Three-dimensional Wire-frame Model Research Articles

Construction of 3D Wireframe Model in Problem of Converting Paper Drawing and Design Documentation into an Electronic Model of an Object

This work is devoted to various stages of the formation of a three-dimensional wireframe model when solving the problem of converting paper drawings into drawing-design documentation. The stages of obtaining geometric-graphic information by an application program and forming a three-dimensional skeleton model are considered in detail. The study of the temporal characteristics of the developed algorithm is also given.

Robust Model-Based Monocular Pose Initialization for Noncooperative Spacecraft Rendezvous

This work addresses the design and validation of a robust monocular vision-based pose initialization architecture for close-range onorbit-servicing and formation-flying applications. The aim is to rapidly determine the pose of a passive space resident object using its known three-dimensional wireframe model and a single low-resolution two-dimensional image collected on board the servicer spacecraft. In contrast to previous works, the proposed architecture is onboard executable and capable of estimating the pose of the client without the use of fiducial markers and without any a priori range measurements or state information. A novel feature detection method based on the filtering of the weak image gradients is used to identify the true edges of the client in the image, even in presence of the Earth in background. The detected features are synthesized using simple geometric constraints to dramatically reduce the search space of the feature correspondence problem, which is solved using the method. This approach is proven to be an order of magnitude faster than the state-of-the-art random sample consensus methods. A fast Newton–Raphson method that minimizes the fit error between corresponding image and model features is employed to refine the pose estimate and to resolve pose ambiguity. The proposed methodology is tested using actual space imagery collected during the PRISMA mission at about a 700 km altitude and a 10 m interspacecraft separation.

Mathematical Model on the Visualization of Axis Straightness Errors

The fundamental theory on the visualization was determined, mathematical model on visualization of axis straightness errors was established. Used the theory of computer graphics and three-dimensional wireframe models, the display of extracted derived feature and associated derived feature on measured axle were achieved; Adopted axonometric projection transformation, the basic geometric shapes was realized; Adopted real space hidden method, the problem of geometrical graph hidden was solved. On the basis of theoretical study, LabWindows/CVI used as a software development platform, the software was developed to realize visualization of axis straightness errors.

Development of an X-ray real-time stereo imaging technique using synchrotron radiation

An X-ray stereo imaging system with synchrotron radiation was developed at BL20B2, SPring-8. A portion of a wide X-ray beam was Bragg-reflected by a silicon crystal to produce an X-ray beam which intersects with the direct X-ray beam. Samples were placed at the intersection point of the two beam paths. X-ray stereo images were recorded simultaneously by a detector with a large field of view placed close to the sample. A three-dimensional wire-frame model of a sample was created from the depth information that was obtained from the lateral positions in the stereo image. X-ray stereo angiography of a mouse femoral region was performed as a demonstration of real-time stereo imaging. Three-dimensional arrangements of the femur and blood vessels were obtained.

Study on fiber openness using image processing technique

It has long been recognized that the quality of yarn depends on the performance of the processes during spinning. This work relates to evaluating the opening action of blow room and aims to develop the openness tester for measuring the openness of fibrous assembly based on the image processing technique. A sequence of shapes taken using black background for high image clarity as radial projections at a fixed angular interval was recorded for image processing for each object. Each shape was treated as a slice of the cross-section of the object taken at a specific angular position. Fast 8-point connectivity, clockwise contour-tracing algorithm was implemented in MATLAB to extract the boundary points on the shape of each slice. With known angular position and the coordinates of boundary points, a three-dimensional wire-frame model has been created for three-dimensional visualization and volumetric measurements. The relation between the apparent volume and the weight of fibrous assembly has been studied. Finally, an apparent specific volume of fibrous assembly has been calculated as a measure of openness of fibrous assembly. The conventional test method (i.e. beaker method) and its openness index were compared with the apparent specific volume of fibrous assembly. Both the methods have shown a similar trend of openness of material. This work has further been extended in comparison of different types of modern blow room lines.

Area and volume measurements of objects with irregular shapes using multiple silhouettes

Surface area and volume measurements provide important information for agriculture and food-processing applications. A machine vision system that uses a nondestructive method to measure volume and surface area of objects with irregular shapes is presented in this paper. The system first takes a series of silhouettes of the object from different directions by rotating the object at a fixed angular interval. The boundary points of each image are then extracted to construct a silhouette. A three-dimensional wire-frame model of the object can be reconstructed by integrating silhouettes obtained from different view angles. Surface area and volume can then be measured by means of surface fitting and approximation on the wire-frame model. System calibration and surface approximation were two major challenges for the design of this machine vision system. A unique centerline calibration method is introduced in this paper. Surface approximation and calculation are also discussed. Examples of applications in agriculture and food processing using this vision system for surface area measurement are included, and its accuracy is verified.

Lifelike talking faces for interactive services

Lifelike talking faces for interactive services are an exciting new modality for man-machine interactions. Recent developments in speech synthesis and computer animation enable the real-time synthesis of faces that look and behave like real people, opening opportunities to make interactions with computers more like face-to-face conversations. This paper focuses on the technologies for creating lifelike talking heads, illustrating the two main approaches: model-based animations and sample-based animations. The traditional model-based approach uses three-dimensional wire-frame models, which can be animated from high-level parameters such as muscle actions, lip postures, and facial expressions. The sample-based approach, on the other hand, concatenates segments of recorded videos, instead of trying to model the dynamics of the animations in detail. Recent advances in image analysis enable the creation of large databases of mouth and eye images, suited for sample-based animations. The sample-based approach tends to generate more naturally looking animations at the expense of a larger size and less flexibility than the model-based animations. Beside lip articulation, a talking head must show appropriate head movements, in order to appear natural. We illustrate how such visual prosody is analyzed and added to the animations. Finally, we present four applications where the use of face animation in interactive services results in engaging user interfaces and an increased level of trust between user and machine. Using an RTP-based protocol, face animation can be driven with only 800 bits/s in addition to the rate for transmitting audio.

Interactive Computer Simulations of Knee-replacement Surgery

Current surgical training programs in the United States are based on an apprenticeship model. This model is outdated because it does not provide conceptual scaffolding, promote collaborative learning, or offer constructive reinforcement. Our objective was to create a more useful approach by preparing students and residents for operative cases using interactive computer simulations of surgery. Total-knee-replacement surgery (TKR) is an ideal procedure to model on the computer because there is a systematic protocol for the procedure. Also, this protocol is difficult to learn by the apprenticeship model because of the multiple instruments that must be used in a specific order. We designed an interactive computer tutorial to teach medical students and residents how to perform knee-replacement surgery. We also aimed to reinforce the specific protocol of the operative procedure. Our final goal was to provide immediate, constructive feedback. We created a computer tutorial by generating three-dimensional wire-frame models of the surgical instruments. Next, we applied a surface to the wire-frame models using three-dimensional modeling. Finally, the three-dimensional models were animated to simulate the motions of an actual TKR. The tutorial is a step-by-step tutorial that teaches and tests the correct sequence of steps in a TKR. The student or resident must select the correct instruments in the correct order. The learner is encouraged to learn the stepwise surgical protocol through repetitive use of the computer simulation. Constructive feedback is acquired through a grading system, which rates the student's or resident's ability to perform the task in the correct order. The grading system also accounts for the time required to perform the simulated procedure. We evaluated the efficacy of this teaching technique by testing medical students who learned by the computer simulation and those who learned by reading the surgical protocol manual. Both groups then performed TKR on manufactured bone models using real instruments. Their technique was graded with the standard protocol. The students who learned on the computer simulation performed the task in a shorter time and with fewer errors than the control group. They were also more engaged in the learning process. Surgical training programs generally lack a consistent approach to preoperative education related to surgical procedures. This interactive computer tutorial has allowed us to make a quantum leap in medical student and resident teaching in our orthopedic department because the students actually participate in the entire process. Our technique provides a linear, sequential method of skill acquisition and direct feedback, which is ideally suited for learning stepwise surgical protocols. Since our initial evaluation has shown the efficacy of this program, we have implemented this teaching tool into our orthopedic curriculum. Our plans for future work with this simulator include modeling procedures involving other anatomic areas of interest, such as the hip and shoulder.

Three-dimensional reconstructions of normal and aneurysmatic left ventricles in vivo using transesophageal echocardiography

Objective: To perform three-dimensional surface reconstructions to provide spatial delineations of a normal and an aneurysmatic left ventricle, using transesophageal echocardiography. Design: Prospective study. Setting: University hospital. Participants: Eight patients in cardiogenic shock admitted to the intensive care unit and two patients undergoing surgery with general anesthesia. Interventions: Using a multiplane transesophageal echocardiography probe, nine echocardiographic cross-sectional images of the heart at approximately 20° angular increments were obtained from midesophageal level in each patient for three-dimensional surface reconstructions. Multiple determinations of cardiac output using the thermodilution principle were also made in each patient to verify the accuracy of three-dimensional data sets. Measurements and Main Results: End-diastolic and end-systolic volumes were determined from three-dimensional data sets using the disc-summation method. Stroke volume was derived as the difference between end-diastolic and end-systolic volumes. Stroke volume was also calculated from thermodilution cardiac output measurements and heart rate. Correlation and limits of agreement between stroke volumes derived by the two methods were determined. Three-dimensional wire-frame models of a normal and an aneurysmatic left ventricle at end-systole were constructed from the nine echocardiographic cross-sectional images. Correlation coefficient between stroke volume derived from three-dimensional data sets using the disc-summation method and that measured by the thermodilution method was 0.91 ( p < 0.001). Wire-frame models reveal a normal symmetric cavity and an aneurysmal cavity in sharp relief. Conclusions: Three-dimensional surface reconstruction can be performed from multiple cross-sectional images obtained using an unmodified commercially available multiplane transesophageal echocardiography probe, to reveal the left ventricular cavity in sharp relief. High correlation between stroke volume calculated from three-dimensional data sets and that measured by the thermodilution method attests to the accuracy of the three-dimensional data sets.

Extraction of compound volumetric features from a three-dimensional wire frame model

This paper reports feature extraction strategy adopted in a computer aided process planning (CAPP) system developed for prismatic parts. Automatic extraction of compound volumetric features from three-dimensional wire frame models created in AutoCAD is discussed. Size, location and shape elements of a feature are used to recognize simple volumetric features like slots, steps, holes and pockets of different profile geometries by considering a hole as a basic feature. Compound volumetric features are defined as a combination of more than one simple volumetric feature such as slot-in-slot, slot-in-step, etc. Connectivity through common surface(s)/edges between member features is used to recognize compound features. The feature extractor output can be used for the generation of manufacturing instructions, namely set-up planning, process selection, sequence generation, machining parameters selection, etc. The unique feature of this system is that it works on a wire frame model of the part and needs no help from the user in extracting features. The working of the system and algorithms used for feature extraction are explained with examples.

Effects of presurgical orthopedic treatment in infants with complete bilateral cleft lip and palate.

To align the protruding premaxilla in infants with bilateral cleft lip and palate (BCLP), an intraoral appliance (i.e., Hotz plate) and an extraoral appliance consisting of a band covering the head and elastics are used as a presurgical orthopedic treatment in our clinic. The aim of this study was to analyze the configuration and position of the premaxilla and the vomer in infants with BCLP and to investigate the factors generating deviation and bending of the vomer and twisting of the premaxilla. Palatal casts were obtained serially from 10 infants with complete BCLP from 1 to 3 months of age. These casts were automatically measured using a highly accurate contact-type measuring apparatus. After three-dimensional wire frame models generated from the serial casts were automatically superimposed, the magnitude and direction of the shift were calculated. A discriminant analysis was used for investigation of predictor variables generating the twisting or bending vomer. The vomer was found to be bent in two infants and the premaxilla was twisted in three infants. In the infants whose vomers were bent, the magnitude of the posterior shift of the premaxilla was greater than that of the inferior shift. A discriminant analysis indicated that at 1 month of age, a greater inclination and a smaller deviation of the vomer and a longer distance between the cleft edges of the lateral segments had a tendency to be associated with bending of the vomer or twisting of the premaxilla.

Computer‐Aided Mapping of Vasopressin Neurons in the Hypothalamus of the Male Golden Hamster: Evidence of Magnocellular Neurons that do not Project to the Neurohypophysis

Abstract Vasopressin-sensitive neurons in the region of the anterior hypothalamus are necessary for the mediation of flank marking behavior in the Golden hamster. The precise nature of the vasopressinergic innervation to the anterior hypothalamus is unknown. In this study we seek to examine the potential sources of this innervation by mapping and counting the vasopressin-immunoreactive neurons that contribute to the hypothalamo-neurohypophysial system, and those that do not. Vasopressin-immunoreactive neurons in the hypothalamus were visualized by immunocytochemistry. Sections were mapped with a computer-aided microscope system, and labeled neurons counted. Two-dimensional maps were stacked into a three-dimensional wireframe model which could be manipulated for further examination. The average number of vasopressin neurons was 3,135, with over 60% of all perikarya localized to the lateral supraoptic nucleus. In a double-labeling study, neurons contributing to the hypothalamo-neurohypophysial system were retrogradely labeled by the injection of horseradish peroxidase into the neurohypophysis. The enzyme reaction product was visualized by treatment with tetramethylbenzidine followed by nickel-conjugated diaminobenzidine. Sections were subsequently stained for vasopressin by immunocytochemistry. Single- and double-stained neurons from serial sections were mapped and counted. Wireframe and contoured three-dimensional representations were generated. The average number of neurons projecting to the neurohypophysis was 5,619. However, an average of 981 neurons was immunoreactive to vasopressin but devoid of horseradish peroxidase. The greatest number of these non-projecting perikarya were found in and around the anterior hypothalamus, localized primarily in the lateral and medial aspect of the supraoptic nuclei, the ventral area of the paraventricular nucleus, and the nucleus circularis. By comparing the number of non-projecting neurons found by double-staining to the total cell count of the entire vasopressin system, it was estimated that approximately 30% of all vasopressin neurons in and around the anterior hypothalamus did not project to the neurohypophysis. Based on the distribution and localization of the non-projecting perikarya, it is speculated that these neurons may provide neurotransmitter for vasopressin-dependent flank marking in the male Golden hamster.