Urban and
architectural 3D fast processing.
Renato Saleri Lunazzi, architecte DPLG, DEA informatique et productique,
master en industrial design.
Laboratoire MAP aria UMR 694 CNRS –
Ministère de la culture et de la Communication.
e-mail
renato.saleri@lyon.archi.fr
keywords : 3D modeling,
generative approaches, automatic texturing, building design, grammars
Introduction
Present computer aided-design tools should be able to assist the former
exploration that leads the entire design process. However, present software
often calls an immediate actualization of geometrical intentions by forcing the
user with pre-set intentional clusters - geometric primitives, textural resources,
design procedures... - often uncompromising, with poor intuitive feedback and
generally restraining imagination spreadout: "most of CAD software act like over-equipped hand-drafting assistants,
assuming the maturity of the designer as much as the maturity of the project
itself." [Chupin - Lequay 2000]
We must quote Donald Shön's opinion, who remarks that research should
concentrate on computer environments able to enhance user's ability to
comprehend, store, manipulate, organize and speculate over project's matter. Many
research projects explored this concept, introducing new operating
methodologies able to schematize
introductory projectual investigations, long before any possible geometric
formalization.
What we aim to achieve is a computer-assisted generation process of
architectural and urban plausible geometries. These self-generated objects are
intended to act like "imagination enhancers" serving conceptual
exploration of architectural design or providing credible 3D environments in
given historical context. Next step, this "pr-object" could not only
be the ponderated completion of a pluridisciplinaric integration process but,
in an autonomous evolution Darwinian paradigm, the actualization of the most
performant genotype, or saying like Celestino Soddu, a generative project is a concept software that works producing
three-dimensional unique […] events as possible and manifold expressions of the
generating idea identified by the designer as a subjective proposal of a
possible world. [Soddu 2002]
Some of the
research tasks depicted hereby take advantage of recent generative methods
developed within the MAP aria research team. They are able to quickly produce
architectural and urban geometric simulations, bringing to life wide 3D
databases connected to some of the most recent 3D terrain browsers. (Virtual
Terrain©, MSN Virtual Earth© or Google Earth©...)
I. INTRODUCING GENERATIVE
PARADIGM
1. Form vs. function
In architecture, a modern acception for spatial interdependancies states
that form should rise from function. Since Franck L. Wright,
Robert Mallet-Stevens and Ludwig Mies van Der Rohe architectural thought , and
enlightened by their sublime work, we believe in such a manichean dogma, wich
could be - to be simple - the main contrast to centuries of academism, and by
the way a brand new unrestricted field of investigation.
Conversely, most examples of classical architecture appear to be in a
complete conceptual opposition, with recurring high geometric-prevalence
regarding function. The question is obviously not here to state about the
overcome of this conceptual dialog between form
and function but to consider further
some hierarchical appraisal when we
will be brought – in our software - to select initial input data.
fig1.
villa Rotonda map : Andrea Palladio – 1556
In
his 'entretien avec les étudiants des écoles d'architecture" even Le
Corbusier asserts how difficult it is to arrange a complex spatial distribution
within simple shapes. According to this point of view, a profuse geometrical
spreadout could rather facilitate the solving of programmatic intricacy… [le Corbu – 1958]
According to R. Wittkower, the most representative width/height ratios
within palladian architecture match the chromatic major musical scale. In this
perspective, a C-G major chord could be quoted with a period ratio of 2:3; a
C-F major will be quoted as 3:4. In this perspective (and it is interesting to
show how the "music interval" notion rests on the latin etymology of intervallum, which literally means
"between the walls") Deborah Howard and Malcolm Longhair underlined
the recurrent use of musical ratios within Palladian architecture, emerging
from a systematic frequency analysis of his major villas geometry and noticing
that such reports are mesureable horizontally and vertically.
G Stiny and W. Mitchell - above many others - pointed out some
parametric grammars able to generate palladian architectural patterns. This
approach clearly refers to Prof. Noam Chomsky linguistics experiments and the
amazing Palladio 1.0 Macintosh© Hypercard Stack [Freedman - 1990] is a
noteworthy example of such a morphological synthesis. This concept is
definitely an oldie but it's achievement could nowadays be handled by emerging
technologies. The leading action of Vitruvius in such domain - a generative or
algorithmic approach to automate the design process - massively influenced
renaissance's conceptual contents; philosophers and architects of this period,
such as Leon Battista Alberti or Il Rossellino and moreover contemporary theorists
- Goethe, Monge, Froebel, Frege and more recently Wittgenstein and Le Corbusier
through the research of Iannis Xenakis - certainly considered and applied
theoretical aspects of this scheme in their very own work.
Morphologic studies of urban framework gave birth to various
investigations; P. Panerai [Panerai -
1992], trying to define precisely "urban framework" (tissu urbain in french is closer to
"fabric" or "cloth") encloses its peculiar meaning within a
combined structural and systemic approach, stating that "urban framework space closely follows roads,
squares, boulevards and lanes spreadout as much as it can be the direct
expression of the parcel's reverse influence"
Beyond the functionalist process that leads architectural and urban
design through the correct response to constructive and programmatic needs, we
can observe some peculiar design processes guided by specific interdisciplinary
connections:
• physical
analogies
• structural
analogies
• geometric similarities
• multi-scale patterns
• …
In the domain of morphologic analysis – here intended as the backtrack
of the conceptual pattern - we must mention the LAF research team, within the
architecture school of Lyon (F). What B. Duprat and M. Paulin [Paulin – Duprat
1991] designate as a "morphological factorization of architecture"
consists in splitting complex architectural arrangements in visible and
pertinent sub-elements. Semantically speaking, this could be achieved in
different manners, according to the specific knowledge we are willing to figure
out: this is why a geometrical description of an architectural system doesn't
necessary match the architectural or even its very deep constructive
expression.
"We only could reason on models" stated Paul Valery describing
this very peculiar representation mode that supports artificial and symbolic
mental depictions. The model, (emerging from the latin "Modulus, from modus, the measure) is resulting from a schematization process able
to select certain discriminant properties of the "real-life system",
providing a plausible simulacre, an homotopic functional structure in a given abstraction level. This principle
describes the model as a full-interactive set of elements, with it's own
organisation, information and knowledge rules.
Noam Chomsky is the Institute Professor Emeritus of linguistics at
the Massachusetts Institute of Technology. Chomsky is credited with the
creation of the theory of generative grammar, considered to be one of the most
significant contributions to the field of theoretical linguistics made in the
20th century.
2. Apophenic approach, a perceptive disruption.
Pareidolia is a type of illusion or misperception involving a vague or obscure
stimulus being percieved as something clear and distinct.
Apophenia is the
experience of seeing patterns or connections in random or meaningless data. The
term was coined in 1958 by Klaus Conrad, who defined it as the
"unmotivated seeing of connections" accompanied by a "specific
experience of an abnormal meaningfulness".
"The propensity to see
connections between seemingly unrelated objects or ideas most closely links
psychosis to creativity ... apophenia and creativity may even be seen as two
sides of the same coin." [Brugger 2001]
It seems that part of the cognitive (re)construction of depicted
artifacts depends on a peculiar misreception of visual data; It's more the
unconscious will to project some personal expectations that tend somehow to
enhance the perceptual efficiency.
We can mark out the very famous painting "ceci
n'est pas une pipe" by Magritte, for stating how far the interpretation of
an object from the object itself could
be...
fig 2. « ceci n’est pas une pipe »: René
Magritte – 1929
What we can call a "look like" effect consists, in some
precise representative paradigm, to act as an imposture, close to perceptive
constructed distortions like anamorphosis - a distorted projection or
representation which, when wiewed from a certain point, appears regular and in
proportion - or "trompe l'oeil" effects. The idea is that - in this
case - the effect is not only specifically geometric but more generically
perceptive. Furthermore, we can observe that there is a very subjective
perceptive limit to the legibility of a significant pattern : we can
observe that this limit could have wide interpersonal variations that tend to
enhance or weaken perceptual aptitudes. At which point do we percieve credible
representations? Are what we percieve as doors, roofs, windows and other single
architectural details making sense together, somehow matching some general
discriminant criteria? Some interesting Malevitch tectonic assemblyes are
"just" geometrical clusters, solely made of boxes, prisms and other
cubic primitives. But these primitives - even the significance of this word is
proper to sustain the idea of an initiatory process - lead us to make
artificial connections able to give sense to such a meaningless assemblage.
fig 3. altered readability
We can here depict a very interesting linguistics concept described as implicit and explicit typology. A culture is a manner of perceiving reality. Perception
is, nevertheles, a subjective phenomenon and what we can perceive - and
describe - is not reality but a possible, personal reality. One's experience
tends to influence his very own perceptive methods. Each cultural content, in a
very generic acception - has two components: what can be said (explicit) and
what isn't said or expressed because it's supposed to be obvious (implicit). Unspoken
concepts are embedded in a bigger
cultural context that imply their belonging in an implicit content.
It is clear that all artificial objects created are linked to a more
generic implicit content, depending on personal, cultural and subjective
factors. The fact is that we can connect them immediately to specific know
how's, related to a (g)local tectonic and structural culture. The architectural
and/or urban readability of depicted objects depends on a specific cognitive
context, provided that all implicit dependancies are fullfilled. According to
this point of view, we believe that any representation needs little apophenic
projection to be undestood, considering that it embeds in any case an implicit
cultural content.
fig 4. plausible or meaningless ? Random-generated
rule-based 3D objects
Even a map or a picture obviously implies some deep intrinsic contextual
knowledge not to be misunderstood: the difficulty encountered in programming
computer-based automatic 3D extraction from 2D images is still a bright proof
of the unbeaten superiority of human thought ; this peculiar ambiguity is
somehow the cornerstone of the following research task.
II EXPERIMENTING WITH GENERATIVE APPROACHES
1.
Integrated fast 3D urban processing system
abstract
The proposal mainly consists in an integrated
architectural and urban semiautomatic model-generation pipe, emerging from
early research tasks about automatic generation of urban and architectural 2D
and 3D patterns. [Saleri 2004]
Our goal in this research task is to rapidly produce
"plausible" urban environments, using existing data, such as digital
maps, DEM's and aerial photographs with a high-level of detail - 16 or 50 cm
resolution.
Early stages of this project produced interesting
results, combining complementary modeling techniques, according to demanded LOD
(Level Of Detail): For instance, we prefer to use hybrid image-based modeling
for relevant architectural objects, demanding high-level recognisability, for
close-up views and close detail identification. If not specified, the model
generation follows a generic approach.
The semi-automated process involved in rapid 3D-modeling for generic
surrounding architecture (architectural sceneries) links two semi-automated
generative processes considering separately 3D elevation and facade generation:
• The 3D elevation step is a
geometrical tool that mainly uses initial manual dot plotting on a aerial map
and elevates the volume according to some simple contextual rules: number of
floors, entresol characteristics and covering type. All we need first is to
point out two vertex on the lower ledge of a roof face that will be kept
horizontal in the next step of the computational process. Then we designate cw
or ccw all of the following coplanar vertices of the same roof face and
validate: according to the initial position of the first two vertices, the
program builds the geometric layout, adding needed facade textures to side
faces, as described in facade generation
step.
fig 5. local database enhancing : geo-related
roof textures and generic facades
• The facade generation step
consists in the prewrite of a specific Texture LookUp Table, previously filled
with "contextualized" facade-like tiles. In this system, the
intrinsic coherence of the texture itself depends on the pertinence of single
texture patches positionning and invoking. The consistence of this approach is
therfore limited by the local applicability of it's generative process: on
demand, we need to bring into conformity the initial set of generative rules,
in order to match to very local architectural components; we recently experimented such a rule-based
generator over the "Vieux Lyon" urban framework, to test the
pertinence of the resulting representation. The visual discriminance at a
certain distance is quite impressive and locally compares to classical virtual
globe urban representations.
fig 6.urban framework
fast processing : GoogleEarth© browser 3D upgrade using local
database enhancing (see fig 6.)
The scientific constriction of this artifact consists its contextual
urban and architectural possible transposition ; the pertinence of
generative rules should balance between a wide low-level geometric descriptors
adaptability and a high-level of detail handling. If the low-level descriptors
are too generic we won’t be able to build a satisfying architectural diversity,
and though, resulting geometries will look too similar. On the other hand, it
will be quite impossible to specify with such a generic approach the immense
variety of architectural or urban expression; therefore we will have to handle
carefully any prior semantic discrimination in order to avoid uncontrolled and
meaningless geometric spreadouts.
2. Physical cellular automata
abstract
This research task involved some post graduated
students within the architecture school of Lyon; it emerges from a collective functional approach to generative
processes as new projectual strategies. The scientific goal of this teamwork
clearly aims to arbitrate very present questions about the pertinence of
computer aided design tools in conceptual, constructive and more universally
about representation processes in architecture and urban planning.
Early development stages of this project consider
basic nurbs primitives within Autodesk Maya© 3D environment as structural
guidelines for spatial specific allocation. Using Autodesk Maya's© embedded
physics engine, the idea consists in assign specific attraction/repulsion
attributes to scene objects according to their respective architectural
programmatic connections. In this case, and within a specific generative
process, we can generate a large number of plausible solutions responding to an
initial set of connection rules. We can for instance force some elements to be
attracted by specific allocation needs, like a panorama, some attractive
topological configuration or - more trivial - the connection with existing
power plants or road networks.
Declarative modeling.
Declarative modeling is quite a recent modeling technique, far from
classical modeling techniques like geometric parametric or primitive-based
modeling. First introduced in 1989 by Michel Lucas, its recent rise is due to
novel projectual needs emerging from architecture design and furniture
planning. Declarative modeling is able facilitate the design process through the implicit knowledge of former
physical, geometric or dimensional rules. In order to simplify what becomes an
interactive settlement of a 3D scene we may introduce implicit
relative-positionning sets of rules such as physical properties and
non-overlapping constraints.
As a matter of fact we find, in the former structure of the research
task introduced as a collaboration with Vincent Berger [Berger – Saleri 2005]
and other post-graduated students within the architecture school of Lyon, the
main aspects of the declarative modeling inputs, listed below as description, generative and - last - evaluation
phase.
• description phase:
typically the foremost properties formulation phase that takes place within a
specific UI, able to gather initial sets of input data. It's inner structure
could match the natural language paradigm or other intuitive descriptive
schemes.
• generation phase: this step
computes plausible solutions matching initial inputs collection. User can
formulate an initial query through a definite assets cluster that will be
translated in some low-level computational constraints. The system should then
be able to generate all the plausible solutions according to the initial model
request. However, if the original description is inconsistent, the system can
either return an incongruous solution or no response at all.
• evaluation phase: initiates
the user-guided appraisal process, considering wether or not the suggested
solutions consistently match initial needs. It should deliver an appropriate
feed-back interface able to re-launch the generative phase with significant
increase of computational constraints pertinence, so as to recursively enhance
the generative solutions.
The environment description is achieved through the description of a set
of properties, as stated above. "Properties" are intended here as
known descriptive elements, formerly defined by the user during description
phase. The system described below finds its solutions through the pseudo-random
agglutination of physical active 3D metaballs: our experiment gives concrete
espression to initial inputs with the use of appropriate 3D geometry:
multi-purpose nurbs spheres - called metaballs - within an Autodesk Maya© 3D
physical solver environment. "Appropriate" means here the direct
connection between size, mass, friction and attraction/repulsion
characteristics - embedded within the nurbs spheres properties - and the
architectural programmatic initial set-up.
fig 7. initial metaball spreadout : major cluster
+ natural light activators.
(V. Berger – R. Saleri 2005)
This means that we can model and handle immaterial connections and
relationships between architectural in and outdoor spaces. For instance, the
"kitchen metaball" will be most effectively connected to other
servant spaces, such as carports or pressoirs as the living room will be more
likely attracted by lobbyes and main entries. Eventually, servant metaball
clusters may be also connected to specific outer-spaces - backyards, secundary
accesses... - as served clusters could be attracted by delightful points of
views or major driveways.
These initial sprouts also embed natural-light activators: clusters of
3D points are generated at a distance in strategic positions: towards sun-path
or around a nice panorama or an attractive topographic configuration. They will
stick to the main metaball cluster according to their initial position and
create dimension-related openings through upcoming walls.
fig 8. geometric transform of former metaballs
cluster. The “light activators“visible as small dots on fig 7.generate
rectangle-shaped openings.
On the other hand, we could
initially state about inner
functional conflicts between listed spaces; these conflicts can merge from
accoustic or environmental pollutions or more generally from structural
discordancies or incompatibilities. Such properties will indeed activate
repulsive reactions between metaballs or heterogeneous sub-spaces when
mismatching combinations are found out.
Through given input classes, we will generate - with such a
pseudo-random process - lots of different geometric solutions, but all of them
structurally isomorph. This automated operation explores possible solutions
within a conceptual pattern that works in a simulated "real life"
design process. Functions, properties and connections are somehow modeled
inside a former input graph that will structurally return many plausible
solutions relatively to intentional programmatic needs.
fig 9. external view of resultant process .
This could be
a very tectonic rebuild of "cellular automata" concept. Former
metaballs suit well to geometric self-investigation: the sphere shape brings an
optimal surface/volume ratio and therefore the maximum combinational freedom.
Computation time is normally less than a minute; it depends on the number of
metaballs clusters, the complexity of the initial constraints graph and the
number of recursive solving processes involved. At the end of the evaluation
phase the user can test-freeze the final solution, which consists in a
geometric transformation of metaball clusters in respective size-related boxes.
Successive boleean operations will then substract inner material and hollow out
openings with subsequent environmental connections as seen on fig 9.
It’s our
belief that such mechanism could shortly be implemented to help handle
conceptual issues within product design and/or urban planning, as soon as we
will be able to digitally master the homotetic nature of human genius :o)
Conclusion
We believe that the scientific goal of such a research task doesn’t
consist in trying to replace the architect’s central responsability within the
design process. On the contrary, one should consider the interest of such
innovative paradigm to offset increasing complexity of today’s architect’s
activity. It’s usefulness will balance between morphologic synthesis within
geometric simulation tools on one hand and and the secret hope of a possible
instrumental operability in the field of urban and architectural management and
design process on the other.
Fortunately it seems that young professionals tend to easily endorse the
mutability of emerging technologies and therefore they should be more prepared
– in future - for embracing the increasing intricacy of surrounding world in
order to grant a sustainable balance between needs and resources…
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