Bit Plane Technology
Posted on 21-Jul-2018 8:32:26
#7 ]
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Joined: 6-May-2007
Posts: 11180
From: Greensborough, Australia

@NutsAboutAmiga

That would be because a modern GPU can superimpose a set of full colour images over each other including small objects into a destination framebuffer. In a sense it is blitting all the images onto each other.

However, I still think the Amiga way and others of doing this in the 80's deserves credit, because the hardware could do it in realtime. Even as the raster was being drawn down the screen.

A modern GPU doesn't do it in the same way, it isn't designed to render it all on screen in realtime, so "cheats" by rendering it all in a framebuffer then displaying it when ready.

Just doesn't have the same shine to it.

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NutsAboutAmiga 
Re: Bit Plane Technology
Posted on 21-Jul-2018 9:02:49
#8 ]
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Joined: 9-Jun-2004
Posts: 12795
From: Norway

@Hypex

Games are most not designed, to do thing in real time. Most of time it doubled buffered.
You draw stuff into a buffer you don't see, you swap it with displayed buffer, then clear buffer you where displaying, and draw new image,

The problem was hardware sprites are limited in number and colors, this way end up with blitter objects.

In additions the shared memory system, also has problems on its own CHIP memory being slow when run high resolutions or display colorful images, having to share time between OCS chipset and CPU.

Bitplans was memory saving feature, the Amiga1000 was originally planned as 128kb system, but luckily they managed to get 512kb into the computer.

Last edited by NutsAboutAmiga on 21-Jul-2018 at 09:04 AM.

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RodTerl 
Re: Bit Plane Technology
Posted on 21-Jul-2018 9:22:03
#9 ]
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Joined: 6-Sep-2004
Posts: 589
From: Rossendale

@NutsAboutAmiga


I beleive Ive seen an article on entropy content of images, how far you can compress the data, and they looked at what seems to be the equivalent of chunky planar, that is, each colour channel is represented by as many bit planes as there is bits of colour accuracy per channel.

8 bit planes per each R, G, B colour channel, then tested a range of compression algorithms, or entropy functions, per bit plane.

The Most Significant bitplane of each colour had lowest entropy, so could be compressed most.

The Least Significant bitplanes entropy was such that the values of the pixels were effectively perfectly random, as in, you couldnt compress the data, but I cant remember if they then checked for randomness as they seemed to say;

After bitplane 6 or 7, the data is effectively random.

Ths implies if true, that the difference between standard 8 bits per channel HD TV plus etc, and HDR10, 10+, 12 etc in bitplanes, is that the extra so called resolution is uncompressible noise, and should be thrown away and recreated at destination by a random number generator.

I was suprised as Ive run a couple very crude and basic experiements in data complexity and the onset is a lot earlier than I was expecting. Given the highest resolution image sensor currently available is 26 bits per channel.

things to try. Take bitplane images, and run through neuralnet.library from Aminet and see how long it takes to learn to analyze DPaint images, using polar coordinate transformation and HSV colour space.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 10:10:10
#10 ]
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Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@NutsAboutAmiga

Quote:
No, it’s the aid of co-processor that good at scrolling graphics,

Wrong (explanation in the previous posts).

Quote:
And about dual playfield's, it can easily be done by shifting and OR'ing two pixel maps on top of etch other, the process is pretty simple and if was done on some external logic it be just as efficient maybe even faster.

Not on classic Amigas: they simply don't have the bandwidth and CPU power to do that at non-crawling frame rates. The way the Amiga generates the display is elegant and efficient, and that's exactly what allows the smooth parallax effects the OP asks about.

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NutsAboutAmiga 
Re: Bit Plane Technology
Posted on 21-Jul-2018 11:32:23
#11 ]
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Joined: 9-Jun-2004
Posts: 12795
From: Norway

@RodTerl

Quote:
8 bit planes per each R, G, B colour channel


OCS has 4 bits per etch R, G, B, (just a nibble), even color table was compressed.
We all know HAM is 4096 colors, but palette is also limited 4096 colors.
Quote:
The Most Significant bitplane of each colour had lowest entropy, so could be compressed most.


One bit, 2 colors, there is no memory loss, but lets say wont 6 planes = 64 colors.

It's like having 6 shift registers.
You latch in 6 bytes from 6 different planes (or memory locations).
You take MSB bit from etch shift registers, but this into color index, you address look up palette table,
you calculate lamination, and modulation frequency, for TV modular.

BytesPerRow 320 pixels, bytesPerPlane 40 bytes * 6 planes = 240 bytes.
If you have 8 bits, you have 320 pixels, 320 bytes.

More colors you need, the slower planar gets, in the end you need the same amount of bytes.

If Dual Playfields you have to share planes.

So don't get 6+6, but you can get 1+5 (2 colors, 32 colors),2+4 (4 colors, 16 colors),3+3 (8 colors, 8 colors)

So you not really getting more colors, the process is bit complicated.

if was going to do Dual Playfields, need two image 320x2=640 bytes per row, so need twice as fast RAM for similar result.


Last edited by NutsAboutAmiga on 21-Jul-2018 at 11:39 AM.
Last edited by NutsAboutAmiga on 21-Jul-2018 at 11:32 AM.

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Karlos 
Re: Bit Plane Technology
Posted on 21-Jul-2018 11:36:42
#12 ]
Elite Member
Joined: 24-Aug-2003
Posts: 4394
From: As-sassin-aaate! As-sassin-aaate! Ooh! We forgot the ammunition!

@Trekiej

Bit planes were more about making more efficient use of available memory. For example, you can create an 8 colour screen using exactly 3 bits per pixel, whereas this is almost impossible to do using other techniques that pack pixels together in bytes. The latter works well for 2,4,16 and 256 colour modes but any other power of 2 is going to be problematic at best. For example, a packed 32 colour screen could use 16 bit words to encode 3 successive pixels but you waste one bit. Similarly you could pack 5 64 colour pixels in a 32-bit word and lose 2 bits for every 5.

The idea that bitplanes are easier to scroll probably comes from the observation that you can scroll bitfields just by shifting or rotating. However, that's not really how scrolling worked anyway as each plane had an offset that you could just update.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 11:53:05
#13 ]
Elite Member
Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@NutsAboutAmiga

Quote:
If Dual Playfields you have to share planes.

So don't get 6+6, but you can get 1+5 (2 colors, 32 colors),2+4 (4 colors, 16 colors),3+3 (8 colors, 8 colors)

Wrong: the 1+5 and 2+4 combinations are not possible in Dual Playfield mode. The Dual Playfield mode simply puts together the odd bitplanes and the even bitplanes, and since bitplanes can be enabled incrementally only, the possible combinations are:
1+1
2+1
2+2
3+2
3+3
4+3 (AGA only)
4+4 (AGA only)

That said, Dual Playfield mode is not mandatory, so one is free to use bitplanes at will (the only restriction being the horizontal scroll offset, which can only be specified for odd/even groups of bitplanes).

Quote:
if was going to do Dual Playfields, need two image 320x2=640 bytes per row, so need twice as fast RAM for similar result.

Last edited by saimo on 21-Jul-2018 at 12:23 PM.
Last edited by saimo on 21-Jul-2018 at 12:00 PM.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 11:58:03
#14 ]
Elite Member
Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@Karlos

Quote:
The idea that bitplanes are easier to scroll probably comes from the observation that you can scroll bitfields just by shifting or rotating. However, that's not really how scrolling worked anyway as each plane had an offset that you could just update.

Just for precision's sake:
* the concept that the OP is about is parallax scrolling, not just scrolling - and bitplanes are definitely what makes it so effortless on the Amiga;
* the bitplanes don't have an offset, but have: a freely-defineable address in CHIP RAM (one for each bitplane) and an horizontal scroll offset (one for the odd bitplanes and one for the even bitplanes).

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ppcamiga1 
Re: Bit Plane Technology
Posted on 21-Jul-2018 12:27:51
#15 ]
Cult Member
Joined: 23-Aug-2015
Posts: 762
From: Unknown

There is nothing special in amiga bitplanes.
Before year 1990 bitplanes were used everywhere - on pc/mac/atari and amiga.
Bitplanes just help saving RAM.

Hardware scrolling may be done using chunky pixels, and it will work as good as on bitplanes.
It works that way on c64.

Hardware scrolling was not added to chunky pixel modes on VGA/SVGA because after 1992 nobody need it.

Last edited by ppcamiga1 on 21-Jul-2018 at 12:28 PM.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 12:42:10
#16 ]
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Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@ppcamiga1

Quote:
Bitplanes just help saving RAM.

Wrong: on the Amiga, they also allow to obtain full screen parallax scrolling at full frame rate and almost without CPU intervetion, plus other effects (e.g. masking, transparencies, lighting effects).


@all

I'm writing this just for the benefit of the Trekiej, who asked two very simple questions, and, in return, obtained answers to different questions (that he didn't ask) and incorrect information.

In particular, his first question is:

Quote:
Is Bit Plane Technology why the Amiga is good a Parallax Scrolling?

He just asked if it's thanks to the bitplanes that Amiga is good at parallax scrolling (and the correct answer is "yes").
He did not ask:
* is the purpose of bitplanes (or, if you want, have been bitplanes created to obtain) parallax scrolling?
* are bitplanes necessary to obtain parallax scrolling in general?

Of course anybody is free to add more information and explore other aspects, but first and foremost it is important to answer correctly and clearly the questions actually asked.

Last edited by saimo on 21-Jul-2018 at 12:46 PM.

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ppcamiga1 
Re: Bit Plane Technology
Posted on 21-Jul-2018 13:20:20
#17 ]
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Joined: 23-Aug-2015
Posts: 762
From: Unknown

@saimo

c64 has chunky pixels and hardware scrolling also work.

Hardware scrolling was not added to chunky pixel modes on pc, because in 1990+ nobody need this crap.

Bitplanes are nothing special, everyone use bitplanes before 1990.

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saimo 
Re: Bit Plane Technology
Posted on 21-Jul-2018 13:34:53
#18 ]
Elite Member
Joined: 11-Mar-2003
Posts: 2450
From: Unknown

@ppcamiga1

Quote:
c64 has chunky pixels and hardware scrolling also work.

1. The C64 does not have chunky pixels.
2. The fact the C64 (or any other machine) has hardware scrolling is totally unrelated to the question in the OP.

Quote:
Hardware scrolling was not added to chunky pixel modes on pc, because in 1990+ nobody need this crap.

Totally unrelated matter and highly questionable.

Quote:
Bitplanes are nothing special, everyone use bitplanes before 1990.

Nobody said bitplanes are special. The OP simply asks "Is Bit Plane Technology why the Amiga is good a Parallax Scrolling?" and the answer is "yes".

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Trekiej 
Re: Bit Plane Technology
Posted on 21-Jul-2018 13:43:52
#19 ]
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Joined: 17-Oct-2006
Posts: 890
From: Unknown

@thread
Thanks.
I studied bitplanes a while back and saw how they could save memory.

Does the A1000 have an 8 or 16 bit data bus?

Does the shift registers rotate or end up being all zeros when done?
A barrel shifter sounds like a good idea.

There was video card that plugged in to video output that was chunky.
How did that work?
I think it made by Newtek.

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Trekiej 
Re: Bit Plane Technology
Posted on 21-Jul-2018 13:52:12
#20 ]
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Joined: 17-Oct-2006
Posts: 890
From: Unknown

@Trekiej

Also, is it possible to send data through the RGB port during blanking interval?

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