Research On Direct Layering Algorithms Of Point Cloud Models Based On Curve

Additive manufacturing technology,as a disruptive manufacturing method that leads the industrial transformation,has been currently paid attention in various fields.This technology converts the three-dimensional data models into the two-dimensional slice models,and then uses the method of adding materials for processing and manufacturing,that is,the principle of layer-by-layer superimposed manufacturing.As the layering technology of how to slice a three-dimensional model into two-dimensional models,it is one of the indispensable links in the early processing in additive manufacturing technology.The point cloud data model is a kind of three-dimensional data model composed of points.At present,many experts and scholars have studied the layered technology based on point cloud data.How to accurately obtain layered contour points and layered contour lines is the key and difficult issues in the current researches of this technology.After extensive literature researches,this paper,based on the existing researches on layered algorithms based on the point cloud models,has carried out researches on the above problem and made some progresses,mainly in the following three aspects:(1)The most commonly used method of projection is to obtain layered contour points by linear projection,but it still needs to use other methods to extract relatively accurate layered contour points from the point set obtained by linear projection,and the steps are tedious;and the research on curve projection is relatively lacking.In this paper,the layering algorithm of the point cloud model based on curve projection is proposed.The quadratic surface is obtained by least square fitting of the selected points and their nearest points in the divided area.The trajectory plane is obtained by using the selected point,its normal vectors on the quadratic surface and the normal vectors of the slice plane.The trajectory line is obtained by intersection of the quadratic surface and the trajectory plane.Then the selected point is projected along the trajectory line onto the slice plane to obtain the initial layered contour point.And then the B-spline curve is used to fit layered contour lines.(2)It can also obtain layered contour points by using the intersection method.The common used method is linked by straight-line.Although the accuracy is higher than the linear projection,there is still a large loss of accuracy.In this paper,the point cloud model layering algorithm based on the intersection of curves is proposed.The nearest distance method is used to select the closest point pair set belonging to the upper and lower regions of the slice plane.The quadratic surface is obtained by the least square fitting method of the selected point in the closest point pair set and its nearest points.The intersection plane is obtained by the normal vector of the slice plane and the line between the selected point and its corresponding point.The intersection line is obtained by the intersection of the quadratic surface and the intersection plane.Then the initial layered contour points are obtained by the intersection of the intersection line and the slice plane.And then the Bspline curve is used to fit the layered contour lines.(3)The layered algorithm based on curve projection can get layered contour points.Because of the larger number of projected points,the operation time of program is longer.Therefore,combined with the method of selecting the nearest point pair in the intersection method,this paper improves the above-mentioned layered algorithm based on curve projection for this problem,that is,only the points in the nearest point pair set selected by the nearest distance method are projected.In order to verify the practicability of the above three algorithms,a variety of point cloud models were used to verify them.The results show that all three algorithms can obtain layered contour points better and have good stability.At the same time,the innovation points as well as the shortcomings of this paper are summarized.And the direction of future research and development of layering algorithms based on the point cloud model can be pointed out,which provides the useful reference for further in-depth study of layering algorithms based on the point cloud model.