1. A method for constructing a graph representation for a 3D object, comprising the steps of: generating an initial graph representation of the 3D object, wherein the initial graph presentation has at least two nodes and at least one edge, each node of the at least two nodes in the initial graph representation corresponds to a component of the 3D object and each symmetric node in the at least two node is associated with a symmetric indication value identifying a symmetric group; selecting a symmetric group that has most symmetric nodes; selecting two nodes from the symmetric group, wherein a distance between the two nodes is the largest; obtaining two set of nodes by expanding separately from the two nodes to their directly connected nodes, wherein if a node is connected directly to both two nodes, the node is excluded from the two set of nodes; and if determining that the two sets of nodes match, updating the graph representation by grouping each set of nodes into one node.