Blob Manipulation

Blob Manipulation
Akira Wakita
Akito Nakano
Metamorphic Architecture Lab
Graduate School of Media and Governance, Keio University
5322 Endo, Fujisawa, Kanagawa, 252-0882, JAPAN
{wakita, akito}@sfc.keio.ac.jp
ABSTRACT
This paper introduces Blob Manipulation, the interaction
technique with fluidic soft matter. Most of the soft matters
are substances between liquid and solid and possess
viscoelasticity. We focus on this materiality and propose a
novel interaction technique. A stirring rod is used as the
input tool. When the system detects a user input such as
touching, rubbing or tapping, the corresponding
transformation will be executed. Six basic operations were
designed to transform fluidic soft matter geometrically and
topologically. Rheological user interface associated with
metamorphose is expected to pioneer new possibilities for
design, education and entertainment.
Figure 1. Overview of Blob Manipulation. The user interacts
with soft matters using the stirring rod.
Author Keywords
Blob, Soft Matter, Rheological
Programmable Matter, Materiality
User
Interface,
subjects in fluid engineering, and the actuation technique is
also difficult to design.
In this paper, we aim at organic shape creation and propose
the input and output methods for shape control of fluidic
soft matters. The research contributes to mainly the
following two propositions: 1) input method and modeling
language for fluid 2) application scenarios for architecture
or interior design. Realizing interaction loops with highly
fluidic soft matters is expected for new possibilities of HCI.
ACM Classification Keywords
H5.m. Information interfaces and presentation (e.g., HCI):
Miscellaneous.
General Terms
Design, Human Factors, Languages, Theory.
INTRODUCTION
In recent years, soft matters become popular gradually as
the materials used in the HCI field as well as hard matters.
Soft materials such as flexible LED, fabric, or paper have a
high affinity with human bodies and triggers natural
operations with both hands. Due to such properties, the soft
materials draw large attention as the materials for organic
user interfaces (OUI) [4]. Among soft matters,
macromolecules or colloids have a high fluidity to lose their
shapes at ordinary temperatures, and few researches have
been done for such materials. Since it is difficult to grasp
such materials directly, tangible interfaces for them are not
easy to design (e.g., we cannot hold milk in our hands, and
it goes away through fingers). In addition, controlling fluid
shapes or behaviors is one of the most technically difficult
RELATED WORKS – RHEOLOGICAL USER INTERFACE
A few researches have been done for approaches to fluidic
materials such as water or colloids. Such materials are
called rheological user interface (RUI) in this paper. One of
the approaches using water, the most familiar fluid, is
Submerging Technologies [2]. As approaches using
ferrofluid, art works series of Kodama are well-known [7].
In entertainment computing, approaches of using ferrofluids
as musical instruments by detecting direct touching to
ferrofluids [6] are also proposed.
This paper focuses attention on liquid materials and
develops input and output methods for the RUI in order to
create organic shapes. This research mainly contributes to
construction of RUIs for versatile transformation by direct
manipulation and development of the interaction style.
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BLOB MANIPULATION
Blob Manipulation proposes the interaction style for shape
operations of fluidic soft matters and the corresponding
modeling language. We selected Programmable Blobs [9]
as the platform for this approach.
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Scratching a blob to split it into two halves separates it.
Unify is the operation opposite to cut.
Translate, stretch and shrink are geometric operations and
cut and unify are topological ones. Every operation has its
opposite operation. This means that all operations can be
recorded and restored like inversion algorithm [8] of 3dimensional CAD systems.
Stir is the operation to stir a blob for creating smaller blobs
with various sizes at any location. The five operations
described earlier are the basic commands for intentional
shape creation, while stir generates unintentional and
emergent shape modeling.
SYSTEM DESIGN
System Overview
As Figure 3 shows, a blob is put in a rectangular water tank
and the magnetic units are arranged at the bottom of the
tank. The water tank has a section where a lump of blob is
stored (source), from which the necessary amount of blob is
moved to the center of the water tank (canvas). The blob
shape and the movement of the stirring rod are detected by
the camera set on the ceiling above the water tank and sent
to the software. According to the detected blob shape and
rod movement, the software determines an appropriate
transformation operation and sends the corresponding
control command to the electronic circuit of the magnetic
units. The software saves contours of the blob at regular
time intervals and creates data for a CAD system.
Figure 2. Examples of blob manipulation. Shapes before
change (left) and the ones after change (right). The red arrows
indicate the path of the rod set by the user and the blue ones
show the blob movement.
Soft matters [3] such as macromolecule, liquid crystal or
colloid have physical properties called viscoelasticity.
Viscoelastic bodies behave elastically for inputs of fast
change and fluidically for those of slow change. Blob
Manipulation is the interaction style using these two
characteristics. If you touch a blob (magnetic slime) with a
stirring rod, its shape will change for a moment. Before the
shape returns to the initial status, if the displacement of the
blob is sensed and magnetic force is generated to extend the
first displacement, the blob shape will be changed. If
transformation progresses to some extent, the displacement
will become definite. Viscosity progresses the
transformation automatically and the blob shape will be
fixed to the changed one.
Figure 2 shows the overview of basic blob manipulations.
Translate is one of the blob operations to move a blob to
the next coordinate. When a blob exists at a coordinate
point, tapping one of the eight adjacent points moves the
blob to the specified point. Stretch elongates a blob. If you
put a rod into a blob and scratch it to some direction, the
blob will be stretched to the specified vector direction.
Shrink degenerates a stretched blob, by putting a rod into a
blob and moving the rod to a direction to be degenerated.
Cut separates a blob into two pieces at the center.
Figure 3. System configuration.
Hardware
We developed the hardware that could supply magnetic
force to blobs for long hours. We obtained a clue to this
hardware from the mechanism of lead screw used in haptic
displays such as FEELEX [5]. The power supplied from the
RCA terminal rotates the DC motor and the screw inserted
in the polyoxymethylene (POM) stick moves up and down.
The aluminum pipe has a groove for the screw to move. A
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neodymium magnet is embedded in the top of a POM stick.
When the DC motor is rotated normally, the magnet moves
up to give magnetic force to a blob. When the motor is
reversely rotated, the motor moves down and magnetic
force to a blob becomes weak.
Drawing of Primitive Elements
Skeleton Approach – Additive Method
The most basic approach to concrete shape creation is to
draw a line by combining two or more blobs. An example
where two blobs are used is shown here. First, move a blob
(b0) from source to canvas by repeating translate operations
(Figure 5). Apply a stretch operation to b0 to draw a line.
Move another blob (b1) to canvas. Apply a stretch operation
to b1 and unite b1 with b0. Repeating the same operations to
blobs draws various shapes. In this approach, a stretched
blob is united with another sequentially to construct a shape
like a skeleton, which can be regarded as an additive
method.
Figure 5. Skeleton creation and parameter adjustment. A
circle represents a point where the magnetic units are valid
and a cross is a point where the unit is set down. The circle
size is proportion to the cylinder height in a magnetic unit.
Volume Approach - Subtractive Method
The volume approach is a subtractive method, where a
certain amount of blob is stretched to create a shape like
clay modeling. As shown in Figure 6, unify operation is
repeated to create a certain amount of blob (volume), and
appropriate parts of the blob are stretched to create a shape.
Figure 4. Magnetic unit.
Software
The height of a magnetic unit is controlled by the program
described in Arduino IDE. As Figure 4 shows, up(int value)
moves up the cylinder and down(int value) moves down it.
value is a voltage given to the DC motor in a magnetic unit.
Blob condition is always detected by the camera set on the
ceiling. Using BlobDetection [1], a general-purpose motion
detection library, the number of blobs and their shapes are
obtained. The tip of the stirring rod is colored for easy
detection. The software judges the location of the tip and
the overlap with blobs and determines the target blobs.
The software saves blob shapes at regular time intervals.
Since a blob can be described as a closed polyline
(coordinate values of two continuous vertices and their
indices), the data can be easily saved. The data is converted
to OBJ or DXF formats to be used in CAD systems.
MODELING PROCEDURE
Figure 6. Volume creation. A certain amount of blob is created,
and it is stretched to create a shape.
We sought a modeling language suitable for blob display as
we referenced Sketchpad, the first computer-aided
modeling system developed by Ivan E. Sutherland. We
judged that the following features of Sketchpad could be
applied to our system: 1) drawing of primitive elements, 2)
adjustment of coordinate values for vertices and 3)
conversion of drawing results to objects.
Coordinate Adjustment and Weighting
Changing the cylinder height in a magnetic unit varies the
degree of attractive force acting on a blob. This means that
weighting on coordinates for skeletons or volumes is
controllable. This is analogous to a general technique in
form finding.
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mechanism to adaptively subdivide resolution of the
actuator is newly required. One of practical solutions is to
set small neodymium magnets and move each magnet up
and down by link mechanism. This enables representation
with higher resolution and moving adjacent magnets
together can vary resolution.
Conversion of Drawing Results to Objects
Recording operation histories and reproducing them might
enable objective drawing. For example, if a square is drawn
with a skeleton approach and it is recorded as an object, the
square would be used as a primitive shape in later
operations. In volume approach, if the operation to create
the first volume (repeating unify N times) is treated as an
object, upper operation languages might be defined.
FUTURE DIRECTION
Our future work is to apply our study to digital fabrication
process. If our system is enhanced, it might fix blob shapes
and work as a 3D printer. For example, if blobs can be fixed
with some methods like light curing resin used in stereo
lithography, the system can be constructed in which
designed blobs will become materials as they are. In the
future, in order to construct the system where such design
and manufacturing are integrated, we want to seek a new
method for creating blobs with controlling their hardness.
APPLICATION - ORGANIC SHAPE DESIGN
When we focus on architecture in recent years, Zaha Hadid,
Frank Gehry or other radical architects have designed a lot
of works with organic shapes. The examples shown here are
the works for which our technique was applied to form
finding for buildings with organic shapes (Blobitecture) or
interior designs (Blobject)[10]. As shown in Figure 7, an
organic shape is created first using volume approach. The
parameters are controlled and other blobs are added to the
created shape to vary it. The contour data saved through the
operations are imported to a CAD system and combined by
skinning operation, so that the outline structure can be
created.
ACKNOWLEDGMENTS
We respectfully express our gratitude to Antoni Gaudi and
Randy Rhoads, who always give us great inspirations.
REFERENCES
1. BlobDetection,
http://www.v3ga.net/processing/BlobDetection/
2. Dietz, P. H., Westhues, J., Barnwell, J., Han, J. Y.,
Yerazunis, W. Submerging technologies. In ACM
SIGGRAPH 2006 Emerging technologies (SIGGRAPH
'06). pp.30, 2006.
3. Hamley, I. W. Introduction to Soft Matter: Synthetic and
Biological Self-Assembling Materials, Wiley, 2007.
4. Holman, D., Vertegaal, R. Organic user interfaces:
designing computers in any way, shape, or form.
Commun. ACM 51, 6 (June 2008), pp.48-55.
5. Iwata, H., Yano, H., Nakaizumi, F., Kawamura, R.
Project FEELEX: adding haptic surface to graphics. In
Proc. SIGGRAPH '01, pp.469-476, 2001.
Figure 7. Organic architecture design. Create an organic
shape with volume approach (top). Import the data to a CAD
system (middle-left). Rendered image (bottom-right).
6. Koh, J.T.K.V., Karunanayaka, K., Sepulveda, J.,
Tharakan, M. J., Krishnan, M., Cheok, A. D. Liquid
interface: a malleable, transient, direct-touch interface.
In Proc. ACE '10, pp.45-48, 2010.
DISCUSSION
Improving Operation Language
In order to design more complex shapes, a further upper
operation language will be necessary. For example, the
operation to select two or more blobs by lasso selection
might be required. If such idiomatic operation languages
are defined, we will be allowed to draw a landscape with a
lot of blobs, existing beyond a single shape design.
7. Kodama, S. Dynamic ferrofluid sculpture: organic
shape-changing art forms. Commun. ACM vol.51, no.6
(Jun. 2008), 79-81.
8. Mäntylä, M. An Inversion Algorithm for Geometric
Models, ACM Computer Graphics, Vol. 16, No.3, In
Proc. SIGGRAPH 82, pp.51-59, 1982.
Scalability
In our system, a shape is created as a blob is stretched for
one or more magnetic units. This is analogous to drawing a
parametric surface (or curve) using control points in
magnetic unit coordinates. Since our system cannot operate
directly the section locating between two magnetic units, a
9. Wakita, A., Nakano, A., Kobayashi, N. Programmable
blobs: a rheologic interface for organic shape design. In
Proc. TEI '11, pp.273-276, 2010.
10. Waters, J. K., Blobitecture: Waveform Architecture and
Digital Design, Rockport Pub, 2003.
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