Research On Weft Knitting Loop 3D Simulation Technology Based On Knitting CAD

Most of the existing basic loop model is represented by a parametric equation,and it is different from real loop.And the realization method of 3D visualization of loop is difficult,resulting the effect of knitted fabric appearance and pattern simulation is not perfect.So simulation has become the bottleneck for the development of CAD technology.Therefore,researching on accurate,perfect loop model implemented easily plays an important role in the development of CAD technology.First of all,the structure of weft loops are analyzed in three dimensional space.And the type value points that determine the shape of loop model are obtained with the actual loops.The craft parameters of the actual loop is measured by experiment,and the relationship between the position of the type value point and the craft parameters of the loop is calculated by using the measured data.Based on the value point,the shape model of the centerline of the weft knitted loops is established by combining the nonuniform rational B spline curve.Due to the application of curve modeling technology(NURBS curve),and value point comes from the actual loop,the geometric model of the loop centerline has a more real effect.In order to achieve the purpose of efficient,true and accurate 3D simulation,and quantifies the geometric model of centerline.By numerical analysis method,the curve fitting analysis of the loop centerline is carried out,and its function expression is piecewise fitted.The structure of the weft knitting loop is accurately described by mathematical method,which provides a necessary condition for the realization of the 3D simulation of the loop.Using the OpenGL function library,selecting the function of sphere,a plurality of overlap arranged by differential method,the center sphere's track is the loop centerline and the diameter of the sphere model is loop diameter.The function relation obtained by curve fitting controls sphere can be arranged in accordance with the loop centerline.The loop model combined with these spheres has a good 3D effect,and the overall surface effect of the model is also consistent with the actual loops.This study has made some achievements in the geometric structure model of weft knitting loops.The centerline model drawn by curve modeling technology has improved the shortcoming of the parameter equation model not consistent with the actual yarn structure.In the aspect of computer 3D simulation,a more simple way is used to draw the solid model,avoid the difficulties caused by the surface modeling,light and texture mapping are used to enhance the simulation effect,which can reflect the structure relationship of the loops.The results of the study contribute to the further improvement of the 3D simulation of weft knitted fabrics.