[Truncated abstract] Virtual sculpting is an interactive 3D modeling process that allows users to create and modify solid objects in a virtual world, with applications in art, rapid proto- typing and design. This thesis investigates methods for a collaborative, voxel-based virtual sculpting with haptic force-feedback. The objective is to devise such a system that operates in real-time. I make three main contributions in the fields of voxel-based virtual sculpting, haptics and collaborative virtual environments. First, I have devised a method for virtual sculpting where a voxel-based sculpture is created using a tool to build up or erode material. In existing real-time systems, due to the complexity of the algorithms that determine which voxels have been touched by the tool in a given time-step, the size or shape of the sculpting tool is limited and can often only be applied at a fixed orientation. My solution allows the tool to take the shape of any arbitrary triangle-based polyhedron that can be applied at any orientation. To determine which voxels are intersected by the tool, the tool is voxelized (converted into its discrete voxel representation) at each time-step against the voxels of the sculpture, which are then modified according to the desired operation. To give the resulting voxel-based sculpture a realistic appearance, I use the well-known Marching Cubes algorithm to form a triangular- mesh isosurface where the voxels representing sculpture material meet free-space. '...' For this I have borrowed concepts from the existing Voxmap-PointShell (VPS) model where the tool is represented by an array of points that cover its surface, each of which is tested for collisions with the sculpture. Each colliding point will form a component force, and the overall collision force is the vector sum of these components. My model is unique in that the component forces are formed in a direction tangential to the isosurface nearest the voxel of collision and can operate while the voxels of the sculpture are changing. While the VPS model is designed for force-feedback on a 6- degrees-of-freedom haptic device (delivers translational and rotational forces to the user), my model is designed to suit commodity 3-degrees-of-freedom (translational forces only) devices which are much more common. Third, I have developed a collaborative virtual sculpting paradigm to allow several users to simultaneously work on the same sculpture from different locations. This allows collaborative design without the requirement of being co-present. I will discuss methods for relaying the rapidly changing voxel and isosurface data between workstations, such that the local environment on each is synchronized in a manner that is immediate and transparent to the users. In addition, collisions between the different users' tools are felt through force-feedback. I implemented a collaborative haptic virtual sculpting simulation using the above methods in order to validate the system. The simulation was used to test the capabilities and limits of each contribution, as well as the real-time capability of the overall system. Ultimately this thesis demonstrates that it is possible to combine these technologies to form a flexible and intuitive collaborative virtual sculpting experience that operates in real-time.
| Identifer | oai:union.ndltd.org:ADTP/222321 |
| Date | January 2008 |
| Creators | Prior, Anthony |
| Publisher | University of Western Australia. School of Computer Science and Software Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Anthony Prior, http://www.itpo.uwa.edu.au/UWA-Computer-And-Software-Use-Regulations.html |
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