Simulation and Analysis of Floodlighting Based on 3D Computer Graphics

The paper presents the opportunities to apply computer graphics in an object floodlighting design process and in an analysis of object illumination. The course of object floodlighting design has been defined based on a virtual three-dimensional geometric model. The problems related to carrying out the analysis of lighting, calculating the average illuminance, luminance levels and determining the illuminated object surface area are also described. These parameters are directly tied with the calculations of the Floodlighting Utilisation Factor, and therefore, with the energy efficiency of the design as well as the aspects of light pollution of the natural environment. The paper shows how high an impact of the geometric model of the object has on the accuracy of photometric calculations. Very often the model contains the components that should not be taken into account in the photometric calculations. The research on what influence the purity of the geometric mesh of the illuminated object has on the obtained results is presented. It shows that the errors can be significant, but it is possible to optimise the 3D object model appropriately in order to receive the precise results. For the example object presented in this paper, removing the planes that do not constitute its external surface has caused a two-fold increase in the average illuminance and average luminance. This is dangerous because a designer who wants to achieve a specific average luminance level in their design without optimizing the model will obtain the luminance values that will actually be much higher.

Abstract 13593: Global Aortic Stiffness in Bicuspid-associated Aortopathy is Independent of Aortic Dimensions and Similar to Tricuspid Aortic Valve Control Subjects

Introduction: Bicuspid aortic valve (BAV) carries high aortopathy risk, and debate exists about relative contributions of altered wall structure vs. BAV-mediated hemodynamics. Pulse wave velocity (PWV), a surrogate for stiffness, can be quantified from 4D flow MRI. Here we use PWV to study wall stiffness in a large cohort of BAV aortic dilatation patients and two control groups. Hypotheses: 1. abnormal thoracic aortic (Ao) wall biomechanics for BAV patients result in altered PWV compared to controls and 2. PWV correlates with Ao diameter. Methods: This retrospective IRB approved study included 483 subjects: 124 healthy (no known cardiovascular disease), 168 BAV patients with ascending Ao (AAo) dilatation—maximal-area AAo (MAA) or sinus of Valsalva (SOV) diameter ≥4cm—and 191 TAV AAo dilatation (see table). No subjects had valve stenosis or ejection fraction ≤50%. Global PWV was assessed from MRI by cross-correlating flow in 80-100 Ao cutplanes and median AAo diameter by geometric mesh analysis of 3D Ao segmentations. Results: In multivariate regression, older age was the most significant predictor of higher PWV (controls: 0.073 m/s / y; TAV: 0.072 m/s / y; BAV: 0.092 m/s / y; all p<1E-4). Increased Ao diameter in controls associated with higher PWV (0.10 m/s / mm, p=0.03). Both BAV and TAV patients had no association between any Ao diameter (MAA, SOV, median) and PWV (p≥0.1 for all metrics). Between subject groups in a given age range, no significant differences of PWV existed except in some younger groups (see image; p≤0.04 in some under-40y). Conclusion: Global Ao wall stiffness from PWV in BAV Ao dilatation patients has minimal/no significant difference from non-BAV control PWV, despite genetic factors and different wall structure in BAV patients. This suggests wall tissue differences of BAV patients do not coincide with globally altered Ao stiffness. However, BAV-mediated Ao flow changes manifest regionally, and further study of localized properties would be valuable.

An Open Source Mesh Generation Platform for Biophysical Modeling Using Realistic Cellular Geometries

ABSTRACTAdvances in imaging methods such as electron microscopy, tomography, and other modalities are enabling high-resolution reconstructions of cellular and organelle geometries. Such advances pave the way for using these geometries for biophysical and mathematical modeling once these data can be represented as a geometric mesh, which, when carefully conditioned, enables the discretization and solution of partial differential equations. In this study, we outline the steps for a naïve user to approach GAMer 2, a mesh generation code written in C++ designed to convert structural datasets to realistic geometric meshes, while preserving the underlying shapes. We present two example cases, 1) mesh generation at the subcellular scale as informed by electron tomography, and 2) meshing a protein with structure from x-ray crystallography. We further demonstrate that the meshes generated by GAMer are suitable for use with numerical methods. Together, this collection of libraries and tools simplifies the process of constructing realistic geometric meshes from structural biology data.SIGNIFICANCEAs biophysical structure determination methods improve, the rate of new structural data is increasing. New methods that allow the interpretation, analysis, and reuse of such structural information will thus take on commensurate importance. In particular, geometric meshes, such as those commonly used in graphics and mathematics, can enable a myriad of mathematical analysis. In this work, we describe GAMer 2, a mesh generation library designed for biological datasets. Using GAMer 2 and associated tools PyGAMer and BlendGAMer, biologists can robustly generate computer and algorithm friendly geometric mesh representations informed by structural biology data. We expect that GAMer 2 will be a valuable tool to bring realistic geometries to biophysical models.