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<title>Evolvotron User Manual</title>
<h1>Evolvotron User Manual</h1>
Evolvotron is interactive "generative art" software to evolve
images/textures/patterns through an iterative process of random
mutation and user-selection driven evolution.
On starting the application, a grid of images is displayed.
Resize or maximise the application if you like, but the more
pixels have to be calculated, the slower it will be.
(For the default 2D image mode, you will need a fast machine or patience.
For the optional animation mode, you will need both.)
Simply repeat the following until bored:
<ul><li>Click (singleclick) on an image you like to
spawn the next generation of its mutant offspring.
</li><li>Wait until variations on it are regenerated in sufficient
detail that you can decide which one you like best again.
IMPORTANT: Initially you should select images with some sort of variation.
If you select a uniform image, you may get stuck in a degenerate zone with
little to mutate and therefore little chance of escape to more interesting
images. You can always reset/restart from the "File" menu (the difference is
that "reset" also resets the mutation parameters to their default values).
Selecting one of the "warp" options from a context menu (right-click on
an image) can also help by introducing an additional opportunity for
mutation on subsequent spawns.
Note that various spirals, grids and tiles, although complex looking,
are actually implemented by a single function node and may leave you stuck too.
<h2>Command Line Options</h2>
The following are equivalent:
<ul><li>evolvotron --grid 12x8
</li><li>evolvotron -g 12x8
<ul><li>-a, --autocool <br>
Enable autocooling by default, and cause resets of mutation
parameters to re-enable autocooling if it was disabled.
<ul><li>-F, --fullscreen <br>
Start in "fullscreen" mode (NB for Qt on X11 this means
a screen-filling borderless/undecorated window is used;
it's not simply maximising the window, and it's not the
sort of framebuffer hijacking used by SDL games). The Qt
documentation claims some window managers may not be entirely
cooperative with this (in which case sorry, you're on your own).
evolvotron actions which bring up dialog boxes (e.g save) seem
to generally behave fairly sensibly but child windows
(e.g enlargements or dialogs) can show some "interesting" behaviour.
Fullscreen mode can be toggled within the application using "F" key.
The "Esc" key will also exit it.
<ul><li>-g, --grid <i>cols</i>x<i>rows</i> <br>
Sets size of the grid of image display cells in the main application area (defaults to 5x6)
<ul><li>-h, --help <br>
Print summary of command line options and exit.
<ul><li>-j, --jitter <br>
Enable sample jittering. Samples will be made at a random position
within a pixel instead of on a regular grid, providing some antialiasing.
<ul><li>-m, --multisample <i>multisample grid</i> <br>
Enables additional antialiasing passes.
Specifying 2 or 3 will provide an additional pass with 2x2 or 3x3 samples per pixel.
Specifying 4 (or higher) will provide a 2x2 and a final 4x4 pass.
Specifying 1 provides the default behaviour of one sample per pixel.
For best rendering quality also specify -j.
<ul><li>-M, --menuhide <br>
Start with menu and status bar hidden. Nice with --fullscreen.
Hiding can be toggled within the application using ctrl-m.
The Esc key will also bring them back.
<ul><li>-p, --spheremap <br>
Images are produced by sampling the underlying 3D function on the
latitude-longitude grid of a sphere. The resulting images should be
usable as spheremaps/spherical environment maps. Animations vary
the radius of the sphere. NB when in spheremap mode,
middle mouse button adjustments do not yet behave like you'd expect.
<ul><li>-S, --startup <i>function_filename</i> <br>
Specify a function filename (evolvotron's XML format) to load on startup
(or reset). The option can be provided multiple times, and this is
also the interpretation of any positional arguments. Startup functions
are placed in the grid from left to right, top to bottom.
<ul><li>-U, --shuffle <br>
Use in conjunction with -S / --startup options, to display the specified
functions in random order, both on application startup and on each
reset of the application.
<ul><li>-f, --frames <i>frames</i> <br>
Number of frames in animations (defaults to 1 i.e no animation)
<ul><li>-l, --linear <br>
Vary z linearly with time rather than sinusoidally.
Sinusoidal variation generally looks better when animations are "bounced"
forwards and backwards, but this option is useful when generating slices to
use as volumetric textures.
<ul><li>-s, --fps <i>framerate</i> <br>
Rate at which frames are displayed per second (integer). (Defaults to 8).
<h3>Power-user & Debug Options</h3>
Note that the usual Qt/X11 options
(for example, -geometry <i>width</i>x<i>height</i> option to set on-screen size in pixels)
are processed and removed before evolvotron options are checked.
<ul><li>-D, --debug <br>
Puts the certain aspects of the app into a more debug oriented mode.
Currently (ie this may change) it simply changes function weightings
so virtually all function nodes are FunctionNoiseOneChannel. By itself
this is a pretty pointless thing to do, but in conjunction with the -X
options it's useful for examining the behaviour of specific functions.
<ul><li>-E, --enlargement-threadpool <br>
Use a separate thread pool for computing enlargements.
Using this option ensures computation of enlargements
continue to make some progress even while the main grid
is being actively worked on. However, this will be at
the expense of main grid rendering performance.
Without this option, enlargements' final high-resolution
renderings are invariably lower priority than computation
for images in the main grid.
See also the -N option to control the priority of threads
in this pool.
<ul><li>-n, --nice <i>niceness</i> <br>
Sets additional niceness (relative to the main application thread)
of the compute (rendering) thread(s).
It's useful to run compute threads at a slightly lower priority
("nice 4" is the default without this option) than the main (GUI)
part of the program (but note that this means other normal/lowish
priority tasks running on your machine may slow evolvotron down
a bit more than expected).
<ul><li>-N, --Nice <i>enlargement niceness</i> <br>
Sets additional niceness (relative to the main application thread)
of the compute thread(s) computing enlargements (default value is 8).
Only effective in conjunction with -E option.
<ul><li>-t, --threads <i>threads</i> <br>
Sets number of compute threads.
If this is not specified, then as many compute threads are created
as there are processors on the system (unless this cannot be
discovered in which case only a single compute thread is created).
Non-linux builds will likely not include code to determine processor count
(suitable patches gratefully received).
<ul><li>-u, --unwrapped <br>
Modifies -F behaviour so that the specified "favourite" function
is NOT wrapped by space/colour transforms. NB For functions without leaf nodes
or parameters (e.g FunctionSphericalToCartesian) this doesn't
leave any scope for variation or future mutation.
Function name recognition is case sensitive.
<code>evolvotron -F FunctionKaleidoscope -u </code>
<ul><li>-v, --verbose <br>
Verbose mode, writes various things to application stderr.
This is primarily intended to assist debugging.
This option used to be useful for getting a list of supported function
names for use with the -F option, but those can also be inspected
via the Settings dialogs.
<ul><li>-x, --favourite <i>functionname</i> <br>
Force a specific "favourite" function type to be used at the top level
of all function trees. The specified function is still wrapped
by spatial and colour warping functions which may disguise
it considerably. A list of all the function names understood
by evolvotron is output during app startup when the -v option
is specified. Function name recognition is case sensitive.
<code>evolvotron -F FunctionSpiralLinear </code>
A left-click on an image in the main window spawns the mutant offspring
of that image to all the other (non-locked) displays in the grid.
<h3>Right-click Context Menu</h3>
Right clicking on an image gets you a few more options:
<ul><li>"Respawn" regenerates just the current image from whatever it was
spawned from (and using recolour or warp, if that's what was used
to produce it).
The main use of this is to make your grid of images look nice
for screendumps, by regenerating any which aren't up to scratch.
NB May not work as expected after an "undo".
<ul><li>"Spawn" is the same as clicking an image. It generates mutated
images to all unlocked images in the grid.
<ul><li>"Recolour" to produce different coloured variants of the selected image
<ul><li>"Warp"'s sub-options produce variants of the image which have been
<ul><li>"Lock" to prevent an image from being overwritten by spawns from other
images (select again to toggle).
<ul><li>"Enlarge" to produce a blow-up of the image in a single window.
Submenu items select either a freely resizable window or
a scrollable view of a fixed size image.
If the application is running in fullscreen mode (NB this is
NOT the same as a simply "maximised" window) then the enlarged
image will also be fullscreen (the "Resizeable" mode is probably
what you want in this case as the image will automatically be
rendered at the correct resolution).
<ul><li>"Save image" to save the image in a file (.ppm or .png).
You generally want to save an enlarged image: if you
save a small image from the grid, the size you see on the screen
is the size you get in the file. Save isn't allowed until the
full resolution image has been generated; if you try to save too
early a dialog box will be displayed telling you to try again later.
<ul><li>"Save function" to store the function to an XML file.
<ul><li>"Load function" to load a stored function from an XML file.
NB if the file was saved from a different version numbered
evolvotron, a warning message will be generated.
Save/load of functions is an experimental feature and you should
not count on future versions of evolvotron being able to load
files saved from old versions, or producing the same image
from a loaded function. Attempting to load functions from later
versions into earlier versions is even less likely to succeed.
<ul><li>"Simplify" prunes the function tree of redundant branches where
possible (the same action can be applied to all images from
the main "Edit" menu). This doesn't change the appearance of
the image, but may make it recompute faster.
<ul><li>"Properties" brings up a dialog box containing some information
about the image (e.g the number of function nodes it contains).
<h3>Middle Mouse Button</h3>
[NB This feature will probably only be of practical use to those with high-end machines].
You can use the middle mouse button to drag-adjust individual images.
This is useful for "final composition" type tweaks, e.g centering an
image's most interesting feature, or just for satisfying your curiosity
about what's off the edge of the image.
It also works on enlarged images, although it's virtually unusable without
a bit of practice on smaller, faster ones (just boldly make the adjustment
you want, release the button... and wait).
Changes made can be rolled-back on the main Edit/Undo menu item,
one drag-action at a time.
An unmodified middle-mouse drag pans the image around following
the mouse motion.
A SHIFT-middle drag zooms the image in and out with scaling
proportional to the distance from the centre of the image. Beware of
generating huge zooms by clicking too near the centre of the image.
An ALT-SHIFT-middle drag is similar but anisotropic: the scaling
may be different in X and Y. Warning: this technique is very
sensitive and can be quite tricky to use! In particular,
if you initially click near the centre axes of the image the zoom factor
can be HUGE, so the best way to start using this is to click about halfway
on a diagonal between the image centre and a corner and gently move in and
out radially. Dragging from one side of the image to the other flips it over
(the degenerate case of infinite zoom at the centre is handled cleanly I think).
If it all goes horribly wrong, undo and try again.
A CTRL-middle drag rotates the image about its centre.
A CTRL-ALT-middle drag shears the image (the best way to see what
this does is to click in the corner of an image and move the mouse
horizontally or vertically).
There are some keyboard shortcuts.
<ul><li>"r"/"t"/"x" perform various starts of reset/restart.
<ul><li>"q" quits the application.
<ul><li>"u" (and also Ctrl-z) does an undo.
<ul><li>"f": full-screen mode (on X11, Qt does this by asking the
window manager for a screen-filling undecorated window, and the
documentation contains some dire warnings about problems with broken
window managers). See also "-F" command line option.
Fullscreen mode propagates to enlarged image display windows.
NB The application may completely disappear from the screen for
a brief interval while switching mode.
<ul><li>"m" : hides status and menu-bar hiding, which can be nice when
in full-screen or window-maximised mode. See also "-M"
command line option. Also note that while the menu bar
is hidden, most of these keyboard shortcuts won't function
as they're tied to the menu system.
<ul><li>Esc : exits full-screen and/or menu-hiding mode, putting the
application into its normal default state.
The image display windows created by selecting "Enlarge" from a
context menu also have a couple of keyboard operations:
<ul><li>"f" : [NB only available with fullscreen build option] toggles
full-screen mode. When returning to normal mode, if the main app
window was fullscreen then it will also drop back to normal mode.
<ul><li>Esc : [NB only available with fullscreen build option]
completely closes a fullscreen-mode enlargement window.
<h3>Main Menu Bar</h3>
Items to restart, reset and quit the application.
The difference between restart and reset is that reset
sets the mutation parameters back the their default values.
The "randomize function weights" version of restart scrambles
the relative probability of the various function types (if you
think evolvotron just keeps generating the same kinds of
images give it a try). The "restart with specific function"
item duplicates the functionality of the "-x" and "-X" command-line
"Undo" lets you undo certain actions: e.g spawn,
middle-button adjustment, simplification and lock/unlock.
There is a large but limited number of levels of undo.
"Simplify" is of curiosity value only: it prunes redundant
branches from images ("junk DNA"); this may help them recompute
faster but at the cost of there being less mutatable material.
"Mutations" brings up a dialog to modify the amount
of change spawned images are subject to.
(See "advanced usage" below.)
"Functions" brings up a dialog to modify the relative probability
of functions being used. By default all functions are equally
likely except for iterative functions and fractals, which are
almost but not completely suppressed. But if you think there
are too many spirals or grids (or not enough fractals) then this
is the place to adjust the frequency with which they appear.
If the software was built with the fullscreen option,
that can also be controlled from this menu.
"Favourite" brings up a dialog which allows you to select a specific
function type to always be used as the root node of any new functions.
The function can be wrapped by some other random stuff, or unwrapped.
See also the -X and -x command line options.
Items to bring up documentation, and the usual "About" box
(which includes the license).
An area on the status bar shows how many compute "tasks" are
outstanding (or "Ready" when there are none). When two task
totals are reported, the first is for the main grid and the
second for any enlargements being computed.
Each "task" is the recomputation of an image at some resolution.
Tasks are prioritised by their number of pixels (small image
implies higher priority). This is why, if the main grid is still
recomputing, recalculations of enlargements will appear to freeze
after they have reached a certain resolution, at least until other
lower resolution tasks have completed.
The status bar also provides some control over the "autocool"
mechanism which reduces mutation strength with time.
See the advanced usage section below.
<ul><li>Don't start a session with any preconceived ideas about the kind
of image you want to get out of it. You will be disappointed.
</li><li>I get the best results when I click the image which most
immediately catches my eye as they start appearing. If you stop
to think about it too much then things seem to go downhill.
</li><li>If you seem to be just getting the same old spirals and grids
all the time, stop clicking on spirals and grids!
(The same goes for random mush).
</li><li>Don't get too hung up on using the warp and middle-mouse drag
adjustments every iteration... use those tools for final
polishing of your masterpiece.
</li><li>You can quickly cycle through a lot of initial images (until
you find one with real potential) by bashing on Ctrl-r to
</li><li>To add variety to an image's mutations, nudge it with a small
middle-mouse drag. This introduces a top level transform, and
therefore more parameters to be varied.
</li><li>Enlargements take a long time to complete their final
high-resolution rendering pass (especially with multisampling
enabled). Most convenient practice seems to be to go away and
leave them to complete, then come back and save them later.
Continuing to click away on the main grid effectively starves
them of CPU, unless the -E command-line option is used.
As of version 0.2.0 evolvotron contains some experimental support
for generation of animations (although so far the results have been
pretty disappointing IMHO, but it's still early days).
NB THIS IS EVEN MORE COMPUTATIONALLY AND MEMORY INTENSIVE THAN
THE STATIC IMAGE MODE.
Simply supply a -f <i>frames</i> command line option and evolvotron will
generate animated sequences with the specified number of frames.
These will be displayed at the frame rate specified by the
optional -s <i>framerate</i> option (default 8). So "evolvotron -s 24"
will generate 3 second long animations. Animations reverse direction
at each end to avoid a sudden jump.
If you save an animation as PPM or PNG, multiple files will
be saved with .fnnnnnn (where nnnnnn is the zero-filled frame
number) inserted in each filename before the filetype qualifier.
For example, if you enter foo.ppm as the filename to save,
files foo.f000000.ppm, foo.f000001.ppm... will be saved.
If you have the ImageMagick tools you can convert these to
an animated GIF playing at approx. 8 frames per second with:
<code>convert -delay 12 foo.f??????.ppm foo.gif </code>
Evolvotron's idea of an image is a function which converts
XYZ co-ordinates to an RGB colour (however we can only display
a 2D plane for now so the input Z is fixed to zero, or varied
with time when animating).
The image functions are constructed from trees of function nodes.
(In the mathematical expression 1+(2*x) the "+" and the "*" would
be function nodes.) Evolvotron's functions tend to correspond to
geometric or colour-space operations or anything else which can be
applied to a 3D vector.
By mutating the structure of the function tree (adding random
branches, for example) and the values of the constant embedded
within it, the image can be changed.
The mutation parameters are under control from the dialogs accessible
via the Settings menu, and the "autocool" mechanism exposed in the
status bar also has some influence.
There are two kinds of mutation: perturbations to the magnitude of constants,
and structural mutations which re-arrange the function tree of an image.
Four types of structural mutations are currently implemented:
<ul><li>replacement of a function branch by a new random stub (a "Glitch" mutation).
</li><li>a random shuffle of a node's sub-nodes
</li><li>insertion of random nodes between a node and it's sub-nodes
</li><li>the substitution of a node with one of a different type,
with sub-nodes unaffected where possible).
The probability (per function node) of these mutations is controlled
from spinboxes on the "Mutation Parameters" dialog (expressed as
chances-in-a-hundred), as is the size of perturbations to constants.
It is useful to think of the perturbations to constant parameters as
being a thermal effect (hence the "heat" and "cool" buttons), while
structural alterations are more drastic and are caused by high energy
gamma rays or something (hence "irradiate" and "shield" buttons to
adjust the probability of structural mutations).
So why would you want to change the mutation parameters from the initial
defaults ? Basically, if you're getting too much variation in spawned images
(this tends to happen after many generations of images, by which time the
function trees have grown quite large and therefore are experiencing a lot
of mutations) then cool and/or shield.
If all the images look too similar, heat and/or irradiate.
The "autocool" mechanism (enabled from the statusbar or mutation parameters
dialog) automatically reduces the strength of mutations from the base
values with successive generations. The cooling can be cancelled by
disabling autocooling or pressing the "Reheat" button to zero the number
of generations counted for cooling. The effect of the cooling is a compound
halving of the mutation strength after some number of generations (this number
is the "half-life" controllable from the mutation parameters dialog).
Note that if autocooling is enabled then eventually, after a number of
iterations more than many multiples of the half-life has passes, spawned
images will differ very little from their parents (hence the need for "reheat").
There is also a dialog accessible from "Functions..." on the "Settings" menu.
This allows control over the relative proportions in which functions occur.
There is a tab showing the relative weighting of all functions (log-2 scale: each
tick halves the probability of the function occurring), and additional tabs
for various classifications of function for quicker access.
The "Randomize" button on each tab assigns random weightings and helps
increase the uniqueness of your session.
The "Functions" dialog also has a "Dilution" tab which allows the average
function-tree branching ratio to be controlled (by changing the proportion
of trivial zero-branch functions added): note that using a high branching
ratio results in very complex images which will take a long time to compute,
while reducing the ratio results in simple, boring images.
3 types of function node are considered fundamental: constant nodes
(which return a constant), identity nodes (which return their
position argument) and transform nodes (which transform their position
argument by random parameters). On the "Dilution" tab of the "Functions"
dialog there are two slider controls to affect things related to these:
<ul><li>"proportion constant" controls the proportion of diluting fundamental nodes
which are constants. Changing this from its default value of 0.5 doesn't
actually seem to have much effect.
</li><li>"proportion transforms" sets the proportion of non-constant nodes diluting
which are transforms (as opposed to identity nodes).
The main effect of this is that images are less commonly obviously centred
on the origin or aligned with the axes. I think this is a good thing, so
the value is at 1.0 by default.
This release also builds some other command-line driven (non-GUI, non-interactive) utilities.
Consult the man pages for full details.
evolvotron_render reads a XML function description from its standard input and renders it to the
evolvotron_mutate reads an XML function description from its standard input and outputs a mutated version.
A command line option allows the "genesis" situation of creating a random function description with no input.
Evolving and mutating on the command line:
<code>evolvotron_mutate -g | tee fn.xml | evolvotron_render /tmp/xxx.ppm ; display /tmp/xxx.ppm </code>
<code>cat fn.xml | evolvotron_mutate | evolvotron_render -j -m 4 /tmp/xxx.ppm ; display /tmp/xxx.ppm </code>
Animating a function ani.xml saved from evolvotron in animation mode:
<code>cat ani.xml | evolvotron_render -f 100 -v -s 256 256 ani.ppm ; animate ani.f??????.ppm </code>
Please check the TODO file first before you send me suggestions!
Please don't ask me to port evolvotron to proprietary platforms.
You are of course Free under the terms of the GPL to do so yourself,
but please read
To those who have contributed feedback, suggestions and patches:
</li><li>"chr_bl" at web.de
And to the anonymous Linspire reviewer who perhaps came up with the best
summary of evolvotron yet: "Fascinating. Utterly pointless, but fascinating."
The friezegroups wouldn't have been possible without
Thanks to www.di.fm, www.somafm.com and Trance4Ever for music to code to.
Thanks especially to a SIGGRAPH conference panel many years ago (likely
including Karl Sims, the pioneer in this area) who first got me interested
in this stuff.
I have always admired those who have the skill to wield a pen or paintbrush
and fill a sheet of paper or a canvas with some striking image from their
imagination. Unfortunately I lack the patience to learn such skills,
and probably the necessary manual dexterity and imagination too.
Evolvotron, and several predecessors developed on and off over a decade
since I first came across the idea, are an attempt to compensate for
this using the skills I do have i.e some mathematical sensibility
and the ability to write working code (well, sometimes). If you like
an image it produces, then as far as I'm concerned that's as satisfying
a result as if you liked something I'd drawn myself.