The Tree
and Plant Designer (in short, TaPD) is a plug-in for Art of Illusion
that allows creation of tree or plant objects. The design of these
objects is based on a procedural fractal-like process. Creation and editing
of the procedure is done in an editing window through creating and
linking modules, much like in the procedural texture editor window
(this manual thus supposes that you are familiar with the basic
concepts of procedural texture creation and editing).
1.1General
overview of a procedure
An object
is created using the following scheme :
A
starting object, presumably a trunk or a stem is designed or imported
from AoI scene;
This
object is decorated with
other objects (branches or leaves) given certain geometric rules;
In
turn those objects are decorated, for example with some other branches;
The
decoration continues until the last decoration process is carried out.
What you,
the user, specifies and design are :
The objects that are decorated or decorate
The geometric parameters for decoration
There is
no such thing as templates for leaves or tree geometry : basically the
concept is to arrange some objects (whatever they are) following
certain geometric rules. In a way, the TaPD is essentially similar to
the Array tool.
The objects and the
geometrical rules are represented by modules
similar to those found in the procedural texture editor. There are
three kinds of modules :
The object modules
The geometric modules
The value modules
The
objects and the geometrical rules are represented by modules similar to
those found in the procedural texture editor. There are three kinds of
modules :
The object modules
The geometric modules
The value modules
The
object modules represent 3D objects like those found in AoI (sphere,
cylinders and such). One kind of module (the AoI object module) holds
any kind of AoI object that has been created in AoI and imported into
the TaPD. The other modules create objects that, at this stage of
development, all have a conic or cylinder shape. These are used for
representing branches and stems, and can be distorted (bent, twisted,
etc.) following certain geometric rules (whereas the shape of plain AoI
objects cannot be modified).
The geometric modules take objects as input and, given certain
parameters, decorate the input object with decorator objects. They can
distort the decorated object and/or decorators during the decoration
process. Value modules are
used to specify some parameters for geometric or objects modules. Many
of the parameters are specified through dialog windows, except for size
parameters that are specified through value modules. The benefits of
this design will become obvious once you become more familiar with the
TaPD.
The following figure illustrates this procedural design. A cone is
specified as the starting object of the decoration process. This module
is unique in the procedure and is shown with a green background. This
object is plugged into a coil module which, as all geometric modules,
shows a maroon background. Another object module corresponding to
another cone is plugged into the decorator input of the coil module.
Specifying some parameters in the coil module and plugging a customised
function into that module yields the result illustrated by the second
figure.
Figure 1
Figure 2
1.2
Getting started
Creating
a TaPD object is quite simple. Before you start, just ask yourself if
you need an AoI object right from the beginning. The 'AoI object' term
refers to any any object created within an AoI view window. TaPD
objects are objects created within the TaPD editor window. Of course,
TaPD objects are AoI objects,
otherwise they wouldn't appear afterwards in AoI views and wouldn't get
rendered, but they also have special abilities that AoI objects don't
have (more about this later on).
So, if you think you need to model a leaf, a trunk or whatever, do it
now in AoI as usual and select it in the object list. If you don't
particularly need such an object, or just want to have a go at the TaPD
editor window, make sure that no object is selected in the object list.
Now, whatever choice you made, select the Tree and plant designer menu
item in the tools menu. A window appears, similar to figure 3 :
Figure
4
If you
didn't select any object before launching the TaPD editor window, you
will notice that the first button of the tollbar is disabled. This
button allows you to insert modules that hold the AoI objects imported
into the TaPD object. Since there is none at this time, the toolbar
button is disabled. The OK button is also disabled : the procedure is
empty and doesn't yet produce a valid object. Click on the tube module,
which is the third blue button on the toolbar (or alternatively select
the appropriate menu item from the Insert
menu). A module is inserted in the working area of the window. It shows
a green background that specifies that this object is the starting
object for the procedure. Usually, it is the main stem of a plant or
the trunk of tree.
Figure
5
Modules can be moved
by
clicking in the background area (the green border in that case) and
dragging. Selection is done in exactly the same way as in the
procedural texture editor. The tube module shows three ports : two
input ports coloured in magenta and one output port coloured in green.
Green ports correspond to object ports whereas magenta ports correspond
to value ports. So this module has two value input ports and one object
output port. There are also two buttons, the one named tube and the
other one with the letter 'P' on it. The first button, if clicked,
brings a dialog window allowing the object contained in the module to
be edited. The second button brings a preview window which allows not
only the object to be previewed, but also in the certain cases the
whole TaPD object or parts of it.
Right now, let's click on the 'P' button. The following preview window
appears :
Figure
6
You will recognise
quite quickly that this window is in fact the AoI main window stripped
of any editing tool. This is only a preview window and the generated
object can't be modified within this window. There is a done button to
exit the preview. Closing the window can also be achieved by clicking
its top right close button or selecting the Done menu item in the Edit menu. The view can be rotated
and translated, and the four views mode is available. The background is
light green to prevent confusion with the true AoI main window.
The preview window can also be rendered using the usual default light
and camera. Selecting Scene
-> Render Scene... brings
out the usual dialog. Often, the camera is too far from the center of
the scene. Its location can modified through use of the new Scene -> Set camera location command, which
is the only way of moving it since there aren't any editing tools in
the preview window. When the preview window is first displayed, the
previewed object is selected, so that a Ctrl-F command frames the object in
case the default scale is too far from ideal.
What you can see from Figure 6 is that the default tube is far from a
stem or trunk shape. The height is too small and the radius at the
bottom is too wide. Click on the done button to dismiss the preview and
click on the tube button.
Figure
7
The white
pane shows the current shape of the tube. The R-Shape button and the
Tube shape button allow the overall shape of the tube to be defined.
Set texture and set material are used to assign a texture or a material
to the tube object, like in AoI main window. The deliver duplicates
checkbox will be explained later on in the manual, we will ignore it
for the time being. Finally, the three usual buttons OK, Apply and
Cancel can be found at the bottom of the dialog. Let's
concentrate on the shape of the tube. Clicking on the Tube shape button brings the
following window :
Figure
8
This window is in
fact the tube editor window. Grids have been added to the view shown in
figure 8 to show that the base vertex lies at coordinates (0,0).
You can do whatever you want with the other vertices, but keep that one
coincident with the local coordinate system origin. Selecting all
vertices and resizing the tube with the top handle gives this result :
Figure
9
Note that there are
only three vertices on the curve that define the tube shape. These
control points are all you get in terms of tube distortion control upon
applying a distortion using a coil or distort module later on in the
procedure. You can have more control points through subdivision of the
tube curve in the tube editor window. Beware, though, that more control
points mean that the tube object uses more memory. The number of
control points must thus be adapted to the use you intend to make of
the tube. For major branches to which branching effects will be
applied, a fair number of control points is needed (maybe up to
twenty). For small branches to which no further branching is attached
four or five vertices will be sufficient. If a preview shows that a
particular kind of tube object does not possess enough control points,
simply edit the tube and subdivide the curve. Another point is that
there is no reason why the points should be evenly spaced. If the
procedure design is such that a tube needs more control points in some
ranges of the curve, simply subdivide these parts of the tube. Since in
our example the tube will remain straight, we will keep the simple
three points design.
Next, we are going to change the radial size at the base of the tube.
Normally, this change is carried out setting the thickness at each
control point of the tube. However, this procedure can quickly get
tedious if you happen to have a more than a few control points. Close
the tube editor window and click on the R shape button. A new window appears
showing a customised function taken from the procedural editor
customised function module. Bring the first control point to 0.5 :
Figure
10
You can
use this function to set any shape along the tube axis. It overrides
the thickness property of the usual AoI tube. If the function shape
shows abrupt variations, the control point density of the tube must be
dense enough for these changes to actually be taken into account in the
final tube shape.
What next ? Insert a coil module (first button of the second button
group in the toolbar, or the appropriate menu command). Select, copy
and paste the tube module. The copy has a blue background, which is the
colour for object modules that are not the starting object of the
procedure. Look at the figure below, and set up links accordingly. When
the line you are dragging from a port of a module correctly ends on a
compatible port of another module, a kind of magnetic effect tells you
that you can release the mouse button to establish the link
Figure
11
Click on the preview
button of the starting object, the green tube module. It shows the
result of this three modules procedure. The starting object preview
button is special : it shows the whole object generated. The preview
button of a usual object module, like the blue tube module, shows only
the object defined by the module. The preview button of the coil module
shows the object generated up to the coil module. Since there is
nothing after the coil module in the procedure, it shows the same
object as the starting object tube module. What the previews tells us
is that :
The tubes
used to decorate are too big;
They have
a constant size along the vertical axis of the "trunk", which is not
what we want.
To address the
first point, we will plug a constant value to the size entries of the
tube module. Click twice on the constant value module button (first
button of the black buttons group in the toolbar) to insert two value
modules and enter a value of 0.4 for the R size input port and 0.6 for
the Y size input port. Setup links as in the figure below :
Figure
12
Next add a customised
function (second black button of the toolbar) and plug it like figure
11. If you want to know what is the nature of each port in a module,
let the mouse stay awhile on a port and a tooltip will tell you what
this port is for. Let's see the result of our work :
Figure
13
Not too bad, but we
could do with curved branches. Click on the tube button of the decorator tube
module (the blue one), click on the Tube
shape button editor window and select all vertices. Subdivide
the curve twice :
Figure
14
Now,
click on the coil button of the coil module. Enter a value of 70
degrees in the vertical angle input box, as shown in figure 15.
Select the second pane named TaPD
object parameters, and enter a value of 35 degrees as shown in
figure 16. This second pane is devoted to distortion parameters that
can be applied only to TaPD objects. Specifying parameters in this pane
for an AoI decorator object has no effect.
Figure
15
Figure
16
Clicking on the
preview button of the starting object yields the result shown in figure
17. Even if it doesn't look like a tree, changing some more parameters
in the coil module could make the difference. It is now the time to
click on the OK button of the toolbar to get a proper object in the AoI
main window (figure 18). This object can be moved, rotated, edited,
etc. like any other AoI object. However, it cannot be resized (yet). To
change its size, it must be edited and the size of each individual
object module changed accordingly.
