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Light Caustics with Pneumatic Elements

Light Caustics with Pneumatic Elements
  • On August 2, 2016

Despite being distinct subjects, light and inflatable architecture share common ground in refraction and space. In 1960s, large volume of inflatable architectures has been built, favored by high-strength, light-weight and low maintenance of new membrane materials. Can inflatable architecture alone be the medium of creating caustics in the soft space? How will refraction of light change with the shape and material of the structure?

There has been growing interest in applications of mechanical systems within the pneumatic architectural design. In particular where structures are composed of dynamic elements that can be used to reconfigure space. Light is also thought to be an architectural way of refining space. In the history of architecture, the Greek architects saw light as a material for constructing space. Many artists and architects have explored the areas of light and pneumatic architecture. Areas of research include pneumatic architecture as a materially method of building in a short time [Ant Farm, 1970]; design of a pneumatic space with the auxiliary of light in relation to the dramatic embodied experience [Loop.pH, 2014]; and collaborations between architects and light artists for investigating the areas of using light in pneumatic structure (Beijing national swimming pool built in 2008).

Using the perception of space as the starting point, this report analyses the interaction between caustics and pneumatic kinetic structure in spatial configuration. This report actuated the technical relationship between caustics and a pneumatic structure with different material, form and air volume.

Light caustics may be seen as an envelope of light continuously focused and diverted through a curved translucent surface, creating an intriguing pattern of varying light intensity. Pneumatic structures, originating in early technical experience of mankind, changing the form of an open and limp membrane surface stressed under air pressure. The same membrane surfaces can also be used to form the curved translucent surface as a medium for light caustics.

Like the water caustics on the bottom of a swimming pool, light caustics can be subtle and dynamic. Moreover, caustic pattern can be casted to produce desired form. However, how can casted caustics be designed to move in a desired pattern? What kind of elements of the refractive surface affect the movement of the caustics pattern? Which of those elements can be transferred into a pneumatic structure?

This report has three basic objectives-(i), Light caustics objective: to test and categories the caustics pattern created by basic pneumatic membrane material and light source property. (ii), Pneumatic elements objective: review the fundamental morphological classification of pneumatic elements and test the caustics effect when they are fully inflated. (iii), Kinetic architecture objective: to examine the way of inflating and deflating the pneumatic elements in different gradient of air volume, in order to control the formation of light caustics when multiple kinetic pneumatic elements are put together.

As a bridging tool between light and pneumatic structure, and as a tools for defining, experiencing and reconfiguring space-this research examines basic systems for casting caustics patterns in pneumatic elements. Accordingly, it investigates both the evolution in kinetic pneumatic elements and analyse the light caustics and rules of optics in pneumatic membrane.

2 Pneumatic structure formation and membrane material

… Maybe concepts like ‘room,’ ‘door’ and ‘window’ are anachronisms.

                                                     ——- Nicholas Negroponte

Pneumatic structures are among the lightest architectural structures known [Gernot, 1976]. The structural system is a static system that is neither formalised nor materialised. Indeed the pneumatic structure is in part controlled by the stabilizing effect of differential air pressure. Using different air pressure for different pneumatic elements can create different space formation-this can be the basic logic for creating pneumatic kinetic spaces.


2.01 Fundamental formation

As Gernot [1976] asserts, architectural pneumatic elements are loadbearing structure, the formation of the elements therefore be chosen accordingly. Loadbearing qualities are affected by the geometric shape of the membrane structure, the junction form and pressure profile.

This report will mainly investigate the basic low-pressure formation of membrane structure. We divided the membrane structure into single and double formation. For the single formation, the space under positive or negative pressure is formed or closed by one membrane. However, the parts of membrane surrounding the support medium are always curved in opposite directions to each other. [Figure 1]


Figure 1 Classification of low pressure systems

Membrane structures under positive pressure is the most common way of building pneumatic architecture. Under positive pressure the curve of the membrane system is always convex. Threrefore, membrane systems under positive pressure do not have to face the danger of water or snow pocket, unlike negative pressure systems which must provide additional structural support on. In the history of inflatable architecture, several experiments of pneumatic structures without additional support have been done since the 1960s. The Clear Air Pod built by Ant Form [Figure 2], is an example of the extreme of architecture—inflatable architecture- challenging the boundary between “building” and “installation”. This showed that architecture can be both soft and temporary. What is more, Ant Farm published a guide book for building basic inflatable architectural structures- in which, basic information about the necessary material properties for building pneumatic elements and air supply system for inflating are laid out. I use this information to inform the basic fundamental technical support for the tests that have been done in this report.


Figure 2 Ant Farm, Clean Air Pod.

Another feature of low pressure systems is additional support. With the additional support, the pneumatic system can be divided into several stable membrane systems using the same air pressure supply. This creates a complex spatial system in inflatable architecture, or using the multiple supported membrane system to create a kinetic pneumatic surface. Researches have been done by many architects and artists, notably. Simon and Mark [1971] created a whole series of supported membrane installations that allow user to create an environment for themselves and manipulate its form [Figure 3]. Combining multiple pneumatic elements together, users were able to configure different shape of space is the main design concept in this project. It was Simon and Mark’s installation that inspired the inflating and deflating multiple pneumatic elements to define a space with different scale.

During the research stage of this project, an advanced air supply system was developed, which makes the concept of sequential inflating and deflating of the pneumatic elements come true. Separating the air supply for each element allows for the selective inflation and deflation individual elements. Furthermore, the system developed is capable of inflating and deflating relatively quickly (about 6 seconds quicker than the old system when inflating a 0.096 m3 pneumatic element), thus the whole installation is particularly responsive to the physical requirement of users. In this research we developed a basic system of control capable of sequentially changing the volume of air in individual pneumatic elements, thus improving users’ control of the multiple pneumatic elements in the project “soft optics”.


Figure 3 Simon Connolly and Mark Fisher, Dynamat, 1971.

2.02 membrane material

For building a pneumatic system, the most important property of the membrane material is impermeability. Polyethylene is the most common material used in pneumatic structures as it is-light-weight, readily available, cheap and is widely recyclable [Ant Farm, 1971]. However, compared with other impermeable membrane materials, polyethylene is not as functional when it comes to the light refraction or reflection.

With the development of inflatable architecture, artists and architects have started exploring a variety of materials for making pneumatic elements.

Pneumatic elements made by Mylar sheet shows an interesting reflection of light from the outer environment.  The Loop.pH studio [2014] created an infinite mirrored inflatable space [Figure 4], constructing for those inside an experience of the pneumatic elements. Transparent polyethylene is the most commonly used material for building pneumatic elements.

In this project, other types of membrane materials were also explored for the caustic propertied. Particularly, the infinite experience created by the light reflecting of the Mylar sheet, enables a combination the shapes and positions of the pneumatic elements, by changing the shape of structure, we are able to change the pattern reflected by the pneumatic elements and the movement of pneumatic system, this can be realised by putting a light source inside of the space created by reflective pneumatic elements.

Figure 4 Loop.PH Osmo, 2014

Using material to create an iridescent effect, there is a kind of iridescent polyethylene sheet that has been used in several Tomas Saraceno’s inflatable art installations, like the poetic cosmos of the breath and air-port-city. Iridescent sheet has a microscopically structured surface that can effectively interfere with visible light. The Peacock tail is an example from nature that can help explain the iridescent property; the tail feathers are brown, but interfering with light makes them reflect iridescently. Tomas [2012] made attempt to create the floating city and buildings using an iridescent dome to create a continuously changing light [Figure 5]. Tomas also experimented with mixing different membranous materials into the everyday life-to get the experience of modern city life [Figure 6].

These two projects provide other examples of membrane materials that can be used to have light caustic effects. Large scaled pneumatic elements using iridescent film enables the creation of scale-changeable colorful spaces above the visitors. Another example is that of mixing materials together to use one single pneumatic element to make a multi tactile and visual experience based on membrane materials. These experience not only help in exploring different membrane material, but also highlight the possibility of mixing membrane materials together. Moreover, in this project, in order to ensure the cosmos element of experience, there are small holes covered by transparent POLYETHYLENE. These small hole coupled with the light source, a blue projector, which gives an experience of putting light with different color outside the Mylar pneumatic element that can make the whole space reflect the same color.


Figure 5 TOMÁS SARACENO Poetic Cosmos of the Breath, 2012


Figure 6 TOMÁS SARACENO Becoming Aerosolar, 2012

This report investigate membranous materials with the refraction of light. Although some membrane materials that can have light caustics have already been explored by artists and architects, there might be other membrane materials. So in the report, tests about optical properties of membranous materials will be explored. The examples of above show evidence for the development of both the technical supply of control the air level of pneumatic elements and the caustic and reflective effect of different material under different light source.

2.03 kinetic pneumatic formation

Most pneumatic elements are designed to be in a stable and still state, once they are settled. However, by deflating and inflating the pneumatic elements one can change the scale of the space created by combining multiple pneumatic systems together. Michael [2006] built an inflatable installation at urban scale [Figure 7]. The air volume of each pneumatic element will change with the pathway of visitor.

Since light caustics will change with the surface of the refraction medium. The scale changing of pneumatic element enables the possibility of creating kinetic light caustics with pneumatic elements. This project is an example of creating continuously changing spatial experience with multiple pneumatic elements with different air volume. This experience is similar to the kinetic spatial experience we want to create, however the air control system used here will need huge pipe for each pneumatic element that would create caustic patterns and shadows. In order to prevent unwanted shadowing, we updated the air control system into a fan air control system.

Figure 7 Bubble, Michael fox, 2006

3 Light caustics in Soft Space

At architectural point of view, light is to shape and define a space. As what Ana [2005] said, The master of light — Louis Kahn treated light as a shaping element, for him, light is mass and light is space: mass – light is the physical constituent of architecture; space — enclose in the masses, and become filled with spirituality thanks to the interplay of natural light and artificial light.

In this report, we mainly dealing the interaction between light and membranous materials[Figure 8]. When light passes through a solid material, there are four different possible outcomes,–light can be reflected, absorbed, scattered or transmitted. Depending on the percentage composition from each of the four phenomenon-materials can be classified as Transparent, Translucent or Opaque. Light caustics are combination of the optical properties of a material and the pattern cast on the caustic received surface. In the report we specifically want to deal with the effect that light and the change of air volume has on each pneumatic element (characterizsed in the form of the scale change of the pneumatic elements in the report) and the material of the membrane system is considered for building the kinetic architectural space. Above all, light caustics are an ideal way used in refining space with pneumatic elements.


Figure 8 different light interactions with solid

Light caustics are a wondrous light phenomenon that appears accidently in daily life. This report is aimed at making this “random”, “accidental” event into a powerful design tool in the specific to the pneumatic architectural space. In this report, we chose pneumatic membrane material as an easy way to capture the beauty of caustics.

3.01 Creating Caustics in Soft Material

Light caustics is one of the most fascination light effect (for example water caustics, diamond caustics): the envelope of light rays continuously diverted and focused by reflective or refractive geometric material, creating repetitive geometric patterns [Figure 9].Caustic patterning depends on the different amount of light refracted on a part of the medium surface and the difference in brightness of light on the surface. Point light and parallel light rays from a point at infinity can both be the light source for caustics. Light caustics in not only the artistic investigation, it could also thought to be the material of architectural relevance.


Figure 9 light caustic process diagram

For the architectural light design, not only the material and light source choosing, but also a careful geometric refraction or reflection control of light and shadow within a site-specific space. Caustics is a random and splendid effect ubiquitous in daily life. Using this light phenomena in the architectural space has enticed numerous artists and architects. For example: the Phillipe Bompas, Nao Tamura and poetic lab, they have done many projects and installation based on light caustics. In current architectural design practice, light caustics is mainly used as organic patterns created by curved surface. Philippe [2012] build the light wave experiential room by using the property of water caustics [Figure 10]. However, a reliable method for controlling moving of caustic patterns has yet to be developed.

Figure 10 Light room experience, Philippe Bompas, 2012

3.02 Common Caustic casting method

Caustics is coming from the Latin word caustics, which means “burned”. Like sunlight passing through a lens, caustics refer to focus of light. In the context of this report, in order to understand the shape of caustics pattern, a useful approach is to build a computer simulation of a given surface. By simulating changes in the geometric patterns on the given surface to one can observe the effect this will have on the caustic properties of the structure [Figure 11].

Data about the precise direction of the incoming light beam, the location and orientation of the reflective surface (pneumatic membrane surface) and the caustic receiver are all required for calculating the resulting caustics patterns. In the computer, we divided the reflective curved surface into discrete height fields. The light distribution on the caustic receiver is divided into a pixel grid of intensity values and, based on the image on the caustic receiver; the computer can calculate the reflective value of the surface.


Figure 11 computer caustic casting schematic

3.03 Caustics architectural art

Momento built by Nao Tamura, is the manufactured casting of caustic light installation [Figure 10]. By transforming the casted molten glass into caustic patterns. Using gentle ripple of caustics refraction to create the experience of a droplet interfere the still water surface, mimicking the caustic phenomena in nature in a controlled formation. The elliptical shaped molten form of the glass guides the light to create the caustics on the table, where the light source is just above the installation. Creating “soft optics” here means using light passed through a refractive surface to create expressive caustic patterns. Using multiple pneumatic elements that create a moving caustics effect in the space is the main aim of “soft optics”.

Figure 12 Momento, Nao Tamura, 2015 Attempts of casting patterns on soft material by light has been done by Julio [Figure 13]. This is an example of projecting patterns on the soft material. However, since the patterns are projected directly on the objects from light source, the pattern move with the movements of the soft material, it can only move with the movement of the light source. In the report, we are exploring the way that the movement of patterns is related to the movement of pneumatic elements. Changing the hanging fabric into kinetic pneumatic elements, and changing the projection lamp into caustic system is the way we are going to test in the “soft optics”.


Figure 13 Lumière en vibration, Julio le Parc, 1968

4 Soft Optics—Design project/combination of caustics and kinetic pneumatic elements

Using pneumatic elements to create a space is the basic concept and has been experimented by many artists and architects. Adding light caustic phenomenon into the space created by the pneumatic elements is what the project “soft optics” is concentrated on. Using refractive pneumatic elements in the middle as the caustic medium to create caustic patterns on reflective pneumatic receivers on the outside. With the scale changing of the caustic medium and caustic receivers to reconfigure the space in the way of the scale and the light pattern.

4.01 Impossible space prototype

Two case studies should be developed in order to create the per-conceived kinetic space formation (concerning design, spatial formation, and pneumatic elements’ movement) that led to an optical kinetic pneumatic system. In this prototype, the problem of controlling air volume within a single pneumatic element is solved and the basic effect of projecting light on the pneumatic element is explored.

4.01.01 Technical analyzation of the installation set up

A pneumatic element was designed to transform a virtual spatial experience to physical tactile spatial perception. This is a technical test for inflating the pneumatic element and combining the inflated soft space with changeable light source.

A 720mm diameter, 1/4 horse power, direct-drive, two-speed fan with a cast-aluminum and sturdy, close-mesh guard 220v fan is used in this prototype. By using the performance curve [Figure 14] and the size of the pneumatic element [Figure 15], the approximate volume of air supply per minute can be confirmed. By calculating these two elements, 1000 CFM fan should be used. In order to achieve this specific air volume, we used Arduino chip to control the speed of the fan. T This basic inflatable element is using the fan system that recommended in the guidebook published by the Ant Farm. Fixing the end of the pneumatic element to the fan and using Arduino controlling the speed of the fan, the air volume of the pneumatic element can be maintained as desired. [Figure 16]

14     15

Figure 14 fan’s performance curve                         Figure 15 the size of pneumatic element

Figure 16 the inflatable process

The light source in this case study is the simple RGB LED Flood Light to simply test the color and brightness changing under the pneumatic material. The transparent polyethylene can diffuse the RGB light. And because of the geometric shape of the pneumatic element, the light projected on the wall of the room is uneven.

This case study confirmed functionality of the air supply calculation system and the transmission effect of colored light on the basic polyethylene material.


Figure 17 the RGB LED Flood light test and the final process photo

4.01.02 Kaleidoscope installation

More pneumatic material tests were done to achieve caustics experience on the pneumatic menbrane material. The materials below have been tested for their caustics qualities. [Figure 18]


Figure 18 pneumatic menbrane material for caustic possiblity test

[i] polyethylene

The advantage the most common pneumatic membrane material, polyethylene, is that it is cheap and easy to be work with. polyethylene’s transparency provides the possibility of light caustics. By using casting simple geometric pattern on the polyethylene and tested with single point light source [Figure 19]. In the test, the caustic pattern changes with the rotating and moving the polyethylene membrane material.

By casting patterns on the polyethylene sheet, the sheet can be the medium for creating caustic patterns. Meanwhile, as was shown during testing for the first prototype, colorful light can transmitted through the polyethylene sheet. This material can also be the caustic receiver.


Figure 19 polyethylene’s caustics after pattern casting


As the effect we seen in the Osmos project. Mylar sheet have the optical property we need-it can reflect the light both from outside and inside. The caustics created by the Mylar sheet is caused by the reflection of light, whilst the color of the reflected pattern can only come from the light source. In this test, computer simulation (3Ds max) is used to preview the caustics result. Mylar sheet is easy to construct patterns with; permanent pattern can be cast by iron, while folding Mylar sheet can create temporary patterns.

The reflection onto Mylar sheet is what was needed for the light to be transformed into a space of “soft optics”. The light caustics need light with precise position and direction. The Mylar sheet must be opaque so that it may divide the installation interfered from environment outside. Moreover, in its opaqueness, the Mylar sheet can not only display the caustic patterns, but also reflect the patterns to create a much more organic affect in the space.


Figure 20 Mylar’s caustics after pattern casting


Figure 21 3Dmax software simulate caustics

[iii] Silk and Linen

Though silk and linen is a common material used as manbrane structure, for the caustic test, both silk and linen did not create caustic phenomena. Therefore these materials are not appropriate for this project.

[iv]Iridecent film

Iridescent phonamena is cause by light diffraction. Diffraction is caused by the rough texture of a surface. Diffracted light brakes into its component colors, this leads to a visual change in color will occur as the angle of view changes.


Figure 22 The weaving diagram of silk and linen


Figure 23 The reflection test of the silk

[iv]Iridecent film

Iridescent phonamena is cause by light Diffraction. Diffraction is cause by the roughness of surface. With the specluar component obey the reflection rule, while diffracted component broke into a rainbow, the visual change in color at various angle of view happens [Figure 24].


Figure 24 Iridescent diagram

Iridecent film is a special polyethylene material that can have structural colorative property. When the light source is angled from different origin, the visual color of the refraction will change, and by casting different patterns on the film, the casutic patterns will also change. Even slight differences in the shape of pneumatic elements made by iridescent film will have great differences under the same light source, the movement change (the change of air volume in the pneumatic elements) can create a range of color and caustic pattern transforming. [Figure 25]

25-1   25-2

Figure 25 iridescent film refracting light in different color and pattern

From the material test above, three materials were chosen from the common menbrane material for caustics phenomena. Each material presents different caustic properties from each other. polyethylene is suitable for pattern casutic refraction, since it can not reflect light and easy to casting paterrn on it. Mylar is the caustic reflection material. Both mylar and polyethylene, the caustic patterns are easy to simulate and control. The iridescent film can not only realise the refraction of caustic pattern, the refracted color is also changed in this case, although this change is hard to simulate by computer. However, the caustic result is splendid, thus Iridescent film is a highly suitable membrane material for light caustics.

4.02 Kinetic soft optics prototype

We developed three prototypes to test the effect of combining the pneumatic elements and light caustics. The first two are mainly dealing with large size of the space created by the multiple layers of pneumatic elements. The third prototype is built on what we learnt from the first two prototypes and focuses on the order of each material the position of the light source.

[i] Soft optics prototype1

In this prototype, the pneumatic elements are developed with single casted material and light is pointed at the middle of the element. Using 1mm thick acrylic board for caustic patterns, during the inflating process of the pneumatic element the caustic pattern moves with the element [Figure 21]. By comparing the index of polyethylene sheet and 1mm acrylic, the acrylic board can refract more light than polyethylene sheet, so that the light refracted by acrylic is more evident than for polyethylene. The light source was put in the middle of the pneumatic elements, so that caustic patterns can be received by the space around the installation. [Figure 26]

Figure 26: the moving process of caustics and pneumatic element

In this prototype, when visitors approach the pneumatic elements it will automatically inflate and create a two layer space. The primary layer functions to display caustic patterns, while the secondary layer is the pure polyethylene pneumatic element. The caustic pattern refracts onto the first layer after reflecting on the surface of second layer, and responds to the movement of both layers. The caustic pattern moves across and brightens the enclosed space of the installation. In this prototype, by using the air bluster that controlled by servo, we realized inflating the multi layers separately [Figure 28].

Figure 27:The simulation of pneumatic movement


Figure 28 air supply system for multiple layers

[ii] Soft optics Prototype 2

By mixing the material that in the test, we updated the installation. With the approaching of the visitor, the pneumatic elements start inflating and the light inside light up. Pneumatic elements and light caustic interplay with each other, creating the moving and color changing pattern inside the pneumatic space, and also around the environment.

In order to control the movement of the two layers of pneumatic elements, DC fan is used as the air supply. The advantage of DC fan is that the fan is light weighted, small scaled and easy to be controlled by Arduino. By using two DC fan (one for inflating and one for deflating), the two layers can inflate and deflate separately.

Figure 29: The movement of prototype 2

Figure 30: The caustic light changing on the moving pneumatic elements

The outside layer is combined with Mylar sheet and POLYETHYLENE sheet. The Mylar sheet and polyethylene sheet is designed to be the medium for the light caustic pattern. Moreover the environment around the prototype is also the place for soft optics expressing itself. The caustics in the outer environment is continuously changing from focus to divert. And the colorful caustic pattern on the first layer created the wondrous space inside the pneumatic element.

In order to experience the splendid reflecting space created by the moving pneumatic iridescent element and light caustic. We built a gigantic single silver space and put the iridescent layer inside in order to experience the space created by two competing caustic reflections [Figure 25]. Using Mylar sheet as the caustic receiver is based on what we learned from the project Osmo. It used giant silver space made by Mylar sheet to create the infinite light reflecting experience.

Figure 31: The soft caustic space experience.

The gigantic silver space created by Mylar sheet breathed slowly during the exhibition time; the inner layer iridescent membrane elements continuously inflating and deflating. This kind of setting created the experience of colorful rotating osmotic space, however, the single giant pneumatic space is incapable of achieving the change in scale along the pathway of the visitors.


[iii] Soft optics prototype3

For the final prototype, in order to create the space that can change in scale continuously along the pathway of the visitors, we look to project Bubbles for inspiration.

Multiple pneumatic elements are used to create a maze space seeing from the outside [Figure 32]. When visitors approach the pneumatic element will inflate and deflate to construct the shape of visitor’s path. The inner pneumatic elements are made from iridescent sheet and the light source (4*12V, 20W LED LAMP) [Figure 33] is placed in the middle of the installation. The pneumatic elements, made from Mylar sheet, are put across the perimeter to receive the caustic pattern, and to isolate the space inside the soft optics from the environment around it.


Figure 32 the section plan of the installation

34         35

Figure 33 light source diagram 36

Figure33 the diagram of the space effect created when visitor is in different position

Three different kind of pneumatic elements is designed. The pneumatic elements using Mylar sheet is designed to have the movement–rolling up and down, when it is switching between inflating and deflating. The one made of polyethylene is designed to change scale in horizontal direction. What’s more, the iridescent pneumatic is designed to dwindle in size during the inflating and deflating of the pneumatic element. These kind of movement create change of the position of the caustic patterns, creating the visual scale of the space. The most inside is the iridescent pneumatic elements. When it is inflate the caustic pattern will ‘inflate’ with the elements. The space will filled up with iridescent caustics patterns and inflated pneumatic elements. When the polyethylene pneumatic elements scale become smaller in horizontal direction, the light caustic made by the inner iridescent can go through and the caustic pattern on the polyethylene pneumatic elements will be smaller The rolling up and down of Mylar pneumatic elements cause the move up and down of the caustic patterns. The movement and the caustic changing on these three kind of pneumatic elements together can help reconfigure the space.

In this prototype, two DC fans [Figure 37] are used to service each pneumatic element: one is used for inflating and another is used for deflating. By controlling the speed of each fan the air volume can be stable at any level. For example, we want to control the Pneumatic elements to stay at level of 50% air volume. The maximum of the 120mm DC fan we used is 45 cubic feet per minute. The volume of the pneumatic elements is around 3 cubic feet. First of all, using the deflating fan in half of the speed and the inflating fan at the full speed for 4 seconds, then turn the deflating fan into full speed. The result is that the pneumatic elements can stay at the 50% air volume state.


The percentage of the air volume: X%

The time of inflatable keeping in half speed: Y seconds



Figure 37: Fan System diagram

4.03 Interactive system

Using the evidence from the prototypes, and the research made into Micheal Fox’s interactive inflatable installation, a combination of caustic pattern movement, pneumatic structure movement and visitors’ movement will be designed as testing for a space reconfiguration based on visitors’ pathway.

Using visitors’ position to control the air volume of each pneumatic element, the caustic light changes as the refractive surface changes its shape. Combining these two kinetic elements together to create both a dramatic space and light flowing experience.

The Kinect camera can only sense objects within a range of 1.5-3.0 meters. Kinect camera was put right up the installation in order to capture most effectively the position of the visitors [Figure 38]. The Kinect camera, combined with the electronic system control chip Arduino, successfully transformed the Fan speed data in the Arduino chip with the help of software vvvv. Using vvvv to get the data of the position of the visitors, and using this data to control the speed of the fan in the vvvv. By connecting vvvv with Arduino, the data of the speed of fan can transmit to Arduino chip. The Arduino chip is a chip that can control the electronic components like fan and lano. The air volume of pneumatic elements is affect by the speed of fan, so that visitors’ position indirectly influences the shape of the pneumatic elements. The result is a physical presentation of the movement of light caustics and pneumatic elements changing in accordance with the pathway of visitors. [Figure 39]


Figure37 the position and range of Kinetic Camera


Figure 39 Interactive control system diagram

5 Conclusion

Reviewing the three objectives set out in the introduction, conclusions can be drawn for each in turn:

  1. Light caustic objective:

Our observations about caustics patterns changing with different membrane materials and movement of the pneumatic elements were tested. As a result, three materials have been selected due to their suitability as both a pneumatic structure and as a caustics medium. Based on the optical qualities of the materials, different positions were settled on for use in constructing the pneumatic elements. The Mylar sheet is used to both reflect the light from the caustic surface and isolate the installation from the outside environment, in order to create a mysterious and private caustic pneumatic space.

  1. Pneumatic elements objectives:

Rolling up, dwindling in size and horizontally scale changing is designed in order to create different effect of light caustics. Using 2DC fan controlling each pneumatic elements to realize the inflating and deflating of the pneumatic elements is the method to build the kinetic pneumatic system.

  1. Kinetic architecture objective:

Using two DC fans to control each of the pneumatic elements and with Arduino controlling the time and the speed of each fan, maintaining can make each pneumatic elements’ level of required air volume. Based on this technique, changing the scale of space under the pneumatic elements was achieved.

The installation contains two fundamental elements: light caustics and pneumatic elements. By using shape changing of pneumatic elements to create the space inside it. Furthermore, the light caustics on the pneumatic elements created light reconfigurations inside the space, this was in turn dependent on the scale changes created by the movement of pneumatic elements.

Future research

This report wishes to feed into the research narrative of how light caustics and pneumatic system work together to create spatial reconfiguring experiences. Looking at the wide spectrum of inflatable architecture, it is clear that there is scope for more research into how to incorporate a visual and spatial experience with the use of light and pneumatic elements.

[Ant Farm, 1970] Ant Farm: Inflatable cookbook, page 28, 1973.
[Loop.pH, 2014] Loop.PH: Osmo, 2014.
[Gernot, 1976] Gernot Minke: Pneumatic buildings-structural design alternatives in pneumatically stabilized membrane structures, page 17, 1976.
[Clark, 1998] Clark, A. and Chalmers, D. (1998). The Extended Mind.
[Michael, 2015] Michael Wihart: The Architecture of Soft Machines, page 341-344, 2015.
[Thomas, 2014] Thomas Kiser: Architectural Caustics – Controlling Light with Geometry, 2014




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