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This fractal-based plug-in is truly wonderful! With this
versatile instrument, you can create amazingly naturalistic
organic shapes, like leaves, flowers, branches, or even whole
trees. (“IFS” stands for “Iterated Function System
”.)
The key to use this plug-in lies in making very small and precise
movements in fractal space. The outcome is always hard to predict, and
you have to be extremely gentle when you change the pattern. If you make
a component triangle too big, or if you move it too far (even ever so
slightly), the preview screen will black out, or more commonly, you'll
get stuck with a big shapeless particle cloud.
A word of advice: When you have found a pattern you want to work with,
make only small changes, and stick to variations of that pattern. It's
all too easy to lose a good thing. Contrary to what you might believe,
it's really much easier to create a leaf or a tree with IFS Compose than
to make a defined geometrical pattern (where you actually know what
you're doing, and end up with the pattern you had in mind).
For a brief introduction to IFS's see Foley and van Dam, et
al,. Computer Graphics, Principles and
Practice[FOLEY01].
13.5.2. Activating the filter
This filter is found in the image window menu under
→ → → .
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The Main Interface
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The plug-in interface consists of the compose area to the left, a
preview screen to the right, and some tabs and option buttons at
the bottom of the dialog. The Default setting (in the preview
window) is three equilateral triangles. (This gives rise to a
fractal pattern called the
Sierpinski Triangle).
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Toolbar
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Some tools are directly visible in this tool bar:
Move,
Rotate, Stretch,
New,
Delete, Undo,
Redo,
Select All.
You can see others, if your window is not wide enough, by
clicking on the drop-down list button on the right of tool bar:
Recenter and
Render Options where you have have
several parameters:
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Render Options
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Memory
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Enables you to speed up rendering time. This is
especially useful when working with a large spot
radius; just remember to use even multiples of the
default value: 4096, 8192, 16384, ...
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Iterations
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Determines how many times the fractal will repeat
itself. (A high value for Subdivide and Iterations is
for obvious reasons a waste of process time unless
your image is very large.)
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Subdivide
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Controls the level of detail.
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Spot Radius
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Determines the density of the
“brushstrokes”
in the rendered image. A low spot radius is good for
thin particle clouds or spray, while a high spot
radius produces thick, solid color strokes much like
watercolor painting. Be careful not to use too much
spot radius -- it takes a lot of time to render.
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Spatial Transformation
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Gives you information on the active fractal, and allows you to
type a value instead of changing it manually. Changing parameters
with the mouse isn't very accurate, so this is a useful option
when you need to be exact.
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Color transformation
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Simple color transformation
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Changes the color of the currently selected fractal
component (default is the foreground color in the toolbox)
to a color of your choice.
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Full color transformation
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Like the Simple color transformation but this time you can
manage the color transformation for each color channel and
for the alpha channel (shown as a black channel).
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Scale Hue/Value
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When you have many fractals with different colors, the
colors blend into each other. So even if you set
“pure red” for a fractal, it might actually
be quite blue in some places, while another “red
” fractal might have a lot of yellow in it. Scale
Hue/Value changes the color strength of the active
fractal, or how influential that fractal color should be.
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Relative Probability
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Determines influence or total impact of a certain fractal.
This is a rather complex plug-in, so to help you understand it, we'll
guide you through an example where you'll create a leaf or branch.
Many forms of life, and especially plants, are built like
mathematical fractals, i.e., a shape that reproduces or repeats
itself indefinitely into the smallest detail. You can easily
reproduce the shape of a leaf or a branch by using four (or
more) fractals. Three fractals make up the tip and sides of the
leaf, and the fourth represents the stem.
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Before invoking the filter: Select
→ .
Add a transparent layer with
→ → .
Set the foreground color in the toolbox to black, and
set the background to white.
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Open IFS Compose. Start by rotating the right and bottom triangles,
so that they point upward. You'll now be able to see the outline of
what's going to be the tip and sides of the leaf. (If you have
problems, it may help to know that the three vertices of a triangle
are not equivalent.)
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To make the leaf symmetrical, adjust the bottom triangle to
point slightly to the left, and the right triangle to point
slightly to the right.
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Press New to add a component to the
composition. This is going to be the stem of the leaf, so we
need to make it long and thin. Press
Stretch, and drag to
stretch the new triangle. Don't be alarmed if this messes up
the image, just use Scale to adjust
the size of the overlong
triangle. You'll probably also have to move and rotate the
new fractal to make it look convincing.
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You still have to make it look more leaf-like. Increase the
size of the top triangle, until you think it's thick and
leafy enough. Adjust all fractals until you're happy with
the shape. Right-click to get the pop-up menu, and choose
Select all. Now all components are
selected, and you can scale
and rotate the entire leaf.
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The final step is to adjust color. Click on the
Color Transformation tab, and choose
a different color for each fractal. To do this, check
Simple and press the right color
square. A color circle appears, where you can click or
select to choose a color.
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Press OK to apply the image, and voilà, you've just made a
perfect fractal leaf! Now that you've got the hang of it,
you'll just have to experiment and make your own
designs. All plant-imitating fractals (be they oak trees,
ferns or straws) are more or less made in this fashion,
which is leaves around a stem (or several stems). You just
have to twist another way, stretch and turn a little or add
a few more fractals to get a totally different plant.
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