PhD Thesis


Ross Smith Graduation In March 2009 I submitted my PhD thesis for assessment and six months later I received my acceptance results. The University of South Australia conferred my completion on the 22nd of October 2009. So if you are interested in deformable computer interactions and feel in the mood then please have a read.Writing a dissertation is a challenging task and there is no way I could have done it alone. I received a tremendous amount of support from friends, family, colleagues and my supervisors. So a special thanks goes out to Wayne Piekarski, Bruce Thomas and the Wearable Computer Laboratory crew for all their support and guidance throughout this challenging and rewarding process.

Please checkout the Digital Foam project page, one of the outcomes of my thesis work.


My PhD thesis research explores the use of deformable surfaces for computer input device technologies. In the physical world performing highly articulate tasks like clay sculpting are very powerful compared to the equivalent emulations we can achieve on a computer. I am exploring how we can capture the complex finger gestures that are used in physical modelling in an effort to create a computer input device that supports similar interactions.Visualise sculpting a skull out of modelling clay, where you use both your thumbs to squash the shape for the eye sockets in a round ball of clay. When you do this your fingers feel the resistance of the clay, this provides a natural feel and you maintain more control compared to manipulating something without and resistance.To achieve similar interactions to what I have described above I developed the Digital Foam surface. Digital Foam is a deformable computer input device that  can capture its own geometry in real-time. It is made using tubes of conductive foam that are embedded into a piece of non-conductive foam. When the foam is squashed or deformed the resistance of the foam changes, this resistance change is captured with a microcontroller and used to reconstruct the deformed shape on a virtual 3D model.


This dissertation investigates deformable computer input device technologies to facilitate capturing complex physical-world gestures.  By capturing the physical gestures and using appropriate haptics, it is possible to create virtual models using pinching and squeezing gestures similar to those used when sculpting clay. To date, most desktop modelling applications employ pointing devices that capture a single cursor location to manipulate a model with tedious sequential steps.  One reason for this is developers have focused efforts on adopting applications to work with generic two-dimensional pointing devices, such as a mouse or digitising tablet.  This is due to the difficulty of developing three-dimensional input tech nologies. In particular, deformable sensors capable of capturing natural sculpting techniques are undeveloped.This dissertation presents a soft material sculpting metaphor, identifies free-form hand shaping techniques and explores deformable input device technologies to capture multiple finger sculpting gestures with appropriate haptic responses.  After exploring existing technologies, the need for a new sensing mechanism was identified that lead to the development of Digital Foam, a deformable input device sensor that captures its own geometry. The frst prototype presented employs a flat deformable surface that demonstrates capturing multiple finger gestures simultaneously. To further leverage sculpting affordances, a second prototype employs a spherical design to optimise the spatial mappings between physical gestures and the virtual models. The purpose of this is to capture existing sculpting skills and provide an intuitive understanding of the operation. For example, when the user deforms the back of the device, this will deform the back of the virtual model. Both technologies are constructed of polyurethane foam and provide a pleasing haptic sensation that is analogous to shaping soft materials like modelling clay.To explore the functionality of Digital Foam, a library of interaction techniques have been developed that support multiple finger manipulation operations.  The algorithms presented further support the spatial mapping between existing virtual models and the spherically shaped Digital Foam device.  To maximise the obtainable resolution of the sensor, an interpolation algorithm was also developed. To determine the accuracy and reliability of the isensor, a computer controlled apparatus was constructed, allowing a real-time comparison between the physical location of the mechanical finger and the touch-point measured on the Digital Foam surface. The results showed a performance improvement using the interpolated location compared to the raw sensor data alone. The development of Digital Foam has allowed the exploration of deformable materials for input device technologies and investigates a novel human computer interaction methodology that shows promising results.

Thesis document

Complete Thesis PDF Complete dissertation download
Chapter 1 Introduction
Chapter 2 Background
Chapter 3 Sculpting Metaphor
Chapter 4 Digital Foam Sensor Conceptualisation and Prototypes
Chapter 5 Digital Foam Interactions, Algorithms and Applications
Chapter 6 Digital Foam Performance Evaluation
Chapter 7 Conclusion
Appendix A Digital Foam Patent
Appendix B Digital Foam Schematics
Appendix C Mechanical Finger Configuration Details
Appendix D Conductive Foam Technical Details
Appendix E Spherical Digital Foam Trial Study
Appendix F Attachments

Update – Digital Foam granted US Patent

After a great deal of hard work, we have finally gone through the process of patenting the Digital Foam Concept. The full US patent was granted on the 9/9/2010 with publication number US 2010/0225340 A1. Below is a clipping of the first page and you can find a full version available for download here.
Digital Foam Patent