AMOS banks are a linear block of memory (there are two Exceptions).
In these chunks various kinds of data is stored.
AMOS uses them mostly for packed graphics, sounds, music, AMAL programs, menus, resources and other data.
Generally, there are four main types of banks:
These banks do NOT consist of an linear block of memory. Therefore you
neither can move, copy, encode, pack them nor make a checksum from them.
In addition, icon and sprites banks must always be in Chip ram.
These banks are called permanent, because they survive calls to Default,
Erase Temp and the start of a program.
Moreover, they are saved along with the program. Normally, permanent banks have the name 'Datas'.
Temporary banks only exist during the execution of the program.
They are erased on every start, testing or saving process or using the commands Default or Erase Temp.
Normally, temporary banks have the name 'Work'.
On Amiga computers, chip ram is the area in memory, which is accessed by both custom chips and the CPU.
At the moment, the size of chip ram is limited to 2 MB (even on A1200 and A4000), and old A500 do only have
512 KB chip ram by default.
For that reason your program should not use more than this 512 KB of chip memory. However, this does NOT mean, that
your program needs to run on 512 KB total memory!
As custom chips access the memory at the same time with the processor, the CPU is slowed down, if the program
is held in chip ram.
This effect is even more severe if the screen uses more than 16 colours in lowres or more
than 8 colours in hires (not A1200/A4000).
Chip ram is mainly required for screens, bobs and sprites, music and sound effects, floppy disk drives and copperlists.
Fast ram is the memory area which the custom chips don't have access to. So the processor is not slowed down, if the program runs in fast ram.
BUT: You must not store any data for bitplanes, bobs and sprites, music
or sound effects and then try to access it by the custom chips.
This has very unpleasant if not lethal results in most cases.
All Amigas excluding the A3000/A4000 do not have fast ram mounted by default.
Ranger ram is a special type of ram: it is neither chip nor fast ram and
only exist on an Amiga A500 that has a trap door slot memory expansion.
The custom chips cannot access this ram, although the memory is not faster at all
There's a way to make ranger ram to chip ram. Just resolder jumper 2 on the main board and switch off the memory expansion. I am not responsible for any possible damage that may occur by doing this.
A bytes has got 8 bits, therefore you can display values from 0 up to 255.
A byte normally has got the suffix '.b' (in assembler).
Two bytes together create a Word, four a Longword.
A word consists of two Bytes so that is 16 bits. With
these 16 bits you can store addresses or data up to 64KB (65536).
A word must be on a even memory address or machines with MC68000 CPU will crash with Guru number $80000003.
Since MC68020 this is not important, but you never should assume that there is no MC68000 in the computer and use odd
addresses!
If you insist on using uneven addresses, check out the installed cpu using the Cpu function, if a 68020 or higher is fitted.
Four bytes result in a unit of 64 bits. These units are called longwords
and are used to address up to four gigabyte of data.
For that reason they are used for every absolute address in memory.
As with Words, they must lie on a even address boundary.
If a number reaches the upper boundary, the number is set to the lower boundary value and vice versa.
Example: UB=31 (upper boundary) LB=1 (lower boundary) N=3 (number) Do Inc N If N>UB Then N=LB If N<LB Then N=UB Print N Loop
The new Amigas A1200, A4000 and CD³² have the AGA-Chipset.
This new chipset makes is possible not only to display 6 Bitplanes but even 8
Bitplanes in nearly every resolution.
These Amigas have 12 additional colour bits to the normal 12 bits ($0RGB) and therefore can use a 24 bit value ($00RRGGBB).
Even if AMOS Pro V2.0 does not currently support AGA, nevertheless AMCAF contains some commands for the
future implementation.
The most important advantages of AGA-Amigas:
My advice: If you still have an old Amiga you should think about buying a new Amiga, it's worth it!
As the Amiga can only display 6 or 8 bitplanes and you need much more colours than 64 or 256 colours to achieve photo quality. The Amiga developers invented a new tricky display mode: The HAM Mode (abbreviation for "Hold And Modify").
HAM6 (without AGA chipset):
The first 16 colours can be set as normal, these are displayed on the screen as usual.
The colours 16 to 31 modify the blue part of the last colour to the left.
Same with the colours from 32 to 47, which alter the green value and the colours from 48-63 change the red value accordingly.
So you can display all the 4096 colours using only 6 bitplanes.
HAM8 (AGA chipset required):
Like the HAM6 mode the first colours are displayed correctly, but in HAM8 the base palette has got 64 colours.
The rest of the colours from 64 to 255 are responsible for the modification of the previous colour like shown above.
Using this technique and a intelligent base palette you can display every colour in the 16777216 colours big palette.
A disk object can be:
The Blitter is a co-processor inside the Amiga which is mainly used to copy and combine data
(therefore BLockImageTransferER). Additionally, it can fill polygons and draw lines.
The Blitter is rather fast at this and works with an unbelievable speed of up to 16 million pixels per second.
All data that is accessed by the Blitter chip must be in Chip ram.
AMOS uses the blitter for Bobs, Icons, Screen Copy and many other commands. The MC68020 and higher is much faster if only need to copy data.
The Blitter works at word boundaries and this results in cutting down the X coordinates to the nearest multiple of 16.
To fill a polygon using the Blitter, the lines must be only one pixel thick. This is the reason why there are two different ways to draw lines.
The Blitter chip knows 256 different copying and combining modes. These are determined in two steps:
Bit Minterm Input-Bit
___
0 ABC 000
__
1 ABC 001
_ _
2 ABC 010
_
3 ABC 011
__
4 ABC 100
_
5 ABC 101
_
6 ABC 110
7 ABC 111
Procedure:
These flags contain information about the type of a certain Disk object.
The protection value consists of following bits: Bit 0=0: File can be erased Bit 1=0: File is executable Bit 2=0: File can be overwritten Bit 3=0: File can be read Bit 4=1: File has not been changed after copying Bit 5=1: Executable can be made resident. Bit 6=1: File is an Amiga-DOS script Bit 7=1: File is hidden (does not actually work)
As you see, this is rather chaotic. So you're advised to use the function Object Protection$ to convert this bitmap into a String in the format "hsparwed".
TOME is an extension for AMOS Creator and recently for AMOS Professional too, which is dedicated to tile and map programming. These tiles are used in many games e.g Jump'n'Runs or strategy games.
As the whole game map would be far to memory hungry when kept as standard bitmap, the main
graphics are cut into small pieces, so that they can be used repeatedly.
The map therefore only consists of one byte per position which points to
the corresponding tile.
The current version of TOME is TOME V4.30.
Version: V1.15
Length : 1964 Bytes
Note : Contrary to most other extensions, the database is not
kept in the AMCAF.Lib file. Therefore AMCAF is very compact
(*only* 40 KB!?).
rsreset ;Stars
St_X rs.w 1 ;0
St_Y rs.w 1 ;2
St_DbX rs.w 1 ;4
St_DbY rs.w 1 ;6
St_Sx rs.w 1 ;8
St_Sy rs.w 1 ;10
St_SizeOf rs.b 0 ;12
rsreset ;Splinters
Sp_X rs.w 1 ;0
Sp_Y rs.w 1 ;2
Sp_Pos rs.l 1 ;4
Sp_DbPos rs.l 1 ;8
Sp_Sx rs.w 1 ;12
Sp_Sy rs.w 1 ;14
Sp_Col rs.b 1 ;16
Sp_BkCol rs.b 1 ;17
Sp_DbBkCol rs.b 1 ;18
Sp_First rs.b 1 ;19
Sp_Fuel rs.w 1 ;20
Sp_SizeOf rs.b 0 ;22
rsreset ;Blitterqueue
Bn_Next rs.l 1
Bn_Function rs.l 1
Bn_Stat rs.w 1
Bn_Dummy rs.w 1
Bn_BeamPos rs.w 1
Bn_CleanUp rs.l 1
Bn_B40l rs.l 1 ;BLTCON0&BLTCON1
Bn_B44l rs.l 1 ;Masks
Bn_B48l rs.l 1 ;Source Address C
Bn_B50l rs.w 1
Bn_B52w rs.w 1 ;Source Address A.w
Bn_B54l rs.l 1 ;Target Address D
Bn_B58w rs.w 1 ;BLTSIZE
Bn_B60w rs.w 1 ;Modulo C
Bn_B62l rs.w 1 ;Modulo B&A
Bn_B64w rs.w 1 ;Modulo A
Bn_B66w rs.w 1 ;Modulo D
Bn_B72w rs.w 1 ;BLTBDAT
Bn_B74w rs.w 1 ;BLTADAT
Bn_XPos rs.w 1
Bn_SizeOf rs.b 0
rsreset ;AMCAF Main Datazone
O_TempBuffer rs.b 80
O_FileInfo rs.b 260
O_Blit rs.b Bn_SizeOf
O_BobAdr rs.l 1
O_BobMask rs.l 1
O_BobWidth rs.w 1
O_BobHeight rs.w 1
O_BobX rs.w 1
O_BobY rs.w 1
O_StarBank rs.l 1
O_StarLimits rs.w 4
O_StarOrigin rs.w 2
O_StarGravity rs.w 2
O_StarAccel rs.w 1
O_StarPlanes rs.w 2
O_NumStars rs.w 1
O_CoordsBank rs.l 1
O_SpliBank rs.l 1
O_SpliLimits rs.w 4
O_SpliGravity rs.w 2
O_SpliBkCol rs.w 1
O_SpliPlanes rs.w 1
O_SpliFuel rs.w 1
O_NumSpli rs.w 1
O_MaxSpli rs.w 1
O_SBobMask rs.w 1
O_SBobPlanes rs.w 1
O_SBobWidth rs.w 1
O_SBobImageMod rs.w 1
O_SBobLsr rs.w 1
O_SBobLsl rs.w 1
O_SBobFirst rs.b 1
O_SBobLast rs.b 1
O_QRndSeed rs.w 1
O_QRndLast rs.w 1
O_PTCiaVbl rs.w 1
O_PTCiaResource rs.l 1
O_PTCiaBase rs.l 1
O_PTCiaTimer rs.w 1
O_PTCiaOn rs.w 1
O_PTInterrupt rs.b 22
O_PTVblOn rs.w 1
O_PTAddress rs.l 1
O_PTBank rs.l 1
O_PTSamBank rs.l 1
O_PTTimerSpeed rs.l 1
O_PTDataBase rs.l 1
O_PTSamVolume rs.w 1
O_AgaColor rs.w 1
O_HamRed rs.b 1
O_HamGreen rs.b 1
O_HamBlue rs.b 1
rs.b 1 ;Pad
O_VecRotPosX rs.w 1
O_VecRotPosY rs.w 1
O_VecRotPosZ rs.w 1
O_VecRotAngX rs.w 1
O_VecRotAngY rs.w 1
O_VecRotAngZ rs.w 1
O_VecRotResX rs.w 1
O_VecRotResY rs.w 1
O_VecRotResZ rs.w 1
O_VecCosSines rs.w 6
O_VecConstants rs.w 9
O_BlitTargetPln rs.l 1
O_BlitSourcePln rs.l 1
O_BlitTargetMod rs.w 1
O_BlitSourceMod rs.w 1
O_BlitX rs.w 1
O_BlitY rs.w 1
O_BlitWidth rs.w 1
O_BlitHeight rs.w 1
O_BlitMinTerm rs.w 1
O_BlitSourceA rs.l 1
O_BlitSourceB rs.l 1
O_BlitSourceC rs.l 1
O_BlitSourceAMd rs.w 1
O_BlitSourceBMd rs.w 1
O_BlitSourceCMd rs.w 1
O_BlitAX rs.w 1
O_BlitAY rs.w 1
O_BlitAWidth rs.w 1
O_BlitAHeight rs.w 1
O_PTileBank rs.l 1
O_BufferAddress rs.l 1
O_BufferLength rs.l 1
O_PowerPacker rs.l 1
O_PPCrunchInfo rs.l 1
O_DiskFontLib rs.l 1
O_DirectoryLock rs.l 1
O_DateStamp rs.l 3
O_OwnAreaInfo rs.b 1
O_OwnTmpRas rs.b 1
rs.w 1 ;Pad
O_AreaInfo rs.b 24
O_Coordsbuffer rs.b 20*5
O_TmpRas rs.b 8
O_FontTextAttr rs.b 8
O_AudioPort rs.b 32
O_AudioIO rs.b 68
O_ChanMap rs.w 1
O_AudioOpen rs.w 1
O_AudioPortOpen rs.w 1
rs.w 1 ;Pad
O_PaletteBufs rs.w 32*8
O_ParseBuffer rs.b 512
O_SizeOf rs.l 0
Let's go for a small tutorial, in which bitplanes and how they work is explained.
1. What is a bitplane?
On an Amiga computer the video picture is created by so called bitplanes. These are linear blocks in chip memory, of which
every single bit represents one dot on the screen.
Using only one bitplane, you can only see two different colours (either bit set or bit clear). If more than one bitplane is placed on top of others, you will get 2^n colours for n bitplanes.
Example:
We have an 16 colours screen. So it has got 4 bitplanes. Normally, the
bitplanes are counted from 0 to n-1...
Binary 0 1 0 1 = Decimal 5
| | | | .---v---v---v---v--------------------
| | | `----+ 1 | | | | Bitplane 0
| | | |--v^--v^--v^--v^--v-------------------
| | `------+--+ 0 | | | | Bitplane 1
| | | |--v^--v^--v^--v^--v------------------
| `--------+--+--+ 1 | | | | Bitplane 2
| | | |--v^--v^--v^--v^--v-----------------
`----------+--+--+--+ 0 | | | | Bitplane 3
| | | |---^---^---^---'
| | | |
| | |
| |
|
You must imagine the bitplanes to be 'overlapped over each other'.
The colour index 5 is displayed in the bitplanes like that.
Which colour the dot on the screen finally has, is determined by the palette settings.
2. Overlapping and Transparency.
Imagine, you draw a figure A in bitplane 0 and a figure B in bitplane 1 only. This produces the following:
The area, on which none of the figures are displayed, has got the colour zero (both bitplanes are cleared: %00).
whereas on regions, where only figure A is appearing, the colour 2^0=1 is used (bit 0 is set, bit 1 is clear: %01).
Figure B alone sets the bit in bitplane 1 and therefore is displayed in colour 2^1=2 (=%10).
If both figures are overlapping, the bits in both bitplanes are set and this results in colour 2^0+2^1=3 (=%11).
Now we can define the palette. For instance:
Palette 0,$F00,$F0,$FF0
The background is black ($000), figure A is red ($F00) and figure B is green ($0F0), when overlapping yellow is generated ($FF0).
By just thinking about this correlation you can achieve nice effects.
Try to find out, how the two figures will look like, when using these palettes:
1. Palette 0,$FFF,$888,$FFF 2. Palette 0,0,0,$FFF
You find the solution below.
3. Glenz and Fade
When e.g a cube appears 'transparent', out of glass or electric, the effect is called 'Glenz'.
This is mostly used for vector effects. There are two major types of Glenz vectors:
a) Wire frame objects:
With Glenz wire frame objects the lines are drawn in a different bitplane per vertical plane keeping the two or
three previous frames intact.
These old and new frames then overlap, and by choosing the right palette (additive colour values per bitplane) the
points where the lines are overlapping look lighter and somehow glitter.
Example for an additive colour palette (eight coloured screen): DARK=$333 : LIGHTER=$666 : BRIGHT=$FFF ' %000 %001 %010 %011 %100 %101 %110 %111 Palette 0,DARK,DARK,LIGHTER,DARK,LIGHTER,LIGHTER,BRIGHT
Just look at the bit values and count the number of set bits to get the right colour value.
By changing the palette permanently you can also create a Motion Blur or Fade effect.
To achieve this, you must set every colour with the bit for the current bitplane, in which you are drawing at
the moment, to the brightest, colour all colours with the bit of the previous bitplane
and not with the bit of the current one to a middle colour and so on...
b) Solid objects:
Glenz on solid object is done like this: the polygons, that are facing
away from the viewer (and therefore cannot actually be seen) are drawn
on an other bitplane than the polygons that face the viewer.
By setting the colours according to the bitplanes, the object will seem to be transparent.
The only thing to do is to mix the colours of the bitplanes, in which the different polygons are drawn.
4. Bitplane modes and their specialities.
The old ECS-Amigas can only display up to 6 bitplanes simultaneously.
So 2^6=64 colours is the maximum (excluding the HAM mode ).
Though there are some special modes:
a) ExtraHalfBright (EHB).
As the OCS and ECS chipset has only 32 colour registers, the other 32 colours are displayed at half the value.
When using EHB you can produce some neat shadow effects by writing into the 6th bitplane.
Note: EHB pictures cannot be faded out perfectly.
b) Hold And Modify (HAM).
HAM is a method, to decompress six bitplanes to twelve bitplanes by hardware. Therefore the colours from 16 to 63
are used reach the wanted colour by changing the red, green or blue value of the previous colour.
Very good for static pictures and pre calculated animation but useless for games and realtime graphics.
The only sensible way to display moving objects on a HAM screen is to use sprites.
c) Dual Playfield.
The Amiga chipset can display all even bitplanes (0,2,4) separated from the odd ones (1,3,5).
It's better to say, he puts the one playfield on top of the other by using colour 0 as 'window' to the other playfield.
In this mode each playfield can have 2^3=8 colours.
The chipset has got separate control registers for even and odd bitplanes each, as each Playfield must be independent for Dual Playfield mode.
BitPLane CONtrol (BPLCON0) $100.
Here you determine the number of bitplanes and the resolution and can toggle the special modes.
Bit table:
15 HIRES Toggle hires mode
14-12 BPUx Number of bitplanes
11 HOMOD Toggle HoldAndModify
10 DBPLF Toggle Dual Playfield
9 COLOR Toggle colour burst output
8 GAUD Use audio input from a genlock
7 8BPL 8 bitplanes (AGA)
6 SHIRES Superhires (ECS/AGA)
3 LPEN Activate lightpen
2 LACE Enable interlace mode
1 ERSY Switch to external synchronization
The scroll register (BPLCON1) $102.
By using this register, the screen can be scrolled to the left by up to 15 pixels.
The bits 0-3 are used for the even bitplanes, the bits 4-7 for the odd ones.
Modulo registers (BPL1MOD/BPL2MOD) $108/$10A.
These registers set the amount of bytes to be added to the memory of the bitplanes after each rasterline.
This is utilized by playfields that are bigger than the visible area.
When writing a negative value you can achieve vertical zoomers or mirror effects.
If you want to alter a register using Set Rain Colour, you can calculate the new 'colour' with the following formula: (REGADR-$180)/2
Note: Enabling 5 to 6 bitplanes in low resolution or 3 to 4 bitplanes in high resolution will cost free
processor time, even if you only display the screen.
This is true when the running program is placed in chip ram or must access chip ram.
5. How can I access all these effects?
Simple: Define a rainbow, call Set Rain Colour and enter the new values for the registers
using Rain() instead of supporting the colours.
The only limitation: Due to the AMOS rainbow restrictions you can only manipulate ONE (!) register per rasterline.
Look carefully at the example programs. These demonstrate every single effect mentioned here.
By the way: You can get the pointer to the single bitplanes using Logbase(planenr) and Phybase(planenr).
Enjoy!
Solution to the questions in 2:
1. Palette 0,$FFF,$888,$FFF
Figure A is white and is moving 'over' figure B, which is grey, because if they overlap the colour white is created.
2. Palette 0,0,0,$FFF
Figure A and Figure B are invisible as long as they down overlap. Only if both are placed over each other colour 3
is created which was set to $FFF (white).