Abstract:Vegetation, terrain, and man-made buildings are the primary parts in a 3D geography scene. Trees, as the main component of vegetation, bring greater difficulties in presentation of themselves in a 3D scene than others due to complex natural forms. Geometry-based model, with huge computational burden to real-time scene rendering, could present 3D tree details much better. However, a simplified tree model based on texture has generally better rendering performance than the geometry-based model, but with rather rough 3D effect. Reasonable compromise on the rendering performance and visual 3D presentation is a big challenge, becoming a research focus in the field of virtual geographic environment. This study proposes a self-adapting billboard to present a tree in a 3D scene. Firstly, a set of tree pictures should be taken from different viewpoints or pre-constructed based on different perspectives of the 3D tree model. Then, a billboard is taken as a geometrical carrier of dynamical texture. While viewpoint moves, the direction from the viewpoint to the target tree will be regarded as a determinative parameter to pick out one best-match picture of the tree from the pre-constructed picture set to replace current texture on the billboard. It makes the rendering effect of trees much similar to the real observations from a relative viewing angle. At last, a 3D scene with many trees is rendered in a browser based on WebGL. The result proves that the rendering efficiency and effect are both acceptable.