Research On The Method Of 3D Scene Modeling For Crowd Evacuation Simulation

Public security is the cornerstone of national security and social stability.Every year,all kinds of public security crises occur frequently,which seriously threatens the safety of people's life and property.How to effectively manage the huge crowd with complex relations in the large-scale public buildings and how to scientifically and effectively evacuate the crowd when the emergency situation occurs are very important.A highly realistic significance should be attached to the contingency plan of emergency evacuation management which is designed according to the facilities,environment and the possibility of various security crises.The emergency plan of traditional evacuation management was once designed by the expert manually.But with the building of the large-scale public facilities and the multiplified types of public security crises,it is impossible to solve the complex security problem without computer.The traditional practice method will be restricted by the staff size and the site condition,so it cannot really verify the effectiveness of the crowd evacuation plan.The crowd evacuation simulation system is to generate a 3D model of public facilities and the crowd with a computer to simulate various possibilities of the security crisis and the corresponding evacuation plan,and display the crowd evacuation scenario in 3D.It can verify the rationality and validity of the evacuation plan by analyzing the simulation results.The crowed evacuation simulation system is mainly composed of four parts:3D scene modeling technology,the scene semantic generation technology,group motion simulation technology and the simulation result analysis technology.The current study of evacuation simulation is mainly focused on evacuation algorithm to simulate the pedestrian behavior in the evacuation.The scene used in most of algorithm is very simple,such as a single room with a few exports,which cause the algorithm limited to simulate the several phenomenon of the crowd evacuation.That cannot simulate the evacuation in large scale scenes,which is unable to verify the rationality and validity of the evacuation management plan.So the crowd evacuation simulation requires a complex scenario model.This paper mainly discusses the scene modeling of evacuation simulation,such as the generation of 3D scene and scene semantic.So the evacuation algorithm can be used in the large crowd scene,which can help the experts to analysis the contingency plans of evacuation management and establish reasonable contingency plans to manage the crowd in an emergency situation to avoid massive casualties.With the popularization of photography,GIS and the internet,the images of scene can be obtained more and more easily,so this article mainly studies the 3D modeling and semantic generation method based on the images.The main contents and innovations of the paper are summarized as follows:1.Proposing a correction algorithm based on main vanishing point with single image.The image obtained from the internet or shooting may be distorted in the process of imaging.With the loss of the Z depth information,the image cannot be corrected without several constraints.But considering the image with simple structure cannot find sufficient constraints,so certain assumptions are needed to achieve mage correction.This paper proposes the correction algorithm,which gets better correction effect,on the basis of main vanishing point with single image by analysis the characteristics of the projection center and the main vanishing point.The contour information of the object is achieved by analyze the corrected image for the use of 3D modeling.2.Proposing a building contour generation algorithm based on SARM homotopy mappingThe building modeling is dependent on the building's contour,so it is very important to quickly get the contour information according to the building's image.Combined with homotopy mapping algorithm,this paper transforms the generation of the building's contour to the homotopy mapping of the profile curves from the bottom to the top of the building.By analysising the characteristics of the existing buildings,the paper summarizes four factors which affect the building exterior outline,and puts forward the building contour generation algorithm based on the SARM homotopy mapping.The algorithm solves the limitation on the contour curve of the homotopy mapping and provides diversity and flexibility for the building contour generation method,which improves the speed of 3D modeling.3.Proposing a building generation method based on shape grammar and SARM homotopy mapping.How to quickly generate the building is related to the efficiency of the whole scene modeling as the building is the main part of the evacuation scene.Considering that the accuracy of the build modeling is not required in crowd evacuation simulation,the paper puts forward the automatic generation method of building modeling based on shape grammar.Through the decomposition of building structure,the paper analyses the characteristics of the building components,and constructs the corresponding shape grammar to control the automatic generation of building.When the contours of each floor of building are obtained by SARM algorithm and the relevant parameters are set,the system can generate the building automatically according to shape grammar,thus greatly accelerate the speed of 3D modeling of the building.4.Proposing a two-layer semantic representation method of scenes.The scene semantic is essential to individual path generation in crowd simulation.When the object contours are accessed in the image,the semantic information of the object will be obtained,but further integration is needed.To facilitate the later use for individual path planning in evacuation simulation,this paper puts forward the two-layer structure semantic representation method by dividing the semantic information into the data layer and the topology layer,and unifying the semantic representation rules.In the data layer,the indoor and outdoor objects are classified into four categories according to the characteristics of the crowd evacuation:feasible regions,doors,obstacles,and stairs,while the topology layer records the topological relations between the feasible regions to support fast path planning.This method makes the scene semantic expression standardization and simplification which is advantageous to the evacuate algorithm realization.