SAMPAIO, Artur Pereira. Uso de refinamento adaptativo em escultura virtual para criação livre de detalhes em malhas triangulares. 2012. 66 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2012. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-08T19:33:44Z No. of bitstreams: 1 2011_dis_apsampaio.pdf: 7747299 bytes, checksum: 3821b45c7bbae1262adf0904941a9d35 (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-14T15:14:00Z (GMT) No. of bitstreams: 1 2011_dis_apsampaio.pdf: 7747299 bytes, checksum: 3821b45c7bbae1262adf0904941a9d35 (MD5) / Made available in DSpace on 2016-07-14T15:14:00Z (GMT). No. of bitstreams: 1 2011_dis_apsampaio.pdf: 7747299 bytes, checksum: 3821b45c7bbae1262adf0904941a9d35 (MD5) Previous issue date: 2012 / Modeling of virtual objects and characters can be tedious and difficult in many situations. A modeling system should be capable of representing any change or feature desired by the user as quickly and transparently as possible, allowing the modeler to focus on the act of creating, as opposed to having to specify the position of each vertex manually. Such a system, if on the one hand offers less control in determining the position of each vertex, being computationally more expensive in some situations, on the other hand greatly simplifies the work of the artist, allowing character modeling to be accessible to any user. This work addressed the problem of traditional sculpting techniques to add details on triangular meshes with adaptive resolution, in regions with low vertex density. The proposed algorithm splits faces and edges in the region of interest of the artist to ensure the existence of a sufficient number of vertices to represent the desired detail, without any additional input requested. The resulting system is capable of bridging the gap between traditional and virtual modeling, improving some of the main methods proposed in the literature regarding the location of the subdivisions. Moreover, it also helps to maintain a good mesh topology and geometric quality, with few vertices of high valence, even if the original mesh is poorly refined, allowing the incorporation of new details. / Modelar objetos e personagens virtuais pode ser uma tarefa tediosa e difícil em várias situações. Um sistema de modelagem ideal deve ser capaz de representar qualquer mudança ou característica desejada pelo usuário da forma mais rápida e transparente possível, abstraindo toda a complexidade topológica e matemática, permitindo ao modelador concentrar-se exclusivamente no ato de criar, em oposição a ter de especificar a posição de cada elemento de forma manual. Tal sistema, se por um lado pode oferecer menor controle na determinação da posição de cada vértice, além de poder ser mais caro computacionalmente em algumas situações, por outro simplifica enormemente o trabalho do artista, tornando a modelagem acessível a qualquer usuário. O presente trabalho abordou o problema das técnicas de sculpting tradicionais de adicionar detalhes em malhas triangulares, com resolução adaptativa e de forma interativa, em regiões com baixa densidade de vértices. O algoritmo proposto busca subdividir faces e arestas na região de interesse do artista de modo a garantir uma quantidade de vértices suficiente para representar o detalhe pretendido, sem necessidade de qualquer informação adicional por parte do usuário. O sistema resultante é capaz de encurtar a distância entre a modelagem tradicional e a virtual, superando alguns dos principais métodos propostos no meio acadêmico no que tange à localidade das subdivisões e a manutenção de uma malha de boa topologia e de boa qualidade geométrica, com poucos vértices de alta valência, ainda que o modelo original seja fracamente refinado, tornando possível a incorporação de novos detalhes.

[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.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Modelar objetos e personagens virtuais pode ser uma tarefa tediosa e difÃcil em vÃrias situaÃÃes. Um sistema de modelagem ideal deve ser capaz de representar qualquer mudanÃa ou caracterÃstica desejada pelo usuÃrio da forma mais rÃpida e transparente possÃvel, abstraindo toda a complexidade topolÃgica e matemÃtica, permitindo ao modelador concentrar-se exclusivamente no ato de criar, em oposiÃÃo a ter de especificar a posiÃÃo de cada elemento de forma manual. Tal sistema, se por um lado pode oferecer menor controle na determinaÃÃo da posiÃÃo de cada vÃrtice, alÃm de poder ser mais caro computacionalmente em algumas situaÃÃes, por outro simplifica enormemente o trabalho do artista, tornando a modelagem acessÃvel a qualquer usuÃrio. O presente trabalho abordou o problema das tÃcnicas de sculpting tradicionais de adicionar detalhes em malhas triangulares, com resoluÃÃo adaptativa e de forma interativa, em regiÃes com baixa densidade de vÃrtices. O algoritmo proposto busca subdividir faces e arestas na regiÃo de interesse do artista de modo a garantir uma quantidade de vÃrtices suficiente para representar o detalhe pretendido, sem necessidade de qualquer informaÃÃo adicional por parte do usuÃrio. O sistema resultante à capaz de encurtar a distÃncia entre a modelagem tradicional e a virtual, superando alguns dos principais mÃtodos propostos no meio acadÃmico no que tange à localidade das subdivisÃes e a manutenÃÃo de uma malha de boa topologia e de boa qualidade geomÃtrica, com poucos vÃrtices de alta valÃncia, ainda que o modelo original seja fracamente refinado, tornando possÃvel a incorporaÃÃo de novos detalhes. / Modeling of virtual objects and characters can be tedious and difficult in many situations. A modeling system should be capable of representing any change or feature desired by the user as quickly and transparently as possible, allowing the modeler to focus on the act of creating, as opposed to having to specify the position of each vertex manually. Such a system, if on the one hand offers less control in determining the position of each vertex, being computationally more expensive in some situations, on the other hand greatly simplifies the work of the artist, allowing character modeling to be accessible to any user. This work addressed the problem of traditional sculpting techniques to add details on triangular meshes with adaptive resolution, in regions with low vertex density. The proposed algorithm splits faces and edges in the region of interest of the artist to ensure the existence of a sufficient number of vertices to represent the desired detail, without any additional input requested. The resulting system is capable of bridging the gap between traditional and virtual modeling, improving some of the main methods proposed in the literature regarding the location of the subdivisions. Moreover, it also helps to maintain a good mesh topology and geometric quality, with few vertices of high valence, even if the original mesh is poorly refined, allowing the incorporation of new details.

SAMPAIO, Artur Pereira. Uso de Refinamento Adaptativo em Escultura Virtual para Criação Livre de Detalhes em Malhas Triangulares. 2011. 58 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Departamento de Computação, Fortaleza-CE, 2012. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-06-02T19:35:28Z No. of bitstreams: 1 2011_dis_apsampaio.txt: 25433 bytes, checksum: 9015898966f69dfce3b6faa62e988c32 (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-06-02T19:42:44Z (GMT) No. of bitstreams: 1 2011_dis_apsampaio.txt: 25433 bytes, checksum: 9015898966f69dfce3b6faa62e988c32 (MD5) / Made available in DSpace on 2016-06-02T19:42:44Z (GMT). No. of bitstreams: 1 2011_dis_apsampaio.txt: 25433 bytes, checksum: 9015898966f69dfce3b6faa62e988c32 (MD5) Previous issue date: 2011 / Modeling of virtual objects and characters can be tedious and difficult in many situations. A modeling system should be capable of representing any change or feature desired by the user as quickly and transparently as possible, allowing the modeler to focus on the act of creating, as opposed to having to specify the position of each vertex manually. Such a system, if on the one hand offers less control in determining the position of each vertex, being computationally more expensive in some situations, on the other hand greatly simplifies the work of the artist, allowing character modeling to be accessible to any user. This work addressed the problem of traditional sculpting techniques to add details on triangular meshes with adaptive resolution, in regions with low vertex density. The proposed algorithm splits faces and edges in the region of interest of the artist to ensure the existence of a sufficient number of vertices to represent the desired detail, without any additional input requested. The resulting system is capable of bridging the gap between traditional and virtual modeling, improving some of the main methods proposed in the literature regarding the location of the subdivisions. Moreover, it also helps to maintain a good mesh topology and geometric quality, with few vertices of high valence, even if the original mesh is poorly refined, allowing the incorporation of new details. / Modelar objetos e personagens virtuais pode ser uma tarefa tediosa e difícil em várias situações. Um sistema de modelagem ideal deve ser capaz de representar qualquer mudança ou característica desejada pelo usuário da forma mais rápida e transparente possível, abstraindo toda a complexidade topológica e matemática, permitindo ao modelador concentrar-se exclusivamente no ato de criar, em oposição a ter de especificar a posição de cada elemento de forma manual. Tal sistema, se por um lado pode oferecer menor controle na determinação da posição de cada vértice, além de poder ser mais caro computacionalmente em algumas situações, por outro simplifica enormemente o trabalho do artista, tornando a modelagem acessível a qualquer usuário. O presente trabalho abordou o problema das técnicas de sculpting tradicionais de adicionar detalhes em malhas triangulares, com resolução adaptativa e de forma interativa, em regiões com baixa densidade de vértices. O algoritmo proposto busca subdividir faces e arestas na região de interesse do artista de modo a garantir uma quantidade de vértices suficiente para representar o detalhe pretendido, sem necessidade de qualquer informação adicional por parte do usuário. O sistema resultante é capaz de encurtar a distância entre a modelagem tradicional e a virtual, superando alguns dos principais métodos propostos no meio acadêmico no que tange à localidade das subdivisões e a manutenção de uma malha de boa topologia e de boa qualidade geométrica, com poucos vértices de alta valência, ainda que o modelo original seja fracamente refinado, tornando possível a incorporação de novos detalhes.