||The real reason I am
uploading this today is to test my new copy of ws_ftp
pro... The probability that your life has been spent
waiting for this program to appear is quite small. But it
*is* a little mesmerizing, so perhaps you will enjoy it.
This program is FREE, not shareware. Just enjoy it.
What Is synBirds?
Basically, it's a silly
little exercise. It models a large number of birds which
fly in a flock. Each bird is actually making its own
independent flight decisions, based upon what it sees
My inspiration was those
flocks of birds you see in the distance where the
individual birds are just dark spots against the blue
sky. Their movement becomes that of a cloud which changes
size and direction dramatically.
Here is a life-size
screen shot of synBirds in action:
[There is NO ScreenShot... It's just Too Trivial]
(I am imitating my Galaxy
here, in case you noticed the mindless duplication of
format). My goal with synBirds was to:
- Have Fun.
- Try something with
a large number of independent 'intelligent'
- Write another
program with an insane number of computations per
second to enjoy my shiny PII 300, even when my
friends are now getting 450MHz machines and
trying to depress me. Intel should give me an
award for slowing down computers better than
Running the Program
Well, just unzip the
executable and run it.
It is a dialog-based MFC
app written in VC++ 4.2b
Right away it starts
animating the 'birds' (Each bird is simply a rectangle of
color (taken from the birds.bmp bitmap if you want to
fiddle a little with the textures). Your only control is
to specify how many birds you want to see. I could see
myself turning this into a screen saver, perhaps. But it
is probable I won't do anything else with it. I think it
would be neat to make the birds react to your voice, so I
might use this as a test case for that someday.
I don't have a lot to
say about the math in this one. There is not a lot going
on. Basically I paint a static background image (alter
pond.jpg to the image of your choice, I will dynamically
scale it to the screen size you select). On top of that I
draw 'the birds' using a simple 3D to 2D conversion. For
each frame, I compute the new bird positions using the
patterns and camera location/viewport:
- Please see synVista's math notes for the
description of Lissajous patterns. Basically
there is a 'key bird' who is flying a lissajous
pattern throughout a 3D 'cube' of space which
sits in front of the viewer. The other birds are
more or less following this leader.
- Given a bird's 3D
position in this 'cube', I compute its on-screen
location using the formula's
Xscreen = zoom *
(XBird - XCamera) / ZBird;
Yscreen = zoom * (YBird - YCamera) / XBird;
Where The 'screen'
is like a piece of glass with your eye (the camera)
on one side and the cube on the other side. Zoom
represents the distance of your eye from the screen.
XBird is the distance of the bird from the
screen-side of the cube.
You've seen me do
this before.... If you're working in fixed point
math, be sure to do all the multiplies before you do
the divide. And avoid dividing by zero...
- The size of square
I use to represent the Bird itself diminishes
with the bird's distance (I simplify and just use
the Bird's Z location value as the distance, and
apply some arbitrary max and min sizes for
- This is the
'interesting' part of this program, if there is
one. Basically I scratched my head and thought
about why birds in flight look as they do. I
decided (with no research) that they basically
were all following each other, with the birds
'more in front' controlling the overall flock
dynamics more than the birds in back.
- So, for each bird I
keep track of both its current position in space,
as well as its current velocity vector (the
direction it is headed, and the speed it is
- Each frame, for
each bird, I update its position by moving it a
little along the path of its velocity vector, and
then I alter its velocity vector a little to
'follow' a bird in front of it. (In fact, I cheat
here. bird 0 is the key bird which is following a
lissajous pattern. The next 5 birds follow bird
zero, and the remaining birds follow one of those
- Initially I tried
just resetting the velocity vector of a bird o
point directly at the bird it was following. This
had the predictable effect of getting the birds
to all fly in a straight line after the key bird.
- Finally, I hit on
'free will' Each bird flies along its current
velocity vector 'for awhile' until turning to
follow its leader bird. This provided very
animal-like behaviour (kind of scary, really).
The amount of free will I give the animal
determines if it looks like birds, bees, or
lightning bugs. The version I uploaded is closer
to 'bee' free-will than bird free-will (I get the
most bird-like effect with a fairly large free
is the property of Synthetic Reality and all rights are
reserved. If we can figure out a way to convince people
to pay for this, you can be sure we'll give it a try. But
for now it is expressly intended to provide a moment of
joy for the math geeks in the audience, looking for
number-crunching programs to show off their power
Thanks for your feedback
Synthetic Reality Co.