3D Visualization Of Wildfire Spread In Virtual Forest Environment

Wildfire brings great loss to people. Complex and changeable wildfire brings fighting difficulties and challenges. Satellite scan is restricted by measuring time, so scan data can’t always reflect the current state of the fire. Basing on the complex fire burning mechanism, it becomes an effective way to use the computer’s realistic simulation of fire spread in order to make up the lack of temporal resolution. Most wildfire is the surface fire, and it takes great destructiveness; In certain conditions, the surface fire may grow into crown fire and it spreads quickly. High combustion temperature, fire intensity and the influence on the forest vegetation bring forest immeasurable loss. Therefore, choosing the surface fire and the crown fire as objects, according to the wildfire spread model, we simulate the spread of fire in the 3D virtual forest environment by using the virtual reality and geography information system, graphics rendering techniques and so on. It deduces the fire development process in an intuitive way, and provides a scientific basis for the prediction of fire behavior and fire boundary. The main contents and results are as follows:(1) In this article we review the research status of the virtual forest environment, wildfire spread model, fuel classification system, crown fire spread model, and the wildfire spread visualization. Then we make the contrastive analysis on related technologies and methods of surface fire and crown fire spread visualization.(2) The Rothermel spread model and the FARSITE wildfire spread and simulation engine are the most widely used model and the simulation engine in the world. But the simulation results mainly were represented by 2D visualization so far. In this article we set up the 3D models before and after the burning with parameterized single tree modeling software ParaTree, using the terrain paging technique to render the 3D terrain and the road model, visualizing the wildfire spread process with particle system. According to the information of the forest map, digital terrain, fire behavior and their spatial relationship, a visual and realistic 3D wildfire environment was built.(3) For the problem of lacking unified general fuel classification standard inland to support FARSITE wildfire spread and simulation engine, according to the forest map and forestry survey data, we referred to the foreign fuel classification system and the description of various models, classify the fuels by selecting the rational fuel model in the Xiongjiang Town, Minqing Country, Fuzhou City.(4) According to incombustibility of the road or the space distribution features of the artificial fire barrier, with the surface fire spread model, it simulates the fire spreading process, and visually expresses the change of the trees and ground cover in the process of combustion; At the same time, with multiple ignition sources it simulates merging the fire boundary to avoid the wrong expression of wildfire still spreads when it has been reached the fire area and to promote the scientificity of the simulation.(5) With the understanding of the crown fire principle and the judgment of the crown fire type, we analyze the fuel, the terrain and the weather conditions in which the crown fire happens and spreads, to simulate the crown fire spread process. Using length information of crown fire and the programmable pipeline, combining with the vertex shader and the fragment shader technology, we simulated the dynamic effect of the crown fire spread. The process of crown fire of the forest stand and single tree was simulated taking Masson pine and Fir prone as examples.(6) With the existing system VisForest in research group, based on the FARSITE wildfire spread and simulation engine, we integrated surface fire, crown fire simulation and 3D visualization methods. With the data in the Xiongjiang Town, Minqing Country, Fuzhou City, the spread in different parameters was simulated.