Real-Time Ray-Tracing of Implicit Surfaces on the GPU

The programmable graphics processor units (GPUs) have high computation capabilities but relatively limited bandwidth for data access. Compact representation of geometry using a suitable procedural or mathematical model and a ray-tracing mode of rendering fit the GPUs well, consequently. Several such representations including parametrics and subdivision surfaces have been explored in recent research. The important and widely applicable category of the general implicit surface has received less attention. In this paper, we present a ray-tracing procedure to render general implicit surfaces efficiently on the GPU. Though only fourth or lower order surfaces can be rendered using analytical roots, our adaptive marching points algorithm can ray-trace arbitrary implicit surfaces exactly, by sampling the ray at selected points till a root is found. Adapting the sampling step size based on a proximity measure and a horizon measure delivers high speed. Combining sampling with ideas from interval arithmetic provides robust root-isolation. Overall, a simple algorithm that fits the SIMD architecture of the GPU results in high performance. We ray-trace algebraic surfaces up to order 18 and non-algebraic surfaces including a Blinn’s blobby with 30 spheres at better than interactive frame rates.

ChemInform Abstract: Heterocyclic Systems Containing Bridgehead Nitrogen Atom: Synthesis and Evaluation of Bio-activity of Thiazolo[3,2-b]-s-triazoles and Isomeric Thiazolo[2,3-c]-s-triazoles.

1883-1885Synthesis of 2-(3'-bromophenyl)-5-(p-bromophenyl) thiazolo[3,2-b]-s-triazoles 4 has been achieved starting from the appropriate 5-mercapto-3-(3'-bromo phenyl)-s-triazole 2. Compound 2 on condensation with α-haloketones gives the ketones 3 which on cyclization with PPA afford 5-(p-bromophenyl)-2-(3'-bromophenyl)thiazolo[3,2-b]-s-triazoles 4 and not the isomeric thiazolo[2,3-c]-s-triazoles 6. This has been established by an unequivocal synthesis of 6 through POCl3 cyclization of 3'-bromobenzoylhydrazino-4-p-bromophenyl-thiazole hydrobromide 5. The diuretic, antibacterial and antifungal activities of some of the compounds have also been evaluated

Heterocyclic systems containing bridgehead nitrogen atom: Synthesis and evaluation of bio-activity of thiazolo[3,2-b]-s-triazoles and isomeric thiazolo[2,3-c]-s-triazoles

1883-1885Synthesis of 2-(3'-bromophenyl)-5-(p-bromophenyl) thiazolo[3,2-b]-s-triazoles 4 has been achieved starting from the appropriate 5-mercapto-3-(3'-bromo phenyl)-s-triazole 2. Compound 2 on condensation with α-haloketones gives the ketones 3 which on cyclization with PPA afford 5-(p-bromophenyl)-2-(3'-bromophenyl)thiazolo[3,2-b]-s-triazoles 4 and not the isomeric thiazolo[2,3-c]-s-triazoles 6. This has been established by an unequivocal synthesis of 6 through POCl3 cyclization of 3'-bromobenzoylhydrazino-4-p-bromophenyl-thiazole hydrobromide 5. The diuretic, antibacterial and antifungal activities of some of the compounds have also been evaluated

Point Based Representations for Hierarchical Environments ∗

The advent of advanced graphics technologies and improved hardware has enabled the generation of highly complex models with huge number of triangles. Point-based representations and rendering have emerged as viable representations for high-quality models in this scenario. These methods have been demonstrated only on high resolution, compact objects so far. They have to be adapted to environments that extend over large areas to be considered serious representations. In this paper, we present an adaptation of the point-based representation to large, hierarchical environments. We show how point-based data can be generated by sampling polygon-based representations. We also show the combination of an object hierarchy and multiresolution point representations and develop rendering algorithms for the same. The multiresolution representation is constructed during the generation process. We then show a hybrid representation in which the more complex portions of the environment are represented using points and others using the original polygon-based representation. This produces better rendering performance by keeping large, flat regions as triangles. We demonstrate the method on the model of the Fatehpur Sikri which has 14000 objects with over 500,000 triangles. 1

Performance of buildings during the 2001 Bhuj earthquake

The performance of buildings during the January 26, 2001, earthquake in the Kachchh region of the province of Gujarat in India is discussed. A majority of the buildings in the earthquake region were either of load-bearing masonry or reinforced concrete framed structure. Most of the masonry buildings were built with random or coursed stone walls without any reinforcement and heavy clay tile roofing supported on wooden logs. A large number of such buildings collapsed leading to widespread destruction and loss of life. Many reinforced concrete frame buildings had infill masonry walls except in the first storey, which was reserved for parking. As would be expected, the open first storey suffered severe damage or collapsed. Observations of failures confirmed the vulnerability of some structural details that are known to lead to distress. However, an important observation to come out of the earthquake was that masonry infills, even when not tied to the surrounding frame, could save the building from collapse, provided such infills are uniformly distributed throughout the height so that abrupt changes in stiffness and strength did not occur