The Research On Modeling Plants In Virtual Environment

Realistic simulation of the natural scene is one of the most important research areas in computer graphics, vegetation and plants ale always the important components of natural scene. It has important applications in virtual reality, computer animation,3D video games, special effects in movies, military emulations, etc. With the rapid development of programmable graphic hardware, people set higher requirements on realism of screen and efficiency in rending. Plants are incredibly complex objects in their own right, usually even a sparse vegetation scene have to be rendered using billions of primitives. With the limited computational power, it is difficult to simulate the dynamic vegetation scene because of liquidity and randomness of wind field additionally.This thesis introduces the modeling methods of plants, and has explored the following problems. First, we improve the typical modeling method of plants-L system, and realize the model of tree. Second, we simulate the dynamic sense. The complex tree structures are good for expressing the realistic plants, but it brings a large number of calculations. Accordingly, it is unrealistic when using simplistic plant model. We seek to find out that animation of plant structures can be accomplished at real-time frame rates without sacrificing performance. The main methods of thesis are mainly in the following aspects:Based on tree's morphologic hierarchy structure, trees are created from a set of parameter values describing the typical geometrical structure by recursive algorithm. Each level has the same set of parameters, and uses cylinders to describe the branches'appearance.Based on the aerodynamics and noise functions, wind is simulated by combining the noise functions. Truck and branches are affected by different noise functions. According to relation between braches and wind direction, we distinguish three different cases:branch of wind-facing side, branch of opposite side, branch of perpendicular to wind direction. We combine all the forces such as like lift, drift, inertia, etc and simulate them as a stochastic process for suiting implement on the GPU. The deformation of trunk and branches are obtained according to the skeletal animation principles. The problem of joint is solved by using indexed vertex blending and unifying the whole model as a single grid.Finally, we achieve the animation of swaying tree by using the simulation levels of detail, instancing, and GPU-accelerated technique.This thesis orients real-time applications such as virtual reality, computer games, and focuses on tradeoffs between realism and efficiency. The simulation does not strictly follow physically correct.