spoon.pdf

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Introduction to T-Splines and Rhino
®
4
Surface from curves
Designing a spoon
Juan Santocono
T-Splines, Inc.
© Copyright 2008 T-Splines, Inc.
PAGE 1
The
T-Splines
for Rhino plugin brings industrial designers new ways to easily create and
modify freeform designs. One T-Splines workflow is to create entire, editable surfaces from
input curves using the
tsSkin
command. This tutorial will show how to use this workflow to
create a spoon. This tutorial assumes the user is generally familiar with Rhino and has success-
fully completed the “Getting Started” tutorials available in the Rhino 4 Help Menu.
In this tutorial, anything in
Blue
is a Rhino command, while anything in
Red
is a T-Splines com-
mand. Type these commands in the command line of Rhino to run them.
The best way to read this tutorial is by looking at the 3D model at the same time. You can fol-
low the model’s progress by selecting the different layers in the file. The model can be down-
loaded at www.tsplines.com.
1
Creating input curves
Reference drawings
Input curves can be obtained by different methods; one way is to draw them directly in Rhino
using hand-drawn concept pictures for reference. Bring the reference pictures into your Rhino
scene using the
_PictureFrame
command. Position and scale them until they are aligned.
PAGE 2
T•Splines
Generating the curves
In one view at a time, carefully draw the contour curves of the spoon using the
_Curve
com-
mand. Always try to use the fewest number of points possible to get the desired curvature.
One way to generate the 3D contour
curves is to use the
_crv2view
command;
this will transform two planar (profile)
curves to a single 3D curve that describes
the 3D shape of the spoon.
Planar curves
3D curve
Once you have the main curves, it is time
to add cross-section curves. While doing
this, keep in mind the following rules of
thumb:
First, create four-sided faces (quad re-
gions) when possible. This will minimize
the number of star points and generate a
smoother surface.
Second, when possible, have 3 or 4 curve
segments intersect at each intersection.
Third, use only the necessary cross sec-
tions to get the desire shape. Extra curves
can yield a less smooth result.
Main curves
PAGE 3
T•Splines
The section curves can be
drawn by hand or by us-
ing the
_CSec
(curve from
cross section profiles)
command.
Since a regular surface
continuity is desired, try
to space the sections
regulary, at approximate-
ly the same distances.
1
2
Main curves
Now all the curves necessary for the tsSkin com-
mand are in place.
Input curves
Section curves
2
tsSkin command
Select all the curves and run
the
_tsSkin
command.
The options dialog box will
appear.
PAGE 4
T•Splines
Display
Once inside the command, the first thing
to do is to set the tolerance for defining
the curve intersections. Often the file
tolerance will recognize all intersections
(it does in this case) but the tolerance can
be increased if your curves don’t exactly
touch. If you’ve laid out your curves well,
you should mainly have intersections with
4 segments (blue dots). In this case some
6-segment intersections (which will be star
points in the final model) are also used to
define a complex part of the shape.
Display
Face layout
Now is the time to define the topology of the surface. tsSkin will automatically try to
define the topology, but won’t always guess right, so you need to provide input by se-
lecting and deselecting the faces. For more help on achieving the correct face layout,
watch this one-minute movie: http://www.youtube.com/watch?v=HP4SBDvX0Es
Face layout
Incorrect topology
Correct topology
Preview
Use the preview option to check how the
final surface will look. In this case, the
surface doesn’t fit to some of the curves as
well as would be desired. To fix this, adjust
the spans.
Preview
Surface needs
to fit better
PAGE 5
T•Splines

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