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Curve Tools
Hand Sketching
An approximation of 3D shape
CAD Curves
Accurate 3D shape
© 2009 Autodesk
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Why Use Curves?
Curves Are Your ‘Language’ – How to Communicate Shapes to Alias
The shape of the
curve, combined with
the ‘logic’ of the
surface tool, creates
a controlled shape.
Mastering the
creation of accurate
curves will give you
control of the shapes
you create in 3D.
© 2009 Autodesk
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Two Types of Curves
Freeform Curves
Keypoint Curves
Curve shape
controlled by CVs
© 2009 Autodesk
Curve shape
controlled by keypoints
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Freeform Curves Terminology
Start
The first CV is
displayed as
The second
CV is shown
as
Control
Vertex
Points used
to shape the
curve/surface
Hull
Lines
connecting a
row of CVs
Edit Point
Points showing
the number of
spans in a curve
Span
Part of a curve
between two
edit points
Together they
show the
direction of the
curves.
Control Panel
Use to change the
number of spans
(and therefore
CVs) in a curve.
At the start and end of
a curve, there is a CV
and an edit point.
© 2009 Autodesk
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Creating New Curves
To Modify
Create NURBS Curves
Place 4+ CV points
Pick>CV
Place 2+ edit points
Transform>Move
Create Keypoint Curves
Place 2 keypoints
Keypoint Curve Toolbox
>Drag Keypoints
Place 3 keypoints
Windows>Information>
Information Window
© 2009 Autodesk
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Where to Position CVs
If you want a constant, regularly changing
curve shape, then the CVs should be
evenly spaced, and you should have as
few CVs as possible.
If you need to create a strong change in the
direction of a curve, you’ll need to bunch
up extra CVs to control the shape.
This method is okay for quick, concept
modeling but not for high-quality,
controllable surfaces—see the technique
below.
Curve 1
Curve 3
Curve 2
© 2009 Autodesk
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One of the skills you will develop is to judge
when a shape should be made out of a
single curve or from separate curves
joined together.
Sketch Circles and Accurate Circles
‘Sketch’ Circle
Not Accurate
Keypoint Circle
Accurate
Use the ‘Sketch’ circle
for circle-like shapes.
Use the keypoint circle
for accurate circles.
Modify the keypoint
circle using the
keypoint tools.
The keypoint circle has
many spans; therefore,
you typically won’t use
it for sculpting.
© 2009 Autodesk
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Avoid Multi-Knots
Linked Line
Multi-Knot
Use Separate Lines Instead
© 2009 Autodesk
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Exercises
EX1-Curves.wire
EX2-Curves-circles.wire
EX3-Car-curves.wire
EX4-Symmetrical-curves.wire
EX5-Flatten-circle.wire
© 2009 Autodesk
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Curve Tools: Curve Section
In this sketch, curves are
drawn across each other.
Even when drawing
accurate curves, it is
sometimes easier to draw
overlapping curves and
then trim them to create the
final design.
© 2009 Autodesk
Curve Edit>Curve Section
This function can
be used to trim or
split curves where
they cross.
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Global Curve Intersect
This is a plug-in that is
useful for complex
layouts such as
numeric keypads.
Curve Techniques: Center-Line Symmetry
When using the Revolve tool, having two CVs perpendicular to the rotation axis gives a smooth transition.
Use snapping and mouse constraints to
align the first two CVs.
© 2009 Autodesk
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Layer Symmetry
If geometry is assigned to a layer, then
Layer Symmetry can be used to
create a mirror image.
If the original geometry is modified, the
mirrored geometry will update.
Layers>Symmetry>Set Plane
Object Edit >Align>Symmetry Plane
Align
To set the direction of mirroring
To create a ‘tangent’ relationship between
the two CVs on the center-line
© 2009 Autodesk
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Other Curve Tools
Curve Edit>
Add Points:
Adds new CV points to the end of a curve (use with Reverse
Curve)
Reverse Curve: Swaps the direction of the curve
Object Edit>
© 2009 Autodesk
Attach:
Connects two curves to create a single curve (but beware,
they will ‘soften’)
Detach:
Splits a curve into two parts
Insert:
Puts an extra edit point (and hence extra span and an extra
CV) into a curve
Extend:
Lengthens or shortens a curve without changing its shape
Offset:
Creates a new curve, offset from the original
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Exercises
EX6-Doorknob.wire
EX7-Curve-section.wire
EX8-Curve-fillet.wire
EX9-Offset.wire
EX10-Layer-symmetry.wire
© 2009 Autodesk
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Projects
P1-2D-mannequin.wire
P2-Peg-and-string.wire
P3-Car-badge.wire
© 2009 Autodesk
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