Realistic Appearance Research Articles

Development of parenchymal abdominal organ models for use in teaching veterinary soft tissue surgery.

Models of the canine spleen, kidney, and liver were made from soft plastic to simulate the organs of the live animal as closely as possible in appearance and tissue handling properties. Each organ model was independently evaluated by five small animal surgeons who performed several common surgical procedures on each model. All models had a realistic appearance and, with the exception of one tissue handling problem with the kidney model, and one with the liver model, tissue handling properties of the models were comparable to those of the organs in the live animal. All models were useful for teaching each of the procedures evaluated.

Natural head position as a basis for cephalometric analysis

In a sample of orthodontic patients (27 boys and 25 girls, 10 to 14 years old), natural head position (NHP) was photographically recorded. A vertical axis was recorded on the photographs with a plumb line and transferred to the lateral head radiographs of the patients. Three cephalometric reference lines (sella-nasion, basion-nasion, and porion-orbitale) were compared with regard to their inclination to the horizontal plane. These angles showed standard deviations of between 4.5° and 5.6°. Reproducibility of NHP, assessed as the error of a single observation, was close to 2°. These findings, in combination with the fact that the NHP represents a realistic appearance of patients, support its use as a basis for cephalometric-analysis of dentofacial anomalies. A strong correlation was found between the inclinations of the three cephalometric reference lines to the horizontal plane. The close anatomic relationship between these lines, in combination with the small random movements of the head around NHP, were believed to explain the covariation. (A M J O RTHOD D ENTOFAC O RTHOP 1992;101:244-7.)

Simple Models for Surface Cracking

AbstractA simple model for crack growth in thin films deposited onto a substrate has been developed. This model results in the generation of cracking patterns which have a remarkably realistic appearance. In the simulations a slow crack initiation period is followed by a period of rapid crack growth in which quite linear cracks are formed. Later on the crack growth process becomes slower and less regular as the cracking process relieves much of the stress in the surface layer. In this model pre-existing defects have a large effect on the crack growth kinetics and morphology.

A characterization of illumination models and shading techniques

The interaction of light with material surfaces was studied in the fields of physics and optics long before the advent of computer graphics. The application of this knowledge to computer graphics is shaped by the dichotomy of attempting to solve the complex problem of generating realistic appearance within both the informational limits imposed by visible surface techniques and the computational constraints imposed by the computing hardware.

Three-dimensional computed tomographic reformation of the spine, skull, and brain from axial images.

Three-dimensional (3D) images were reconstructed from axial computed tomographic scans using the new 3D83 (General Electric Co.) software. Images were reformatted as a movie in multiple frames, each consisting of a discrete 3D scene, and were rotated 360 degrees in 3D space. Improvement in shading and surface algorithm has been made from the previous 3D82 program so that 3D images now have a realistic appearance. Soft tissue and bone modes are available; the latter reconstructs best in 3D because of its high density pixels, which provide a more exclusive threshold. 3D reconstructions of the spine were the most rewarding because the complex anatomy of the spine seems to be best suited for 3D imaging. By hemisection of the spine by subregion, the intervertebral foramina can be evaluated for stenosis. Some drawbacks in this program are the need for user interaction, the lengthy time of reconstruction, and the dependence on high quality axial images.

Simulators for assisting the teaching of observational astronomy. Part III: UBV photometry

For pt.II see ibid., vol.4, no.4, p.198-204 (1983). A simulator is described which, in conjunction with the photometer described in part II, enables students to practise the techniques of quantitative UBV stellar photometry under laboratory conditions. Silica fibre optics are employed to obtain both a realistic appearance and the required ratios and intensities of ultraviolet, blue and yellow light to simulate stars of differing spectral classes at various distances.

Simplified technique for implanting hair into a facial prosthesis

In past years, characterization of extraoral prosthetics had to be performed through time-consuming techniques. As technology and materials have improved, so has the realistic appearance of today's prostheses. The device used in this article simulates a sewing machine effect that allows placement of up to 14 half-inch hairs in less than 30 seconds. These hairs can be shaped and contoured to simulate realistic hair strands (Figs. 9 and 10). By use of such a device, gluing, painting, and matting of hair have become techniques of the past.

A Model for the Simulation of Atmospheric Turbulence

A method that produces realistic simulations of atmospheric turbulence is developed and analyzed. The procedure makes use of a generalized spectral analysis, often called a proper orthogonal decomposition or the Karhunen-Loève expansion. A set of criteria, emphasizing a realistic appearance, a correct spectral shape, and non-Gaussian statistics, is selected in order to evaluate the model turbulence. An actual turbulence record is analyzed in detail providing both a standard for comparison and input statistics for the generalized spectral analysis, which in turn produces a set of orthonormal eigenfunctions and estimates of the distributions of the corresponding expansion coefficients. The simulation method utilizes the eigenfunction expansion procedure to produce preliminary time histories of the three velocity components simultaneously. As a final step, a spectral shaping procedure is then applied. The method is unique in modeling the three velocity components simultaneously, and it is found that important cross-statistical features are reasonably well-behaved. It is concluded that the model provides a practical, operational simulator of atmospheric turbulence.

A New Method of Terrain Representation

HE oldest method of depicting landforms on maps is to draw perspective or side views of mountains or hills placed in their approximate position on otherwise flat maps. These representations, ranging from the crude sugar loaves of ancient maps to the sophisticated symbolism of present-day physiographic or landform maps, have one major defect in common: the side view of a landform having a vertical dimension requires horizontal space, and on an ordinary map horizontal space is reserved for planimetric position. example, if a single mountain is drawn on a map as seen from the side or in perspective, the peak or base and most or all of the profile will be in the wrong place planimetrically. This fundamental defect of landform maps has been recognized by the cartographers who draw them but has, properly, been justified on the ground that the realistic appearance obtained more than outweighs the disadvantages of planimetric displacement.' On the other hand, map users and makers are not consistent in their concern about this error. On a small-scale map deviations from correct planimetric positioning that on the earth might amount to tens or scores of miles bother few, but an error of a mile or two on a large-scale map seems to be quite unacceptable. Whatever the reason, there have been few physiographic maps at topographic scales, and their rarity is certainly not due to lack of knowledge of terrain. Planimetric displacement becomes serious at large scales. Raisz states: For this reason [planimetric displacement] landform maps are not recommended for any larger scale than 1: 1,ooo,ooo. larger scales the map should be transformed to an obliquely-seen block diagram.12 One way to reduce planimetric displacement as scale increases is to adopt a high oblique angle of view. The authors had discussed this possibility but had not had an opportunity to put it to a test. When the Environmental Protection Division, Quartermaster Research & Development Center, Natick, Mass., indicated interest in having a landform drawing prepared of the Camp Hale area in Colorado at the scale of 1: 50,000, a proposal was

Characterization of dentures

Abstract 1. This process of characterizing dentures is founded upon the principles of (a) Adapting laminations of Colorblend resins in the flask so there will be a life-like blending of those colors exposed on the labial and buccal surfaces of the oral tissues. (b) Embedding color fast fibers in the laminations to simulate veins, and hence reproduce the startling realistic appearance so characteristic of healthy oral tissues. 2. The process allows the dentist to construct a denture whose intrinsic worth to the patient sets a high economic value. 3. The colors of the powders and fibers provide innumerable cross blendings to produce any shade indicated or desired. 4. One of the notable advantages of this process is that finishing and polishing, subsequent adjustments, or relining cannot change the characterization. 5. Dentures made by this process permit their anatomic development after processing. 6. The colors of natural tissue can be reproduced so faithfully that partial dentures are no longer a cosmetic problem.