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object_types.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>object_types.html</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="background-color: rgb(245, 225, 151);">
<font face="tahoma" size="2">
</font>
<div align="left"><font face="tahoma" size="2"><a href="modelling.html"><b><font size="4">Previous:
Modelling</font></b></a></font></div>
<font face="tahoma" size="2"><br>
</font>
<div align="right"><font face="tahoma" size="2"><a href="modelling_tools.html"><b><font size="4">Next:
Modelling Tools</font></b></a></font></div>
<font face="tahoma" size="2"><br>
<font face="tahoma" size="6"><strong>2. Modelling</strong></font>
<img src="man_title_small.jpg" align="middle"><br>
<br>
<br>
<strong><font color="#3300cc" size="5">2.1
Object Types</font></strong><br>
<br>
<a name="primitives"><strong><font color="#ff6633" size="4">2.1.1 Primitives</font></strong></a><br>
<br>
There are 3 basic geometric primitives available in Art of Illusion: <b>cube</b>,
<b>sphere</b> and <b>cylinder</b> objects,
which can either be created using the modelling tool icons in the upper
left corner of the screen or via the top menu bar as follows:<br>
<br>
Using the modelling tool icons allows immediate creation of the
primitive. Simply click on the relevant icon:<br>
<br>
cube: <img src="modelling/cube.jpg"> sphere: <img src="modelling/sphere.jpg"> cylinder: <img src="modelling/cylinder.jpg">
<br>
<br>
then click and drag on any viewport to define two of its initial
dimensions. The 3rd dimension will have to be altered if necessary
using the scaling tool <img src="modelling/scale.jpg">
in one of the other viewports. Alternatively, holding shift while
dragging forces all 3 dimensions to be equal.<br>
<br>
<a name="cyl">For cylinders</a>, the top:bottom
ratio can be set to form tapered cylinders (including cones) prior to
drawing by double-clicking on the cylinder icon. This ratio can also be
edited after drawing (see <a href="editing_objects.html#edit_object">editing_objects</a>).
<table>
<tbody>
<tr>
<td><img src="modelling/cube_dial.jpg"></td>
<td><font face="tahoma" size="2">Creating
the primitive via the menu bar is achieved by selecting <b>Object
-> Create Primitive </b>and then selecting the
appropriate shape. Cones can also be created directly using this
method. This method brings up a dialogue box similar to that on the
left which allows the exact size, position and orientation of the
object to be specified.</font></td>
</tr>
</tbody>
</table>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">Primitives
have limited use for creating realistic objects as such objects are
rarely that simple in real life. However they can be useful for
cartoon-like scenes or for building up more complex models using
Constructive Solid Geometry (CSG) via the <a href="modelling_tools.html#boolean">Boolean tool</a>
like in the simple example on the right:<br>
<br>
Primitives are also important as they can be the starting points for
creating triangle meshes. See <a href="#triangle_meshes">2.1.4</a>
below.<br>
</font></td>
<td><img src="modelling/boolean_example.jpg"></td>
</tr>
</tbody>
</table>
There is one other important primitive object: the <b>Null</b>
object. Null objects do not show up on renders as
they have no geometry. Their main use in is grouping other geometrical
objects together. For example
you might want to create a car out of a set of geometric objects
representing the car body, wheels,
windscreens etc. A neat way to keep all the parts together would be to
create a Null object and to group
the geometric objects as children of that Null (see the <a href="layout.html#object_list">Object List</a> for
more details). Nulls are represented as crosses in the viewports.<br>
<br>
<br>
<a name="curves"><strong><font color="#ff6633" size="4">2.1.2 Curves</font></strong></a><br>
<br>
These are one dimensional objects and thus are not directly visible when you
render a scene.
However, they can be used in a <a href="modelling_tools.html">variety
of ways</a> to create 3-D objects. <br>
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">Curves
are created by defining a series of points in any of the viewports.
They can have one of two types of smoothing: 'Interpolating', for which
the curve is forced to pass through the points and 'Approximating'
where the curve does not have to pass through all the points but
is still controlled by them.<br>
<br>
To create a curve, click on <img src="modelling/inter_curve_icon.jpg"><br>
<br>
Then click a series of locations on a viewport to define the points as
shown on the right. Shift-click to create a sharp corner.<br>
<br>
To define the last point on the curve and thus end curve point
definition, double click. If you wish to automatically close the curve,
press the control key and double click. Alternatively to end
the curve without adding more points, press Enter to end without
closing or control-Enter to close
the curve.
<p>
To control whether you are creating an interpolating or approximating curve,
double click <img src="modelling/inter_curve_icon.jpg">. A window will appear
where you can select the type of curve to create.
</font></td>
<td><img src="modelling/inter_curve.jpg"></td>
</tr>
</tbody>
</table>
<br>
Closed curves can also be filled to create 2D objects by converting
them to <a href="#triangle_meshes">triangle meshes</a>.<br>
<br>
Another way to create a curve is to use the polygon tool. A polygon is
any flat shape with 3 or more sides. To create a polygon curve, double
click on <img src="modelling/polygon.jpg"> which brings
up this dialogue box: <br>
<table>
<tbody>
<tr>
<td><img src="modelling/polygon_dialogue.jpg"></td>
<td><font face="tahoma" size="2">You
can specify how many sides the polygon has and the type of smoothing of
the edges. Selecting 'angled' gives the polygon straight edges, while
choosing either 'interpolating' or 'approximating' creates rounded
edges. Because 'approximating' smoothing
does not require the curve to pass through all the points, this results
in a smaller overall shape for the 'approximating' polygon.</font></td>
</tr>
</tbody>
</table>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">The
figure on the right shows the differences between the 3 types of
smoothing for a 3-sided polygon curve:<br>
<br>
These were created by clicking once on the polygon tool icon and
dragging a rectangular area on one of the viewports to define its size.
<br>
<br>
Note: The Polygon tool can also be used to create 'filled polygon
surfaces' which are triangle
mesh objects. This is achieved by holding <ctrl> while
dragging. <br>
</font></td>
<td><img src="modelling/triangle_types.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Editing Curves</b><br>
<br>
Once polygon edges or curves have been created, the points defining
them can be edited by double-clicking on them in the Object List. For
example, double-clicking on the interpolated 3-sided polygon displays
the editing window below:<br>
<img src="modelling/editing_curve.jpg"><br>
Points are selected and deselected using the Select/Move tool. Multiple
points can be selected by pressing <shift> before
clicking on each point. Points can also be selected using a marquee
method by dragging a rectangular box over a group of points.
<Shift> selects works for the marquee selection also. All
points can be selected using the appropriate option from the Edit menu.<br>
<br>
To deselect points, simply click or <shift> click on
them. Alternatively a group of points can be deselected by pressing
<ctrl> and dragging a rectangle over the required points.
<br>
<br>
Selected points can be moved using the Select/Move tool or rotated,
skewed, scaled and tapered with the appropriate tools shown on the
left. Most of the tools activated from these icons are
self-explanatory. Resting the cursor over the icons will bring up a
tooltip to describe its function. The operation of most can be modified
by pressing <shift> or <ctrl> - see the
bottom of the editing window for details relevant to each tool.In
general, handles around the selected point(s) can be dragged to effect
the operation. Pressing <shift> while dragging causes the
operation to be a uniform one, whilst <ctrl> centres it.
The spacebar can be used to switch between tools quickly; pressing it
toggles between the
Select/Move tool and the last tool used.<br>
<br>
The view in the curve editor is controlled as in the main view windows,
i.e. yhrough use of the camera move/rotate icons or the keyboard
shortcuts. See <a href="layout.html#view_windows">here</a>
for more details.
<br>
Additional editing is possible through the top menu bar.<br>
<br>
This is the <strong><font color="#009933">Edit</font></strong>
Menu:<br>
<table>
<tbody>
<tr>
<td><img src="modelling/curve_edit_menu.jpg"></td>
<td><font face="tahoma" size="2"><b>Undo/Redo</b>
- undoes the last action or redoes something you have just undone,
including selections.<br>
<br>
<b>Select All </b>- selects all points in curve.<br>
<br>
<b>Extend Selection </b>- automatically selects
adjacent points to those already selected.<br>
<br>
<b>Invert Selection </b>- deselects all currently
selected points and selects all currently deselected
points. </font></td>
</tr>
</tbody>
</table>
<b>Freehand Selection </b>- enters a selection mode that
allows you to trace a freehand path - all
points enclosed by the path are selected. This mode can be toggled
on/off.<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2"> <b><a name="curvetension">Curve Tension</a> </b>-
This controls the amount by which adjacent points
(and possibly beyond) move with currently selected points. Selecting
this option produces the dialogue box on the right.
The <b>Maximum Distance</b> is the number of points each
side of the currently selected point that are
affected. The <b>Tension</b> is strength of the attractive
effect so that a 'very high' tension will move the affaected points
significantly whereas a 'very low' tension will move them only a
little. </font></td>
<td><img src="modelling/curve_tension.jpg"></td>
</tr>
</tbody>
</table>
<br>
The <strong><font color="#009933">Curve</font></strong>
Menu looks like this:<br>
<table>
<tbody>
<tr>
<td><img src="modelling/curve_curve_menu.jpg"></td>
<td><font face="tahoma" size="2"><b>Delete
Selected Points </b>- deletes all selected points !<br>
<br>
<b>Subdivide Selection </b>- A way of adding points
to an existing curve, this tool adds a point between each pair of
currently selected points.<br>
<br>
<b>Edit Points </b>- Allows you to explicitly define
the coordinates of any point or group of points. A realtime preview of
the effect of values entered in the dialogue is shown on the actual
curve - cancelling the dialogue causes the curve to revert back to its
original shape.<br>
<br>
<b>Randomise Points </b>- translate points by a
random number below a user-specified maximum in any or all 3 axes.<br>
</font></td>
</tr>
</tbody>
</table>
<table>
<tbody>
<tr>
<td width="400"><font face="tahoma" size="2"> <b>Transform Points </b>- brings up
the dialogue on
the right to allow points to be moved, scaled or rotated accurately.
Can also transform about centre of selection or origin of object.<br>
</font></td>
<td><img src="modelling/transform_points_dialogue.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Centre Curve</b> - moves the curve object so that its
centre coincides with the origin (0,0,0).<br>
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2"> <b>Set
Smoothness </b>- If either interpolating or
approximating smoothing is used, it is possible to specify the
smoothness of individual points. In the example on the right, a heart
shape was created
with the approximating curve tool. To 'sharpen' the curve in the right
places, the points shown
were selected and their <b>Smoothness</b> set to 0. This
makes them completely sharp but values between
0 and 1 can be used to obtain intermediate smoothnesses. A realtime
preview of the effect of smoothness values entered in the dialogue is
shown on the actual curve - cancelling the dialogue causes the curve to
revert back to its original shape. </font></td>
<td><img src="modelling/curve_smoothness.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Smoothing Method </b>- This is the method used to
smooth the curve. The choices are None (straight lines between points),
Interpolating or Approximating.<br>
<br>
<b>Open Ends </b>- if the curve is closed, i.e. a complete
loop, this will break it and <i>vice versa</i>.
<br>
<br>
The <strong><font color="#009933">View</font></strong>
Menu looks like this:<br>
<br>
<table>
<tbody>
<tr>
<td><img src="modelling/curve_view_menu.jpg"></td>
<td><font face="tahoma" size="2"> <b>Display
Mode</b> is irrelevant for curve objects.<br>
<br>
<b>Show</b> allows the editor to view the <b>Curve</b>
or the <b>Entire Scene</b> for the currently
highlighted window. Only the curve,however, can be edited.<br>
<br>
<b>Coordinate System</b> can either be <b>Local</b>
or <b>Scene</b>. In the former case, all objects
are displayed in a coordinate system that has the curve at the origin.
The latter option displays
objects as they are in the main view.<br>
<br>
<b>One View/Four Views</b> toggles between having the
four view display or a one view display of the
currently selected window<br>
<br>
<b>Grids</b> allows a grid to be visualised and
snapped to. See <a href="layout.html#grids">here</a>
for more details. </font></td>
</tr>
</tbody>
</table>
<br>
<b>Show/Hide Coordinate Axes</b> toggles display of the x,y
and z axes as shown <a href="layout.html#coordaxes">here</a>.<br>
<br>
<b>Show/Hide Template</b> displays or hides the image
selected as the background in the next menu option.<br>
<br>
<b>Set Template Image...</b> allows an image (in .jpg, .png
or .gif format) to be used as the background
in the editor. This is useful as a reference when modelling. Selecting
this displays a dialogue to
allow selection of the image which can then be turned on/off with the
previous menu entry.<br>
<br>
<br>
<a name="splines"><strong><font color="#ff6633" size="4">2.1.3 Spline Meshes</font></strong></a><br>
<br>
Splines are smooth surfaces the shape of which are determined by
control points and the type of smoothing applied. Splines can
be created by applying the various <a href="modelling_tools.html">modelling_tools
</a>to existing objects (usually curves) or directly by clicking
on <img src="modelling/spline_icon.jpg">
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">Before
doing that, you can select some of the spline properties by
double-clicking on that same icon. This brings up the dialogue box on
the right:<br>
<br>
<br>
The U and V size boxes determine the physical dimensions of the spline
mesh 'sheet', i.e the number of control points in each of the two
dimensions.<br>
<br>
<br>
The shape can be either flat, a cylinder or a torus. In the latter 2
cases, to understand the U and V dimensions it may help to think of a
rolled-up sheet. For a cylinder, U-size is the number of points around
the circumference and V-size is the number of points along its axis.
Similarly for a torus, U is along the circumference and V-size is the
number of points around the cross-section.<br>
<br>
<br>
The smoothing method can be either 'approximating' or 'interpolating'.
See <b><a href="object_types.html#curves">2.1.2</a></b>
for an explanation of these terms.<br>
<br>
<br>
The <b>Thickness</b> parameter is only relevant for the
torus and controls the cross-sectional diameter as shown on the right.</font></td>
<td> <img src="modelling/spline_dialogue.jpg"><img src="modelling/torus_splines.jpg"></td>
</tr>
</tbody>
</table>
<br>
<br>
Once the spline has been created, it can be edited by double-clicking
on the object in the Object List. This brings up an editing window
similar to this:<br>
<img src="modelling/spline_editting.jpg">
<br>
As in the <a href="layout.html#view_windows">main
viewports</a>, the orientation, scaling and type (parallel or
perspective) of view can be controlled using the familiar camera
control icons/keyboard shortcuts and drop down menus at the top of the
view. The type of shading can also be altered by selecting <b>Mesh
-> Display Mode </b>(see <a href="layout.html#display_mode">Display Mode</a> for
details on this)<br>
<br>
The editing utility allows both <i>vertices</i> ('points')
or <i>curves</i> to be edited. The editing mode is
selected by clicking on the appropriate button at bottom left. The
icons on the left allow points and curves to be transformed in various
ways as identified on the diagram above. The points or curves to be
transformed must be selected first by clicking on individual points or
curves. Multiple
selections are achieved by holding down <shift> while
successively clicking on further points/curves. A marquee
('rubber band') selection is also possible and is performed by dragging
the mouse while holding the left mouse button to highlight a rectangle.
Note that for curves, you need to enclose the whole curve
within the selection marquee for this to work. Pressing
<ctrl> while clicking or dragging a marquee de-selects
all currently selected points/curves. There is also a freehand
selection mode
which is enabled through the<a href="#spline_edit_menu">
Edit</a> menu. Having selected the vertices/curves to
edit, the tool is actioned by dragging on the red arrow handles that
will appear.<br>
<br>
Most of the tools activated from the icons are self-explanatory.
Resting the cursor
over the icons will bring up a tooltip to describe its function. The
operation of most can be modified by pressing <shift> or
<ctrl> - see the bottom of the editing window for details
relevant to each tool. The tools available are a subset of those for
triangle meshes; see <a href="object_types.html#mesh_tools">here</a>
for more details. The spacebar can be used to switch between tools
quickly; pressing it toggles between the
Select/Move tool and the last tool used.<br>
<br>
Skeletons are discussed in detail in <a href="#skeletons">Section
2.1.5</a>.<br>
<br>
<b><font color="#0000ff">MENUS</font></b><br>
<br>
Further useful tools are found on the top menu bar:<br>
<br>
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">The <strong><font color="#009933"><a name="spline_edit_menu"></a>Edit</font></strong>
menu looks
like this: </font></td>
<td><img src="modelling/spline_edit_menu.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Undo/Redo</b> - undoes the last action or redoes
something you have just undone, including selections.<br>
<br>
<b>Select All</b> - selects all points or curves.<br>
<br>
<b>Extend Selection</b> - expands selection by adding
points/curves adjacent to those currently selected.<br>
<br>
<b>Freehand Selection </b>- enters a selection mode that
allows you to trace a freehand path - all
points or curves enclosed by the path are selected. This mode can be
toggled on/off.<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2"><a name="mesh_tension"><b>Mesh Tension</b></a>
- introduces a neighbour attraction effect so that moving a point/curve
also results in (lesser) movement in the points/curves adjacent to it.
The mesh tension dialogue box is shown on the right.<br>
<br>
The <b>Maximum Distance </b>defines the number of points
affected. For example setting this to 2 means that vertices within 2
points along all edges of the mesh will undergo some transformation the
magnitude of which decreases with distance from the selected point. The
example on the far right illustrates this. The pink point is the
selected vertex; the green points are those that would be affected if
Maximum Distance was set to 2.<br>
<br>
The <b>Tension</b> defines the strength of the attractive
effect so that a 'very high' tension will move adjacent points
significantly whereas a 'very low' tension will move them only a little.<br>
</font></td>
<td><img src="modelling/mesh_tension.jpg"></td>
<td><img src="modelling/mesh_tension_ex.jpg"></td>
</tr>
</tbody>
</table>
<br>
<br>
The <strong><font color="#009933">Mesh</font></strong>
menu is shown below. Note that some items on this menu will not be
available depending on which mode you are working in. These are the
options available in curve editing mode.
<table>
<tbody>
<tr>
<td><img src="modelling/spline_curve_menu.jpg"></td>
<td><font face="tahoma" size="2"> <b>Delete
Selected Curves</b> - deletes all selected
curves<br>
<br>
<b>Subdivide Selection </b>- this only works on a
set of adjacent curves and creates a new curve between each adjacent
curve as shown below. This can help produce a smoother finish and in
adding small details to a mesh.<br>
<br>
<img src="modelling/spline_curve_subd_small.jpg"> </font></td>
</tr>
</tbody>
</table>
<br>
<b>Edit Points</b> allows you to specify absolute x, y and
z co-ordinates for selected points and to specify skeleton properties
(see <a href="#skeletons">Skeletons</a>). A
realtime preview of
the effect of values entered in the dialogue is shown on the actual
mesh - cancelling the dialogue causes the mesh to revert back to its
original shape.<br>
<br>
<b>Transform Points </b>allows you to move, rotate and
scale selected points/curves by explicitly entering the values in the
x, y and z axes.
<br>
<br>
<b>Randomise Points </b>causes random variations in
position within a user-defined tolerance. This is useful, for example,
in simulating imperfections found in real life.<br>
<br>
<b>Texture Parameters </b>is discussed in detail in <a href="textures2.html#tex_param">
textures_and_materials</a><br>
<br>
<b>Centre Mesh </b>translates the mesh so that its centre
lies at (0,0,0).<br>
<br>
<b>Extract Selected Curve </b>creates a copy of the
currently selected curve as a new object. Only works if a single curve
is selected.<br>
<br>
<b>Set Smoothness </b>allows you to define how sharp the
mesh is at the selected points/curves. In the example below, the
smoothness of 3 of the curves was changed from 1 to 0
on the right hand image, causing sharp creases. A realtime preview of
the effect of smoothness values entered in the dialogue is shown on the
actual mesh - cancelling the dialogue causes the mesh to revert back to
its original shape.<br>
<img src="modelling/spline_smoothness.jpg"><br>
<br>
<b>Smoothing method </b>is either interpolating or
approximating. Both are a type of subdivision to create smooth surfaces
from a mesh of control points.<br>
<br>
<b>Closed</b> determines which of the spline curves is
closed, i.e. a complete loop. This can be set to U only, V only, both
or neither. In the example above, the U curves are closed forming a
circular cross-section for the bowl.<br>
<br>
<b>Invert Surface Normals</b> - in some circumstances faces
do not display correctly as the surface normals have become flipped.
This remedies the problem.<br>
<br>
<b>Render Preview - </b>produces a raytraced render of the
mesh so that you can check that everything is going to look as it
should in the final render.<br>
<br>
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">The <strong><font color="#009933">View</font></strong>
menu is like this: </font></td>
<td><img style="width: 212px; height: 204px;" alt="" src="modelling/mesh_view_menu.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Display Mode</b> - switches between wireframe, shaded,
smooth or transparent display for the currently
highlighted view, as in the main window.<br>
<br>
<table>
<tbody>
<tr>
<td width="400"><font face="tahoma" size="2">The <b>Color Surface By</b> submenu
allows the surface to be
coloured according to bone weights (if the object has a skeleton) or by
texture parameters (if any have been set)</font></td>
<td><img src="modelling/color_by_menu.jpg"></td>
<td width="400"><font face="tahoma" size="2">See the <a href="#color_by">section</a>
on
triangle meshes for more details. </font></td>
</tr>
</tbody>
</table>
<br>
<br>
<table>
<tbody>
<tr>
<td width="400"><font face="tahoma" size="2">The <b>Show</b> submenu allows various
items to be
displayed or hidden on the view. </font></td>
<td><img src="modelling/view_show_menu.jpg"></td>
<td width="400"><font face="tahoma" size="2">See the <a href="#mesh_show">section</a>
on
triangle meshes for more details. </font></td>
</tr>
</tbody>
</table>
<br>
<br>
<b>Coordinate System</b> - Here you can choose to work with
the mesh in its Local coordinate system or
in the Scene coordinate system. This will affect the orientation and
position of the mesh.<br>
<br>
<b>Grids</b> - As in the <a href="layout.html#grids">main
window</a>, Grids can be shown and, if necessary, used to snap
objects to.<br>
<br>
<b>Show/Hide Coordinate Axes</b> toggles display of the x,y
and z axes as shown <a href="layout.html#coordaxes">here</a>.<br>
<br>
<b>Show/Hide Template</b> displays or hides the image
selected as the background in the next menu option.<br>
<br>
<b>Set Template Image...</b> allows an image (in .jpg, .png
or .gif format) to be used as the background
in the editor. This is useful as a reference when modelling. Selecting
this displays a dialogue to
allow selection of the image which can then be turned on/off with the
previous menu entry.<br>
<br>
<br>
The <strong><font color="#009933">Skeleton</font></strong>
menu is described in detail in <a href="#skeletons">Section
2.1.5</a>.
<br>
<br>
<br>
<a name="triangle_meshes"><strong><font color="#ff6633" size="4">2.1.4. Triangle Meshes</font></strong></a><br>
<br>
<br>
Triangle meshes are similar to spline meshes in that they are a way of
creating complex surfaces. The surfaces, however, are not defined by
curves as in the case of splines, but through a mesh of triangular
facets. The example below shows the difference between a sphere surface
represented by a spline mesh and by a triangular mesh: <br>
<img src="modelling/spline_v_tri.jpg"><br>
<br>
The fact that the surface is composed of triangles means that triangle
meshes are more versatile than spline meshes. Meshes are either created
directly from objects or by using modelling_tools on existing mesh
objects (see <a href="modelling_tools.html">
modelling_tools</a>).<br>
<br>
To create a triangle mesh version of any existing geometric object,
simply click on the object in the Object List and select <b>Object
-> Convert to Triangle Mesh. </b>Depending on the
selected object, you may be prompted for a surface accuracy. This is
because most geometries contain curves which can only be approximated
with a mesh and so you need to tell the program how accurate to be.
Basically, the lower the surface accuracy specified, the greater the
number of triangles making up the mesh. It is worth bearing in mind,
however, that you do not necessarily need to specify a particularly
high accuracy as the smoothing options that the mesh is capable of will
be able to produce smooth meshes from a relatively few number of
points/triangular faces. Converting a cube to a triangle mesh can be
done exactly and so there is no prompt for accuracy.<br>
<br>
Double-clicking on a triangle mesh object brings up the triangle mesh
editor as shown below. Meshes can be edited in either point, edge or
face mode by selecting the appropriate button from bottom left.<br>
<img src="modelling/mesh_editor.jpg"><br>
<br>
As in the <a href="layout.html#view_windows">main
viewports</a>, the orientation, scaling and type (parallel or
perspective) of view can be controlled using the familiar camera
control icons/keyboard shortcuts and drop down menus at the top of the
view. The type of shading can also be altered by selecting <b>Mesh
-> Display Mode </b>(see <a href="layout.html#display_mode">Display Mode</a> for
details on this)<br>
<br>
<br>
<a name="mesh_tools"><b><font color="#0000ff">MODELLING
TOOLS</font></b></a><br>
<br>
The icons on the left side are largely the same as for the spline mesh
editor. There are
additional tools for triangle meshes, though, and each tool can be
applied to points, edges or faces. Most of these tools are fairly
self-explanatory. Resting the cursor over the icons will bring up a
tooltip to describe its function.
The operation of most can be modified by pressing <shift>
or <ctrl> - see the bottom of the editing window for
details relevant to each tool. The spacebar can be used to switch
between tools quickly; pressing it toggles between the
Select/Move tool and the last tool used. Below is more information on
each tool.<br>
<br>
<br>
<table>
<tbody>
<tr>
<td><img src="modelling/move_icon.jpg"></td>
<td><font face="tahoma" size="2">The
move/select tool allows vertices, edges or faces to be selected and
moved. Selected geometry is shown
in pink and will be affected by any tool then activated. Geometry is
selected either by clicking directly
on the point/edge/face or by dragging a rectangular region or marquee
around the geometry you want to
select. A freehand tool is also available via the <b>Edit</b>
menu. Further geometry can be added to
the selection by holding Shift while clicking on currently unselected
geometry. Geometry can be removed from the selection by Shift clicking
already-selected points/edges/faces or by Ctrl dragging a region over
the part of the model that needs to be de-selected.<br>
<br>
This tool also allows selected geometry to be moved by clicking on part
of the selecting and dragging or by using the arrow keys - pressing
Ctrl with the
up and down arrow keys moves selected geometry in and out of the screen
plane. Holding ALT while pressing the arrow keys moves the points by 10
pixels.<br>
<br>
The remaining tools will be demonstrated as their effect on the
selection shown on the left. </font></td>
</tr>
<tr>
<td><img src="modelling/scale_point_icon.jpg"></td>
<td><font face="tahoma" size="2">The
mesh scale tool stretches or squashes the current selection by
grabbing one of the handles and
dragging. The scaling operation can be controlled using the Shift and
Ctrl keys; pressing Shift
while dragging performs a uniform scale (i.e. keeps the proportions of
the selected geometry the same)
and pressing Ctrl centres the scale. The image of the right is the
result of applying a scaling
operation to the points selected; in this case both Shift and Ctrl keys
were pressed. </font></td>
</tr>
<tr>
<td><img style="width: 350px; height: 235px;" alt="" src="modelling/rot_points_icon.jpg"><br>
</td>
<td><font face="tahoma" size="2">This
tool rotates the currently selected geometry as shown on the left.
The choice of handle dictates
the axis in which the rotation is carried out. The centre of the
rotation is shown by the red cross;
this can be moved by pressing Ctrl and clicking on the desired centre. </font></td>
</tr>
<tr>
<td><img src="modelling/skew_icon.jpg"></td>
<td><font face="tahoma" size="2">This
tool deforms the selected geometry by performing a skew operation,
i.e. geometry is shifted according to its distance from the handle, as
shown on the left. Pressing
Shift while dragging performs a uniform skew and Ctrl performs a
centred skew operation. </font></td>
</tr>
<tr>
<td><img src="modelling/taper_icon.jpg"></td>
<td><font face="tahoma" size="2">The
taper tool scales geometry depending on its distance from the
handle used, as shown on the left.
As with many of the other tools, the operation can be modified to a
uniform one by Shift-dragging and a
centred one by Ctrl-dragging. The result on the left was obtained by
Ctrl-dragging the top handles inward. </font></td>
</tr>
<tr>
<td><img src="modelling/outward_icon.jpg"></td>
<td><font face="tahoma" size="2">This
tool deforms geometry by moving vertices inward or outward along
their normals. There are no handles for this tool; the operation is
performed by simply dragging up or down on the viewport. In some
situations the result is often quite similar to a centred uniform scale
as seen on the left but, in
other cases, the results are markedly different. </font></td>
</tr>
</tbody>
</table>
<br>
<br>
The <a name="gizmo"></a>Compound Move/Scale/Rotate
'gizmo' tool <img src="modelling/gizmo_icon.jpg" style="width: 32px; height: 31px;" alt=""> is a
powerful way to carry
out a range of operations on selected geometry. To use,
select the icon and then select the points/edges/faces to be modified
in the usual way. A 'gizmo' centred on the selection is
displayed as shown below.<br>
<table>
<tbody>
<tr>
<td width="250"> <font face="tahoma" size="2">The 'gizmo'
consists of 3 circles, each defining a rotation plane, 3 coordinate
axis lines and a sphere at the centre. Each axis has a letter (x, y or
z) in a square and a diamond handle.<br>
<br>
Free movement of the entire selection is performed by dragging the
central sphere. Movement in a particular axis is acheived by clicking
and dragging left/right on the appropriate letter square.<br>
<br>
Scaling in a particular direction is achieved by clicking and dragging
on the appropriate diamond. Uniform scaling is performed by holding shift
whilst dragging.<br>
<br>
Rotation is achieved by clicking on the appropriate circle and dragging
in the required direction.<br>
<br>
The entire 'gizmo' can be resized by holding the control key whilst
dragging on any
of the diamond handles. <br>
</ctrl></shift></font></td>
<td> <img src="modelling/gizmo.jpg" style="width: 766px; height: 617px;" alt=""></td>
</tr>
</tbody>
</table>
<br>
The axes of the 'gizmo' are initially shown as x, y and z but other
coordinate axes can be set instead, as shown below, by clicking W.
The left image is the x, y and z mode. The centre
image shows a 2D mode where u and v are horizontal and
vertical axes parallel to the screen. The 3rd mode, shown in
the right hand image, allows transformations along the axis, N, normal
to the selection and the 2 corresponding orthogonal axes P and Q. <br>
<img src="modelling/gizmo2.jpg" style="width: 665px; height: 233px;" alt=""><br>
<br>
<a name="Bevel_tool">The Bevel/Extrude</a> tool <img src="modelling/bevel_icon.jpg"> is a very powerful way of
extending the mesh geometry. This tool works in exactly the same way as
the Bevel/Extrude function accessible from the
Mesh menu (see below) but in a more interactive way. Bevel and extrude
can be applied in a single
operation to vertices, edges or faces and the resulting geometry is
left selected to allow further
bevel/extrudes to be applied immediately. To use the tool, select the
geometry to be bevelled/extrude
using the Move/Select tool. Then select the Bevel/Extrude tool and the
mode of operation (i.e.
point/edge/face). Dragging up/down on the viewport extrudes the
geometry and dragging left/right
applies a bevel. The operation can be constrained to a pure extrude by
Shift dragging up/down and
constrained to a pure bevel by Shift clicking left/right. The images
below show the results of
applying this tool to some sample geometry in the different modes. Note
that for faces, double-clicking
the icon displays a dialogue that allows faces to be extruded as
separate entities or on the selection
as a whole.<br>
<img src="modelling/bevel_extrude.jpg"><br>
<br>
<br>
The <a name="create_vert">Create Vertex </a> tool <img src="modelling/add_vert_icon.jpg"> allows new geometry to be
created in
a number of ways depending on which modelling mode is used, i.e.
points/edges/faces.<br>
<table>
<tbody>
<tr>
<td width="300"><font face="tahoma" size="2"> In <b>Point</b> mode,
dragging on an existing vertex creates a new point which is attached to
the original one as shown
in the figure on the right: </font></td>
<td><img src="modelling/create_v_point.jpg"></td>
</tr>
</tbody>
</table>
<br>
<br>
In <b>Edge</b> mode, this tool allows you to create new
vertices at a selected position on mesh simply
by clicking at that position. In the example below, moving to the
position shown in 1 and clicking
results in a new vertex (and additional edges) as shown in 2. Similarly
clicking at position 3 produces
the new geometry shown in 4 etc.<br>
<img src="modelling/create_v_edge.jpg"><br>
<br>
<table>
<tbody>
<tr>
<td width="300"><font face="tahoma" size="2">In <b>Face</b> mode, you can create
new vertices in the
middle of faces by clicking at the appropriate
location. In the example on the right, a new vertex is created by
clicking at the location shown in 1, as shown in 2. Similarly for 3 and
4. </font></td>
<td><img src="modelling/create_v_face.jpg"></td>
</tr>
</tbody>
</table>
<br>
<br>
<br>
<br>
<b><font color="#0000ff">MENUS</font></b><br>
<br>
<br>
The top menu bar has additional tools to the spline editor to reflect
the greater versatility of triangle meshes.<br>
<br>
<table>
<tbody>
<tr>
<td><font face="tahoma" size="2">This
is the <strong><font color="#009933">Edit</font></strong>
menu:<br>
</font></td>
<td><img src="modelling/mesh_edit_menu.jpg"></td>
</tr>
</tbody>
</table>
<br>
<b>Undo</b> - undoes last action, including selections.
This changes to Redo if you have just undone something.<br>
<br>
<b>Clear</b> - deletes selected points, edges or faces. Has
the same effect has pressing <delete>.<br>
<br>
<b>Select All </b>- selects all points, edges or faces.<br>
<br>
<b>Extend Selection -</b> expands selection by adding
points, edges or faces adjacent to those currently selected.<br>
<br>
<b>Invert Selection</b> selects any currently deselected
points and deselects any currently selected points.<br>
<br>
<table>
<tbody>
<tr valign="top">
<td width="300"><font face="tahoma" size="2"> <a name="special_sel"><b>Select
Special</b></a>
allows selection of geometry using several options from the below
sub-menu:<br>
<br>
<img src="modelling/mesh_special_sel_menu.jpg"><br>
</font></td>
<td width="200"> <font size="1"><b>Boundary
of Object </b>-
if part of the mesh is open, you can select the boundary by selecting
this option. See example below:<br>
<br>
<img src="modelling/select_boundary.jpg"><br>
<br>
<b>Boundary of Current Selection </b>- this tool
selects the edges which outline the currently
selected geometry as in the example below:<br>
<img src="modelling/mesh_sel_boundary_selection.jpg">
</font></td>
<td width="200"> <font face="tahoma" size="1"><b>Edge
Loop of Current Selection </b>- selects edges that are close to
parallel and are joined to form an edge loop as below:<br>
<br>
<img src="modelling/edge_loop_selection.jpg"> </font></td>
<td width="200"> <font face="tahoma" size="1"><b>Edge
Strip of Current Selection </b>- selects edges which are close
to parallel but are separated
by one edge. This is often useful when followed by edge subdivision of
the resulting selection to
produce a new edge loop:<br>
</font> <br>
<img src="modelling/mesh_sel_edge_strip.jpg"> <br>
<br>
</td>
</tr>
</tbody>
</table>
<br>
<a name="tol_sel"></a>
<b>Tolerant Selection Mode </b>- This alters the way the
marquee selection tool works on edges and faces. If this is not set,
then only those edges/faces completely within the selection rectangle
are selected. If Tolerant Selection in enabled, any edges/faces having