1. A computing device comprising: an input device, a display device, and at least one processor; and a storage device storing a computer-readable program comprising instructions that, when executed by the at least one processor, causes the at least one processor to performing operations comprising: obtaining a point cloud of an object and converting the point cloud into a plurality of triangulated grids using a plurality of triangles; selecting a part of the triangulated grids from the point cloud to be simplified, and receiving a number of simplification passes to simplify the triangulated grids from the input device; classifying the triangulated grids into different types of triangles according to a shape of each grid and a location of each grid in the point cloud; simplifying each type of the triangulated grids to obtain a plurality of simplified grids by performing a loop triangular grid function with the number of simplification passes; and smoothing the simplified grids to obtain a point cloud model of the object, and displaying the cloud model of the object on the display device; wherein the loop triangular grid function is performed by operations of: determining two neighboring vertexes V 0 and V 1 for each of the triangulated grids, and using two neighboring vertices V 0 and V 1 to form a side of the triangulated grid; if two neighboring triangles share with the side of the triangulated grid, determining a first triangle ΔV 0 V 1 V 2 and a second triangle ΔV 0 V 1 V 3 neighboring to the first triangle ΔV 0 V 1 V 2 , determining four angles of two neighboring triangles, generating a new vertex denoted as v new = 3 8 ⁢ ( v 0 + v 1 ) + 1 8 ⁢ ( v 2 + v 3 ) in the side of the triangulated grid if each of four angles is a sharp angle; generating a new vertex denoted as v new = 3 8 ⁢ ( v 0 + v 1 ) + 1 4 ⁢ v 3 in the side of the triangulated grid if one of four angles is not a sharp angle, and no new vertex being generated in the side of the triangulated grid if two of four angles are not a sharp angle; if only one triangle adjoins the side of the triangulated grid, determining the triangle ΔV 0 V 1 V 2 according to the side of the triangulated grid, and determining two angles shared with side of the triangulated grid, generating a new vertex denoted as v new = 3 8 ⁢ ( v 0 + v 1 ) + 1 4 ⁢ v 3 if each of two angles is a sharp angle, and no new vertex being generated in the side of the triangulated grid if one of two angles is not a sharp angle; and performing the loop triangular grid function on each side of each triangulated grid to generate a plurality of new vertexes, and connecting the plurality of new vertexes with original vertexes of each triangulated grid to generate the simplified grids in the point cloud.