Shadow-casting Method Research Articles

A Fast and Simple Machine Vision Framework for Approximating the Volume of Axi-Symmetric Objects Using Shadow Ray Casting

The volume measurement using machine vision system is contactless techniques that play an important role in industries now a day. Basically, three-dimensional reconstruction is required to determine a depth using a special lighting system or multiple cameras. This increases the complexity of the measurement system. A fast and simple machine vision framework called RayVol for estimating the volume of axisymmetric objects in near real-time using a single camera and simple illumination is presented. The RayVol framework employs a shadow casting method to reconstruct the 3D shape of the object by tracing rays from the object’s shadow pixels to the light source location. The result of this technique shows a significant accuracy improvement from the area-projection method. A virtual slice representing the cross-section of an object is reconstructed using a cubic spline approximation from baseline points derived from the boundary pixels of the object image and a shadow casting method. The volume estimation was calculated by restricted integration using the Riemann sum estimation algorithm, and the closed area of the virtual slices was calculated using the shoestring algorithm. Mangoes were used as a case study of the RayVol framework. The volume estimation provides the correlation coefficient of 0.9849 between the developed system and the water replacement method.

Real-Time Shadow Detection From Live Outdoor Videos for Augmented Reality.

Simulating shadow interactions between real and virtual objects is important for augmented reality (AR), in which accurately and efficiently detecting real shadows from live videos is a crucial step. Most of the existing methods are capable of processing only scenes captured under a fixed viewpoint. In contrast, this article proposes a new framework for shadow detection in live outdoor videos captured under moving viewpoints. The framework splits each frame into a tracked region, which is the region tracked from the previous video frame through optical flow analysis, and an emerging region, which is newly introduced into the scene due to the moving viewpoint. The framework subsequently extracts features based on the intensity profiles surrounding the boundaries of candidate shadow regions. These features are then utilized to both correct erroneous shadow boundaries for the tracked region and to detect shadow boundaries for the emerging region by a Bayesian learning module. To remove spurious shadows, spatial layout constraints are further considered for emerging regions. The experimental results demonstrate that the proposed framework outperforms the state-of-the-art shadow tracking and detection algorithms on a variety of challenging cases in real time, including shadows on backgrounds with complex textures, nonplanar shadows, fast-moving shadows with changing typologies, and shadows cast by nonrigid objects. The quantitative experiments show that our method outperforms the best existing method, achieving a 33.3% increase in the average Fmeasure on a self-collected database. Coupled with an image-based shadow-casting method, the proposed framework generates realistic shadow interaction results. This capability will be particularly beneficial for supporting AR applications.

Structure and thermal behavior of zirconium tungstate under heating

The morphology and properties of powders ZrW2O7(OH)2·2H2O and ZrW2O8, obtained under the conditions of hydrothermal synthesis was studied. Using the high-temperature X-ray analysis, the mechanism of formation of zirconium tungstate was established. The influence of temperature on the structure and properties of materials was studied using shadow-casting method.

Electron microscope studies of antigen—antibody complexes

Purified rabbit antiferritin—ferritin complexes have been examined in the electron microscope by the negative-staining and shadow-casting techniques. Negatively stained preparations were consistently satisfactory for ferritin molecules, but rarely so for antibodies. The shadow-casting method masks details in the complex revealed by negative staining, but it yields gross information that the latter does not under the conditions used. It was observed that under certain conditions the distance between antigen molecules in the complex increases with increased antibody concentration in the reaction mixture, whereas under other conditions apparent antigen to antigen aggregation could be seen. It was also observed that upon sequential additions of antibody to the reaction mixture, an envelope of molecules other than antigen is built around the initial complex formed by the first addition of antibody. The results are considered to be most easily explained by the anti-antibody theory of antigen—antibody complex formation.

Liquid Thermometer Recorder

The recording liquid thermometer described below was designed primarily to record the water temperature in the field with an accuracy of 0.05°C or less.Cook, L.O., in 1940, designed a similar recorder, in which the record was obtained by casting the shadow of a flat section mercury column of a glass thermometer on to bromide paper. The shadow casting method, however, is not so good for precision recording, because light fluxes passes through the vacuous column of the glass thermometer are dispersed and do not make distinctive contrast against the shadow of the mercury column.Instead of mercury, the present author utilizes a transparent liquid with the suitable coefficient of expansion and refractive index μ. The value of μ is decided as it makes the glass tube with the liquid column a thick lens, which has a proper focus length.The instrument consists of four parts; a liquid thermometer, a drum carrying the bromide paper, a light source and multiflex mirrors, and a constant clock. The thermometer has a round section liquid column and an accurately graduated scale and its bulb is courted with black lacquer or covered by a thin-walled tube to cut off light penetration into the thermometer. Light from a 4V point-source lamp reaches the thermometer through a slit after reflecting between two mirrors and with full path of 75cm.A constant clock has two functions; driving the drum carrying the bromide paper and operating the light switch intermittently.Specimen records are shown with the vertical lines making the time, and the horizontal lines half degree with the heavy line at 10°C as an index.

Shadow microscopy for measurement of height

THIS note describes a simple optical microscope shadow technique which permits measurement to be made of the heights of small objects such as particles, spores, steps on surfaces, etc., and also reveals qualitative surface topographical features in a striking manner. This is an optical analogy to the familiar metallic shadow-casting method which is used with electron microscopes. I have used it with powers up to that of a 4-mm. objective.

Shadow microscopy for measurement of height.

THIS note describes a simple optical microscope shadow technique which permits measurement to be made of the heights of small objects such as particles, spores, steps on surfaces, etc., and also reveals qualitative surface topographical features in a striking manner. This is an optical analogy to the familiar metallic shadow-casting method which is used with electron microscopes. I have used it with powers up to that of a 4-mm. objective.