Browsing by Author "Samavati, Faramarz F."

Now showing 1 - 18 of 18
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    3D mesh watermarking
    (2008) Eshraghi Boroojeni, Mahsa; Samavati, Faramarz F.
    3D watermarking methods embed a hidden watermark into 3D models for the main purpose of copyright protection and content authentication. The growing use of 3D models in various fields of industry, such as games, animation, virtual reality, and cultural heritage, along with the possibility of easy reproduction and distribution, has drawn the attention to copyright protection of 3D models. This thesis develops a watermarking framework for polygonal meshes that attains robustness against a list of accessible attacks. A watermark is embedded into the geometry of a mesh by perturbing the mesh vertices along t heir tangent space to achieve invisibility. The mesh capacity for the embedded watermark can be as high as the number of its vertices, which is usually a fairly large number. To sort out the issue of robustness, a list of the most accessible attacks through common graphics tools is proposed that includes affine transformations, geometrical deformations, topological attacks, subdivision attacks, vertex reordering, and combination of these attacks. To achieve robustness against the proposed list of attacks, a set of attack recovery techniques are developed. Geometric segmentation is proposed to recover the inserted watermark against geometrical deformations and topological attacks. Geometric indexing is performed to resist vertex reordering attacks. Robustness against affine transformations is achieved through a coordinate normalization scheme. Finally, a resolution normalization scheme is proposed to resist the subdivision attacks.
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    Constraining Wavelets for Multiresolution
    (2006) Olsen, Luke Jonathan; Samavati, Faramarz F.; Costa Sousa, Mário
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    Constraint-based surface deformation
    (2009) Pusch, Richard Allen; Samavati, Faramarz F.
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    Curve synthesis by example
    (2006) Brunn, Meru; Costa Sousa, Mário; Samavati, Faramarz F.
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    Focus+Context via Snaking Paths
    (2013-06-14) Packer, Jeffrey F.; Samavati, Faramarz F.; Mitchell, Joseph Ross
    Focus+context visualizations reveal specific structures in high detail while effectively depicting its surroundings, often relying on transitions between the two areas to provide context. We present an approach to generate focus+context visualizations depicting cylindrical structures along snaking paths that enables the structures themselves to become the transitions and focal areas, simultaneously. A method to automatically create a snaking path through space by applying a path finding algorithm is presented. A 3D curve is created based on the 2D snaking path. We describe a process to deform cylindrical structures in segmented volumetric models to match the curve and provide preliminary geometric models as templates for artists to build upon. Structures are discovered using our constrained volumetric sculpting method that enables removal of occluding material while leaving them intact. We find the resulting visualizations effectively mimic a set of motivating illustrations and discuss some limitations of the automatic approach.
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    Geometric modeling with l-systems
    (2008) Shirmohammadi, Mitra; Samavati, Faramarz F.
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    GEOPHYS: Design and Fabrication of Geospatial Physicalizations
    (2021-07-14) Djavaherpour, Hessam; Samavati, Faramarz F.; Levy, Richard M.; Oehlberg, Lora; Dawson, Peter
    Geospatial datasets are complex, difficult to understand, and hard to visualize. Although web maps have provided visualization of geospatial datasets using computer-generated 2D maps, such visualizations significantly deal with misinterpretations of areas and distances due to the mapping distortions. Digital Earth (DE) is an alternative solution for overcoming 2D map distortions and integrating various geospatial datasets. However, virtual 3D models of the Earth still suffer from common issues caused by projecting 3D scenes to 2D screens, such as losing one spatial dimension and inaccessibility for direct manual interaction. By providing tactile exploration and physical interaction, physical models facilitate cognition and understanding of data. This thesis argues that using 3D physical models supporting visualizations of geospatial datasets at different scales and resolutions can address challenges related to understanding and analyzing such datasets. To shed light on this hypothesis, we introduce a framework, GEOPHYS, to make tangible multi-resolution/multi-scale representations of geospatial data. Furthermore, GEOPHYS introduces a comprehensive, accurate, and repeatable physical rendering method for various applications and visualization scenarios, using accessible digital fabrication tools. A pipeline forms the core methodology of this thesis, which consists of data transformation, digital design, digital fabrication, evaluation, and the introduction of the final framework. In this thesis, the design and fabrication stages work hand-in-hand to transform the conceptual form into a visual representation, investigate the model for its manufacturability, and bring it into the physical world. Evaluations in the context of this thesis are technology-centred and human-centred. This thesis contributes to geovisualization and physicalization by introducing a method to visualize multi-resolution geospatial datasets in Large Areas, a physical rendering approach for creating landscape models, and a tactile representation of the RADAR imagery to facilitate the sea-ice travel for Inuit. We also provide an in-depth review of various methods by which physicalizations can be physically rendered. The results of our studies prove that models made using GEOPHYS are beneficial learning tools capable of creating interest and engagement to explore geospatial concepts.
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    Image-assisted modeling from unconstrained sketches
    (2011) Olsen, Luke Jonathan; Samavati, Faramarz F.
    In this thesis, several outstanding problems in sketch-based interfaces for 3d modeling (SBIM) are addressed in two major areas of focus: understanding and identifying the components of a complex sketch (analysis), and using those identified components to construct a 3d model (interpretation). Unlike previous approaches that assume simple or rigorously constrained input sketches, the goal in this research was to support natural, unconstrained sketching with many pen strokes. An image-based tracing method is used to blend the input and extract salient strokes, followed by a stroke classification method that captures how the strokes define the boundary, regions, and features of objects. Unconstrained sketches that contain numerous strokes of different classes require a new approach to mesh construction. A feature-based method is proposed to embed all input lines into the underlying geometry. Furthermore, using an initial sparse triangulation followed by a subdivide-and-snap approach results in an output mesh with subdivision connectivity. By offering a direct connection between the sketch and the underlying geometry, the output is suitable for further refinement and use in later parts of the modeling pipeline. This construc­tion enables a set of feature-based annotations, in which the user specifies the cross-section, holes, bumps, and extrusions by marking up a sketch with simple, evocative gestures. These advancements are united in an image-assisted interface in which user-provided images are used actively in the modeling process. Input strokes can be automatically aligned with image edges, accelerating the process of tracing an object feature. The image can also be used as texture and shape information to enhance the 3d model. Taken together, this thesis advances the state of SBIM in several important ways. The main contributions are the stroke classification, feature-based subdivision surface creation, image-assisted interface, and region-based annotations for shape deformation. To demon­strate the combined power of these components, several results and applications are presented, along with a user study that argues for the usability of the overall approach.
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    Incremental subdivision
    (2005) Pakdel-Sefidgar, Hamid-Reza; Samavati, Faramarz F.
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    Interactive volume manipulation
    (2008) Chen, Hung-Li Jason; Samavati, Faramarz F.; Costa Sousa, Mário
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    Parameter Aligned Surface Trimming
    (2018-01-18) Halbert, Shannon; Samavati, Faramarz F.; Prusinkiewicz, Przemyslaw; Costa Sousa, Mario; Yanushkevich, Svetlana
    Parametric surfaces are widely used for surface modelling because of their easy editing and fast rendering properties. However, trimming these models is not as straightforward as it is with other surface types and doing so often results in the loss of some or all of the parametric properties of the original surface. This thesis introduces a new representation for trimmed parametric surfaces which preserves the parametric properties of the surface. Given a set of trimming curves in the parameter space of a surface, this method defines local subspaces aligned to the global parameter axes which surround groups of trimming curves. When multiple trimming curves are present, intersecting subspaces are further segmented using local Voronoi curve diagrams, allowing any shared subspace to be distributed equally between the trimming curves. Transition patches are then used to define local subspaces around the trimming curves each with their own parametrization that accommodates the trimmed edges. Coons patches are then created to map these local spaces to the global parameter space during rendering. This allows for high quality interpolation of the trimmed edges without affecting the parametric properties or continuity of the trimmed surface.
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    Real-time super resolution contextual close-up of clinical volumetric data
    (2006) Taerum, Torin; Costa Sousa, Mário; Samavati, Faramarz F.
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    Sketch-based assembly of subdivision surfaces
    (2006) Severn, Aaron Robert Law; Samavati, Faramarz F.
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    Sketch-based modeling of parametric surfaces using few strokes
    (2006) Cherlin, Joseph Jacob; Costa Sousa, Mário; Samavati, Faramarz F.
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    Synthesizing techniques based on multiresolution
    (2007) Wecker, Lakin Christopher; Samavati, Faramarz F.; Gavrilova, Marina L.
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    Terrain modeling by example
    (2005) Brosz, John David Lynn; Samavati, Faramarz F.; Costa Sousa, Mário
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    The flexible projection framework
    (2011) Brosz, John David Lynn; Samavati, Faramarz F.
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    Using virtual reality to improve design communication
    (2012) Liu, Chao; Levy, Richard M.; Samavati, Faramarz F.
    A major challenge that faces designers is creating solutions within specific constraints. Creating acceptable design proposals requires designers to work closely with their clients to determine their exact needs and specifications. Good communication between clients and designers is thereby essential to a favourable outcome. Traditional communication approaches such as face-to-face discussions are sometimes insufficient for clarifying clients' requirements. ln these cases, expressing design intent using graphics is more intuitive and provides greater clarity. Unfortunately, for clients who lack sophisticated drawing skills, it may be very difficult for them to express ideas with freehand sketches. To improve this situation, this thesis proposes a web-based communication tool to help clients express design ideas using computer graphics. Currently, computer-aided design (CAD) is a typical choice for professional designers and engineers, due to its high demands of operating skills and computer support. The premise of this thesis is that web­based virtual reality (YR) can remove these technical barriers. By creating an easy-to-use tool that works inside a web browser, there is the potential for clients to explore design options early in the design process without having to learn CAD. To prove its technical feasibility, this thesis presents a proof-of-concept, YY3D, which enables clients to explore interior design solutions. YY3D is equipped with interactive functions that allow its user to select and arrange furniture from an online catalogue into a 3D virtual interior space. This thesis reviews the theoretical and technical background of virtual design, introduces the methodology to develop the proposed communication tool, and walks through the creation process of the proof-of-concept. The research results would be useful in creating applications to solve communication problems in other design fields.