Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.32
Julia Taylor-Hell
We present a method for creating tree models with realistically curved branches, useful in the portrayal of natural scenes. Instead of attempting to replicate a tree’s final shape by observation, we obtain this shape as nature does — by considering the tree’s development in the context of its environment. The final shape of the branches results from their growth in length, girth, weight and rigidity under the influence of gravity and tropisms. Using the framework of L-systems, we extend Jirasek’s biomechanical simulation of a plant axis to correctly represent an entire tree. Our model also simulates the reaction wood which actively re-orients a leaning branch by differentiating the wood production in angular portions of the branch cross-section. To obtain realistic and controllable tree architectures, we regulate growth elements in the model using functions based on botanical findings. We create a multi-year simulation of tree growth under environmental influences, obtaining a realistic tree shape at every stage of its development.
{"title":"Incorporating Biomechanics into Architectural Tree Models","authors":"Julia Taylor-Hell","doi":"10.1109/SIBGRAPI.2005.32","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.32","url":null,"abstract":"We present a method for creating tree models with realistically curved branches, useful in the portrayal of natural scenes. Instead of attempting to replicate a tree’s final shape by observation, we obtain this shape as nature does — by considering the tree’s development in the context of its environment. The final shape of the branches results from their growth in length, girth, weight and rigidity under the influence of gravity and tropisms. Using the framework of L-systems, we extend Jirasek’s biomechanical simulation of a plant axis to correctly represent an entire tree. Our model also simulates the reaction wood which actively re-orients a leaning branch by differentiating the wood production in angular portions of the branch cross-section. To obtain realistic and controllable tree architectures, we regulate growth elements in the model using functions based on botanical findings. We create a multi-year simulation of tree growth under environmental influences, obtaining a realistic tree shape at every stage of its development.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115912825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.46
G. M. Faustino, L. H. Figueiredo
We present an algorithm that creates a mosaic effect for an image in an adaptive and automatic fashion. The algorithm is automatic because it does not need user intervention, except for the choice of a couple of parameters. The algorithm is adaptive because it creates tiles whose sizes are adapted to the features of the image. This is achieved by using a centroidal Voronoi diagram with a density function that emphasizes image features.
{"title":"Simple Adaptive Mosaic Effects","authors":"G. M. Faustino, L. H. Figueiredo","doi":"10.1109/SIBGRAPI.2005.46","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.46","url":null,"abstract":"We present an algorithm that creates a mosaic effect for an image in an adaptive and automatic fashion. The algorithm is automatic because it does not need user intervention, except for the choice of a couple of parameters. The algorithm is adaptive because it creates tiles whose sizes are adapted to the features of the image. This is achieved by using a centroidal Voronoi diagram with a density function that emphasizes image features.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123415569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present in this work a new method for the tomographic reconstruction with Poisson noise corrupted projections. The reconstruction method is a hybrid estimation theoretic-POCS (Projection Onto Convex Sets) method performed by first estimating the noisy projections using Anscombe Transformation, Discrete Wavelet Transform and pointwise Wiener filter and subsequently reconstructing the images through a parallel POCS method. The use of a previous filtering of the projections imposes a tighter restriction on the observation of the POCS method, allowing a better reconstruction, with a very little increase in computational cost.
{"title":"A Hybrid Estimation Theoretic-POCS Method for Tomographic Image Reconstruction","authors":"F. V. Salina, N. Mascarenhas","doi":"10.1109/SIBGRAPI.2005.4","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.4","url":null,"abstract":"We present in this work a new method for the tomographic reconstruction with Poisson noise corrupted projections. The reconstruction method is a hybrid estimation theoretic-POCS (Projection Onto Convex Sets) method performed by first estimating the noisy projections using Anscombe Transformation, Discrete Wavelet Transform and pointwise Wiener filter and subsequently reconstructing the images through a parallel POCS method. The use of a previous filtering of the projections imposes a tighter restriction on the observation of the POCS method, allowing a better reconstruction, with a very little increase in computational cost.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"211 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115943804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.14
C. Morimoto, T. T. Santos, Adriano S. Muniz
This paper introduces a fast, robust and accurate iris segmentation technique based on active lighting. The geometry of the light sources, a single camera and the eye facilitates the detection of the pupil and the automatic selection of the most appropriate image for biometric identification from the video stream, minimizing the effects of noise, distortion and occlusion during the image acquisition process. Two near infrared (NIR) light sources (that are invisible to the human eye) are synchronized with the video signal. One of the light sources is placed near the optical axis of the camera, and generates a bright pupil image. The second light is placed off-axis, generating dark pupil images. These two images can be easily combined to segment the pupil region, and the corneal reflection of the light sources can be used to select best quality images. The pupil position is then used to segment the iris and eyelids using a coarse-to-fine strategy. Experimental results with a real-time prototype show the quality of the iris segmentation.
{"title":"Automatic Iris Segmentation Using Active Near Infra Red Lighting","authors":"C. Morimoto, T. T. Santos, Adriano S. Muniz","doi":"10.1109/SIBGRAPI.2005.14","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.14","url":null,"abstract":"This paper introduces a fast, robust and accurate iris segmentation technique based on active lighting. The geometry of the light sources, a single camera and the eye facilitates the detection of the pupil and the automatic selection of the most appropriate image for biometric identification from the video stream, minimizing the effects of noise, distortion and occlusion during the image acquisition process. Two near infrared (NIR) light sources (that are invisible to the human eye) are synchronized with the video signal. One of the light sources is placed near the optical axis of the camera, and generates a bright pupil image. The second light is placed off-axis, generating dark pupil images. These two images can be easily combined to segment the pupil region, and the corneal reflection of the light sources can be used to select best quality images. The pupil position is then used to segment the iris and eyelids using a coarse-to-fine strategy. Experimental results with a real-time prototype show the quality of the iris segmentation.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"246 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123010986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.24
T. Lewiner, Cynthia O. L. Ferreira, M. Craizer, Ralph Teixeira
This work proposes a scheme for multi-resolution representation of union of balls in the plane. This representation is inspired by curvature motion for smooth curves. More precisely, the proposed evolution of centres and radii of the balls are based on equations of evolution of the medial axis of a curve that performs curvature motion. The results obtained are very close to the pixel approximation of curvature motion.
{"title":"Curvature Motion for Union of Balls","authors":"T. Lewiner, Cynthia O. L. Ferreira, M. Craizer, Ralph Teixeira","doi":"10.1109/SIBGRAPI.2005.24","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.24","url":null,"abstract":"This work proposes a scheme for multi-resolution representation of union of balls in the plane. This representation is inspired by curvature motion for smooth curves. More precisely, the proposed evolution of centres and radii of the balls are based on equations of evolution of the medial axis of a curve that performs curvature motion. The results obtained are very close to the pixel approximation of curvature motion.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132188953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.36
E. F. Morais, M. Campos, F. Pádua, R. Carceroni
In this paper we study the use of computer vision techniques for for underwater visual tracking and counting of fishes in vivo. The methodology is based on the application of a Bayesian filtering technique that enables tracking of objects whose number may vary over time. Unlike existing fish-counting methods, this approach provides adequate means for the acquisition of relevant information about characteristics of different fish species such as swimming ability, time of migration and peak flow rates. The system is also able to estimate fish trajectories over time, which can be further used to study their behaviors when swimming in regions of interest. Our experiments demonstrate that the proposed method can operate reliably under severe environmental changes (e.g. variations in water turbidity) and handle problems such as occlusions or large inter-frame motions. The proposed approach was successfully validated with real-world video streams, achieving overall accuracy as high as 81%.
{"title":"Particle Filter-Based Predictive Tracking for Robust Fish Counting","authors":"E. F. Morais, M. Campos, F. Pádua, R. Carceroni","doi":"10.1109/SIBGRAPI.2005.36","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.36","url":null,"abstract":"In this paper we study the use of computer vision techniques for for underwater visual tracking and counting of fishes in vivo. The methodology is based on the application of a Bayesian filtering technique that enables tracking of objects whose number may vary over time. Unlike existing fish-counting methods, this approach provides adequate means for the acquisition of relevant information about characteristics of different fish species such as swimming ability, time of migration and peak flow rates. The system is also able to estimate fish trajectories over time, which can be further used to study their behaviors when swimming in regions of interest. Our experiments demonstrate that the proposed method can operate reliably under severe environmental changes (e.g. variations in water turbidity) and handle problems such as occlusions or large inter-frame motions. The proposed approach was successfully validated with real-world video streams, achieving overall accuracy as high as 81%.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125153939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.31
A. Cuadros-Vargas, L. G. Nonato, R. Minghim, Tiago Etiene
Generating triangular meshes from images is a task important to many applications. Usually, techniques that can do that either take as starting point a segmented image or generate a mesh without distinguishing different structures contained in the image. In both cases the results can be satisfactory for a number of applications, but the pre-segmentation and the absence of well defined structures imply in difficulties using the resulting mesh for simulations. Furthermore, guarantee of good quality meshes is also a common problem in previous results. In this work we present a new technique for mesh generation that handles these problems well. First, it eliminates the need for pre-processing by building the segmentation into the mesh generation process. Second, the mesh generation process takes into acount the quality of the mesh elements, producing as result meshes of better quality than previous techniques.
{"title":"Imesh: An Image Based Quality Mesh Generation Technique","authors":"A. Cuadros-Vargas, L. G. Nonato, R. Minghim, Tiago Etiene","doi":"10.1109/SIBGRAPI.2005.31","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.31","url":null,"abstract":"Generating triangular meshes from images is a task important to many applications. Usually, techniques that can do that either take as starting point a segmented image or generate a mesh without distinguishing different structures contained in the image. In both cases the results can be satisfactory for a number of applications, but the pre-segmentation and the absence of well defined structures imply in difficulties using the resulting mesh for simulations. Furthermore, guarantee of good quality meshes is also a common problem in previous results. In this work we present a new technique for mesh generation that handles these problems well. First, it eliminates the need for pre-processing by building the segmentation into the mesh generation process. Second, the mesh generation process takes into acount the quality of the mesh elements, producing as result meshes of better quality than previous techniques.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129153219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.25
M. S. Nery, A.M.C. Machado, M. Campos, F. Pádua, R. Carceroni, J. P. Queiroz-Neto
We present a novel fish classification methodology based on a robust feature selection technique. Unlike existing works for fish classification, which propose descriptors and do not analyze their individual impacts in the whole classification task, we propose a general set of features and their correspondent weights that should be used as a priori information by the classifier. In this sense, instead of studying techniques for improving the classifiers structure itself, we consider it as a "black box" and focus our research in the determination of which input information must bring a robust fish discrimination. All the experiments were performed with fish species of Rio Grande river in Minas Gerais, Brazil. This work has been developed as part of a wider research [3], which has as main goal the development of effective fish ladders for the Brazilian dams.
{"title":"Determining the Appropriate Feature Set for Fish Classification Tasks","authors":"M. S. Nery, A.M.C. Machado, M. Campos, F. Pádua, R. Carceroni, J. P. Queiroz-Neto","doi":"10.1109/SIBGRAPI.2005.25","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.25","url":null,"abstract":"We present a novel fish classification methodology based on a robust feature selection technique. Unlike existing works for fish classification, which propose descriptors and do not analyze their individual impacts in the whole classification task, we propose a general set of features and their correspondent weights that should be used as a priori information by the classifier. In this sense, instead of studying techniques for improving the classifiers structure itself, we consider it as a \"black box\" and focus our research in the determination of which input information must bring a robust fish discrimination. All the experiments were performed with fish species of Rio Grande river in Minas Gerais, Brazil. This work has been developed as part of a wider research [3], which has as main goal the development of effective fish ladders for the Brazilian dams.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"352 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116675064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.28
C. Hofsetz, N. Max
This paper presents a method to accelerate algorithms that need a correct and complete visibility ordering of their data for rendering. The technique works by first pre-sorting primitives using three lists - one for each axis, and then combining them using graphics hardware, by either clipping the projected primitives while rendering, according to the current list being processed, or by rendering each list to a texture and merging the textures in the end. We show that our algorithm works by applying it to the splatting technique using several types of rendering, including classic splatting and volume rendering.
{"title":"Hardware-Assisted Visibility Ordering for Point-Based and Volume Rendering","authors":"C. Hofsetz, N. Max","doi":"10.1109/SIBGRAPI.2005.28","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.28","url":null,"abstract":"This paper presents a method to accelerate algorithms that need a correct and complete visibility ordering of their data for rendering. The technique works by first pre-sorting primitives using three lists - one for each axis, and then combining them using graphics hardware, by either clipping the projected primitives while rendering, according to the current list being processed, or by rendering each list to a texture and merging the textures in the end. We show that our algorithm works by applying it to the splatting technique using several types of rendering, including classic splatting and volume rendering.","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116042667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-10-09DOI: 10.1109/SIBGRAPI.2005.39
J. Gambini, M. Mejail, J. Jacobo-Berlles, A. Frery
In this paper a new approach to polarimetric Synthetic Aperture Radar (SAR) image region boundary detection is presented. It is based on a new model for polarimetric SAR data and the use of B-Spline active contours for image segmentation. In order to detect the boundary for a region, an initial B-Spline curve is specified and the proposed algorithm uses a deformable contours technique to find the boundary. In doing this, the statistical parameters of the polarimetric G^H model for the data are estimated, in order to find the transition points between the region being segmented and the surrounding area. This algorithm can be regarded as a local one, in the sense that it works on the region to be segmented instead of on the whole image
{"title":"Polarimetric SAR Region Boundary Detection Using B-Spline Deformable Countours under the G^H Model","authors":"J. Gambini, M. Mejail, J. Jacobo-Berlles, A. Frery","doi":"10.1109/SIBGRAPI.2005.39","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2005.39","url":null,"abstract":"In this paper a new approach to polarimetric Synthetic Aperture Radar (SAR) image region boundary detection is presented. It is based on a new model for polarimetric SAR data and the use of B-Spline active contours for image segmentation. In order to detect the boundary for a region, an initial B-Spline curve is specified and the proposed algorithm uses a deformable contours technique to find the boundary. In doing this, the statistical parameters of the polarimetric G^H model for the data are estimated, in order to find the transition points between the region being segmented and the surrounding area. This algorithm can be regarded as a local one, in the sense that it works on the region to be segmented instead of on the whole image","PeriodicalId":193103,"journal":{"name":"XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127648507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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