Abstract: Bark textures realization is a major problem in the field of visualization for virtual trees.It is a tough job to simulate abundant details on the bark’s surface and the progressively-variant transition effects across different locations on the trunk.A method for synthesizing realistic bark textures is presented.The method adopts the idea of patch-based sampling strategy，and can generate a whole piece of trunk according to some bark texture samples.The generated bark textures can efficiently avoid the seam problem caused by common texture mapping approach.Furthermore，by controlling the synthesis probability，the method can successfully simulate the progressively-variant transition effects between the old parts of bark to the tender parts.In addition，this paper also simulates the scar effects on the bark by using scar samples and utilizing edge melting method.Experimental results show that the realistic bark textures synthesized by this method can exhibit the features of tree growth change so as to satisfy the need of realistic tree representation.

Key words: texture synthesis, bark texture, progressively-variant textures, edge melting

摘要： 树皮的真实感表达是树木可视化中的一个重要问题。树皮表面纹理具有丰富的细节，并且树干不同部位的纹理质地可能会发生渐变，要真实模拟树皮纹理的这些效果并不简单。提出一种真实感树皮纹理的合成方法。该方法基于块纹理合成的思想，可以根据几块树皮样图纹理，实现树干部分整张树皮纹理的合成。采用这种合成方法，有效避免了采用一般纹理拼接方法所造成的纹理接缝问题。并且，该方法采用一种控制合成概率的策略有效实现了不同质地的树皮纹理之间的渐变，从而能够真实表现出树皮由老到嫩逐渐变化的效果。基于样本及边缘融合的方式实现了树皮疤痕效果的生成。实验表明，该方法可以有效生成带有生长变化特征的真实感树皮纹理，满足真实感绘制的需求。

关键词: 纹理合成, 树皮纹理, 纹理渐变, 边缘融合