High Resolution Surface Reconstruction of Cultural Heritage Objects Using Shape from Polarization Method

Nowadays, three-dimensional reconstruction is used in various fields like computer vision, computer graphics, mixed reality and digital twin. The three- dimensional reconstruction of cultural heritage objects is one of the most important applications in this area which is usually accomplished by close range photogrammetry. The problem here is that the images are often noisy, and the dense image matching method has significant limitations to reconstruct the geometric details of cultural heritage objects in practice. Therefore, displaying high-level details in three-dimensional models, especially for cultural heritage objects, is a severe challenge in this field. In this paper, the shape from polarization method has been investigated, a passive method with no drawbacks of active methods. In this method, the resolution of the depth maps can be dramatically increased using the information obtained from the polarization light by rotating a linear polarizing filter in front of a digital camera. Through these polarized images, the surface details of the object can be reconstructed locally with high accuracy. The fusion of polarization and photogrammetric methods is an appropriate solution for achieving high resolution three-dimensional reconstruction. The surface reconstruction assessments have been performed visually and quantitatively. The evaluations showed that the proposed method could significantly reconstruct the surfaces' details in the three-dimensional model compared to the photogrammetric method with 10 times higher depth resolution

Quick-Time VRTM: when medical education meets virtual reality

Learning medicine is a difficult process to undertake, partially due to the complexity of the subject and limitations of traditional methods of teaching (lectures, textbooks, laboratory and anatomical dissections). These resources have been effective for decades, even though presenting intrinsic drawbacks. Textbooks are non-interactive education tools and do not provide any three dimensional experience. Cadaver dissection is an invaluable aid to learn anatomy. It provides an immersive, interactive experience allied with an inimitable tactile feedback. However, it has several limitations, including availability of specimens, costs and a substantial time commitment. Computer based virtual reality methods may overcome these drawbacks and provide interesting alternatives for medical training. Technological advances have generated great expectations for the use of computer-based virtual reality technologies in medical education, mainly anatomy and surgery. However, these Virtual Reality tools for general medical education are expensive due to the equipment necessary to create highly detailed, immersive three-dimensional image environments with real time friendly user interactivity. The concepts of Virtual Reality methods that generate immersive environments, as well as those that create simulated objects with interactive viewing features may be contemplated by the QuickTimeTM which is one of the technologies that can be successfully used for interactive, photorealistic displaying of medical images (radiological, anatomical and histological) and interaction on current generation of personal computers at a low and accessible cost. In this paper, the authors provide an overview of the Quick Time Virtual Reality methods aimingLearning medicine is a difficult process to undertake, partially due to the complexity of the subject and limitations of traditional methods of teaching (lectures, textbooks, laboratory and anatomical dissections). These resources have been effective for decades, even though presenting intrinsic drawbacks. Textbooks are non-interactive education tools and do not provide any three dimensional experience. Cadaver dissection is an invaluable aid to learn anatomy. It provides an immersive, interactive experience allied with an inimitable tactile feedback. However, it has several limitations, including availability of specimens, costs and a substantial time commitment. Computer based virtual reality methods may overcome these drawbacks and provide interesting alternatives for medical training. Technological advances have generated great expectations for the use of computer-based virtual reality technologies in medical education, mainly anatomy and surgery. However, these Virtual Reality tools for general medical education are expensive due to the equipment necessary to create highly detailed, immersive three-dimensional image environments with real time friendly user interactivity. The concepts of Virtual Reality methods that generate immersive environments, as well as those that create simulated objects with interactive viewing features may be contemplated by the QuickTimeTM which is one of the technologies that can be successfully used for interactive, photorealistic displaying of medical images (radiological, anatomical and histological) and interaction on current generation of personal computers at a low and accessible cost. In this paper, the authors provide an overview of the Quick Time Virtual Reality methods aiming to introduce them to medical educators and illustrate their application on medical training

Tool for 3D analysis and segmentation of retinal layers in volumetric SD-OCT images

With the development of optical coherence tomography in the spectral domain (SD-OCT), it is now possible to quickly acquire large volumes of images. Typically analyzed by a specialist, the processing of the images is quite slow, consisting on the manual marking of features of interest in the retina, including the determination of the position and thickness of its different layers. This process is not consistent, the results are dependent on the clinician perception and do not take advantage of the technology, since the volumetric information that it currently provides is ignored. Therefore is of medical and technological interest to make a three-dimensional and automatic processing of images resulting from OCT technology. Only then we will be able to collect all the information that these images can give us and thus improve the diagnosis and early detection of eye pathologies. In addition to the 3D analysis, it is also important to develop visualization tools for the 3D data. This thesis proposes to apply 3D graphical processing methods to SD-OCT retinal images, in order to segment retinal layers. Also, to analyze the 3D retinal images and the segmentation results, a visualization interface that allows displaying images in 3D and from different perspectives is proposed. The work was based on the use of the Medical Imaging Interaction Toolkit (MITK), which includes other open-source toolkits. For this study a public database of SD-OCT retinal images will be used, containing about 360 volumetric images of healthy and pathological subjects. The software prototype allows the user to interact with the images, apply 3D filters for segmentation and noise reduction and render the volume. The detection of three surfaces of the retina is achieved through intensity-based edge detection methods with a mean error in the overall retina thickness of 3.72 0.3 pixels

Visualization of spectral images

Spectral image sensors provide images with a large number of contiguous spectral channels per pixel. Visualization of these huge data sets is not a straightforward issue. There are three principal ways in which spectral data can be presented; as spectra, as image and in feature space. This paper describes several visualization methods and their suitability in the different steps in the research cycle. Combinations of the three presentation methods and dynamic interaction between them, adds significant to the usability. Examples of some software implementations are given. Also the application of volume visualization methods to display spectral images is shown to be valuabl

Perceptual Display Strategies of Hyperspectral Imagery Based on PCA and ICA

This study investigated appropriate methodologies for displaying hyperspectral imagery based on knowledge of human color vision as applied to Hyperion and AVIRIS data. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) were used to reduce the data dimensionality in order to make the data more amenable to visualization in three-dimensional color space. In addition, these two methods were chosen because of their underlying relationships to the opponent color model of human color perception. PCA and ICA-based visualization strategies were then explored by mapping the first three PCs or ICs to several opponent color spaces including CIELAB, HSV, YCrCb, and YUV. The gray world assumption, which states that given an image with sufficient amount of color variations, the average color should be gray, was used to set the mapping origins. The rendered images are well color balanced and can offer a first look capability or initial classification for a wide variety of spectral scenes

Inner ear morphology in the Atlantic molly Poecilia mexicana

Fishes show an amazing diversity in hearing abilities, inner ear structures, and otolith morphology. Inner ear morphology, however, has not yet been investigated in detail in any member of the diverse order Cyprinodontiformes. We, therefore, studied the inner ear of the cyprinodontiform freshwater fish Poecilia mexicana by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods. P. mexicana occurs in different ecotypes, enabling us to study the intra-specific variability (on a qualitative basis) of fish from regular surface streams, and the Cueva del Azufre, a sulfidic cave in southern Mexico. The inner ear of Poecilia mexicana displays a combination of several remarkable features. The utricle is connected rostrally instead of dorso-rostrally to the saccule, and the macula sacculi, therefore, is very close to the utricle. Moreover, the macula sacculi possesses dorsal and ventral bulges. The two studied ecotypes of P. mexicana showed variation mainly in the shape and curvature of the macula lagenae, in the curvature of the macula sacculi, and in the thickness of the otolithic membrane. Our study for the first time provides detailed insights into the auditory periphery of a cyprinodontiform inner ear and thus serves a basis--especially with regard to the application of 3D techniques--for further research on structure-function relationships of inner ears within the species-rich order Cyprinodontiformes. We suggest that other poeciliid taxa, or even other non-poeciliid cyprinodontiforms, may display similar inner ear morphologies as described here