In this paper, we propose the utilization of a kd-tree based hierarchy as an implicit object representation. Compared to an octree, the kd-tree based hierarchy is superior in terms of adaptation to the object surface. In consequence, we obtain considerably more compact implicit representations especially in case of thin object structures. We describe a new isosurface extraction algorithm for this kind of implicit representation. In contrast to related algorithms for octrees, it generates 2-manifold meshes even for kd-trees with cells containing multiple surface components. The algorithm retains all the good properties of the Dual Contouring approach [10] like feature preservation, computational ef.ciency, etc. In addition, we present a simplification framework for the surfaces represented by the kd-tree based on quadric error metrics. We adapt this framework to quantify the in.uence of topological changes, thereby allowing controlled topological simplification of the object. The advantages of the new algorithm are demonstrated by several examples.