Study On Generating Method For Controllable And Realistic Terrain Based On FBM

The generation algorithm of realistic terrain is always the important part of computer graphics, and techniques of environment simulation with natural effects have been becoming more and more important with the development of computer graphics. Fractional Brownian Motion (FBM) is the most important stochastic process in the modern non-linear time series analysis, which can not only express many non-linear phenomena in nature, but also be the best stochastic process to describe real terrain so far. Most fractal terrain models have been based on one of five approaches: Poisson faulting, Fourier filtering, random midpoint displacement, successive random additions, and summing band-limited noises. Random midpoint displacement is a representative algorithm of terrain simulation because of its good visual effects of generated terrain and high practicability of the algorithm's implementation. But the generated terrain by this method is unpredictable beforehand and uncontrollable, for example, we can not predict and control the number of the generated mountain peak, the position and elevation of the mountain peak, the color and roughness of the mountain and so on. Aiming at resolving the problem above, this paper does the research mainly from two aspects (generating module and display module) as follows:(1) Generating module: based on the fractional Brownian motion model this paper presents a new method for generating controllable and realistic natural terrains. In the generating procedure, the whole base-plane of the terrain is first divided into several triangles by using the coordinates of a few known characteristic points on the plane. And then for each triangle, the three dimensional data of the terrain are recursively generated according to a subdividing criterion based on the refined random midpoint displacement method. We can get the data model of Multi-peak Mountain, general terrain, and complex terrain which people expect.(2) Display module: the realistic visualization of the generated terrain data is implemented in PC computer by using VC++6.0 and OpenGL software programming. The involving work contains the implementation of 3-D transformation, hidden line and surface, color, light and material. In order to make the generated terrain more realistic, the generated terrain'background is the blue sky generated by midpoint displacement, and colorful terrain (Snowy Mountain and flat ground) is obtained since different terrain is made different colors. The simulation results show that the proposed algorithm provides a good performance in generating various shape-controllable and more realistic terrains such as multi-peak mountains, general planner terrain, and general combined terrains; and it is a better solution to the shape uncontrollable problem encountered in the traditional fractional Brownian motion based methods in modeling the fractal terrains.