Abstract:

Objective The design process of knitted fabrics is long and high in cost, including material cost and time cost. Computer simulation technology can greatly simplify the design process, but knitted fabrics are difficult to simulate due to their complex structural characteristics. This study represents an effort to provide a solution to this problem by three-dimensional (3-D) modeling of stitches and real-time rendering of knitted fabrics.
Method The three-dimensional simulation of needlework mainly includes two stages, i.e., three-dimensional modeling and real-time rendering. In the modeling stage, the yarn center trajectory curve is generated by the improved non-uniform Catmull-Rom curve pyramid algorithm, and the three-dimensional model of the yarn is generated by sweeping, so as to realize the rapid modeling of complex stitch based on basic stitch. In the rendering stage, the ambient light occlusion Phong algorithm and the Kajiya-Kay lighting simulation algorithm are adopted to render the main part and burr part of the yarn model respectively, so as to obtain real-time realistic effects.
Result Based on the actual operation needs of knitting designers, this study refers to relevant general weaving methods at home and abroad, and uses the improved non-uniform Catmull-Rom curve pyramid algorithm to generate the yarn center trajectory curve and then sweep to generate the yarn three-dimensional model, realizing the parametric modeling of positive stitches, reverse stitches, and twisted stitches, and perfectly solving the modeling problems that are easy to appear, such as yarn distortion and model penetration. The parametric needle design mode is not only compatible with the commonly used conventional weaving methods, but also expands the designer's free innovation design capabilities. In addition, the design implements a user-defined stitches library module, including details such as stitches type, number of knitting rows and stitches, and topological relationship of stitches nodes. Various distinctive complex stitches can be independently designed and stored, providing data support for designers' personalized innovative designs. Users can design various stitches and automatically load them into the model library as basic stitches for expansion. In the rendering stage, this paper uses OpenGL to achieve realistic real-time rendering of yarn fiber details of knitted garments, uses line elements to simulate the fibers in the yarn model to improve rendering efficiency, and uses the ambient occlusion Phong algorithm and the Kajiya-Kay lighting simulation algorithm to render the main body and burr part of the yarn model, respectively, taking into account the characteristics of different rendering subjects, and obtains realistic rendering effects while having good rendering efficiency. In addition, the stitches model generated by sweeping the center line of the yarn has a good compatibility with this rendering algorithm. Since the process of calculating the center point of the yarn is omitted, it has a faster computing speed, which further improves the rendering efficiency. The rendering result diagram well reflects the structural characteristics and design elements of the stitches method.
Conclusion The 3-D simulation method is utilized to expand and simulate various stitches, which significantly improves the efficiency of knitted clothing design. The improvement of design efficiency is mainly reflected in two aspects. (1) A module for user-defined stitch library is designed to facilitate the design and use of various stitches, and (2) the real-time display of knitted fabric simulation effects is achieved through 3-D modeling and real-time rendering technology of stitches, which is convenient for designers to improve design elements.

Key words: knitted garment, stitch modeling, module of stitch library, stitch design, real-time rendering, three-dimensional simulation