Free adaptive tessellation strategy of bézier surfaces

[Abstract] Rendering of Bézier surfaces is currently performed by tessellating the model on the GPU and rendering the highly detailed triangle mesh. Whereas non-adaptive strategies apply the same tessellation pattern to the whole surface resulting in a uniform tessellation of the patch, adaptive approaches make it possible to reduce the number of triangles generated without a loss of quality. However, the most usual approaches to adaptive tessellation have little flexibility and do redundant computations and memory accesses, as each sample is independently evaluated in the Domain Shader of the DirectX11 pipeline. In this paper an adaptive tessellation technique based on the exploitation of the spatial coherence data within each surface is presented. The GPU implementation of this technique is simple and efficient and, as consequence, the tessellation of complex models can be performed in real-time. The analysis of the GPU performance and limitations for different adaptive degree of the tessellation performed suggest innovations in future graphics card generations for supporting a larger degree of adaptivity without a penalty

Efficient Culling Techniques for Interactive Deformable NURBS Surfaces on GPU

[Abstrtact] InfoValue: NURBS (Non-uniform rational B-splines) surfaces are the standard freeform representation in Computer-Aided Design (CAD) applications. Rendering NURBS surfaces accurately while they are interactively manipulated and deformed is a challenging task. In order to achieve it, the elimination from pipeline in early stages of back-facing surfaces or surface pieces is a key advantage. Furthermore, an effective interactive manipulation implies that all the culling computations should be performed for each frame, facing the possibility of fast changes in occlusion information. In this paper, different interactive culling strategies for NURBS surfaces are presented and analyzed. These culling techniques are based on the exploitation of the geometric properties presented in a NURBS surface, that allow easily to find bounds for it in screen space for each frame. Furthermore, the culling overhead for our proposals is small compared to the computational saving, outperforming a proposal without culling. An implementation of these strategies using current GPUs is presented, achieving real-time and interactive rendering rates of complex parametric models.Xunta de Galicia y fondos FEDER; GRC2013/055Ministerio de Economía y Competitividad y fondos FEDER; TIN2013-42148-

Synthesis of Multiresolution Scenes with Global Illumination on a GPU

[Abstract] The radiosity computation has the important feature of producing view independent results, but these results are mesh dependent and, in consequence, are attached to a specific level of detail in the input mesh. Therefore, rendering at iterative frame rates would benefit from the utilization of multiresolution models. In this paper we focus on the rendering stage of a solution for hierarchical radiosity for multiresolution systems. This method is based on the application of an enriched hierarchical radiosity algorithm to an input scene with low resolution objects (represented by coarse meshes), and the efficient data management of the resulting values. The proposed encoding makes it possible to apply the color values obtained for the coarse objects to detailed versions of these objects during the rendering phase. These finer meshes are obtained by a standard mesh subdivision strategy, such as the Loop subdivision scheme. Our solution performs the whole rendering stage of this multiresolution approach on the GPU, implementing it in the geometry shader using Microsoft HLSL. Results of our implementation show an important reduction in computational costs

Aprender Arquitectura de Computadores con la herramienta Simula3MS

En este artículo se presenta la experiencia de uso de la herramienta Simula3MS en el laboratorio de las asignaturas de Arquitectura de Computadores en los estudios impartidos en la Facultad de Informática de la Universidade da Coruña y la Escuela Técnica Superior de Ingeniería de la Universidade de Santiago de Compostela. El objetivo de las prácticas es ilustrar, mediante un juego de ejercicios realizados sobre el simulador Simula3MS, cómo trabaja el procesador del computador. El simulador usa un subconjunto de instrucciones MIPS y varias configuraciones diferentes del procesador que se escogen según el objetivo de los ejercicios prácticos. En el artículo se describen los ejercicios que se proponen a los estudiantes en el laboratorio y se muestra un análisis sobre el impacto que ha tenido el uso del simulador en la actividad docente.Peer Reviewe

Experimental research of the effect of surface orientation on the subcooled flow nucleate boiling of water at low pressure

The toughening emission standards and the costs saving requirements are pushing to the limits the design of compact heat exchangers in the automotive industry, meaning that today’s heat exchangers need to operate with a controlled level of boiling in their coolant side. Most of the experimental literature available tackle boiling in horizontal flat plates or vertical tubes, while the information regarding other orientations is much scarcer. However, in a compact heat exchanger all orientations are present therefore orientation parametrizations in boiling models are particularly important since upper-heating orientations have a strong influence on heat transfer mechanism and the critical heat flux due to the cancelation of the bubbles floatability forces that help their departure. Therefore the limiting heat flux in those parts is generally governed at boiling orientations not determined with precision. The experimental work presented in this paper analyses the dependence of the heat transfer coefficient with the inclination of the heated surface under subcooled boiling regime. Due to the heating method selected, the test part consists in an AISI 316 thin strip with a thickness of 0.5 mm brazed to a copper base, to ensure an industry-like heat exchange material as primary surface but avoiding unmanaged temperatures and heating powers. Experimental tests have been carried out on a single face heated rectangular channel under several operating conditions of bulk velocity, temperature, pressure and flow orientation: 0.1-0.9 (m/s) – 76.5-93.5 (°C) – 110-190 (kPa) – 0- 180 (°), to cover some of the most common conditions found in the automotive compact heat exchanger industry. The heat flux employed in each test ranged from 0.1 to more than 1 MW/m². After the data analysis some main dependences were identified and suggested that a global boiling model should include some parameters accounting for the relative orientation of the heated part and the coolant flow. This could be a valuable tool during the development of an automotive heat exchanger in which nucleate boiling is present.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

CFD Transient Simulation of a Breathing Cycle in an Oral-Nasal Extrathoracic Model

Knowledge of respiratory flow behaviour is important in many respiratory medical fields. The usefulness of numerical models in providing a better understanding of flow phenomena has made the Computational Fluid Dynamics (CFD) an indispensable research tool due to the difficulty of measuring in vivo data. In this research, the extrathoracic airways and the upper tracheobronchial region, trachea and main bronchus bifurcation were modelled. Oral and nasal breathing routes have been considered under steady and cyclic unsteady conditions. A realistic far boundary condition was imposed as the flow inlet. Different ventilation levels and frequencies were simulated. The model presented has been validated successfully by two parts: nasal and oral models. The airflow distributions through oral and nasal routes were determined, analysed and compared under different breathing conditions. The flow behaviour and respiratory effort during inhalation and exhalation phases change from rest to high activity; the flow can increase 40% with the same respiratory effort, opening the mouth during the inspiration. Significant differences in turbulent intensity contours in steady and unsteady cases have been observed. This study demonstrated the relevance of considering different breathing patterns and more realistic unsteady conditions

Acylcarnitine profile in neonatal hypoxic-ischemic encephalopathy: The value of butyrylcarnitine as a prognostic marker

Optimal prognostic markers evaluating early neuroprotective interventions in neonatal hypoxic-ischemic encephalopathy (HIE) are lacking. This study was designed to assess the prognostic value of acylcarnitines in neonatal HIE.An observational cohort study was conducted over 10 years in 67 HIE. Variables analyzed included sex, blood cord pH, Apgar score, hypothermia treatment (yes/no), neuron-specific enolase (NSE) levels, and clinical outcome (neurological examination, brain magnetic resonance imaging [MRI], and electroencephalogram) before discharge and at 6 months. Acylcarnitine profiles were analyzed by tandem-mass spectrometry on dried-blood spots collected on day 3 for newborn screening. A cohort of healthy newborns was used as control group.HIE patients had significantly increased C4, C5, C5:1, C6, C6-OH, C8 levels (all P < .01) and decreased long-chain acylcarnitine levels (P < .03). Hypothermia treatment was associated with a decrease in C4 levels (p = 0.005) and an increase in most long-chain acylcarnitine levels (P < .01). A significant association was found between C4 levels and NSE on day 1 of hypothermia treatment (P = .002) and abnormal brain magnetic resonance imaging (MRI) at discharge (P = .037). In the hypothermia group, C4 levels decreased in patients with favorable outcomes but remained high in those who progressed unfavorably.C4 appears to be a good prognostic marker in HIE, as blood levels correlated with NSE levels and abnormal MRI findings. Furthermore, hypothermia did not lead to decreased levels in patients with adverse outcomes

Empty Urbanism: the bursting of the Spanish housing bubble

The depth of the Spanish housing crisis manifests itself in the collapse of construction activity and in the amount of housing and land stocks. The geography of the crisis shows its widespread nature, and the intensity of the previous bubble explains spatial differences. Resulting from this collapse are some problematic areas of 'empty urbanism'. An enormous land bubble, emerging from the peculiar Spanish urban development model, was a key factor in the impacts - caused by the crisis - on the territory and land-use plans. The crisis has demonstrated the unsustainability of this and the urgency of change in the existing land-use plans

Powder Compaction: Compression Properties of Cellulose Ethers

Effective development of matrix tablets requires a comprehensive understanding of different raw material attributes and their impact on process parameters. Cellulose ethers (CE) are the most commonly used pharmaceutical excipients in the fabrication of hydrophilic matrices. The innate good compression and binding properties of CE enable matrices to be prepared using economical direct compression (DC) techniques. However, DC is sensitive to raw material attributes, thus, impacting the compaction process. This article critically reviews prior knowledge on the mechanism of powder compaction and the compression properties of cellulose ethers, giving timely insight into new developments in this field