关键词: 圆堆图, 空间曲线, 点云, 三角网格, 纱线模型

Abstract:

Objective The three-dimensional yarn simulation is an important part for yarn design and fabric development. The use of computer simulation technology to simulate and visualize the yarn appearance is the key part of the current research. At present, most yarn simulations are carried out in two-dimensional or three-dimensional space, so that the appearance and shape of the yarn are limited. Therefore, it is necessary to design a fast and real three -dimensional yarn modeling method.

Method Circle stack diagram is first established based on the space circle and the Circle library, and then the spatial spline curve is established by combining the spiral twist equations of the circle stack diagram in different quadrants. According to the twisting characteristics of the fibers in the yarn, the curve is divided into multiple equidistant line segments, the spatial circle represented by the 3-D point cloud is established with the line segments as the normal vector, and the point cloud meshing algorithm is used to construct the point cloud as the initial triangular mesh model. The Loop subdivision algorithm is used to subdivide the mesh model.

Results The effectiveness of the 3-D yarn model based on point cloud method is verified and analyzed, and the 3-D yarn model established by different methods was compared and demonstrated. According to the effect of the 3-D yarn model established in literature, the geometric tube is modeled according to the input yarn parameters to match these fibers, and several single yarns with different structures are simulated, which shows that this is an effective yarn modeling and rendering method. In the three-dimensional yarn model based on the point cloud method, the distribution of fibers in the yarn cross-section is uneven, therefore it is necessary to deal with the regular circle pile diagram established by the regular yarn cross-section. Through the randomness of the starting point of fiber generation and the twisting state of the fiber, combined with the spiral twisting formula of different quadrants, the three-dimensional spatial spline without splicing state can be continuously generated. According to the twisting characteristics of the fibers in the yarn, the curve is divided into multiple equidistant segments, and the spatial circle represented by the 3-D point cloud is established with the line segments as the normal vector. Then, the point cloud grid algorithm is used to construct the point cloud as an initial triangular mesh model. Finally, the Loop subdivision algorithm is used to subdivide the surface of the mesh model, and the number of subdivisions is set according to the required model accuracy to improve the overall smoothness of the 3-D yarn model. In addition, the hairiness on the 3-D yarn model is formed by one end of the fiber protruding from the surface of the yarn body, which is consistent with the generation state of the actual yarn hairiness. Experiments show that the method can quickly generate a real 3-D yarn model, and the model contains multiple feature points such as number of fibers, fiber diameter, yarn twist direction, hairiness, and so on, which further illustrates the effectiveness of the method.

Conclusion Based on the importance of 3-D yarn simulation in yarn design and fabric development, a method for parametric modelling of 3-D yarn based on point cloud is proposed. The starting point of 3-D yarn model establishment is the circle stack diagram, the spatial spline curve composed of multiple equidistant line segments is created according to the custom conditions, and the spatial scattering circle expressed by 3-D point cloud is generated with the line segments as the center of the circle, and then the 3-D point cloud reconstruction algorithm is used to construct the point cloud between multiple spatial scattering circles into a triangular mesh model, and finally the surface subdivision of the initial 3-D yarn model is carried out to obtain the 3-D yarn model with high accuracy. The experimental results show that the 3-D visual effect of the yarn model is more obvious based on the number of constructed point clouds and the optimization of subdivision. At the same time, the algorithm realistically expresses the geometric characteristics of the simulated object, such as yarn thickness, hairiness, twist direction and fiber diameter, and so on, and can be adjusted according to the actual situation. The simulation is easy to operate and runs fast, which can better assist yarn design and development for practice.

Key words: circle packing, spatial curve, point cloud, triangular grid, yarn model