1. Digital Architectures
Computer Graphics for Architects in 2003-04 (Arch5302) Marc Aurel Schnabel
Wednesday, 7 October, 2003
Introduction “Having abandoned the discourse of style, the architecture of modern times is characterized by its capacity to take advantage of the specific achievements of that same modernity: the innovations offered it by present-day science and technology. The relationship between new technology and new architecture even comprises a fundamental datum of what are referred to as avant-garde architectures, so fundamental as to constitute a dominant albeit diffuse motif in the figuration of new architectures.�
Ignasi de Sola Morales: 1997, Differences: Topographies of Contemporary Architecture, MIT Press, Cambridge.
Quote “Integrating computer-aided design with computer-aided fabrication and construction [...] fundamentally redefines the relationship between designing and producing. It eliminates many geometric constraints imposed by traditional drawing and production processes— making complex curved shapes much easier to handle, for example, and reducing dependence on standard, mass-produced components. [...]. It bridges the gap between designing and producing that opened up when designers began to make drawings.�
Mitchell, W. and M. McCullough. (1995). Prototyping (Ch. 18). In Digital Design Media, 2nd ed., 417-440. New York, Van Nostrand Reinhold.
Digital Architectures Digital architectures refer to the computationally based processes of form origination and transformations. Several digital architectures are identified based on the underlying computational concepts such as: i.
topological space (topological architectures)
ii.
isomorphic surfaces (isomorphic architectures)
iii.
motion kinematics & dynamics (animate architectures)
iv.
keyshape animation (metamorphic architectures)
v.
parametric design (parametric architectures)
vi.
genetic algorithms (evolutionary architectures)
i
Topological architectures
In “architectural curvilinearity” Greg Lynn offers examples of new approaches to design that move away from the deconstructivism’s “logic of conflict and contradiction” to develop a “more fluid logic of connectivity.” This is manifested through folding that departs from Euclidean geometry of discrete volumes, and employs topological, “rubber-sheet” geometry of continuous curves and surfaces. In topological space, geometry is represented by parametric functions, which describe a range of possibilities. The continuous, highly curvilinear surfaces are mathematically described as NURBS – Non-Uniform Rational B-Splines. What makes NURBS curves and surfaces particularly appealing is the ability to easily control their shape by manipulating the control points, weights, and knots. NURBS make the heterogeneous and coherent forms of the topological space computationally possible.
Guggenheim Bilbao by Frank Gehry
ii
Isomorphic Architectures
Blobs or metaballs, or isomorphic surfaces, are amorphous objects constructed as composite assemblages of mutually inflecting parametric objects with internal forces of mass and attraction. They exercise fields or regions of influence, which could be additive or subtractive. The geometry is constructed by computing a surface at which the composite field has the same intensity: isomorphic surfaces. These open up another formal universe where forms may undergo variations giving rise to new possibilities. Objects interact with each other instead of just occupying space; they become connected through a logic where the whole is always open to variation as new blobs (fields of influence) are added or new relations made, creating new possibilities. The surface boundary of the whole (the isomorphic surface) shifts or moves as fields of influence vary in their location and intensity. In that way, objects begin to operate in a dynamic rather than a static geography.
Cardiff Opera by Greg Lynn BMW-Pavilion by B. Franken
iii
Animate Architectures
Animation software is utilized as medium of form-generation. Animate design is defined by the copresence of motion and force at the moment of formal conception. Force, as an initial condition, becomes the cause of both motion and particular inflections of a form. While motion implies movement and action, animation implies evolution of a form and its shaping forces. The repertoire of motion-based modeling techniques are keyframe animation, forward and inverse kinematics, dynamics (force fields) and particle emission. Kinematics are used in their true mechanical meaning to study the motion of an object or a hierarchical system of objects without consideration given to its mass or the forces acting on it. As motion is applied, transformation are propagated downward the hierarchy in forward kinematics, and upward through hierarchy in inverse kinematics.
House in Long island by Greg Lynn
Kinematics
Port Authority Bus Terminal in NY by Greg Lynn
Dynamic simulations take into consideration the effects of forces on the motion of an object or a system of objects, especially of forces that do not originate within the system itself. Physical properties of objects, such as mass (density), elasticity, static and kinetic friction (or roughness), are defined. Forces of gravity, wind, or vortex are applied, collision detection and obstacles (deflectors) are specified, and dynamic simulation computed.
iv
Metamorphic architectures
Metamorphic generation of form includes several techniques such as keyshape animation, deformations of the modeling space around the model using a bounding box (lattice deformation), a spline curve, or one of the coordinate system axis or planes, and path animation, which deforms an object as it moves along a selected path. In keyshape animation, changes in the geometry are recorded as keyframes (keyshapes) and the software then computes the in-between states. In deformations of the modeling space, object shapes conform to the changes in geometry of the modeling space.
Offices of BFL Software ltd. by Peter Eisenman
v
Parametric Architectures
In parametric design, it is the parameters of a particular design that are declared, not its shape. By assigning different values to the parameters, different objects or configurations can be created. Equations can be used to describe the relationships between objects, thus defining an associative geometry. That way, interdependencies between objects can be established, and objects’ behavior under transformations defined. Parametric design often entails a procedural, algorithmic description of geometry. In this “algorithmic spectaculars”, i.e., algorithmic explorations of “tectonic production” using mathematica software, architects can construct mathematical models and generative procedures that are constrained by numerous variables initially unrelated to any pragmatic concerns. Each variable or process is a ‘slot’ into which an external influence can be mapped, either statically or dynamically.
algorithmic spectaculars by M Novak
vi
Evolutionary architectures
Evolutionary architecture proposes the evolutionary model of nature as the generating process for architectural form. Architectural concepts are expressed as generative rules so that their evolution and development can be accelerated and tested by the use of computer models. Concepts are described in a genetic language which produces a code script of instructions for form generation. Computer models are used to simulate the development of prototypical forms which are then evaluated on the basis of their performance in a simulated environment. Very large numbers of evolutionary steps can be generated in a short space of time and the emergent forms are often unexpected. The key concept behind evolutionary architecture is that of the genetic algorithm. The key characteristic is a “a string-like structure equivalent to the chromosomes of nature,� to which the rules of reproduction, gene crossover, and mutation is applied. Optimum solutions are obtained by small incremental changes over several generations.
“pseudo-organisms” by J. Frazer
vii
Virtual Environments
The use of computer modeling and simulation to enable a person to interact with an artificial threedimensional visual or other sensory environment. VR applications immerse the user in a computergenerated environment that simulates reality through the use of interactive devices, which send and receive information and are worn as goggles, headsets, gloves tracking devices, CAVES and other media.
Augmented Reality
Head Set
CAVE
Workbench
Illusion-hole
Immersive VE
2. Digital Architectural Tools
Introduction It was only within the last few years that the advances in computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies have started to have an impact on building design and construction practices. They opened up new opportunities by allowing production and construction of very complex forms that were until recently very difficult and expensive to design, produce, and assemble using traditional construction technologies. The consequences will be profound, as the historic relationship between architecture and its means of production is increasingly being challenged by new digitally driven processes of design, fabrication and construction.
Quotes “Architecture is recasting itself, becoming in part an experimental investigation of topological geometries, partly a computational orchestration of robotic material production and partly a generative, kinematic sculpting of space�
Zellner, Peter. (1999). Hybrid Space: New Forms in Digital Architecture. New York: Rizzoli.
Digital Fabrication Digital architectural fabrication refer to the computationally based processes of form production and fabrication based on a digital architectural model. Several digital fabrication processes are identified based on the underlying computational concepts such as: i.
2D Fabrication
ii.
Subtractive Fabrication
iii.
Additive Fabrication
iv.
Formative Fabrication
v.
Assembly
vi.
Rapid Prototyping
Digital Fabrication Implications of new digital design and fabrication processes enable the use of (vii) Virtual Environments (VE), (viii) rapid prototyping (RP) and computer-aided manufacturing (CAM).
Technologies, which offer the production of small-scale models and full-scale building components directly to and from 3D digital models. Mass-customization is a development of repetitive nonstandardized building systems through digitally controlled variation and serial differentiation. Geometries are precisely described and their construction is perfectly attainable by a computer numerically controlled (CNC) fabrication processes.
i
2D Fabrication
CNC (computer numerically controlled) cutting, or 2D fabrication, is the most commonly used fabrication technique. Various cutting technologies, such as plasma-arc, laser-beam, or water-jet, involve two axis motion of the sheet material relative to the cutting head and are implemented as a moving cutting head, a moving bed, or a combination of the two. In plasma-arc cutting an electric arc is passed through a compressed gas jet in the cutting nozzle, heating the gas into plasma with a very high temperature (25,000F), which converts back into gas as it passes the heat to the cutting zone.
Plasma-arc CNC cutting of steel supports for masonry walls in Frank Gehry’s Zollhoff Towers in Düsseldorf
Aluminum space frame for ABB Architects’ BMW Pavilion is cut directly from digital data using CNC water-jet technology.
In water-jets, as their name suggests, a jet of highly pressurized water is mixed with solid abrasive particles and is forced through a tiny nozzle in a highly focused stream, causing the rapid erosion of the material in its path and producing very clean and accurate cuts.
Laser-cutters use a high intensity focused beam of infrared light in combination with a jet of highly pressurized gas (carbon dioxide) to melt or burn the material that is being cut. There are, however, large differences between these technologies in the kinds of materials or maximum thicknesses that could be cut. Laser-cutters can cut only materials that can absorb light energy; water-jets can cut almost any material. Laser-cutters can cost-effectively cut material up to 5/8�, while water-jets can cut much thicker materials, for example, up to 15� thick titanium. Digital Fabrication: Manufacturing Architecture in the Information Age 3 The production strategies used in 2D fabrication often include contouring, triangulation (or polygonal tessellation), use of ruled, developable surfaces, and unfolding. They all involve extraction of two-dimensional, planar components from geometrically complex surfaces or solids comprising the building’s form. Which of these strategies is used depends on what is being defined tectonically: structure, envelope, a combination of the two, etc.
Structural frames in Frank Gehry’s Experience Music Project in Seattle & Bernard Franken’s BMW Pavilion
In contouring, a sequence of planar sections, often parallel to each other and placed at regular intervals, are produced automatically by modeling software from a given form and can be used directly to articulate structural components of the building, as was the case in a number of recently completed projects.
Complex, curvilinear surface envelopes are often produced by either triangulation (or some other planar tessellation) or conversion of double-curved into ruled surfaces, generated by linear interpolation between two curves. Triangulated or ruled surfaces are then unfolded into planar strips, which are laid out in some optimal fashion as two-dimensional shapes on a sheet, which is then used to cut the corresponding pieces of the sheet material using one of the CNC cutting technologies. For example, Frank Gehry’s office used CATIA software in the Experience Music Project in Seattle to “rationalize” the double-curved surfaces by converting them into “ruledevelopable” surfaces, which were then unfolded and fabricated out of flat sheets of metal.
Triangulated complex surfaces in Frank Gehry’s DG Bank Building in Berlin & use of ruled surfaces in the Water Pavilion by NOX in the Netherlands.
Gaussian analysis of the surface curvature
The surface data could be also used to directly generate a wire frame abstraction of the building’s structural framework, which could be then processed by the structural analysis software to generate the precise definition of all structural members. In Gehry’s Bilbao project the contractor used a software program from Germany called Bocad to automatically generate a comprehensive digital model of the structural steel, including the brace-framed and secondary steel structures for the museum. More importantly, that same program was used to automatically produce the fabrication drawings or CNC data to precisely cut and pre-assemble the various components.
ii
Subtractive Fabrication
Subtractive fabrication involves removal of specified volume of material from solids using multi-axis milling. In CNC milling a dedicated computer system performs the basic controlling functions over the movement of a machine tool using a set of coded instructions static geography.
The CNC milling has recently been applied in new ways in building industry – to produce the formwork (molds) for the off-site and on-site casting of concrete elements with double-curved geometry, as in one of the Gehry’s office buildings in Düsseldorf, and for the production of the laminated glass panels with complex curvilinear surfaces, as in Gehry’s Conde Nast Cafeteria project and Bernard Franken’s BMW Pavilion.
Milling of molds for the production of double-curved acrylic glass panels BMW-Pavilion by B. Franken
Milling of Styrofoam molds for the casting of reinforced concrete panels for Gehry’s Zollhof Towers
In Gehry’s Zollhof towers, the undulated forms of the load bearing external wall panels, made of reinforced concrete, were produced using blocks of lightweight polystyrene (Styrofoam), which were shaped in CATIA and CNC milled to produce 355 different curved molds that became the forms for the casting of the concrete.
iii
Additive Fabrication
Additive fabrication involved incremental forming by adding material in a layer-by-layer fashion, in a process converse of milling. It is often referred to as layered manufacturing, solid freeform fabrication, rapid prototyping, or desktop manufacturing. All additive fabrication technologies share the same principle in that the digital (solid) model is sliced into two-dimensional layers. The information of each layer is then transferred to the processing head of the manufacturing machine and the physical product is incrementally generated in a layer-by-layer fashion.
A number of competing technologies now exist on the market, utilizing a variety of materials and a range of curing processes based on light, heat, or chemicals:
Stereo lithography (SLA) is based on liquid polymers which solidify when exposed to laser light. Selective Laser Sintering (SLS) laser beam melts the layer of metal powder to create solid objects. In 3D Printing (3DP) layers of ceramic powder are glued to form objects. Sheets of material (paper, plastic), either precut or on a roll, are glued (laminated) together and laser cut in the Laminated Object Manufacture (LOM) process. In Fused Deposition Modeling (FDM) each cross section is produced by melting a plastic filament that solidifies upon cooling. Multi-jet manufacture (MJM) uses a modified printing head to deposit melted thermoplastic/wax material in very thin layers, one layer at a time, to create three-dimensional solids. Sprayed concrete were introduced to manufacture large-scale building components directly from digital data.
Trypiramid: Polshek’s Rose Center for Earth - Sciences, NY & HKU Students’ work
iv
Formative Fabrication
In formative fabrication mechanical forces, restricting forms, heat, or steam are applied on a material so as to form it into the desired shape through reshaping or deformation, which can be axially or surface constrained. For example, the reshaped material may be deformed permanently by such processes as stressing metal past the elastic limit, heating metal then bending it while it is in a softened state, steam-bending boards, etc. Double curved, compound surfaces can be approximated by arrays of height-adjustable, numerically-controlled pins, which could be used for the production of molded glass and plastic sheets and for curved stamped metal. Plane curves can be fabricated by numerically-controlled bending of thin rods, tubes, or strips of elastic material, such as steel or wood, as was done for one of the exhibition pavilions designed by Bernard Franken for BMW.
Forming: Kolatan & Macdonald’s house in Connecticut
“The idea of a structural skin not only implies a new material, but also geometries, such as curves and folds that would enable the continuous skin to act structurally, obviating an independent static system: The skin alone does the heavy lifting.” Giovannini, J. 2000. Building a Better Blob. In Architecture 89(9): 126-128.
The building is made of polyurethane foam sprayed over an egg-crate plywood armature that was CNC-cut, thus forming a monocoque structure that is structurally self-sufficient without the egg-crate, which will remain captured within the monocoque form
v
Assembly
After the components are digitally fabricated, their assembly on site can be augmented with digital technology. Digital three-dimensional models can be used to determine the location of each component, to move each component to its location, and finally, to fix each component in its proper place. New digitally-driven technologies, such as electronic surveying and laser positioning, are increasingly being used on construction sites around the world to precisely determine the location of building components. For example, Frank Gehry’s Guggenheim Museum in Bilbao was built without any tape measures. During fabrication, each structural component was bar coded and marked with the nodes of intersection with adjacent layers of structure. On site bar codes were swiped to reveal the coordinates of each piece in the CATIA model. Laser surveying equipment linked to CATIA enabled each piece to be precisely placed in its position as defined by the computer model.� Similar processes were used on Gehry’s project in Seattle. This processes are common practice in the aerospace industry, but relatively new to building.
algorithmic GPS technology was used on Gehry’s Experience Music Project in Seattle to verify the location of components
vi
Rapid Prototyping
Computer Numerically Controlled (CNC) fabrication processes are cutting, subtractive, additive, and formative fabrication. Rapid Prototyping (RP) involves incremental forming by adding material in a layer-by-layer fashion. The digital (solid) model is sliced into two-dimensional layers; the information of each layer is then transferred to the processing head of the manufacturing machine and the physical product is incrementally generated in a layer-by-layer way.
CNC Bernard Cache’s “Objectiles” Gehry’s "Zollhof" in Duesseldorf Bernard Franken’s "BMW Pavilion"
Mass Customization: Bernard Cache’s “Objectiles�
The ability to mass-produce irregular building components with the same facility as standardized parts introduced the notion of mass-customization into building design and production (it is just as easy and cost-effective for a CNC milling machine to produce 1000 unique objects as to produce 1000 identical ones). Mass-customization, sometimes referred to as systematic customization, can be defined as mass production of individually customized goods and services, thus offering a tremendous increase in variety and customization without a corresponding increase in costs.
End
Wednesday, 8 October, 2003; marcaurel@hku.hk