目的 视景建模中,采用“公告板”贴图法对同树种不同个体树建模时,需生成各种形态各异的树木纹理图像,为此提出一种新的生成树木纹理图像的随机变形网格方法。方法 首先将树木的原始纹理图像进行网格划分,再对网格顶点进行随机变形,最后将生成的不规则网格中的图像映射到新图像中相应的规则网格上,得到变形后的纹理图像。结果 应用随机参数控制树木图像的变形,模拟出成长环境因素对树木形态的影响。本文方法比采集多幅个体树图像贴图方法更简便,容易实现;比用同一幅图像进行多个个体贴图的视觉效果更真实。结论 本文方法生成的树木纹理图像应用于“公告板”贴图时,在视景模型中能较好地模拟出同一树种的多个个体树情景。该方法基于图像的局部变形,仍然保持原始图像内容的整体基本形态和内部结构的连续性,因此,同样适用于其他不规则形状的自然景物(如山峦、河流、海浪等)的图像处理。

Objective To address the problem of how to produce variform individual texture images of tree from the same tree species through the method of “bulletin board” mapping in scene modeling, a method to generate tree texture images through the use of a random transmogrification mesh is proposed. Method The original mesh is utilized to divide tree texture images. Then, random transmogrification of the mesh vertexes is conducted. Lastly, the generated irregular mesh images are mapped on a corresponding regular mesh in the new images; texture images are obtained after transmogrification. The effects of mesh division quantity, transformative coefficient of the mesh, and quantity of mapping nodes on the transformative results are simulated. Result By selecting the mesh division number, transformative coefficient of the mesh, and quantity of mapping nodes appropriately, the original texture images of trees after transmogrification can be converted into multiple ones that have similar basic forms but different details. Experimental results indicate clearly that the problem of texture image generation of different individual tree from the same species can be solved by the proposed method. The proposed method involves a stochastic parameter to control the local transmogrification extent of tree images; the environmental impact on the individual form exerted by various random factors in their growing environment is reflected. The method is much easier and more convenient than individual tree image mapping. Additionally, the visual effects produced by this method are more real than those produced by mapping multiple individuals in the same image. Conclusion A new method to generate tree texture images through the use of a random transmogrification mesh is proposed. The transmogrification extent of tree images is controlled by a stochastic parameter; the effects on the individual forms exerted by various random factors in their own growing environment are simulated. Images of individuals with various shapes in the same species can be obtained by selecting the appropriate transformative parameters. Experimental results show that when the tree texture image produced by the proposed method is applied in “bulletin board” mapping, the scene of multiple individuals of the same species can be simulated well in scene modeling. Local transmogrification of the image shows that the continuity of the original image content remains, including the overall basic shape and internal structure. Therefore, this method is also applicable to image processing of several other out-of-shape natural scenes (e.g., mountains, rivers, ocean waves).