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From Pattern Making to Acoustic Panel Making Utilizing
Shape Grammars
Ecenur Yavuz1, Birgül Çolakoğlu2, Begüm Aktaş3
1Istanbul Technical University, Institute of Informatics, Graduate Program of Ar-
chitectural Design Computing 2,3Istanbul Technical University
1,3{ecenuryavuz|aktasbegum}@gmail.com 2bigi@alum.mit.edu
This paper presents the application of shape grammars in a real case design
problem. The design problem is stated as developing computational acoustic
panel solution for classroom with various acoustic problems by modifying 2D
pattern, which basically utilizes shape grammars. The study demonstrates
interdisciplinary environment of design education and discussions of shape
grammars in acoustic panel design and making. It includes different methods to
design, like intuitive tendencies, computational thinking, computational tools,
and computer simulations. The rule sets of the 2D (pencil-paper-based) pattern
are intuitively created by the designer with simultaneous studies of understanding
shape grammars. The study consists of three stages. The first stage illustrates 2D
pattern generation utilizing computational thinking via shape grammar
methodology, second stage illustrates computer generation of 2D pattern with the
help of computational tools, and the third stage utilization and modification of
this 2D pattern into 3D acoustic panel with feedbacks of computer simulations.
Keywords: computational design, computer-generated geometrical design,
shape grammar, acoustic, odeon
INTRODUCTION
Shape grammar has been used for generating ge-
ometries and forms as a generative design tool, sys-
tem, and language. According to Stiny, a shape
grammar defines a set called language (Stiny, 1980).
From the introduction of the shape grammar to de-
sign methodology onwards, shape grammar, that is
widely used in design education and practice has
been evolved as a generative design tool by recur-
sively applying shape rules to the initial shape. As
Knight stated that, “A shape grammaris a set of shape
rules that apply in a step by step way to generate
a set, or language, of design. Shape grammars are
both descriptive and generative. The rules of a shape
grammar generate or compute designs, and the rules
themselves are descriptions of the forms the gener-
ated designs.” (Knight, 2000). Novel use of the shape
grammar in design education in practice enrich the
abilities of designers as well as providing design al-
ternatives to designers.
In the early 1970s, George Stiny and James
Gips first presented shape grammar theory to de-
sign methodology. As Stiny and Gips point out,
shape grammars are similar to phrase structure gram-
SHAPE, FORM & GEOMETRY | Applications - Volume 2 - eCAADe 36 |477
mars, which were introduced by Chomsky in lin-
guistics. Where phrase structure grammars are de-
fined over an alphabet of symbols and generate one-
dimensional strings of symbols, shape grammars are
defined over an alphabet of shapes and generate n-
dimensional shapes (Stiny & Gips, 1971). Through
development and application in shape grammar ap-
proaches, the generation of complex forms and pat-
terns are defined by basic formal rule sets. Within this
context, a designer has a chance to formalize or de-
sign the generation of any shape. Thus, shape gram-
mar is not only capable of generation of complex de-
signs, but also a powerful tool for computational pat-
tern generation.
In the design education and practice, shape
grammars have been used as a tool for teaching com-
putational thinking and design to architects and de-
signers in various graduate level courses and design
practice. “The first two decades of shape grammar
applications focused almost exclusively on analysis.”
(Knight, 1999). In the earlier stages of the shape
grammar approach, shape grammar is utilized as de-
veloping new design languages based on existing
ones as well as capturing the inferring grammar of
the design, transferring the defined rule sets to gen-
erate designs as an infinite number of new designs
such as new design language or style. Knight (1999)
states that shape grammars are used by students to
understand the design language and manipulate the
existing design with its rules to generate a new de-
sign. Within this context, initially, students analyse
the existing patterns which could be architectural
styles or design languages to formulate (extract) their
own rules for their designs. Therefore, analysing pro-
cess has potential in design education and practice.
“There is no better way to learn about styles or lan-
guages of designs (at least compositionally) than by
either studying shape grammars already written for
languages or by writing grammars oneself.”(Knight,
1999). Shape grammars, on the other hand, have a
basis of cognition-oriented design theories as com-
putational theory and making. Cognitive computa-
tion in the shape grammar is conducted with the em-
bedded integration of seeing and doing as is hand-
eye coordination in the design and making process
in the creative design process like as Stiny concludes
that; “What you see is what you get”(Stiny, 2006). Un-
dergone a relationship between seeing and doing,
shape grammars is defined as computation design
and thinking as cognitive computation.
As a way of understanding the trajectory of
Stiny’s ideas of shape grammar as are the importance
of the integration of the seeing and doing, and a ba-
sis of the mathematics behind the whole process is
maintained as follows; “I am going to use my formula
to get the idea that calculating is visual if it can deal
with shapes like this. I want to use rules to determine
what parts I see and what I can say about them, and to
allow for what I see and what I say to change freely as
I calculate. And I want this to happen every time I try
a rule.”(Stiny, 2006) Therefore, the pattern analysing
process is driven recursively depending on the cog-
nitive computation, while seeing the sub-shapes on
the pattern and intuitively decoding the sub-shapes
of the pattern to determine the geometric definition
of the pattern. Computer application of shape gram-
mar make geometric logic embedded in pattern easy
to understand, enabling better control, modification,
and construction. This study differs from the earlies
studies where rules for pattern making are extracted
from analyses of existing pattern. Here, the rules of
the pattern are created by the designer as a cogni-
tive computation based pattern. Then, they are trans-
formed to mathematical rules for automatic genera-
tion of the patterns.
The study consists of three stages. The first stage
illustrates 2d pattern generation through the shape
grammar theory with developing a computational
thinking, second stage illustrates computer genera-
tion of 2d pattern with the help of digital tools, and
the third stage utilization and modification of this 2d
pattern into a 3d acoustic panel with the feedbacks
of computer simulation results.
478 |eCAADe 36 - SHAPE, FORM & GEOMETRY | Applications - Volume 2
FIRST STAGE - Paper Based Pattern Genera-
tion
Shape grammar is the computational design
methodology, derived based on mathematics and
algorithmic thinking. The shape grammar based de-
sign process, uses geometric elements, shapes as ba-
sic elements of the design like applying mathemati-
cal operations to compute calculations with shapes.
The rules of the shape grammar generate designs
by computing directly with shapes made of basic
spatial elements (points, lines, planes, and solids),
rather than with symbols, words, numbers, or other
abstract structures that represents visual shapes indi-
rectly (Knight, 2018). Within the context of the shape
grammar definitions, the hexagon is accepted as the
initial shape of the pattern. The designer defined the
rule sets of the 2D pattern with simultaneous lectures
and shape grammars.
In the first stage of the study, main objective was
to create paper-based 2D geometric pattern, basic
(initial) pattern making steps are defined for creating
the hexagonal grid to generate the hexagon-based
pattern. The smallest unit, the hexagon shape is cho-
sen intuitively by the designer. Hexagon is a six-sided
polygon and the total of the internal angles of any
simple (non-self-intersecting) hexagon is 720°. Fol-
lowing this step, the smallest repetitive unit is cre-
ated based on defined rule sets. This hexagon’s pe-
ripheral length is conceived as a single total length
and it is divided into 12 and all the division points are
numerated from 0 to 11 counters to clockwise. Then
4 lines: from 0 to 4 L1, from 0 to 5 L2, from 10 to 4
L3, and from 10 to 6 L4 are drawn on the hexagon,
and then all these lines are mirrored vertically (on
the y axe). 8 lines are acquired at the end of the de-
sign process (Figure 1). As a consequence of applying
rule sets pattern generation process, pattern genera-
tion process could easily be controlled by changing
rules. While generating pattern, making changes on
the rule sets can be clearly seen through the whole
pattern.
SECOND STAGE - Computerization of 2D
Pattern
In the second stage of the study, the embedded al-
gorithm of the pattern was coded in the Grasshop-
per as enabling designer to do changes in the rule
sets which are defined according to the shape gram-
mar operations (Figure 2). In the digital environment,
hexagonal grid system is defined to create alterna-
tives and variations in the pattern.
In the coding process, defined rule sets trans-
posed to digital environment, while the number of
division of the peripheral length of the hexagon pro-
vide alterable values to designers. While the num-
ber of the division changes from 12 to 36 on the
hexagon the location of the points on the hexagon
change, resulting changing the location of the lines
on the hexagon. As consequence the entire pattern
changes (Figure 3). In grasshopper coding, changing
the value of one component or altering the number
of the division of the hexagon changes the entire pat-
tern easily.
To get dynamic complex patterns, an attraction
point was defined in the Grasshopper code. While
coding the entire pattern, the construction point was
defined to control the starting point of the pattern in
case of the need for the change of the starting point
of the pattern. In addition to construction point, at-
traction point is defined which led the changes in the
number of the division on the hexagon. Attraction
point was defined as the distance between the attrac-
tion point and grids which were defined as the cen-
tre of the hexagons. Varied values of the distance be-
tween the attraction point and the entire grid gener-
ates irregular gradient pattern alternatives (Figure 4).
Mathematically defined algorithms in grasshop-
per generate hundreds of complex pattern alterna-
tives that can be used in different designs such as
ceramic design, fabric design, facade panel designs,
etc.. The use of these designs as ceramic tiles and di-
vider panel is illustrated in (Figure 5).
SHAPE, FORM & GEOMETRY | Applications - Volume 2 - eCAADe 36 |479
Figure 1
Rule set of the
pattern making the
process of the
study.
Figure 2
Grasshopper code
of the pattern.
480 |eCAADe 36 - SHAPE, FORM & GEOMETRY | Applications - Volume 2
THIRD STAGE - Acoustic Panel Design
Acoustics is important performance criteria which
determines the quality of an architectural space. Ac-
cording to Peters (2009), as light illuminates our vi-
sual environment, sound sources illuminate our sonic
environment. ... Human activities produce sound,
and our architecture constantly interacts with us
through its modification of the sounds we create (Pe-
ters, 2009). Since then, computer aided tools be-
come apparent in the architectural acoustic designs
as well as light design in architecture. Altering the
acoustic performance of a space by changing the ma-
terial properties, surface geometries, and etc is an
important factor that stated the acoustic quality of
the space. Since the widespread use of the com-
putational tools, firstly in architectural design, and
then, acoustical practices, provided acoustically well-
balanced space designs.
Third stage of the study investigated how pat-
tern generated in stage two can be utilized in acous-
tic cloud panel making. Here, real classroom acous-
tic problem in the Architectural School of Istanbul
Technical University Classroom 214 used as a case
(Figure 6). In this stage, first design students make
3D model of the classroom, then graduate students
of the building physic analyse acoustics of the class-
room, using 3D model in Odeon simulation soft-
ware. As the consequences of the analysis and sim-
ulations of Classroom 214 has acoustical problems
which are mainly related with speech are identified
as the persistence of the sound in the classroom and
the speech intelligibility across the listeners.
Reverberation time is one of the primary impor-
tance of acoustic parameters that gives the first idea
Figure 3
Varied pattern
designs as a result
of diverse dividing
options.
SHAPE, FORM & GEOMETRY | Applications - Volume 2 - eCAADe 36 |481
Figure 4
Dynamic pattern
design depending
on the location of
the attraction point.
Figure 5
Ceramic art wall
design alternatives.
Figure 6
Architectural
School of Istanbul
Technical University
Classroom 214.
about an acoustical behaviour of a room. (Figure
7). Wallace Sabine is the founder of the science of
the Architectural Acoustic, discovered the relation-
ship and effects between sound, space, and material
of acoustic quality of the space. By knowing the sur-
face area of the constituent materials, their absorp-
tion coefficients, and the volume of the space, the
reverberation time can be predicted (Peters, 2010).
Reverberation is an objective measurable indicator
of the persistence of a sound after its source turned
off and it is mainly depended on the volume and ab-
sorption amount of the room. As the absorption de-
482 |eCAADe 36 - SHAPE, FORM & GEOMETRY | Applications - Volume 2
Figure 7
Recommended
reverberation times
(Long, 2005).
Figure 8
Reverberation times
of the classroom for
different frequency
bands. creases and reflection increases, reverberation time
gets longer and the room sound dies in a long time
in the room. A larger volume also affects the rever-
beration time to be longer. Reverberation time de-
fines the appropriate acoustical conditions for differ-
ent functions. A longer reverberation time causes the
speech to be less understandable which it is not a
preferred situation for a room.
While site visit to classroom 241, very long rever-
beration time that affects speech intelligibility is ex-
perienced as is also observed in Odeon software sim-
ulation. The simulation results for different frequency
bands are listed below (Figure 8). As it can be seen
from the results the large volume of the class and a
large number of reflective surfaces, cause reverbera-
tion time to be much higher than the criteria. How-
ever, reverberation time does not change too much
around a room as a constant average level is perva-
sive that gives an idea of the speech intelligibility in a
room while it is not the only parameter that effects it.
The understanding of the speech depends on many
different things while the main factors are the char-
acter of the source, the distance between the source
and receiver, and the background noise.
There are different ways to measure the speech
intelligibility. One of most common and standard-
ized objective method is the speech transmission in-
dex Speech Transmission Index (STI). It is an index
gives a result between 0 and 1, which indicates worst
and best speech intelligibility respectively (Figure 9).
Odeon Software was used to measure the STI for
different positions in the simulated classroom. Under
the assumptions about the speaker, surface materials
and background noise, STI values as grid response of
the whole classroom can be seen in the figure 10. As
expected from the experience the results are very low
and even at the front seats conditions are poor to un-
derstand the speaker.
SHAPE, FORM & GEOMETRY | Applications - Volume 2 - eCAADe 36 |483
Acoustic Proposal and Pattern Modification
While proposing an acoustical element to enhance
the indoor quality, it is considered that the building’s
being listed as a first-class historic building. To avoid
closing the ribs on the ceiling and making a perma-
nent change, the absorptive sound panel in other
saying an acoustical ceiling cloud was proposed. It
is thought that they have an advantage in terms of
barely attaching to the ceiling and does not entirely
cover and close the ribs. Acoustical ceiling clouds
are widely used for noise reduction and reverberation
control in auditoriums, restaurants, atriums and mul-
tipurpose rooms.
During the studies of the acoustic ceiling cloud
design, the entire pattern as structure and substruc-
tures were analysed to design fabrication steps and
system for the acoustic ceiling cloud design pattern.
To enable design for this, a mathematical connec-
tion between acoustics and architecture is required
(Reinhardt, Cabrera, & Hunter). In this process, the
pattern was optimized according to construction re-
quirements as defining continuous and discontinu-
ous axes on all lines in the acoustic cloud pattern (Fig-
ure 11). The line from 0 to 5 and the line from 0 to
7 were discontinuous lines in the pattern which were
hard for implementation of the acoustic ceiling cloud
pattern. Thus, these lines were removed from the
entire pattern. As it can be seen in the new single
hexagon module, the red axe was added to the pat-
tern structure to make the pattern more rigid (Figure
12).
To construct this 3D composition, the 2D pat-
tern was transformed in 3D cloud by transforming 2D
lines into 3D surfaces. Afterwards, the pattern struc-
ture was treated like a Lego consisting of 5 layers to
increase both the number of reflective surfaces as an
acoustic solution and to prevent the cutting of the
each and every element of the pattern. In the layer
system of the pattern for construction, pattern struc-
ture was named as from the top to bottom as the
first layer is the top layer, the third layer is the mid-
dle layer, and the fifth layer is the bottom layer that
the structures were designed without slits between
layers which provide nesting to all the layers easily in
the construction process (Figure 13). And the metal
pipe was designed to hang the acoustic cloud design
to the ceiling from the four corners of the rectangu-
lar acoustic cloud. Therefore, acoustic cloud panel is
designed as a self-supporting system to provide the
acoustic solutions to the classroom 214.
Figure 9
Distribution of STI
in three different
cases.
Figure 10
Acoustic properties
of the classroom as
ODEON outputs.
Figure 11
Analysis of structure
and substructures.
Figure 12
Rules of the new
structure.
Figure 13
Layer system of the
acoustic panel unit.
Figure 14
Acoustic panel
design renders for
the classroom 214.
484 |eCAADe 36 - SHAPE, FORM & GEOMETRY | Applications - Volume 2
Figure 15
Absorption
coefficients of
Basotect 50mm
Figure 16
Frequency bands in
which human
speech is most
effective for three
different cases.
Figure 17
Distribution of STI
in three different
cases.
SHAPE, FORM & GEOMETRY | Applications - Volume 2 - eCAADe 36 |485
It is aimed to reduce the reverberation time in ac-
cordance with the speech function by increasing the
absorptive surface in the classroom, and to provide
a more homogeneous distribution of sound in the
volume. The coffered slab at the ceiling is a part of
the architectural character of the building, so a sus-
pended ceiling which would conceal the slab and
lower the volume was not possible. So, a transpar-
ent absorptive sound baffle was suggested by the
designer to overcome the problem. The desired ab-
sorption was aimed to be provided with the material,
depth, and complexity of the suspended structure as
well as acoustic panel design (Figure 14).
50mm Basotect® melamine foam is used as the
absorbing material because its absorption efficiency
is 50mm (Figure 15). Sound baffles positioned at a
distance of 2m from the ceiling which is expected
to enhance its effect. The room is modelled with-
out and with the ceiling baffles and the reverbera-
tion time results are listed below for before and after
the acoustical treatment (Figure 16). It is seen that
baffles would be mostly effective. Especially for the
mid-frequencies 250Hz, 500Hz, 1000Hz in which hu-
man speech is most effective the reverberation times
are lowered to the recommended levels as 0,70-1,00
s. The simulated STI results for the speech intelligibil-
ity are listed below for before and after the acoustical
treatment (Figure 17).
According to the simulation outputs, the rever-
beration time is decrease in frequency bands where
human speech is most effective with the final design.
CONCLUSION
This study explored computational thinking and
making from paper-based 2D geometric pattern gen-
eration to its evolution into 3D acoustic panel and its
realization. It also includes various methods as intu-
itive tendencies, collaborative multi-disciplinary re-
search conducted with building physics students by
utilizing integrative thinking and making.
Consequently, the 3D pattern not only have a
graphical value that could be described as an art, but
also alter the acoustic conditions of the classroom.
However, when the geometry was structurally anal-
ysed and materialized, it has become an architectural
element at the end. As a result of the analysis made
for the acoustic panel design, the absorptive acous-
tic panels to be designed at the ceiling to reduce the
reverberation time and create more suitable environ-
ments for lectures as well as other functions. The
complexity of the pattern with the accurate material
would provide most of the solutions for the long re-
verberation.
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486 |eCAADe 36 - SHAPE, FORM & GEOMETRY | Applications - Volume 2
