基于多层次特征结构的二维形状渐变

二维形状渐变在二维角色动画、模式匹配、几何造型中有着重要的应用.已有方法大多根据边长、角度、面积等局部几何属性来完成形状之间的最佳对应和渐变,忽略了形状的内在特征结构.为此,提出一种基于多层次特征结构的二维形状渐变方法,首先将源形状和目标形状分解为若干个视觉显著性特征,并通过一种用户启发式的半自动方法建立2个形状的特征对应关系;然后根据形状的特征信息构建源形状和目标形状的多层次特征结构,分别表示形状特征的整体位置和朝向、形状特征的局部朝向和形状特征的局部细节;最后组合不同特征层次上的插值结果,重构出中间形状.在源形状到目标形状的渐变过程中,针对不同层次上的特征信息分别使用近似保刚性插值、边角插值以及弹性线性插值方法进行过渡.实验结果表明,该方法简单高效,有效地避免了形状的内部扭曲,保持了形状的局部特征,可产生自然、光滑且视觉真实的形状渐变序列.

2D Shape Blending Based on Multi-Level Feature Structures

2D shape blending has been widely used in 2-D character animation,pattern matching,and geometric modeling.Previous algorithms mostly tend to use local geometric elements such as edge lengths,angles and areas,to associate the regions on the two shapes which look alike,but oblivious to the intrinsic feature structures of the shapes.This paper presents a new method that blends planar shapes in terms of their intrinsic feature structures.Firstly,the source and target shapes are decomposed into several pairs of features,respectively,which are further associated via a semi-automatic approach that is based on user’s heuristic.Secondly,a multi-level feature structure is defined,representing the global positions and orientations,local orientations,and local details of the shape features.During the shape blending,the feature structure is interpolated from its source to target configurations at each level.Lastly,intermediate shapes are derived from the interpolated results of all levels of the feature structure.Experimental results show that the method can effectively avoid shape distortion and preserve local shape features,as well as generate smooth,natural and visually pleasing effects.