Efficient conservative collision detection for populated virtual worlds

Large virtual worlds, with considerable level of detail are starting to emerge everywhere, from large areas of actual cities to archaeological reconstructions of large sites. Populating a virtual world adds an extra touch to the visualization of these worlds, but unfortunately it also brings an extra burden to the system. Several tasks are required when adding animated characters to a virtual world, such as collision detection, path planning and other AI algorithms, rendering of dynamic geometry, amongst others. In here a method for efficient and scalable conservative collision detection is presented, that is able to deal with large scenes and thousands of avatars. This method does not perform exact collision detection, hence it is conservative. The method is suitable as a basis for path planning algorithms and other AI algorithms where an avatar is often regarded as 'something' that can be bounded by a cylinder, or a box. The algorithm is capable of dealing with arbitrarily complex 3D worlds, and does not require any a priori knowledge of the geometry.ACM Siggraph, EG, GGC

Virtual reality haptic device for mental Illness treatment

Schizophrenia is a mental disorder that alters mental functioning and can cause hallucinations, mental disorientation, and a variety of other symptoms, which results in a separation of schizophrenics from society. Despite the fact that the condition has been known about for a long time, there is still an urgent need for research and testing to develop better therapies. Virtual reality (VR) has had interesting outcomes when used to treat illnesses, and it is gradually emerging as a viable technical choice for the healthcare sector due to its immersion, which offers better and more intense user experiences. Once linked to a serious game, it can introduce the user to a number of situations that, when combined with medical assistance, aid in their rehabilitation and treatment. The use of haptic devices enhances VR immersion by enabling users to comprehend virtual environments with greater nuance, which increases their level of believing in the new environment they are in. When used in conjunction with VR, it can improve the efficacy of the treatment, making its use viable for the treatment of psychic diseases. The goal of this research is to develop haptic vest interactions using a three-dimensional virtual testing scenario to support and improve the use of VR for rehabilitation and therapy for schizophrenia. The established functionalities can be applied to a further serious game with the same focus.info:eu-repo/semantics/publishedVersio

Efficient conservative collision detection for populated virtual worlds

Large virtual worlds, with considerable level of detail are starting to emerge everywhere, from large areas of actual cities to archaeological detailed reconstructions of sites. Populating a virtual world adds an extra touch to the visualization of these worlds, but unfortunately it also brings an extra burden to the system. Several tasks are required when adding animated characters to a virtual world, such as collision detection, path planning and other AI algorithms, rendering of dynamic geometry, amongst others. In here a method for efficient and scalable conservative collision detection, that is able to deal with large scenes and thousands of avatars, is presented. This method does not perform exact collision detection, hence it is conservative. The method is suitable as a basis for path planning algorithms and other AI algorithms where an avatar is often regarded as ’something’ that can be bounded by a cylinder, or a box. The algorithm is capable of dealing with arbitrarily complex 3D worlds, and does not require any a priori knowledge of the geometry

Moving least-squares in finite strain analysis with tetrahedra support

A finite strain finite element (FE)-based approach to element-free Galerkin (EFG) discretization is introduced, based on a number of simplifications and specialized techniques in the context of a Lagrangian kernel. In terms of discretization, a quadratic polynomial basis is used, support is determined from the number of pre-assigned nodes for each quadrature point and quadrature points coincide with the centroids of tetrahedra. Diffuse derivatives are adopted, which allow for the use of convenient non-differentiable weight functions which approximate the Dirac-Delta distribution. Due to the use of a Lagrangian kernel, recent finite strain elasto-plastic constitutive developments based on the Mandel stress are adopted in a direct form. These recent developments are especially convenient from the implementation perspective, as EFG formulations for finite strain plasticity have been limited by the previous requirement of updating the kernel. We also note that, although tetrahedra are only adopted for integration in the undeformed configuration, mesh deformation is of no consequence for the results. Four 3D benchmark tests are successfully solved

Internal drainage and nitrate leaching in a typic hapludox under a maize-brachiaria-maize succession at different nitrogen fertilizer rates

A adubação nitrogenada ideal deve ser definida para satisfazer a necessidade da cultura, mas com o mínimo de risco ao ambiente. Para isso, é necessário que a recomendação da adubação nitrogenada seja a mais exata possível. O presente trabalho foi desenvolvido em um solo de textura areno-argilosa, com o objetivo de avaliar a drenagem interna e a lixiviação de NO3- à profundidade de 0,80 m com o tempo, em uma sucessão de culturas sob plantio direto, utilizando-se sulfato de amônio marcado com o isótopo estável 15N, em diferentes doses. As avaliações foram feitas em dois cultivos de milho safrinha, o primeiro no ano agrícola de 2006 e o segundo em 2007, e em um de braquiária na entressafra. Os tratamentos consistiram de doses de N de 60, 120 e 180 kg ha-1, na forma de sulfato de amônio marcado (15N), e um tratamento testemunha, sem aplicação de N. O adubo marcado foi aplicado em subparcelas previamente definidas, apenas no primeiro cultivo do milho (safra 2006). A drenagem interna foi obtida a partir da densidade de fluxo de água calculada pela equação de Darcy-Buckingham, na qual a condutividade hidráulica e o gradiente de potencial total foram estimados a partir de leituras diárias de tensiômetros de mercúrio, instalados nas profundidades de 0,70, 0,80 e 0,90 m. A condutividade hidráulica em função do potencial mátrico na profundidade de 0,80 m foi determinada, no campo, pelo método do perfil instantâneo, usando tensiômetros e curvas de retenção. A densidade de fluxo de água foi também usada, juntamente com a concentração de NO3- e a porcentagem de átomos de 15N da solução no solo, para estimar a lixiviação do NO3-total e daquele derivado do fertilizante. A solução no solo foi coletada por meio de extratores com cápsula porosa, instalados na profundidade de 0,80 m. A drenagem interna diminuiu com o aumento das doses de N aplicadas para a sucessão de culturas estudada, variando de 31,5 a 73,4 % da precipitação pluvial total (97 mm) durante o primeiro cultivo de milho, de 26,1 a 58,1 % da precipitação pluvial total (695 mm) no cultivo da braquiária e pousio e de 56,6 a 87,4 % do total de 419 mm de precipitação pluvial no segundo cultivo de milho. A lixiviação de NO3-total (do fertilizante e outras fontes) foi muito baixa no primeiro cultivo de milho em todas as doses de N e significativa para as doses de 120 e 180 kg ha-1 nos períodos da cultura de braquiária mais pousio (26,16 kg ha-1 para a dose de 120 e 39,8 kg ha-1 para a de 180 kg ha-1) e da segunda cultura de milho (aproximadamente 23 kg ha-1 para ambas as doses). A lixiviação de NO3-proveniente do fertilizante foi praticamente nula no primeiro cultivo de milho e, em geral, baixa durante o cultivo de braquiária e o segundo cultivo de milho.The ideal N fertilization should be defined to satisfy the crop needs, but with minimum environmental risk. For this purpose, N fertilizer recommendations must be as accurate as possible. This study was carried out in a sand-clay soil (22 º 42 ' 30 '' S; 47 º 38 ' 00 '' W; 546 m asl) and the objective was to evaluate the internal drainage and nitrate leaching during the cycles of three crops in succession under no-tillage at a soil depth of 0.80 m, using different doses of 15N -labeled ammonium sulphate. The crop succession consisted of: maize in 2006 followed by brachiaria plus fallow and finally maize in 2007. Labeled N fertilizer rates of 60, 120 and 180 kg ha-1 and a control (no N) were tested. The labeled fertilizer was applied to previously defined subplots, only to maize in 2006. Internal drainage was derived from the soil-water flux density calculated by the Darcy-Buckingham equation in which the hydraulic conductivity and total water potential gradient were estimated based on daily readings of Hg tensiometers at depths of 0.70, 0.80 and 0.90 m. The hydraulic conductivity was determined in the field as a function of soil-water matric potential at a depth of 0.80 m, by the instantaneous profile method, using tensiometers and soil-water retention curves. The soil-water flux density was also used, together with nitrate concentration and the 15N atom % in soil solution, to estimate nitrate leaching of both total and fertilizer nitrate. Internal drainage decreased with the increase of applied N levels to the crop succession, changing from 31.5 to 73.4 % of the total rainfall (97 mm) in the first maize, from 26.1 to 58.1 % of the total rainfall (695 mm) in brachiaria + fallow, and from 56.6 to 87.4 % of the 419 mm of total rainfall in the second maize crop. The leaching of total nitrate (from fertilizer and other sources) was very low in the first maize crop for all applied N levels and significant for the rates of 120 and 180 kg ha-1 in the periods of brachiaria plus fallow (26.16 for 120 kg ha-1 and 39.8 for 180 kg ha-1) and of the second maize crop (approximately 23 kg ha-1 for both levels). There was no N leaching from fertilizer in the first maize crop and N leaching was very low in the brachiaria and second maize crop.FAPES

Path planning for complex 3D multilevel environments

The continuous development of graphics hardware is contributing to the creation of 3D virtual worlds with high level of detail, from models of large urban areas, to complete infrastructures, such as residential buildings, stadiums, industrial settings or archaeological sites, to name just a few. Adding virtual humans or avatars adds an extra touch to the visualization providing an enhanced perception of the spaces, namely adding a sense of scale, and enabling simulations of crowds. Path planning for crowds in a meaningful way is still an open research field, particularly when it involves an unknown polygonal 3D world. Extracting the potential paths for navigation in a non automated fashion is no longer a feasible option due to the dimension and complexity of the virtual environments available nowadays. This implies that we must be able to automatically extract information from the geometry of the unknown virtual world to define potential paths, determine accessibilities, and prepare a navigation structure for real time path planning and path finding. A new image based method is proposed that deals with arbitrarily a priori unknown complex virtual worlds, namely those consisting of multilevel passages (e.g. over and below a bridge). The algorithm is capable of extracting all the information required for the actual navigation of avatars, creating a hierarchical data structure to help both high level path planning and low level path finding decisions. The algorithm is image based, hence it is tessellation independent, i.e. the algorithm does not rely on the underlying polygonal structure of the 3D world. Therefore, the number of polygons does not have a significant impact on the performance, and the topology has no weight on the results.Fundação para a Ciência e a Tecnologi

Finite element mesh generator: GMALHA

The mesh generator GMALHA was developed for the construction of non-structured triangular meshes used in sea wave propagation finite element models. For a given coastal zone delimited by a boundary line and characterised by its bathymetry, GMALHA generates an optimal triangular mesh. The boundary, which sometimes can be very complex, includes a coastline with port infrastructures, beaches, marinas, islands, etc. . . Based on that boundary and bathymetric information within it, GMALHA, first generates a rough triangular mesh that fills the domain. The mesh is then subjected to post-processing, such as: local refinement and optimization (control of elements uniformity, repositioning of points to correct angles and edge swaps to correct node valence). This paper describes the generation, refinement and optimization algorithms of GMALHA. The advantages of this generator are also illustrated with some practical cases of sea wave propagation in coastal areas.Peer Reviewe

Aplicação de apoio para a aeronave P-3C CUP+ ORION : Weight & Balance : desenvolvimento de uma aplicação de apoio à distribuição do peso na aeronave que equipa a Esquadra 601 da Força Aérea Portuguesa

Simpósio realizado no Porto de 4-5 de setembro de 201

Path planning for complex 3D multilevel environments

The continuous development of graphics hardware is contributing to the creation of 3D virtual worlds with high level of detail, from models of large urban areas, to complete infrastructures, such as residential buildings, stadiums, industrial settings or archaeological sites, to name just a few. Adding virtual humans or avatars adds an extra touch to the visualization providing an enhanced perception of the spaces, namely adding a sense of scale, and enabling simulations of crowds. Path planning for crowds in a meaningful way is still an open research field, particularly when it involves an unknown polygonal 3D world. Extracting the potential paths for navigation in a non automated fashion is no longer a feasible option due to the dimension and complexity of the virtual environments available nowadays. This implies that we must be able to automatically extract information from the geometry of the unknown virtual world to define potential paths, determine accessibilities, and prepare a navigation structure for real time path planning and path finding. A new image based method is proposed that deals with arbitrarily a priori unknown complex virtual worlds, namely those consisting of multilevel passages (e.g. over and below a bridge). The algorithm is capable of extracting all the information required for the actual navigation of avatars, creating a hierarchical data structure to help both high level path planning and low level path finding decisions. The algorithm is image based, hence it is tessellation independent, i.e. the algorithm does not use the underlying polygonal structure of the 3D world. Therefore, the number of polygons as well as the topology, do not affect the performance

Effect of a mobilization and active exercise program on the range of motion of bedridden patients with disuse syndrome

Disuse syndrome is a disorder that is most often associated with acute or chronic disease complications. Despite disuse syndrome may affect all organs and systems, the impact of range of motion limitations caused by immobility on functional capacity to perform activities of daily living is often very severe. Mobilization and active exercise have beneficial effects that counteract the impact of immobility on the body. This study aims to assess the effect of a mobilization and active exercise program on the range of motion of bedridden patients with disuse syndrome. A quasi-experimental study was developed. The sample consisted of 26 persons that have been bedridden for more than six months at home. A mobilization and active exercise program was design, fitting patient individual needs and implemented 2 times/week for 2 months. Caregivers where trained to transfer the patient from bed to chair and to repeat active exercise every day. Data collection was performed before and after intervention, using the Barthel Index and a goniometer for range of motion evaluation. 26 participants, aged 77.19 ± 11.67 and bedridden for 18 months (18.73 ± 15.25) were enrolled, but only 24 completed the intervention program. There was a minimal difference in the sex distribution with 7.6% more women than men. Results showed a statistically significant increase on range of motion of the shoulder, elbow, wrist, hip and knee. There was statistical significance in plantar flexion but not on the dorsiflexion. Barthel Index score has increase significantly (28,65±21,28vs31,46±23,28; p=0,035) after the mobilization and active exercise program. A mobilization and active exercise program implemented regularly may contribute to improve range of motion of bedridden with disuse syndrome. Thus, based on these results, it is believed that the intervention of rehabilitation nurse was an added value, contributing to an increase in range of motion and independence of patients