1. A method for constructing a graph representation for a 3D object, comprising: generating an initial graph representation of the 3D object, wherein the initial graph presentation has a first set of nodes and at least one edge, each node of the first set of nodes in the initial graph representation corresponds to a component of the 3D object, and each symmetric node in the first set of nodes 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 a second and third 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 second and third sets of nodes; and if determining that the second and third sets of nodes match, updating the graph representation by grouping the second and third sets of nodes into one node.