# -------------------------------------------------------------------
# OBJECTPROCESSOR (c) Copyright 1995-1996 Nat! & KKP
# -------------------------------------------------------------------
# These are some of the results/guesses that Klaus and Nat! found
# out about the Jaguar. Since we are not under NDA or anything from
# Atari we feel free to give this to you for educational purposes
# only. Thanks to NEUROMANCER for many worthy corrections and
# the GPU-object info.
#
# Please note, that this is not official documentation from Atari
# or derived work thereof (both of us have never seen the Atari docs)
# and Atari isn't connected with this in any way.
#
# Please use this informationphile as a starting point for your own
# exploration and not as a reference. If you find anything inaccurate,
# missing, needing more explanation etc. by all means please write
# to us:
# nat@zumdick.rhein-main.de
# or
# kkp@gamma.dou.dk
#
# If you could do us a small favor, don't use this information for
# those lame flame-wars on r.g.v.a or the mailing list.
#
# HTML soon ?
# -------------------------------------------------------------------
# $Id: op.html,v 1.28 1997/03/30 02:27:13 nat Exp $
#
# If there are two theories I put the more likely one first.
# -------------------------------------------------------------------
Things to know about the Objectprocessor (OP):
==============================================
-1 Imagine a phrase being an entity of 64 bits (or 8 bytes for that
matter).
0. The object list is a linked list.
1. The object list is traversed by the object processor for
each! scanline.
2. The Objectprocessor probably works like this:
Whenever a new linebuffer needs to be filled, the OP is called to do
its chore, while the videosystem is busy displaying the other linebuffer.
The OP does its work by traversing the objectlist and interpreting
each object in sequence. Each object has per linebuffer the chance ONCE
to fill the linebuffer. (Note: that this does not mean necessarily
per scanline, since with the special HDB2-mode
it can happen that two linebuffers are used for each scanline!)
It fills the linebuffer at a specified horizontal position for a
specified width. The data in the linebuffer is always overwritten
(except when the Read-Modify-Write bit is set). If the active object
has the transparent bit set, it will not overwrite values in the
linebuffer when its source pixel has the value zero. The 'transparency'
check is done before looking up the pixel's color in the CLUT
(1 - 256 color modes).
2.1 The sooner a object appears in the list the more in the background it
appears. The linebuffer is initialized by the video chip with the
linebuffer-backgroundcolor (BG) before the OP starts filling the
linebuffer.
One may also assume that the OP normally traverses the
linebuffer from left to right, except when the horizontal flip
bit is set. (Very useful information indeed! (har) )
Each bitmap object is made up of pixels. These pixels can be either
contain the color itself (direct) as in CrY and True-Color modes
or be an index into a Colorlookuptable (indirect).
2.2 We assume that the OP writes into the linebuffer locally, so that
the object-data is read over the bus, but not written into the
linebuffer over the bus (which would be way evil)
2.3 If all these theories are true, then the OP has on the average one
scanline time to prepare the linebuffer. (In a setup where one
linebuffer is used per scanline)
2.4 The videosystem can deal with 16bit RGB/CrY-color and 24bit RGB
pixels, the size of the pixels the OP writes into the linebuffer
and pulls out of the CLUT, depends on the pixel-type chosen for
the videosystem.
2.5 The object in the objectlist are *modified* by the OP. This means
that an object list is only good for one frame. You need to
continually refresh your object list each VBLANK.
3. The last object must be a STOP object.
4. The Objectlist must be double-phrase aligned. This means
that the lower nybble of the address must be zero.
(Maybe this is wrong and it is just object alignment that you
should take into account)
5. The address of the image of an object must be (as expected)
phrase aligned (zero in the lower 3 bits)
6. There are five different objects that the Objectprocessor knows
about. These are:
1. Bitmapped Object
2. Scaled bitmapped object
3. GPU-Object (interrupts the GPU)
4. Branch object
5. Stop object (marks the end of the object list)
The objects have different sizes. The minimum size of an object
is a "phrase". Also note the alignment constraints.
Object type Number Size in phrases Alignment in phrases
-------------------------------------------------------------
BITMAP 0 2 2
SCALE 1 3 4 !!
GPU 2 1 1
BRANCH 3 1 1
STOP 4 1 1
7. To keep the Objectprocessor from fetching data (and wasting bandwidth)
during the VBLANK you usually put two branch objects at the beginning
of the display list, that branch to the stop object if the first
displayable scanline has not been reached or the last displayable
scanline has already been displayed.
7.1 The OP mustn not take than a scanlines worth of time to process the
object list, else the display tears. (If using a single linebuffer
per scanline)
8 The OP usually hogs the bus, when doing data transfers, since it is
normally the most highly priorised
(interesting) device on the bus.
9 In the special mode where two linebuffers are used for each scanline,
you should remember that the OP executes the object list twice. That
will give you quite some headaches. For example sprites crossing
the "boundary" will have to be split in two objects, which will be
really painful, if those sprites are scaled objects.
Look for the branch object about an idea how
to setup separate lists, for each linebuffer.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
9 Your friendly OP-registers
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
RW: OLP ($F00020)
~~~~~~~~~~~~~~~~~
32 28 24 20 16 12 8 4 0
+--------^---------^---------^--------+--------^--------^--------^--------+
| low_word | high_word |
+-------------------------------------+-----------------------------------+
low_word:
high_word:
The address of the object list. The 32 bit address is word swapped.
So you gotta store it like this:
move.l #objlist,d0
swap d0
move.l d0,OLP
It seems a good idea to set this on every VBL. (My programs run more
predictable this way)
RW: OB ($F00010)
~~~~~~~~~~~~~~~~
32 28 24 20 16 12 8 4 0
+--------^---------^---------^--------^--------^--------^--------^--------+
0 | object-data |
+-------------------------------------------------------------------------+
64 60 56 52 48 44 40 36 32
+--------^---------^---------^--------^--------^--------^--------^--------+
1 | object-data |
+-------------------------------------------------------------------------+
object-data:
This is used to pass data/pointer to the GPU when using a GPU object.
Lord knows what the second phrase is for...
R: OBF ($F00026)
~~~~~~~~~~~~~~~~
32 28 24 20 16 12 8 4 0
+--------^---------^---------^--------^--------^--------^--------^-----+--+
| data :f |
+----------------------------------------------------------------------+--+
data + flag (f):
The STOP objects' data field is copied here.
flag (f):
The object processor flag. You can hook up an IRQ (Level 2) (?)
to this bit, which can in turn serve to interrupt the GPU and
the 68K (and possibly also the DSP).
This can be used to generate HBLANK-like interrupts, although the STOP
does seldom occur in the blanking period of the video chip, but
much sooner!
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
10 This is what a branch object looks like:
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Phrase #0:
63 56 48 40 32 24 16 8 3 0
+--------^---------^-----+---^--------^--------+--------+--+-----^----+---+
| unused | Link-address | unused |CC| VCnt |011|
+------------------------+---------------------+--------+--+----------+---+
42..........24 23..16 15.14 13...3 2..0
21bits 8bit 2bit 11bits 3bits
The branch objects are used to compare the current scanline
with the value stored in the branch object. Depending on the
branch instructions comparison mode, the branch is taken
either on < == != or >. The taken branch taken uses the information
from the Linkinfo and branches to the phrase-indexed
object. If the comparison fails it simply examines and handles
the next object in the list.
Link-address:
See the bitmapped object for more infos on the link address.
VCnt:
This is the value you compare the vertical scanline
counter with (VC). For CC code 10 the operation goes:
if( object->YCnt < VC)
goto object->link;
Condition codes (CC):
Values Comparison/Branch
--------------------------------------------------
000 Branch on equal (VCnt==VC)
001 Branch on less than (VCnt>VC)
010 Branch on greater than (VCntHC in the video chip (maybe for
every scanline (?), you can branch when the OP detects, that it is
filling the second linebuffer.
Other theory: CC is 3 bits long and there exists a fifth value:
100 Branch if on second halfline
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
11 This is what a stop object looks like:
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Phrase #0 (1 of 1):
63 56 48 40 32 24 16 8 0
+--------^---------^---------^--------^--------^--------^--------^----+---+
| data |100|
+---------------------------------------------------------------------+---+
data:
Data is copied into the object status register.
The lowest bit can be used to trigger IRQs, the rest of can
be used at the programmers whim.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
12. This is what a bitmap object looks like:
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Phrase #0 (1 of 2):
63 56 48 40 32 24 16 8 0
+--------^---------^-----+------------^--------+--------^--+-----^----+---+
| data-address | Link-address | Height | YPos |000|
+------------------------+---------------------+-----------+----------+---+
63 .............43 42.........24 23....14 13....3 2.0
21 bits 19 bits 10 bits 11 bits 3 bits
(11.8)
data-address: Pointer to the bitmap ***DESTROYED BY THE OP***
link-address: Pointer to the next object
height: Height in pixels
y-pos: Vertical position ***DESTROYED BY THE OP***
type: Object type
data-address: bits 63-43
An address is a memory address in terms of phrases. To get the
byte address you have to shift it up by 3. (or in this example
to get the data-address you would fetch the upper lword with
the 68K and do):
move.l (a0),d0 ; fetch it (bits 63-32)
moveq #11,d1 ; or some other less lame way
lsr.l d1,d0 ; shift it down for phrase address
lsl.l d1,d0 ; shift it up for byte address
link-address: bits 42-24
The link address strings the object list together. So it really
is a linked list, not just an array. OK an array would have
been better and the link could have been a number of phrases
to skip. It misses the upper two bits two form a proper full
24 bit address. This means that objects must reside in the
lower 4 MB. This is addresses a phrase also, not a byte. For
the byte address shift it up by three.
height:
The height of the object is also stored in the first phrase.
This is the number of pixels an object has in it vertical extent.
ypos:
The YPos is predictably the vertical position of the object on
the screen. The vertical position is the halfline vertical
position. In video terms the first theoretically possible
_visible_ position (depending on your overscanning) will be
at VDB See Video
Therefore for non interlaced screens this value is Y * 2 + VDB,
for interlaced just Y + VDB.
Theory 1:
Like on the Falcon the screen is divided into two horizontal
halflines. Except for really wide screens in excess of 1024
pixels horizontally, you always stay in the first halfline.
(That's why its eleven bits, and the height is only 10 bits.)
A problem with this theory is, that the Xpos field is 12 bits
anyway...
Theory 2:
This means that in interlace mode this is the "true"
vertical position on the screen. In non-interlaced modes
(non-flicker) modes, you should multiply your Y-Pos by two and
stuff that into the object.
(That's why its eleven bits, and the height is only 10 bits.)
type:
Lastly the object type indicates with a 0 (000) that this object
is a normal non-scaled bitmap object.
Phrase #1 (2 of 2):
63 56 48 40 32 24 16 8 0
+--------^-+------+^----+----^--+-----^---+----^----+---+---+----^--------+
| unused |1stpix| flag| idx | iwidth | dwidth | p | d | x-pos |
+----------+------+-----+-------+---------+---------+---+---+-------------+
63...55 54..49 48.45 44.38 37..28 27..18 17.15 14.12 11.....0
9bit 6bit 4bit 7bit 10bit 10bit 3bit 3bit 12bit
(6.4)
Curiously there seem to be some unused bits in the top half of
this second phrase. Anyway starting from the left:
1stpix: Pixels to skip
flags (flag): How to handle the source data
index (idx): Index into the CLUT
iwidth: Width of the image
dwidth: Offset to the next line of the image
pitch: Increment for the Datapointer
depth: Pixeldepth of the bitmap
x-pos: Horizontal position of the object
1stpix: bits 54-49
this is a field of 6 bits that contains the number of
'bits' to skip before fetching the first pixel. This must be
used whenever your bitmap data isn't phrase aligned.
Maybe most often used for CLUT modes.
You get the value you want to write here by calculating:
pixelindex * bits_per_pixel (f.e. 8 for 256 color mode)
flags: bits 48-45
You can tell the Objectprocessor the way it should
handle the display data. These are the values you set here:
Bit3 Bit2 Bit1 Bit0
----------------------------------------------------------------
Release Transparent ReadModifyWrite Horizontal Flip
Horizontal flip / aka Reflect:
Lets the Objectprocessor run its path from the other end
of the sprite data, which should effectively flip your
sprite data.
Ex:
an eight bit sprite is normally drawn as
01234567
flipped 76543210
^
|
start at XPOS.
ReadModifyWrite:
The object processor reads the the pixel from the line
buffer does something with the bitmap pixel value and the
linebuffer pixel value and stores the result back into the
linebuffer.
For CrY-color the lower byte of the bitmap pixel value is
sign extended and added to the lower byte of the
linebuffer pixel value, thereby increasing or decreasing
(depending on the sign) the intensity of the linebuffer
pixel. This is a 'saturating add' meaning that you don't
wrap around, but subtractions stick at 0 and additions stick
at 255.
The cry hues (upper byte) are mangled even more strangely,
the effect could (with the right values) be like looking
through a colored glass (your bitmap object with the
RMW-flag set) onto the background (the other bitmap objects
below it)
This might be similar to what happens when gouraud-shading.
Refer to the blitter docs.
Transparent:
When the source pixel is zero, this pixel will not be written.
This is the way to achieve transparent sprites with the GPU.
(Both CLUT and non-CLUT pixels)
Release:
If cleared then the OP 'hogs' the bus for the time it takes to
fetch the scanline data of the object. If this bit is set,
then the bustime is shared with other processors. If you have
lotsa interrupts going, this might be worthwhile.
Should apparently NOT be set on objects with more than 8
bitplanes, probably because then the OP might glitch.
index (idx): bits 44-38
Index into the ColorLookUpTable (CLUT)
This information is only used for 1 - 2 or 4 bitplane objects,
to determine the offset in the CLUT to use.
1 bitplane 2 bitplane 4 bitplane
-------------------------------------------------------
iiiiiiii iiiiii0 iiiii00
The value is shifted left once and then used as an index into
the CLUT. Note that in 2 + 4 bitplane modes not all bits are in
used, because the lower bits are replaced with the pixel value.
For example in 4-bits-per-pixel mode pixel #7 and an idx value
of 64 gives you an index of (64*2)+7 -> 135
So you preload the CLUT with the colors you want to use, for
example green at index #241. When you want to display a small
green arrow on the screen (as a pointer) for example you set
your object to transparent, and the index to 120. When the
object pointer fetches a set pixel, it will write the green
value into the linebuffer.
iwidth: bits 37-28
Tell the OP how many *phrases* to draw in each line. This is
the actual number of phrases to draw, not the horizontal index
to index the next line (dwidth). This is probably not just
#pixels_to_draw / bits_per_pixel,
but rather the number of phrases the object spans. If a 32bit
object spans two phrases you should enter a two here.
dwidth: bits 27-18
The horizontal phrase offset the OP should use to index to the
next line. If you data is laid out in consecutive strips of
horizontal data like this:
screen :
00000000000
11111111111
22222222222
33333333333
memory :
00000000000111111111112222222222233333333333
then this will be just the same as . But if your data
is laid out like this:
00000000000xxxxx11111111111xxxxx22222222222xxxxx33333333333xxxxx
you should set to the proper offset so that adding
to the phrase-address will bring you to the next line.
(This might be useful for 'horizontally scrolling' objects).
pitch (p): bits 17-15
If you so desire you can organize your bitmap data in even
stranger ways than one would think possible. With this value
you control the data-pointer that the OP uses to traverse your
bitmap data. This value is added to the data-pointer after the
last fetch. If you use a 0 you will be always fetching the same
phrase over and over again. Normally you set to 1, to
advance through memory contiguously.
This will come more into play, if you want to use
Z-buffering or/and optimize
your screen layouts for blits.
depth (d): bits 14-12
The number of bits of each pixel. This specifies the rez of the
object. You have the choice between direct pixel modes (16 or
24/32 bits) and indirect (CLUT) pixel modes. Note that using
transparency effectively reduces the number of available colors
by one (color #0).
Values:
0 1 bits per pixel 2 colors CLUT
1 2 bits per pixel 4 colors CLUT
2 4 bits per pixel 16 colors CLUT
3 8 bits per pixel 256 colors CLUT
4 16 bits per pixel 65536 colors CRY
5 24 bits per pixel 16 Mio Colors TrueColor
6 unused
7 unused
xpos: bits 11-0 (-2048 to +2047)
The horizontal position of the object on the screen (or in the
linebuffer if you will).
Therefore xpos=0 is the leftmost pixel in the linebuffer. If you
are overscanning (linebuffer (HDB) starts outside the visible
area of the screen), then you will have some cut off.
See the video documentation
If you have a really big sprite, like f.e. a huge "scrolling"
background bitmap, you should remember that the data which goes off
to either side of the screen still requires memory fetches! Therefore
it might be wise to change the object definition.
Modify your big objects so that only what is seen is drawn.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
13. This is what a scaled bitmap object looks like.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Phrase #0 (1 of 3):
63 56 48 40 32 24 16 8 3 0
+--------^---------^-----+---^--------^--------+--------^--+-----^----+---+
| data-address | Link-address | Height | YPos |001|
+------------------------+---------------------+-----------+----------+---+
63 .............43 42..........24 23 ..... 14 13 ..... 3 2.0
21 bits 19 bits 10 bits 11 bits 3 bits
Except for the type, which is different, this is just
the same as the first phrase of the bitmap (non-scaled)
object.
Phrase #1 (2 of 3): This is the same as the the 'bitmapped' object
Phrase #2 (3 of 3):
63 56 48 40 32 24 16 8 0
+--------^---------^---------^--------^--------+--------+--------+--------+
| unused | remain | VScale | HScale |
+----------------------------------------------+--------+--------+--------+
23..16 15...8 7....0
8bit 8bit 8bit
remainder: Keeps the VScale remainder ***DESTROYED BY THE OP***
v-scale: Vertical scaling factor
h-scale: Horizontal scaling factor
The scale is a fractional representation, using 3 bits for the integer
part and 5 bits for the fractional part. Or in ASCII-Graphics:
76543210 00100000 or 0x20 is 1.0
iiifffff 00010000 or 0x10 is 0.5
The remainder is used by the objectprocessor for the vertical scaling,
as a memory place. You should initialize it to 0.5 for best results,
although in a lot of demo-code its initialized to 1.0.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
14. The elusive GPU-object
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Phrase #0 (1 of 1):
63 56 48 40 32 24 16 8 3 0
+--------^---------^---------^--------^--------^--------^--+-----^----+---+
| data | ypos |010|
+----------------------------------------------------------+----------+---+
63................................14 13.....3 2..0
ypos:
when the VC matches the value in ypos,
then the GPU object is active. If all ypos bits are set then the GPU
object is always active.
The GPU gets an interrupt, it is believed that the OP is not halted
because of this action. You might want to stuff some information
into the unsused parts, which the GPU could then read from the OP
registers. The GPU can then be used to control OP program flow using
OBF (F00026) and branch object condition 3.
The whole GPU-object is copied to OB, so that the GPU can examine the
data part to see which GPU object has triggered the IRQ.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
15 You can also look at the object in terms of C-structs, that's how
they'd look like.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
/* DON'T USE THESE BITFIELDS WITH ANYTHING ELSE THAN A
***GOOD*** C-COMPILER AND A MOTOROLA PROCESSOR
*/
#define byte unsigned char
#define word unsigned short
#define lword unsigned long
#define phrase unsigned long long
typedef struct
{
lword data:21;
lword link:19;
word height:10;
word ypos:11;
word type:3;
} bitmap_obj_phrase_0;
typedef struct
{
word unused:9;
word firstpix:6;
word flags:4;
word index:7;
word iwidth:10;
word dwith:10;
word pitch:3;
word depth:3;
word x_pos:12;
} bitmap_obj_phrase_1;
typedef struct
{
lword unused:24;
word remainder:8;
word v_scale:8;
word h_scale:8;
} scale_obj_phrase_2;
typedef struct
{
lword unused:21;
lword link:19;
word conditioncode:2;
word unused:8; ;; maybe index to register ?
word ypos:11;
word type:3;
} branch_obj_phrase_0;
typedef struct
{
phrase unused:61;
word type:3;
} stop_obj_phrase_0;
typedef struct
{
phrase unknown:61;
word type:3;
} gpu_obj_phrase_0;
typedef struct
{
stop_obj_phrase_0 p0;
} stop_obj;
typedef struct
{
branch_obj_phrase_0 p0;
} branch_obj;
typedef struct
{
gpu_obj_phrase_0 p0;
} gpu_obj;
typedef struct
{
bitmap_obj_phrase_0 p0;
bitmap_obj_phrase_1 p1;
} bitmap_obj;
typedef struct
{
bitmap_obj_phrase_0 p0;
bitmap_obj_phrase_1 p1;
scale_obj_phrase_2 p2;
/* need one padding phrase ? */
} scale_obj;
BUGS:
=====
This might be a bug or not but you should be aware, that the OP is
a high priority bus device, that does not like to be interrupted
by higher priorised devices.
(See: Priorities for more info).
While the OP is walking along its object list and filling the linebuffer,
it is effectively shutting out the rest of the system during that time.
This might not be too convenient, if you have a high frequency interrupt
going (like maybe the DSP playing a Tracker module).
The RMW-flag is said to be buggy, in that the last pixel of the RMW object
might be corrupted, unless the first pixel of the first following object
is cleared (strange!!)
SMALL DISCUSSION:
================
Since the object processor walks the object list for each
scanline, you should consider the following:
If you have 64 bitmaps objects in your object list and a
vertical rez of 240 lines going and a refreshrate of 60Hz
the Objectprozessor is pulling
60 hz * 240 lines * 64 objects * 2 phrases = 1.8 Mio phrases/s
~ 14.7 Mio bytes/s for the object processor list alone!
(ca. 14% of the systems bandwidth)
If you figure you're using 128x128x16bit sprites fully visible,
you're doing:
128x128*16bits/64bits = 4096 phrases a sprite
64 sprites in 60hz = 3840 sprites
yields 15728640 phrases/s or 120 Mbytes/s
So it is fairly easy to unknowingly saturate the bus with
a nice object list. (TEST THIS, possibly the OP is smart
enough to detect, when the scanline is needed by the Video
chip and stops processing the object list)
It should be obvious that non-"truecolor" sprites still make
lotsa sense, when you're using the OP heavily.
It would have been better in our opinion, if Atari had used a
small 2-Kbit hitbuffer (or single bit Z-Buffer) and reversed
the object order, so that the nearest object comes first and
the background last in the object list.
With such a slightly more complicated scheme,the OP could
run at a rather constant:
hrez * vrez * refresh * average_bits_per_pixel
---------------------------------------------- phrases/s
64
If it is true that the OP has on average one scanline time to
prepare the linebuffer, we can do a quick estimate how complex
such a line can be:
NTSC
30 Hz refresh rate (2 refreshs a 1/60s)
525 lines frame
Therefore 525*30=15750 lines/s
13.3 mio phrase/s / 15750 lines ~ 825 phrases / scanline
or ~ 3300 truecolor pixels / scanline
this means that on a 320 pixel display you can have approximately
ten layers of overlapping truecolor parallax (sans sprites)!!
Or if you have a 320 pixel background, you can have about 80
32 bit wide truecolor sprites on the same scanline.
Its doubtful that you'll reach these limits...
Since the OP with a 320x200 rez is pulling data only on 200 lines
of 525 scanlines, you can use up (without producing display errors)
only ~40% of the Jaguars bus resources this way. Nice!
Soon you'll find out that the designers did not give the branch
object a second link phrase, so that it would seeem that in effect
you're forced to assemble your OP-list in one continous memory
block anyway. Or you would be restricted to using branch objects
only at the beginning of your OP-List, like this:
+------------+
/ \
/ v
branch....branch....stop
|
v
bitmap ----> scaled ----> stop
BUT, you can also deploy double branch objeczs, one acting as a Bcc
the other as a BRA two get a two way connection.
NEEDED STUFF:
Need to document the logic setting up objects, that cross
boundaries (especially the scaled bitmaps)