The Lightweight 3D Tree Modeling And Applications

Fast rendering a complex forest scene is an extremely challenging problem in computer graphics, and trees are more representative plants in the forest scene. Because of the complex geometric detail and the huge amount of mesh data for the existing tree model, it influences the model rendering efficiency and fast visualization application of forest scene. In response to the above questions, this paper has conducted the research for the lightweight 3D tree model modeling. According to the relative distance of viewpoint and tree models, divided nearly, middle and far three levels, this paper adopts different tree simplification strategies to construct the lightweight 3D tree models. The main work and results of this paper are as follows:(1) A large proportion of data in 3D tree model is the information of leaves, and in order to reduce the amount of data for 3D tree model, this paper proposes a divide and conquers method of leaves simplification for preserving visual perception. This method combines the similarity of texture color with geometric shape of leaves for the selection and merging of similar leaves. Then it uses a divide and conquers method based on the topology of branches or spatial distribution of leaves to partition the leaves simplification regions, as well as speed up the process of merging leaves to realize the 3D tree models simplification for preserving visual perception characteristics. Experimental results show that this method can effectively decrease the amount of geometric data of tree models, improve the rendering efficiency, and be applied to realistic fast rendering of the close-range trees.(2) For further reduce the amount the geometric mesh of 3D tree models near the viewpoint, this paper proposed a skeleton-based simplification method of 3D branches, based on the 3D leaves simplification. The method uses a homogeneous layered simplification strategy for branches, extracts the skeleton of branches and constructs similar cylindrical surface or intersect trapezoid to reconstruct the trunk, branches, in order to achieve the lightweight purpose for geometry of the branches.(3) It is important for the rapid visualization of large scale forest scene to preserve the visual perception. In order to preserve the geometric features and visual perception of tree model, this paper presents a real-time recombination method of 3D tree model on visual importance. This method adopts visual attention model and the visual characteristic of tree structures, then uses geometry-based and image-based methods to simplify tree models and construct a hybrid representation model for the 3D tree models based on visual perception. The hybrid representation model reflects the visual perception features of 3D tree models that can embody topological semantics in dynamic simulation. In addition, this method automatically extracts the representation information of 3D tree model based on visual perception, and recombines model information in real time according to the dynamic viewpoint of virtual scene. Experimental results show that this method can not only preserve better visual perception for 3D tree models, but also effectively decrease the geometric data of forest scene, and improve the rendering efficiency and walkthrough speed of forest scene.(4) The realization of complex forest scene. Based on the LOD strategy, this paper combined with the dynamic viewpoint of forest scene and integrated different simplification strategies of tree model, dynamically invoke and recombine tree models with different geometric detail to achieve forest scene rapidly visualization.