3D Simulation Of Warp-knitted Jacquard Seamless Fabric Based On Stitch Structure

Warp-knitting jacquard seamless technology realizes seamless knitting of the warp-knitted fabric from yarn to product without cutting and sewing,avoiding the appearance of seam connection marks on both sides.However,the design difficulty increases due to its complex structure and patterns.3D(three-dimensional)simulation of warp-knitted jacquard seamless fabric needs to be carried out in the design process to solve the above problems.The stitch structure and the pattern effect of warp-knitted jacquard seamless fabric can be seen by developers using 3D simulation before making samples.Thus they can make timely modifications when designing,which can shorten the product development process and reduce labor and resource waste.Although the existing warp-knitting CAD software can design warpknitted fabrics well and some software has flat fabric simulation functions,the research on the3 D simulation of products,especially the warp-knitted jacquard seamless fabric,is still in a blank state.Therefore,studying the 3D simulation of the warp-knitted jacquard seamless fabric is an urgent need for the development of warp-knitting CAD software,which has far-reaching significance for the deep promotion of warp-knitting CAD software in China.In this study,fabric structure mesh models based on the analysis of the knitting process of the warp-knitted jacquard seamless fabric are established,solving the problem of seams on both sides of the existing models for the front fabric piece and the back fabric piece.Firstly,the geometric shape of the stitch is determined by measuring the actual stitch size,and the coordinates of the value points are calculated.According to the stitch interlocking relationship,the stitch is simplified into a geometric mesh model controlled by two mesh points.Then,based on the analysis of the knitting process of the warp-knitted jacquard seamless fabric,a flat mesh model of the warp-knitted jacquard seamless fabric is established.The warp-knitted jacquard seamless fabric is divided into single-tube and multi-tube structures,and the position relationship between different kinds of tube structures and fabric flat mesh models is established.The flat fabric is simplified into a matrix of flat mesh point points as mass points,and an improved mass-spring model is established based on the jacquard pattern.Combining the stitch position distribution of different tube structures,the deformation of the fabric flat mesh model is realized.Finally,based on the fabric flat mesh model,a fabric 3D tube mesh model is established by rotating the mesh points.By calculating the proportional relationship of the distance of the mesh points on the deformed flat mesh model,the rotation angle of each mesh point on the 3D tube mesh model of the fabric is obtained.Based on the distribution characteristics of stitches in different tube structures,single or multiple 3D tube mesh models of the warp-knitted jacquard seamless fabric are established.Based on the establishment of the flat and 3D tube mesh models,the problem in the existing fabric model that the matching relationship between the mesh model and knitting process has been solved.Firstly,the 3D model is voxelized and the initial skeleton of the 3D model is obtained by using a refinement algorithm.Then,the Least Squares Method is used to fit curves to the scattered points of the 3D skeleton,and the inflection points of the fitted curves are calculated by second-order differentiation,obtaining the final simplified 3D skeleton model.Next,combined with the pattern courses,the skeleton is segmented along the vector direction as the skeleton subdivision point,and the model cutting plane is calculated with the subdivision point as the center.At the junction of each section of the skeleton,a cutting plane angle gradient region is established according to the vector direction of adjacent skeletons to achieve continuous cutting along the direction of the model skeleton.Finally,the fabric 3D tube mesh model is bent along the axis of the 3D skeleton,so that the center points of each layer of the tube mesh model and the cutting plane have a common center point,and both are in the same plane.The mapping point of the mesh point on the 3D model is calculated by the intersection point on the cutting plane contour of the connecting line of the tube mesh point and the center point.Through the mesh spatial matching relationship between the flat mesh model and the 3D tube mesh model,the coordinate system transformation relationship of two triangles in a quadrilateral between the flat and 3D models is established to achieve the transformation of the stitch value point from the plane to the curved surface.After completing the surface mesh division of the 3D model and obtaining the coordinates of the stitch-shaped value points on the 3D model,a method for fiber ply modeling and texture mapping was proposed to achieve a realistic simulation of the stitch.Firstly,a geometric tube path was established along the stitch-shaped value points using cubic spline curves,and the mesh parameters of the geometric tube in the axial and radial directions were set.Based on the interpolation points of the path,the position of the surface mesh points of the geometric tubes was calculated.Then,the effects of axial and radial mesh parameters on the stitch surface and the fabric surface were analyzed.On the basis of ensuring the visual effect,a parameter combination that axial segments 15 and radial segment 5 with higher rendering efficiency was selected for simulation.Next,the distribution patterns of various fibers in the yarn were analyzed,and geometric tube models were established for fiber bundles,long hairiness and short hairiness.For fiber bundles with a large amount of fiber,the bump mapping method was used to achieve the stereoscopic simulation of a large number of fibers.Finally,the rendering efficiency of the geometric parameters,the number of geometric tubes and the bump mapping texture were tested.The results showed that the rendering time increased with the increase of the number and complexity of geometric tubes,and the rendering time of the bump mapping method was slightly longer than that of the smooth tube rendering,but the texture size had little effect on the rendering time.Based on the research on the establishment of the fabric mesh model,the surface mesh division of the 3D model,and the simulation of the stitch realism,an EBC(electronic binary control)seamless 3D fabric simulation software was developed using C# and Java Script languages in Visual Studio 2015 development environment,assisted by Matlab R2022 a software.The rendering of the knitted fabric was implemented using the Web GL graphics programming interface.Firstly,the software architecture was established,the interface functions were determined,and the development of the parameter layer,the view layer,and the function layer were implemented.Then,the results of the EBC seamless 3D fabric simulation were displayed,and the simulation efficiency was analyzed.The results showed that the proposed method could simulate EBC seamless knitting fabric quickly and effectively.Compared with existing fabric simulation methods,the simulation efficiency was greatly improved.The research is closely focused on the 3D simulation of circular knitted seamless fabrics in four aspects.Based on the knitting principle and structure of circular knitted seamless fabrics,the software for simulation is developed.The research focuses on the establishment of fabric mesh models and 3D model mesh division,proposes a 3D cylindrical mesh model,and solves the seamless problem on the side of the circular knitted seamless fabric model.By visualizing the results of the 3D simulation,an efficient design process for circular knitted seamless fabrics is achieved,which shortens the development cycle and lays a solid foundation for further simulating complex fabrics in three dimensions.