| Whole knitting technology is one of the current research hotspots as the most advanced knitting method in the knitting field.Products knitted with this technology in 3-D,effectively eliminating post-processes such as the cutting and sewing processes,saving the cost and improving the production efficiency.However,the pattern design processes of whole garments are complex,and patterns are made in different ways for different kinds of styles.The existing computer aided design systems for whole garments at home and abroad mainly provide pattern design methods and pattern libraries for some basic styles(such as pullovers,vests,skirts,etc.).When new products outside the pattern library need to be developed,designers must make patterns manually,which not only takes a long time,but also relies heavily on manual experience.This greatly limites the development of whole knitting technology.In addition,the existing computer aided design systems for whole garments also have great limitations on the size modification of the pattern,and only provide some fixed specifications for each style.Designers need to modify each part one by one if the specifications outside the system are designed,which is tedious and error-prone.In view of the development demand of new whole garment products and the shortcomings of the existing computer aided design system in pattern design,this work studied the mathematical models and data structure for the pattern design of whole garments and focused on the design methods of 2-D paper pattern based on parameterization.Finally,a pattern design system for whole garments was developed based on the research results.Firstly,the basic knitting processes of whole garments and the graphic expression methods of knitted pattern design were studied,then the mathematical models and data structure of whole garment pattern design were constructed.Knitting processes studied based on the knitting principle of whole knitting technology provided theoretical basis for the process design of knitted patterns.The graphic representation methods were analyzed based on multi-view representation and color code representation,and the results showed that the color code representation has more advantages in the process of constructing data structure for knitted patterns.Based on the parametric design methods and the characteristics of knitted garment pattern design,the mathematical models of paper patterns and knitted patterns were constructed in matrix form,respectively,in which the mathematical models of paper pattern include parametric mathematical model and key point mathematical model.The final shape of paper patterns was determined by editing or modifying the parameters,and the rapid transformation from paper pattern to knitted pattern was realized by extracting the key points of paper patterns.Based on mathematical models and color code representation,the data structure of paper patterns and knitted patterns used to store parameters and key points were constructed,respectively.Knitted pattern data structure included color code information data structure and graphic display data structure that was established based on quadtree structure and color code information data structure and was utilized to display graphics in blocks.Secondly,the feasibility and transformation modes of knitting 3-D fabric on computerized flat knitting machine were analyzed and the knitting models of whole garments were established,realizing the transformation from 3-D style to 2-D pattern for whole garments.By constructing the mathematical models of needle beds and 3-D fabrics,this work analyzed the conditions directly knitting the tubular shape and open shape on computerized flat knitting machine onetime in theory.The results showed that 3-D tubular fabrics must meet two conditions at the same time,that is,the fabric has two layers at most and the width of the two layers is equal,while 3-D open fabrics only need to meet one condition,that is,the fabric has two layers.The premise of the above conditions was that the width of the fabric does not exceed the width of the needle bed and the above analysis realized the feasibility prediction of knitting whole garments.Based on the forming condition knitting fabrics,this work put forward three methods converting garments that cannot be directly knitted on computerized flat knitting machine to the ones that can be directly knitted on the machine,namely,changing knitting direction,changing garment structure and changing knitting technology.Taking advantage of the above three transformation methods,the knitting models of whole garments were established,and the rapid transformation from 3-D styles to 2-D patterns for different types of whole garments were realized based on the knitting models and garment structure.Thirdly,the geometric entity constraint relations between 2-D paper patterns of whole garments were constructed,and the establishment of constraint graphs and constraint data models were finished,achieving the parametric design of 2-D paper patterns.Based on the mathematical description between geometric elements of 2-D paper patterns,the elements were expressed in computer and encapsulated to geometric entities.According to the drawing characteristics of 2-D paper patterns of whole garments,the geometric entity constraint relations of 2-D paper patterns were constructed,including parameter constraint relations and geometric constraint relations.Among them,parametric constraints reflect the attributes of geometric entities,such as shape,size,etc.,while geometric constraints reflect the constraint relations among geometric entities,including parallel constraints,vertical constraints,rotation constraints,ray constraints,extension constraints,point and line constraints,line and line constraints,line and arc constraints,line and curve constraints and proportional constraints.Then,the geometric constraint graph of 2-D paper pattern based on graph theory was constructed and the transformation from the processes drawing 2-D paper pattern to the processes establishing constraint relation was realized.The geometric constraint graph reflected the constraint and influence of the current geometric entity on the subsequent geometric entity,and a driven constraint graph was constructed to realize the constraint and influence of the previous geometric entity on the current geometric entity.The geometric constraint data model and the driven constraint data model were established respectively based on the geometric constraint graph and driven constraint graph.The constraint solving of geometric entities was realized,achieving the parametric design of 2-D paper pattern.By marking,extracting and saving the key points of 2-D paper patterns,it laid the foundation for the transformation from2-D paper pattern to 2-D knitted pattern.Finally,the algorithms converting 2-D paper pattern to 2-D knitted pattern were investigated,and the pattern design system of whole garments was developed.Based on the key points of 2-D paper pattern and the data structure of color code information,two kinds of algorithms for converting 2-D paper pattern to 2-D knitted pattern were studied,namely,asynchronous filling algorithm and synchronous filling algorithm.Through the test,it is found that the execution efficiency of synchronous filling algorithm was significantly better than that of asynchronous filling algorithm.In addition,under the same conditions,with the increase of filling scale,the slope of the time curve of synchronous filling algorithm increases the slowest,verifing the robustness and stability of synchronous filling algorithm.Based on the data structure of graphic display,the drawing and display in blocks of the garment piece were achieved.Based on the principle of image pyramid,the multi-resolution model of whole garments was constructed,realizing the graphic scaling.A cache data replacement strategy based on LRU algorithm was proposed,solving the problem that it took too much time to load large-scale data from the hard disk to the screen.And the difficulties displaying slowly or jamming caused by large data information due to memory limitation was also solved.The above four aspects were practically discussed around the research on parametric design system of whole garments,which is based on knitting processes and graphic expressions of knitted fabrics,and focused on parametric design.For the purpose of realizing the whole garment pattern design system with various functions and easy operation.It improves the proofing efficiency of products and provides a foundation for personalized customization of whole garments. |
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