A New Method To Simulate Fancy Yarn And Fabric Based On Fractal Theory

So far, the fabric CAD technology is always one of important computer application and research in textile field. Fabric CAD, as a high-tech method, has provided convenience for the textile design and production. The simulation of fabric appearance can forecast the effect of fabric appearance in the design stage, which plays the role of replacing making sample and enhance the efficiency of developing new products and new varieties. Therefore, the research of fabric CAD has great practical value and wide application prospect. Simulation of yarn and fabric appearance is one of important parts of the fabric CAD system.The present situation of fabric CAD systems and some methods of simulating yarn and fabric are analyzed in this paper. Based on analysis of yarn's physical and geometrical structure of fancy yarn and the theory of making yarns, the mathematical model of some kinds of common fancy yarn are constructed. The realistic simulation effect of twisted yarn under shining is generated by set up illuminating model on the surface of yarn. And some fractal theories are applied into simulating random fluffy effect of yarn and random drape effect of fabric.Firstly, according to physical and geometrical structure of fancy yarns, the principle of weave and parameter of craft, the mathematical model of yarn appearance is established, as well as the yarn surface illumination model and hairiness algorithm. The paper has mainly simulated single yarn and twisted yarn as well as knot yarn, loop yarn, wave yarn and chenille yarn. The effect of fancy yarns embedded into fabrics has also been simulated at the same time.Secondly, the paper studies the basic model of fractal growing theory -- Diffusion Limited Aggregation (DLA) model. The method of computer simulation for DLA model is analyzed and achieved. Evolvement of the model is discussed in the paper and multiple styles of aggression effect are figured out. Combining with DLA model and conclusions of simulating yarns, double-side leaner DLA algorithm generates the fluffy template, and texture synthesis with basic yarn image to simulate the fluffy effect.Thirdly, the paper studies the principles of the fractal brown motion using RMD algorithm, and fractal curve by linear-RMD algorithm and surface by planar-RMD algorithm are realized. And linear-RMD algorithm is used to simulate fluffy effect of fancy yarn. The paper has put forth discrete grads searching texture mapping algorithm, and random folding and crooked effect of fabric surface is simulated by synthesizing RMD surface template and fabric effect. The experimental results show that, RMD algorithm is efficient to cerate random bump texture, and it also can be used to create other kinds of random texture.The creativeness of this paper is that it proposes using improved algorithms of DLA and RMD into simulating fluffy effect of fancy yarns. The algorithms studied in this paper are effective to reflect the fluffy characteristics of fancy yarns, which are irregularity, random diversity and local self-similarity. The methods of discrete grads searching texture mapping algorithm is put forth firstly in this paper to map on irregular and random surface, which are proved feasible and effective on simulating random bump texture of fabrics with the results of experiments on them. The methods in this paper open a new way to simulate yarns and fabrics. It is sure that those methods will be greatly meaningful by perfecting it and applying it to the textile CAD.