This paper proposed a model for 2.1D sketch based on primalsketch [6,7] and a corresponding algorithm based on
SWC(Swendsen-Wang Cut)[1,2]. Given a primal sketch graph, all boundaries' color and curvature information can be
gotten from the dictionary of image primitives of the primal sketch. Suppose all curves in the sketch graph can be
combined into closed contours and then contour can be combined into regions. Calculating boundaries similarity energy
of two regions by comparing the comparability using the color and curvature information of boundaries, then the energy
is regarded as the proposal of SWC. All regions are regarded as nodes of graph space, then the 2.1D sketch problem can
be looked as graph partition problem. In each step, all curves will be reorganized into contours and then contours
generate regions. Some experiment results based on above model and algorithm are given in the paper.