Conceptual paper
Fugue: an Interactive Immersive Audiovisualisation and Artwork using an Artificial Immune System Peter J. Bentley, Gordana Novakovic and Anthony Ruto Department of Computer Science, University College London, London WC1E 6BT, UK
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Abstract. Fugue is the result of a collaboration between artist, musician and computer scientists. The result is an on-going project which provides a new way of communicating complex scientific ideas to any audience. Immersive virtual reality and sound provide an interactive audiovisual interface to the dynamics of a complex system – for this work, an artificial immune system. Participants are able to see and interact with immune cells flowing through a lymphatic vessel and understand how the complex dynamics of the whole are produced by local interactions of viruses, B cells, antibodies, dendritic cells and clotting platelets.
Fugue: an Interactive Immersive Audiovisualisation and Artwork using an Artificial Immune System
Conceptual paper
Abstract. Fugue is the result of a collaboration between artist, musician and computer scientists. The result is an on-going project which provides a new way of communicating complex scientific ideas to any audience. Immersive virtual reality and sound provide an interactive audiovisual interface to the dynamics of a complex system – for this work, an artificial immune system. Participants are able to see and interact with immune cells flowing through a lymphatic vessel and understand how the complex dynamics of the whole are produced by local interactions of viruses, B cells, antibodies, dendritic cells and clotting platelets.
1 Introduction Science often involves abstract formalisms, typically mathematical, of the tangled complexity of the phenomena under study. Communicating these ideas is not easy, whether between colleagues or to the general public. To aid in such endeavors there is a significant need for scientists to employ more direct methods – audio and visual – of representing the systems with which they deal. In scientific education, it has become clear that traditional formal methods of study are increasingly alien to students who have grown up in a world dominated by digital media; at least initially, they require more familiar means of accessing science. Likewise, in communicating science to non-scientists, the constraints of the printed page or the talking head mean that is often necessary to simplify the subject matter to the point where too much is lost or excluded. Our intention in this work is to examine a new approach. We propose that the best way of enabling both scientists and non-scientists to understand a complex functioning system is not just to present it to him as a spectacle, but to engage him as a participant, and to enable him to interact with the system in a multisensory way, directly appreciating cause and effect, variability, intrinsic dynamics, periodicity, and so on. To achieve this, direct input from an artist and a musician is used to guide the visual and audio experience. In other words: we propose to exploit artists’ knowledge of the relation between interactivity and perception, and harness it in the communication of scientific complexity. Artists and scientists are both concerned with understanding the world and our being in the world, but while the view of the scientist is rooted in consensus and endeavors towards objectivity, the artist emphasises the values of the personal and subjective
investigation of philosophical questions. Such a dichotomy suggests potential conflict: does the participation of an artist in the communication of science run the risk of introducing some bias antithetical to the very idea of science? And if so, can this potential conflict be managed satisfactorily within the collaborative process? Taken together, these two questions raise a wide range of issues, and as yet there are no definitive answers. The Fugue Project aims to frame and focus the questions in the context of transdisciplinary collaboration in the area of representing the functional dynamics of one of the most complex systems known – the human immune system. This will be achieved by the creation of an immersive virtual reality immune system, which enables participants to interact with and understand various cellular behaviours inside a lymphatic vessel. The hope is that the information uncovered by this research will help to structure future more comprehensive investigations of these fascinating and important issues, for art and science.
2
Background
The human immune system is so complex that it is currently impossible to produce a tractable model of the whole. Nevertheless, computational models are increasingly been seen as important tools to aid our scientific understanding [17]. Separate from immunobiology, the field of artificial immune systems (AIS) has grown dramatically in the last five years. AIS algorithms are computer programs modeled on different aspects of the human immune system and used to tackle a wide variety of problems, from computer virus detection to data mining, to robot control [14]. Additionally, in recent years issues of public health (from simple allergies to the expansion of AIDS and recent global epidemics of extremely dangerous flu variations) have led to increased and widespread public interest in the immune system [13]. There is a clear need for the lay population to be much better informed about the operation of the one of the most complex and enigmatic biological systems. The confluence of these three factors has both inspired and enabled this research, and forms a strong context for the project. Audiovisualisation is still a new methodology for presenting scientific findings. Only one virtual reality approach, Planetary Seismology (a Virtual Reality audio/visual representation of seismic phenomena) produced by the German scientist Dombois in 2001 [4], is available for participants at present. Only a handful of immune system visualisations currently exist. They have all been produced exclusively by scientists (Steven Kleinstein, IMMSIM, 1999 [6]; Christian Jacob, 2004 [5]), and the presentational styles are barely accessible to non-experts. (For example, IMMSIM uses a very abstract 2-dimensional lattice representation based on cellular automata.) To date, these visualisations have been presented only within a closed circle of scientists and have not been released for the general public. Audiovisualisation offers significant advantages for understanding hugely complex systems: it offers a much wider bandwidth than vision alone, and engages both serial and parallel modes of perception. In addition, the intention is to explore the potential of contemporary Virtual Reality technologies for enabling users to actively engage
with the production of phenomena, rather than merely observing them passively, within a custom designed virtual reality environment. The user will be able to control certain parameters of the modeled immune system, and will also be able to choose the particular function, particle, or interaction to follow. There are good theoretical reasons pointing in this direction, in particular Merleau-Ponty’s analysis of the role of the ear in visual perception [11]. As Dombois, the author of Planetary Seismology, wrote in 2001: ‘From philosophical research (…) we can learn that the eye is strong in recognising structure, surface and steadiness. (…..) Now at the same time philosophy finds the ear strong in the recognition of time, dynamics of a continuum and tensions between remembrance and expectation.’ [4]
3
Artistic Concept and Method
The development and usage of tools that support visualisation, or audification, usually involves collaborative efforts among scientists, artists, programmers and other expert staff. This is often defined as a Renaissance Team [2]. To achieve the aim of producing interactive, audiovisual representation of a highly complex biological function, that demands full engagement of both artists and scientists, our team is composed of a media artist, Gordana Novakovic (artistic concept); a computer scientist and expert in digital biology, Dr. Peter Bentley; Rainer Linz, a new music composer; Dr. Julie McLeod, and expert in immunology; and computer scientist Anthony Ruto. The aim of creating a scientific tool strongly influences the content and behaviour of the system; however from the point of view of the two artists involved in the creative process, Fugue is an integral interactive art project. Yet, from the scientific point of view, it is essential to ensure the scientific correctness of the underlying model. Will it be art, or will it be science? Our claim is that the first responses to the prototype made it clear that it may be seen as either, depending on the perspective of the user. The basic concept tests the form of the interaction between the sound and the vision in a way that is inspired by the complexity of one of the greatest musical forms: the art of fugue. The art of fugue is a highly disciplined form of composition of complex structure and exact relationship of parts. The title – Fugue – serves as a metaphor for the transdisciplinary nature of the project, and for the method applied: of interweaving the different perspectives of artists and scientists, different aesthetics, various skills and expertise, and personal philosophies, and uniting them into evolving polyphonic synergy. The emergent, evolving nature of Artificial Immune System algorithm, repetition as a succession of variations of ‘events’, and the complex structural and functional interrelationship of the particular elements and processes that can be related to the counterpoint, was one of the inspirations for the fugue concept. The Artificial Immune System software creates the dynamics of the virtual immune system drama, and also constructs and implements the architecture of the fugue by providing the functional structure for the communication channels between the visuals and the sound. On the other hand, this method is well grounded in the already successfully applied artistic method of interweaving, cross-connecting different specialists and specialisms,
in an effective cross-disciplinary framework for the emergence of synergy through collaboration; a method resembling the structure of the fugue. In parallel with providing the functional structure for the communication channels between the visuals and the sound, the Artificial Immune System algorithm is a bridge between the scientific and artistic aspect of the project. To establish an appropriate balance between art and science, artists and scientists have been working closely together on both experimentation and evaluation throughout the whole research process, integrating their own assessments with the external feedback. (This method also distinguishes this concept from the mere application of entertainment industry oriented software packages for audiovisualisation.) Finally, the fugue structure helps to achieve one of the major aims, by not only representing all the processes involved, but also at the same time painting a larger picture of the role of the immune system in the functioning of the human body and mind. This will illustrate the immune system’s intimate interconnectedness with the total sum of particulars that constitute each human being. This approach affirms holism as one of the fundamental principles of transdisciplinarity, as seen for example in the neurophenomenology of Varela, Maturana, and Thompson, and the biology of Margulis and Goodwin. Because we will work towards facilitating a better understanding of the function of the immune system, rather than simply creating 'beautiful imagery', much of our work will be concentrated on processes. The aesthetics of the Fugue are emergent, based upon the essential, fundamental and hidden beauty of the organic processes manifested through the dynamics of the real-time generated, unpredictable Artificial Immune System.
4 The Fugue Architecture Fugue is designed to be an immersive system, capable of running on platforms ranging from a desktop PC or Macintosh to a full virtual reality CAVE system using SGI IRIX workstations. As such, the hardware may vary from installation to installation, but the software components will remain largely the same. The current prototype is implemented in C++, using OpenGL graphics libraries and TCP/IP communication between processes. 4.1 Hardware The immediate target for Fugue is to move from the current desktop-based demonstrator to a full-sized system capable of withstanding the rigors of exhibitions. Figure 1 provides an illustration of a possible exhibition installation. An overhead LCD projector and surround-sound speakers will provide the main output, to be experienced by several participants simultaneously. One or more free-standing rotatable LCD “windows” will also be placed in the arena (the exact number depending on the floor area available). These will provide individual views into the same virtual world and permit
views from different players in the system (i.e., from a B-cell, or a virus). By rotating the window, the participant rotates their view within the virtual world, enabling interactive control of their immersive experience. The LCD windows will be constructed for the Fugue project and will comprise 17 inch LCD monitors mounted in metal stands, rotatable through at least 300 degrees, with rotation measured by optical sensors and fed back to the server.
Figure 1 Illustration of proposed exibition arena, comprising main projection, surround sound speakers and rotatable LCD “windows”. (The shape of the projection wall will depend on the space allocated at each venue.)
Figure 2 The Fugue hardware comprises graphics server (top left) driving projector and VGA screens, networked to the audio server (top right) driving amplifier and speakers.
Two servers are used to run the Fugue software: a graphics server, which calculates the artificial immune system and corresponding three-dimensional visualisation, and a sound server to calculate corresponding audio. The servers are networked together. Communication between the servers is through TCP/IP. Output from the graphics server feeds to an LCD projector (and the free-standing screens if installed). Output from the sound server feeds to a surround-sound amplifier, which is linked to a minimum of four speakers. Input from sensors such as the window rotation sensors is fed to the graphics server, see figure 2.
4 . 2 Software Fugue software comprises five main components, see figure 3. The graphics engine and the audio system demand the most computational power and so these each have their own dedicated servers (the graphics server and audio server). All other components require minimal computational power and so are executed as parallel processes on the graphics server.
Figure 3 The Fugue software comprises graphics engine, artificial immune system, interaction processing, a communication process and the audio system.
4.2.2 Artificial Immune System The artificial immune system (AIS) forms the heart of Fugue. The dynamic interplay between the agents in this system feed all outputs, while input from the user alters the dynamics in different ways. Implemented in C++, the AIS is currently a basic population-based infection model. Several agents are currently implemented: platelets, B-cells, macrophages, antibodies and viruses. All exist in a virtual lymphatic vessel, which is modeled as a large torus (with randomized cross-sectional diameter) to simplify the flow of the agents through the “body” (they simply go round and round inside the torus). Like Jacob’s work [5], the spatial modeling is a crucial part of the AIS – all immune activities occur when agents randomly collide and pass or receive information from each other. Movement is computed using force calculations to derive acceleration vectors for each agent, every time step, similar to a swarm algorithm [5]. The major forces are: • Collision avoidance: agents coming into contact with each other receive a force pushing them apart. • Wall avoidance: agents too close to the walls of the torus receive a force pushing them away from the wall.
Pulse: agents are pushed through the vessel in pulses. This is the largest force used in the system. The force (which has a sinusoidal magnitude with frequency equal to the current pulse value) is exerted on every agent in a direction determined by the nearest attractor point, where a series of attractor points are pre-calculated around the inside circumference of the torus. This approach enables future versions to flow within a vessel of arbitrary shape and complexity. Movement of individual agents can be overridden by the movement of other agents. For example, antibodies stuck to the surface of a cell will have their movement entirely determined by the moment of the cell they are stuck to. A dead cell being consumed by a macrophage has its movement entirely determined by that macrophage and remains in the centre of the macrophage. A virus that has infected a cell will always be in the centre of that cell (with a random oscillation to highlight the infector). In addition, when platelet cells come close enough to an injury, they receive a force pushing them to the source of the injury, with the effect of the pulse and wall avoidance reduced. The result of these forces produces stochastic and complex three-dimensional dynamics of cell and molecule flow, with completely unpredictable interactions. Nevertheless, although the detail is always different, the general dynamics of the system are determined by preset cellular and molecular behaviours. The current prototype has the following basic behaviours (these are chosen more for demonstration purposes than biological accuracy at this stage; behaviours are designed to be easily extendible or changeable): • All cells have a cell type: currently either macrophage, B-cell, or platelet, and all live for a randomized lifespan. When their lifespan is reached, the cell type becomes deadcell and the resulting inactive cell continues to exist in the environment until either consumed by a macrophage or sufficient time has passed to allow it to decay to nothing. When a cell is lost from the environment, a new cell of random type is introduced back into the system to replace it. • A single site of injury is introduced into the environment at the start of the run. When a free-floating platelet comes close enough to the site it becomes a clotting platelet and moves to plug the hole where it will stay until it dies. • Three virus molecules are released into the environment at the site of injury. A virus will decay to nothing after a short period of time unless it comes into contact with either a platelet or B-cell, in which case it infects the cell. If the infected cell is not consumed by a macrophage in time, it will cause its host cell to die after a period of time and release a number of new viruses into the environment. • If a macrophage (dendritic cell) comes into contact with a dead cell or a cell marked with antibodies, it will consume that cell (the cell it consumes is removed from the system after a short period of digestion). Should the cell it consumes be infected with a virus, the macrophage then becomes an antigen-presenting-cell. • If a B-cell comes into contact with an antigen-presenting-cell it releases antibodies in response. Currently in this demonstrator it is assumed that the antibodies will always be designed to counter the current viral pathogen. • If an antibody comes into contact with an infected cell, it sticks to the surface of that infected cell. All antibodies decay to nothing after a fixed period of time. •
This basic infection model results in a rapid spread of infection through cells in the initial stages, followed by a response from B-cells and macrophages, which controls the infection. To provide continuous and open-ended“interesting” behaviour, the lifespans, and virus and B-cell production rates are tuned to ensure the infection is controlled but never eradicated from the environment. Maximum population sizes also provide a method of controlling the dynamics (and keep the real-time 3D rendering manageable); currently a 1Ghz PowerBook G4 processor is able to maintain 60 cells, 60 antibodies and 40 viruses and render in real-time at a resolution of 1024 by 768 without difficultly. 4.2.1 Graphics Engine The 3D graphical visualization of the artificial immune system is created by an OpenGL rendering environment using the Glut interface1. It also contains a VRML parser to read in virtual cell surfaces created from clay models (see below). These cells are loaded when the system is started and their different properties are rendered within the OpenGL environment using display lists for efficiency purposes. System dynamics are used to control the movement of both the cells and view of the immune system through the position and manipulation of the cell display lists. This allows for the best overall performance in terms of speed and aesthetics. The display can also support the stereoscopic display of the virtual elements through the Glut interface used. This would enable true 3D effects to be experienced by viewers using appropriate hardware (and also enables the support of multiple monitors). The shape of each cell is not arbitrary in Fugue. Clay sculptures of cell objects made by Gordana Novakovic were scanned using a Hamamatsu Photonics body scanner2 to produce 3D point clouds at up to a 1mm resolution. A surface reconstruction process was then used to form canonical representations of the scanned cell point clouds from which a surface was then constructed. This method is commonly used in the 3D scanning of bodies to establish regular sets of points for captured data [12,15] and provides a simple solution for constructing surfaces once the canonical representation has been established. The detail on the reconstructed scan surfaces was reduced in order to speed up the performance of the immune system display by lowering the level of detail. More examples of cells where constructed through the 3D sculpturing of sphere quadrics using an open source 3D editing tool called Blender3. The detail on the reshaped quadric surfaces was also reduced through the use of a mesh reduction algorithm provided as part of the Blender software. Both scanned and reshaped cells were stored in a VRML format so that they could be easily imported into the immune system display. From the point cloud data, a population of randomized cells is created (the different cell images are randomly distorted to create unique shapes). These cell shapes are then translated to the appropriate locations and rendered, each iteration. All cells have a slow random rotation to produce a subtle tumbling effect as they move. Where possiGlut Open GL: http://www.opengl.org/resources/libraries/glut.html Hamamatsu Photonics : http://www.hamamatsu.co.uk 3 Blender : http://www.blender.org 1 2
ble, all movement, scaling and rotations are performed using OpenGL functions on the display lists (rather than recalculating point cloud data), which maximizes rendering speed by exploiting the graphics hardware of the computer. Viruses and antibodies are rendered as small, glowing OpenGL spheres. Viruses also emit light, designed to light up an infected cell from within (visible because of the partial translucency of cells). When platelets begin to clot, random “tendrils” are rendered from its centre to represent the emission of fibrin. The “lymphatic vessel” environment is rendered as a torus with walls of partially translucent spheres to represent cells. The radius of the spheres is an inverse function of the sinusoidal pulse used to move the floating cells. This provides the illusion that the internal diameter of the vessel expands and contracts in time with the pulse. The graphics engine currently supports two viewing modes: a view from a fixed point, and a “free-floating” view. The former enables a participant to “cut to” an interesting predefined view in the torus, and use basic keyboard controls to rotate and move the view from that point. (Such controls would be replaced by the rotation sensor on the LCD windows or sensors for head mounted displays in a CAVE system.) The freefloating view creates a virtual agent, which is subject to the same forces as all the cells and molecules in the environment, then displays the virtual world from the point of view of that agent. To avoid a disconcerting somersaulting view, the viewing angle is kept at right angles to a vertical axis at the torus centre, ensuring the view is always towards the centre of the torus. There are also options to look backwards or simplify the view by showing wireframe only or the torus without the cells on its walls. Future work on Fugue will extend the viewing modes and interactivity of the system, enabling more control over the perception and allowing participants to take the role of any cell or molecule and both see and interact with the virtual world from their chosen perspective. 4.2.3 Communications On execution, the Graphics Engine spawns a communication process to send and receive signals to and from the Audio System without incurring visible computation overheads on its graphical output. The comms process uses TCP with a streaming UNIX domain socket to communicate with the Graphics Engine (the comms process acts as server and both processes run on the same processor). It uses TCP with an Internet socket to communicate with the Audio System (the audio system acts as server; the use of Internet sockets enables the two computers to communicate over any network, including the Internet). Data is squirted from the artificial immune system, to the comms process and onwards to the audio system on every pulse. A 25-byte packet of data representing the main population sizes, views and other global dynamics indicators updates the audio system with details of the main behaviours, enabling it to alter the audio in synchronization with the changes occurring in the artificial immune system.
4.2.4 Audio System Composer and Sound Artist, Rainer Linz, will be creating the audio system for Fugue. Written in Java, the system will interpret the data sent from the communications process and provide an audio accompaniment designed to complement the current system dynamics and view chosen by the participant. Because the system data is received in pulses, the audio will inevitably mirror the pulses in its own dynamics. This provides the rhythm for the piece, a rhythm that will speed up or slow down depending on the pulse of the “virtual organism”. It is not proposed that an explicit heartbeat or other biological noises be duplicated in Fugue. The audio is intended as a second method of communicating information to the participant. ‘Sound is emphatically not just for sound tracks’: as Brown observed in 1994: ‘Sound does not merely enhance the beauty of a presentation; it can be used to give fundamental information.’[1] The sound, envisaged as a ‘mental soundsacpe’; a resonance of the function of immune system in the body, will provide a major channel for interaction. By overlaying and modulating the sonic pulsation, cycles - such as circadian, or other inputs such as stress level, will be introduced. The dynamics of the sound system may be fed back to the artificial immune system (changing the pulse, increasing stress levels) causing another level of fascinating dynamics for the participant. This aspect of Fugue is still under development.
5 Performances A prototype of Fugue has been implemented and DVD movie of the project been created (under the name of Algorithmica). Running on a desktop computer, the prototype did not have the audio system or communications described above. It was also producing output in shades of red instead of black and white, and did not have the “pulsing” feature of Fugue. The work was presented at several venues in early 2005: • the GAGE Festival, Hull Time Based Arts, Hull • the Creative Evolution Conference, Goldsmith's College • Smartlab Seminar, Central St Martins College of Art and Design • EVA Conferences (Electronic Imaging & the Visual Arts), UCL • Hypermedia Research Centre, University of Westminster. The response has been overwhelmingly positive from both the artistic community and the science community. The validity of the approach, both artistically and scientifically has clearly been demonstrated, and work is now underway to improve both, through: (1) enhancements to existing visuals and audio (2) enhancements to hardware, through large-scale projection and audio broadcasting (3) additions to the methods of interaction with the components of the immune system by participants (4) collaboration with immunobiologist Dr Julie McLeod to improve cell imagery through digital microscopy photographs and (5) improvements to cellular behaviours by using more scientifically plausible artificial immune systems. Figure 4 show some example screen shots from the current version of Fugue (as described in this paper).
6 Conclusions Fugue is an on-going project which aims to explore a new way of communicating complex scientific ideas to any audience. Immersive virtual reality and sound provide an interactive audiovisual interface to an artificial immune system. Participants are able to see and interact with immune cells flowing through a lymphatic vessel and understand how the complex dynamics of the whole are produced. Fugue is a demonstration of the benefits to be gained from art/science collaborations. The response so far has been overwhelming positive from both the artistic community and the scientific community. Further work and plans for several new exhibitions are underway.
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Figure 4 Screenshots from the Fugue prototype. Top: cells are pulsed through the vessel; Middle: platelets begin to clot at the site of the injury; Bottom: an infected cell attracts antibodies on its surface.
