Research On Visualization Of Phase-Field Simulation

The Phase-field method is a one of Computational Materialssolutions,which gets the instantaneous state of the system in time and space by solving the differential equation based on Ginzburg-Landau theory.And then we can study the performance of materials in various aspects.The analysis and extraction of useful information in the data is of great significance for the simulation under the specific parameters.The simulation results often describe the spatial distribution of various physics fields in a text way,how to effectively process these data,and get the visual and intuitiveprocessing results become the focus of the study in Computational Materials Science.However,there are many characteristics such as various types,scale and dimensionsin the simulation results,which bring some difficulties to the visualization of phase field simulation.The purpose of this thesis is totransform the abstract text information into graphics and image signal with a certain shape and color.With the aid of computer graphics technology,we carry out the volume rendering and geometryvisualization of the simulation results,and then get the high quality image of the material structure and the abstract physics field in the whole spatial distribution and the detail.We make full use of the strengths of hardware in computation and storage,to improve the efficiency of real-time rendering of large data sets.Here are three aspects of the main work:1)In this thesis,the key technologies of 3D visualization are analyzed,and the application of visualization in the field of phase-field simulation is explored.We analyze the format of original data file,through the conversion of data format to the target visualization file to build structured points set based the voxel model.Unstructured grid models based on tetrahedral elements are generated by threshold filtering of structured points set.2)We design and implement the ray casting algorithm based-on voxel model,and design different transfer functions and image composition methods to meet the different requirements of visualization,thenrealize the three-dimensional display of themicro structure of the phase-field simulation.We compare the ray casting algorithm based-on voxel model with the volume rendering algorithm based on unstructured grid in efficiency and effectiveness.In effect,both of them can outputvisual picture with high quality.Under the same data scale,the rendering efficiency based on the voxel model is better than that of the tetrahedral unstructured grid,but the efficiency is not high and the difference between them is not obvious.In addition,through the use of the computing ability and texture resources of hardware,we achieve the acceleration of the ray casting algorithm,to a certain extent,and solve the problem of low efficiency of real-timerendering oflarge data sets.The volume rendering of concentration and dendrite structure can not only display the overall distribution and spatial details of the system,but also can display the isosurface of a certain component.3)We extract the contour of each individual element,realize the contour extraction of the same material in the material,and display the structure of the specified composition in the material.The overall picture of the electric field and the polarization vector field is displayed by placing a3 D glyph which is defined by the vector in the space.The vector field is regarded as the velocity field,and the streamline of the electric field is generated by the streamline integral algorithm.The streamline whose seed point at the system boundary is helpful to the study of the oxygen defect movement in the material.There are strain field and stress field in the study of the elastic properties of the composite materials,whose type is two order tensor.The tensor ellipsoidsshow the whole distribution of the tensor field.We construct ellipsoids to show the whole distribution of the tensor by the tensor eigenvalues and eigenvectors.For the stress field,the hyperstreamlins are constructed by creating a streamline through one of the three eigenfields,and then sweeping a geometric primitive along the streamline.Typically,an ellipse is used to the geometric primitive,where the remaining two eigenvectors define the major and minor axes of the ellipse.Sweeping the ellipse along the eigenfield streamlineresults in a tubular shape.The hyperstreamline represents the continuous change of aneigenfield in color and track.In general,the tensor ellipsoids and the hyperstreamline show the distribution of the strain and the stress field and the shape of the local continuous change of the stress field.