The representation of geometric models by trimmed NURBS surfaces has become a standard in the CAD industry. In CAD applications, the rendering of surfaces is usually solved by tessellation followed ...up by z‐buffer rendering. Ray tracing of NURBS surfaces has not been widely used in industry due to its computational complexity that hinders achieving real‐time performance in practice. We propose novel methods achieving faster point location search needed by trimming in the context of ray tracing trimmed NURBS surfaces. The proposed 2D data structure based on kd‐trees allows for faster ray tracing while it requires less memory for its representation and less preprocessing time than previously published methods. Further, we show the current state of the art for ray tracing trimmed NURBS surfaces on a GPU. With careful design and implementation, the number of rays cast on a GPU may reach real‐time performance in the order of tens to hundreds of million rays per second for moderately to large complex scenes containing hundreds of thousands of NURBS surfaces and trimming curves.
We propose an extension to the state‐of‐the‐art text rendering technique based on sampling a 2D signed distance field from a texture. This extension significantly improves the visual quality of sharp ...corners, which is the most problematic feature to reproduce for the original technique. We achieve this by using a combination of multiple distance fields in conjunction, which together provide a more thorough representation of the given glyph's (or any other 2D shape's) geometry. This multi‐channel distance field representation is described along with its application in shader‐based rendering. The rendering process itself remains very simple and efficient, and is fully compatible with previous monochrome distance fields. The introduced method of multi‐channel distance field construction requires a vector representation of the input shape. A comparative measurement of rendering quality shows that the error in the output image can be reduced by up to several orders of magnitude.
We propose an extension to the state‐of‐the‐art text rendering technique based on sampling a 2D signed distance field from a texture. This extension significantly improves the visual quality of sharp corners, which is the most problematic feature to reproduce for the original technique. We achieve this by using a combination of multiple distance fields in conjunction, which together provide a more thorough representation of the given glyph's (or any other 2D shape's) geometry. This multi‐channel distance field representation is described along with its application in shader‐based rendering. The rendering process itself remains very simple and efficient, and is fully compatible with previous monochrome distance fields.
A field trial was established in 2006 and in 2007 at two localities. The first one was in Lednice (district Břeclav) at an experimental plot of Department of Breeding and Propagation of Horticultural ...Plants. The second one was in Stařeč (district Třebíč). As model plants Acer pseudoplatanus and Quercus robur were used. As soil conditioners the following products were chosen: TerraCottem, Agrosil LR and Hydrogel. Both species were used at each stands. Model plants were planted out on plots with soil conditioners in 4 treatments (including a control treatment without soil conditioners) and 3 replications each. In the course of growing season, physiological parameters of plants were followed using special instruments Porometer AP 4 (stomatal conductivity), SunScan AT (PAR), and Chlorophyll Meter CCM 200 (chlorophyll contain index). Morphological parameters (i.e. the length of shoots and dry matter of leaves) were measured at the end of the growing season. The obtained data were statistically analyzed using the program Statgraphics Plus. The best results were obtained in treatments with soil conditioners. The soil conditioners influenced significantly both morphological and physiological parameters and eliminated effects of abiotic stressors on young plants of Acer pseudoplatanus and Quercus robur.
Fulfilling the goals of space-based exoplanetary transit surveys, like Kepler and TESS, is impossible without ground-based spectroscopic follow-up. In particular, the first-step vetting of candidates ...could easily necessitate several hundreds of hours of telescope time—an area where 2 m class telescopes can play a crucial role. Here, we describe the results from the science verification of the Ondřejov Echelle Spectrograph (OES) installed on the 2 m Perek telescope. We discuss the performance of the instrument as well as its suitability for the study of exoplanetary candidates from space-based transit surveys. In spite of being located at an average European observing site, and originally being conceived for the study of variable stars, OES can prove to be an important instrument for the exoplanetary community in the TESS and PLATO era—reaching accuracies of a few tens of ms−1 with reasonable sampling and signal-to-noise for sources down to V ∼ 13. The stability of OES is demonstrated via long-term monitoring of the standard star HD 109358, while its validity for exoplanetary candidate verification is shown using three K2 candidates EPIC 210925707, EPIC 206135267 and EPIC 211993818, to reveal that they are false positive detections.
Fulfilling the goals of space-based exoplanetary transit surveys, like Kepler and TESS, is impossible without ground-based spectroscopic follow-up. In particular, the first-step vetting of candidates ...could easily necessitate several hundreds of hours of telescope time—an area where 2 m class telescopes can play a crucial role. Here, we describe the results from the science verification of the Ondřejov Echelle Spectrograph (OES) installed on the 2 m Perek telescope. We discuss the performance of the instrument as well as its suitability for the study of exoplanetary candidates from space-based transit surveys. In spite of being located at an average European observing site, and originally being conceived for the study of variable stars, OES can prove to be an important instrument for the exoplanetary community in the TESS and PLATO era—reaching accuracies of a few tens of m s−1 with reasonable sampling and signal-to-noise for sources down to V ∼ 13. The stability of OES is demonstrated via long-term monitoring of the standard star HD 109358, while its validity for exoplanetary candidate verification is shown using three K2 candidates EPIC 210925707, EPIC 206135267 and EPIC 211993818, to reveal that they are false positive detections.
Fulfilling the goals of space-based exoplanetary transit surveys, like Kepler and TESS, is impossible without ground-based spectroscopic follow-up. In particular, the first-step vetting of candidates ...could easily necessitate several hundreds of hours of telescope time-an area where 2 m class telescopes can play a crucial role. Here, we describe the results from the science verification of the Ondřejov Echelle Spectrograph (OES) installed on the 2 m Perek telescope. We discuss the performance of the instrument as well as its suitability for the study of exoplanetary candidates from space-based transit surveys. In spite of being located at an average European observing site, and originally being conceived for the study of variable stars, OES can prove to be an important instrument for the exoplanetary community in the TESS and PLATO era-reaching accuracies of a few tens of m s−1 with reasonable sampling and signal-to-noise for sources down to V ∼ 13. The stability of OES is demonstrated via long-term monitoring of the standard star HD 109358, while its validity for exoplanetary candidate verification is shown using three K2 candidates EPIC 210925707, EPIC 206135267 and EPIC 211993818, to reveal that they are false positive detections.
We present a simple method for visual simulation of refraction phenomena in the Earth's atmosphere. The method divides the atmosphere into a set of spherical layers and the rays are approximated by ...circular arcs within the layers. The curvature of arcs is related to the variations of the refractive index. The path of the ray through the atmosphere is found by intersecting the circular arcs with the layers boundaries. The curved rays produce the shape and position distortions of the objects observed through the atmosphere. Depending on the type of distortion we distinguish a large variety of refractive phenomena such as mirages, omega sunsets, fata morgana, green flashes, etc. The described method has been embedded into the simple ray tracer and some images are shown to demonstrate our approach.
Affecting the quality of nursery produce by soil conditioners Sloup, J.,Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic). Ustav Slechteni a Mnozeni Zahradnickych Rostlin; Salas, P.,Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic). Ustav Slechteni a Mnozeni Zahradnickych Rostlin
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis,
2009, Letnik:
57, Številka:
4
Journal Article
Recenzirano
Odprti dostop
In 2006, a field trial was established in two localities, Lednice and Starec, with two model plants, Acer pseudoplatanus and Quercus robur. TerraCottem, Agrosil LR and Hydrogel were tested as soil ...conditioners. Four variants (each of the conditioners and control) were tested in 3 replications. Several physiological characteristics were followed during the growing season using special equipments, viz. Porometer AP 4 (stomatal conductivity), SunScan AT (photosynthetically active radiation) and Chlorophyllmeter CCM 200 (chlorophyll content index). Morphological characteristics (i.e. length of shoots and dry mass of leafs) were measured to the end of the growing season. The best results were obtained with the soil conditioner Hydrogel. The soil conditioners showed a significant effect on both morphological and physiological characteristics of the experimental plants. Soil conditioners eliminated the influence of abiotic stressors on both tree species.
Tapeworms parasitize at sites that are important for the management of micronutrients, including zinc. Therefore, it has been hypothesized that tapeworms will significantly affect the excretion of ...zinc in the feces of a host. The aim of this work was to evaluate the effects that tapeworms have on the excretion of zinc in the feces of the host. Rats were divided into 4 groups: groups 0T and MT (infected with
(Rudolphi, 1819)) and groups 00 and M0 (uninfected). The experimental groups (M0 and MT) were fed a standard rodent compound feed (ST-1) with added zinc lactate; the daily zinc intake was 20.5 mg. The control groups (00 and 0T) were fed only ST-1 with 1.75 mg of added Zn per day. For six weeks, the amount of consumed feed was recorded and fecal samples were taken. The samples were then analyzed by optical emission spectrometry (ICP-OES), and levels of excreted zinc were subsequently calculated as a percentage. The most signifi cant difference in zinc excretion levels between the experimental groups was observed in the third week, when rats infected with tapeworms (MT) excreted substantially lower levels of zinc than did uninfected rats (M0). This difference amounted to 28.36 % (p <0.01). In the control groups, tapeworms affected the excretion of zinc in the feces to a lesser extent, and the most substantial difference in zinc levels was seen in the fifth week (8.46 %). However, there was no signifi cant difference in zinc excretion levels between the control groups during any of the monitored weeks. Tapeworms in the host affect levels of zinc excreted in the feces. However, this is dependent on the amount or form of zinc ingested.
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