2. Basic Modeling
All 3D modeling programs contain certain basic
geometric shapes that can be combined with or
subtracted from other shapes to form more
complex objects.
Some programs contain more objects than
others, but a sample list of basic primitives
includes:
Sphere
Cube or box
Cylinder
Torus
Cone
Plane
3. Basic Modeling
Arcs, ellipses, circles,
curves, and freehand curves
are basic 2D shapes
typically provided within
modeling programs. Shapes
may be combined to create
complex objects.
Polygons are plane figures
made with three or more
straight sides (curves).
Regular polygons have
equal length sides and equal
angles.
4. Basic Modeling
Splines are curves or
polygons that are composed
of segments that can be
manipulated by control
points placed along the
curve.
Control points may be
made “active” and then
dragged using a handle
attached to the point.
5. Basic Modeling
Some programs require
the user to define
parameters of the
primitive prior to importing
it into the scene; others
will bring in a “standard”
sized object and place it in
a selected position.
Typical parameters include
center point, radius,
height, width, etc.
6. Basic Modeling
Parameters affect the
size, placement, and
orientation of the object.
Values provided
automatically by the
software are called the
defaults. A typical default
would be to bring in an
object oriented in a
certain direction with
respect to a construction
plane.
7. Modeling Techniques
Boolean tools or operations are used to
create objects by combining, subtracting,
or determining the common intersections
of various objects such as primitives.
Union or Addition (+ or ∪) is used to
combine objects together into one new
object.
Subtract or Difference (−) is used to
remove part or all of an object where
objects overlay each other.
Intersection (* or ∩) is used to calculate
the overlapping volumes of objects so that
the overlap becomes the object.
Named for the British mathematician
George Boole.
8. Modeling Techniques
Extrusion, sweeping, or
lofting allows you to
create a 2D shape and
then extend it along a
path or curve to form a
3D object. The 2D
shape may be open
(curves that do not
connect back onto the
beginning or closed
(lines connect back onto
the beginning).
9. Modeling Techniques
A variation of sweeping is
lofting, where a series of
curves (open or closed) is
lofted or spaced parallel to
each other, and then a
surface is generated that
connects the contours.
Lofting may also be done
using a profile shape and a
curve along which the
profile is lofted. An
example of where lofting is
used would be for
modeling boat hulls and
terrains.
10. Modeling Techniques
Revolve or lathe operations allow the
user to create a 2D shape and then
revolve it around an axis.
Lathe operations emulate the lathe
found in manufacturing shops. A
lathe is a tool used to rotate and
shape material by bringing cutting
tools against the material while it
spins.
The revolution may be a full 360
degrees or any smaller angle.
Lathe operations are often used to
model objects such as bowls, bottles,
and dishes.
11. Modeling Techniques
Transformations or
Transforms are
actions that scale,
rotate, and move
objects
Scale changes the
size or proportions of
an object along one
or more axes.
12. Modeling Techniques
Rotate refers to tilting or
changing the direction that an
object is facing.
Rotation is usually assigned to
a particular axis. For
example, the object might be
rotated along its X-axis.
Most programs assign a
default location for rotational
axes. This location (pivot
point) may need to be
relocated to create to the
desired movement.
Rotation is usually specified
using degrees relative to a
beginning point.
13. Modeling Techniques
Move is used to advance an
object from one position to
another.
Linear distance along the
X-, Y-, or Z-axis is used to
measure movement.
Movement may be
constrained by a snap or
grid setting. Snap allows
the object to be moved only
at set intervals of distance.
Movement can also be
restricted to a grid so that
the object jumps from grid
line to grid line.
14. Modeling Techniques
Deformations are used to
modify an existing shape.
Selected vertices, control
points, polygon faces, or cross
sections of an object may be
used to control and influence
the deformation process.
Deformation tools emulate the
process of working a piece of
clay.
Examples include taper, bend,
twist, smooth, and stretch.
15. Modeling Techniques
Copy or Clone tools
allow selected
objects to be
reproduced in their
exact size and form.
Mirror tools allow
selected shapes to be
copied or flipped
about a defined
center.
