KEYWORDS: Brain, 3D metrology, Neuroimaging, Image processing, 3D image processing, Photogrammetry, Automatic tracking, 3D modeling, Cameras, 3D acquisition
This paper presents the preliminary results of applying multi image photogrammetric techniques for the three-dimensional monitoring of the intraoperative brainshift. The "brainshift" is the motion of cerebral structures occurring in neurosurgery after the craniotomy (opening of the skull in order to access the brain for surgical repair). The causes of this effect are mainly the changes of pressure and loss of cerebrospinal liquid. The phenomenon of brainshift can influence negatively the planning and execution of neurosurgical intervention. A research project at the Clinic of Neuroradiology and Neurosurgery of the Medical University of Innsbruck (Austria) aims at the quantification of the intraoperative brainshift by means of photogrammetry. The goals of the project are: (i) the development of a multi-image photogrammetric system for the quantitative monitoring of intraoperative brainshift by means of 3D measurements performed on the surface of the brain during neurosurgery after craniotomy, (ii) transformation of the pre-operative performed MR and CT datasets in function of the quantified intra-operative brainshift. This paper presents the proposed multi-image photogrammetric system, as well as, the first results achieved, in collaboration with Hometrica Consulting, for the automatic 3D measurement and tracking of selected points on the surface of the brain.
KEYWORDS: 3D modeling, Scanners, 3D metrology, 3D scanning, Laser scanners, 3D image processing, Data modeling, Systems modeling, Head, Projection systems
This paper presents an overview of 3D body scanning technologies with applications to the fashion and apparel industry.
Complete systems for the digitization of the human body exist since more than fifteen years. One of the main users of
this technology with application in the textile field was the military industry. In fact, body scanning technology is being
successfully employed since many years in military bases for a fast selection of the correct size of uniforms for the entire
staff. Complete solutions were especially developed for this field of application.
Many different research projects were issued for the exploitation of the same technology in the commercial field.
Experiments were performed and start-up projects are to time running in different parts of the world by installing full
body scanning systems in various locations such as shopping malls, boutiques or dedicated scanning centers. Everything
is actually ready to be exploited and all the required hardware, software and solutions are available: full body scanning
systems, software for the automatic and reliable extraction of body measurements, e-kiosk and web solutions for the
presentation of garments, high-end and low-end virtual-try-on systems. However, complete solutions in this area have
still not yet found the expected commercial success. Today, with the on-going large cost reduction given by the
appearance of new competitors, methods for digitization of the human body becomes more interesting for the fashion
and apparel industry. Therefore, a large expansion of these technologies is expected in the near future.
To date, different methods are used commercially for the measurement of the human body. These can be divided into
three major distinguished groups: laser-scanning, projection of light patterns, combination modeling and image
processing. The different solutions have strengths and weaknesses that profile their suitability for specific applications.
This paper gives an overview of their differences and characteristics and expresses clues for the selection of the adequate
method. A special interest is given to practical examples of the commercial exploitation of human body digitization with
applications to the fashion and apparel industry.
This paper presents an overview of the different 3D surface digitization technologies commercially available in the European market. The solutions for 3D surface measurement offered by major European companies can be divided into different groups depending on various characteristics, such as technology (e.g. laser scanning, white light projection), system construction (e.g. fix, on CMM/robot/arm) or measurement type (e.g. surface scanning, profile scanning). Crossing between the categories is possible, however, the majority of commercial products can be divided into the following groups: (a) laser profilers mounted on CMM, (b) portable coded light projection systems, (c) desktop solutions with laser profiler or coded light projectin system and multi-axes platform, (d) laser point measurement systems where both sensor and object move, (e) hand operated laser profilers, hand held laser profiler or point measurement systems, (f) dedicated systems. This paper presents the different 3D surface digitization technologies and describes them with their advantages and disadvantages. Various examples of their use are shown for different application fields. A special interest is given to applications regarding the 3D surface measurement of the human body.
In this paper we report on the historic development of human body digitization and on the actual state of commercially available technology.
Complete systems for the digitization of the human body exist since more than ten years. One of the main users of this technology was the entertainment industry. Every new movie excited with attractive visual effects, but only few people knew that the most thrilling cuts were realized by using virtual persons. The faces and bodies of actors were digitized and the "virtual twin" replaced the actor in the movie. Nowadays, the state of the human body digitization is so high that it is not possible any more to distinguish the real actor from the virtual one. Indeed, for the rush technical development has to be thanked the movie industry, which was one of the strong economic motors for this technology.
Today, with the possibility of a massive cost reduction given by new technologies, methods for digitization of the human body are used also in other fields of application, such as ergonomics, medical applications, computer games, biometry and anthropometrics. With the time, this technology becomes interesting also for sport, fitness, fashion and beauty. A large expansion of human body digitization is expected in the near future.
To date, different technologies are used commercially for the measurement of the human body. They can be divided into three distinguished groups:laser-scanning, projection of light patterns, combination modeling and image processing. The different solutions have strengths and weaknesses that profile their suitability for specific applications. This paper gives an overview of their differences and characteristics and expresses clues for the selection of the adequate method. Practical examples of commercial exploitation of human body digitization are also presented and new interesting perspectives are introduced.
KEYWORDS: Image processing, Video, Calibration, Cameras, 3D modeling, 3D image processing, Imaging systems, Detection and tracking algorithms, Systems modeling, 3D metrology
In this paper is presented a method to capture the motion of the human body from multi image video sequences without using markers. The process is composed of five steps: acquisition of video sequences, calibration of the system, surface measurement of the human body for each frame, 3-D surface tracking and tracking of key points. The image acquisition system is currently composed of three synchronized progressive scan CCD cameras and a frame grabber which acquires a sequence of triplet images. Self calibration methods are applied to gain exterior orientation of the cameras, the parameters of internal orientation and the parameters modeling the lens distortion. From the video sequences, two kinds of 3-D information are extracted: a three-dimensional surface measurement of the visible parts of the body for each triplet and 3-D trajectories of points on the body. The approach for surface measurement is based on multi-image matching, using the adaptive least squares method. A full automatic matching process determines a dense set of corresponding points in the triplets. The 3-D coordinates of the matched points are then computed by forward ray intersection using the orientation and calibration data of the cameras. The tracking process is also based on least squares matching techniques. Its basic idea is to track triplets of corresponding points in the three images through the sequence and compute their 3-D trajectories. The spatial correspondences between the three images at the same time and the temporal correspondences between subsequent frames are determined with a least squares matching algorithm. The results of the tracking process are the coordinates of a point in the three images through the sequence, thus the 3-D trajectory is determined by computing the 3-D coordinates of the point at each time step by forward ray intersection. Velocities and accelerations are also computed. The advantage of this tracking process is twofold: it can track natural points, without using markers; and it can track local surfaces on the human body. In the last case, the tracking process is applied to all the points matched in the region of interest. The result can be seen as a vector field of trajectories (position, velocity and acceleration). The last step of the process is the definition of selected key points of the human body. A key point is a 3-D region defined in the vector field of trajectories, whose size can vary and whose position is defined by its center of gravity. The key points are tracked in a simple way: the position at the next time step is established by the mean value of the displacement of all the trajectories inside its region. The tracked key points lead to a final result comparable to the conventional motion capture systems: 3-D trajectories of key points which can be afterwards analyzed and used for animation or medical purposes.
Modeling and measurement of the human face have been increasing by importance for various purposes. Laser scanning, coded light range digitizers, image-based approaches and digital stereo photogrammetry are the used methods currently employed in medical applications, computer animation, video surveillance, teleconferencing and virtual reality to produce three dimensional computer models of the human face. Depending on the application, different are the requirements. Ours are primarily high accuracy of the measurement and automation in the process. The method presented in this paper is based on multi-image photogrammetry. The equipment, the method and results achieved with this technique are here depicted. The process is composed of five steps: acquisition of multi-images, calibration of the system, establishment of corresponding points in the images, computation of their 3-D coordinates and generation of a surface model. The images captured by five CCD cameras arranged in front of the subject are digitized by a frame grabber. The complete system is calibrated using a reference object with coded target points, which can be measured fully automatically. To facilitate the establishment of correspondences in the images, texture in the form of random patterns can be projected from two directions onto the face. The multi-image matching process, based on a geometrical constrained least squares matching algorithm, produces a dense set of corresponding points in the five images. Neighborhood filters are then applied on the matching results to remove the errors. After filtering the data, the three-dimensional coordinates of the matched points are computed by forward intersection using the results of the calibration process; the achieved mean accuracy is about 0.2 mm in the sagittal direction and about 0.1 mm in the lateral direction. The last step of data processing is the generation of a surface model from the point cloud and the application of smooth filters. Moreover, a color texture image can be draped over the model to achieve a photorealistic visualization. The advantage of the presented method over laser scanning and coded light range digitizers is the acquisition of the source data in a fraction of a second, allowing the measurement of human faces with higher accuracy and the possibility to measure dynamic events like the speech of a person.
In cooperation of the Department of Veterinary Surgery at the University of Zurich and the Institute of Geodesy and Photogrammetry at ETCH Zurich, a system for the measurement of 3D deformations of hose hooves under different load conditions has been developed. The paper describes the basic design of the system, discusses a calibration strategy and presents first results.
Currently three different angiographic techniques are used to measure and visualize major blood vessels in the human body: magnetic resonance (MR), computer tomography (CT) and digital subtraction (DS) angiography. Although these imaging systems have been already qualitatively compared, a quantitative assessment is still missing. The goal of this work is to provide a tool enabling a quantitative comparison of the three imaging techniques to an unbiased reference. MR-, CT- and DS-angiographies are first performed on a corpse. Then, a casting of the abdominal aorta and its main branches is prepared, removed from the body and measured with photogrammetric methods. The elongated and thin cast is fixed in a 3D frame with 16 signalized small spheres used for calibration and orientation purposes. Three fixed CCD cameras acquire triplets of images of the casting, which is turned in 8 positions. In order to perform multi-image matching, an artificial random texture is projected onto the object. For each triplet of images, a semi-automated matching process based on least squares matching determines a dense set of corresponding points. Their 3D coordinates are then computed by forward intersection, with a mean standard deviation of about 0.2 mm. The result from the 8 positions are merged together into a 3D point cloud and an adequate filter is applied to remove the noise and the redundancy in the overlapping regions. The paper depicts the basic design of the system and the measurement methods. Furthermore some preliminary results are presented.
In this paper, we show that, given video sequences of a moving person acquired with a multi-camera system, we can track joint locations during the movement and recover shape information. We outline techniques for fitting a simplified model to the noisy 3-D data extracted from the images and a new tracking process based on least squares matching is presented. The recovered shape and motion parameters can be used to either reconstruct the original sequence or to allow other animation models to mimic the subject's actions. Our ultimate goal is to automate the process of building complete and realistic animation models of humans, given a set of video sequences.
Today's consumer market digital camcorders offer features which make them appear quite interesting devices for virtual reality data capture. The paper compares a digital camcorder with an analogue camcorder and a machine vision type CCD camera and discusses the suitability of these three cameras for virtual reality applications. Besides the discussion of technical features of the cameras, this includes a detailed accuracy test in order to define the range of applications. In combination with the cameras, three different framegrabbers are tested. The geometric accuracy potential of all three cameras turned out to be surprisingly large, and no problems were noticed in the radiometric performance. On the other hand, some disadvantages have to be reported: from the photogrammetrists point of view, the major disadvantage of most camcorders is the missing possibility to synchronize multiple devices, limiting the suitability for 3-D motion data capture. Moreover, the standard video format contains interlacing, which is also undesirable for all applications dealing with moving objects or moving cameras. Further disadvantages are computer interfaces with functionality, which is still suboptimal. While custom-made solutions to these problems are probably rather expensive (and will make potential users turn back to machine vision like equipment), this functionality could probably be included by the manufacturers at almost zero cost.
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