3DP分层切片中基于点云射线投影的NURBS曲面切片算法  

Research on Ray-NURBS Slicing Method Directly from Point Cloud for 3DP

作　　者：李娜[1] 程继红[1] 杨继全[1] 

机构地区：[1]南京师范大学电气与自动化工程学院,南京210042

出　　处：《机械科学与技术》2015年第2期242-246,共5页Mechanical Science and Technology for Aerospace Engineering

基　　金：国家自然科学基金项目(61273243);江苏省高技术研究项目(BG2006042);江苏省高校自然科学基金项目(09KJD46004)资助

摘　　要：给出用于三维打印机的分层切片算法。利用打印模型点云图像不同方向的分形维数参数和切片层数来确定切片方向;通过建立点云在切平面映射的NURBS曲线来拟合模型轮廓线,然后产生打印机使用的指令G代码。设计λ进制数来确定切片方向。λ进制数由两个要素组成,其一是分形维数D,其二是切片层数N,D和N都是越小越好。确定了打印方向后,可进行切片处理,得到切平面。点云图像的散乱点映射到切平面,这些点用带一定偏移量的射线来划分,射线与点云交点就是形成NURBS曲线的控制点。详细给出控制点寻找以及建立NURBS曲线及曲面的过程。首先引入分形维数参数D作为重要参数来确定切片方向,使用λ进制体系优化打印方向,提出高效的射线分割算法来分割点云,并使用NURBS曲线拟合来获得精确的边界轮廓。通过两个模型验证该算法误差都在公差允许范围内,优化了打印方向,提高了打印速度。A method for slicing the 3D model directly from point cloud data is presented for three dimension printer( 3DP). The first is the direction of slicing which is determined according to the fractal dimension( D) and the sum of slice layers. The contour curves generation for rapid prototyping model via ray cutting according to the density of the data point. The number system was firstly used which is composed by D and N,and the smaller of the better for slice plate. After getting the slice plate the point cloud data set is segmented along the building direction to a number of slice layers. The points are projected to the mid-plane of the layer to form a 2D band of scatted points. A number of points are picked up along the band and a NURBS curve is fitted to construct a boundary curve using ray shooting method which is called Ray-NURBS. And the last G codes are given for print according to the NURBS curve. The fitted NURBS curve represent a boundary contour which is more accurately close to the entity and more precise image matching can be gotten. Firstly,used to determine the direction for slicing and the ray shooting method is adopted to define the control points for NURBS curve. The experimental results demonstrate the calculation errors are within the tolerance,and the print time is deduced largely.

关 键 词：三维打印机(3DP) 切片算法 点云 射线投影法 NURBS曲线 

分 类 号：TP334.8[自动化与计算机技术—计算机系统结构] TP391.7[自动化与计算机技术—计算机科学与技术]