APPLICATION CAD METHODS IN 3D CLOTHING DESIGN

: Modeling virtual garments is known as a very laborious process, which includes designing 2D patterns, positioning, and sewing them in 3D, performing a physically-based simulation, and then iteratively adjusting patterns and parameters, repeating the process until the expected eff ect is achieved. The aim of this paper is to make a 2D pattern and 3D simulation of a men’s shirt. First, the computer construction of the men’s shirt model was made on a sketch-based, i.e. a 2D pattern is developed. Secondly, 2D pattern is developed by fl attening 3D surface patches, then a 3D fi ne garment is formed directly based on the information of sewing relations and correspondence between 3D surfaces and 2D patterns. The method is able to design 3D garments and 2D patterns effi ciently and accurately.


INTRODUCTION
Garment CAD technology is the use of computer technology to assist in the design of garment products.Early garment CAD focused on 2D pattern drafting and modifi cation.To release the heavy dependencies on pattern-masters' experience in 2D systems, 3D garment CAD methods with the technologies of human body measurement are studied and proposed as an alternative solution to non-expert users.The key techniques include 3D human body measurement and modeling, 3D garment design on digital human models, 3D draping simulation, and 2D pattern generation from 3D space.Sketch-based design methods provide a promising process of 3D garment design, which automatically creates a 3D garment model from user-sketched 2D silhouettes of the garment [1][2].Wang et al. [3] presented a feature-based 3D garment design through 2D sketches.In this method, a feature template for creating a 3D garment is defi ned according to the features of a human model, and the profi les of the 3D garment are specifi ed through 2D sketches.3D cloth simulations are either geometrical based or physical based.Because of the contributions from the computer graphics community, the simulation accuracy and speed have been much improved in recent years [4,5].In the fi eld of clothing and textiles, 3D simulation is considered to be of great potential for fi t analysis, and a number of commercial clothing CAD systems have deployed 3D simulation modules.Typically, a 3D virtual fi t model is fi rstly created and then the clothing patterns are virtually sewn around the 3D model as if the garment worn by the customer.The fi t model can be customized based on customers' body dimensions.It can be an excellent tool for clothing product development because the costly sample making and fi tting process can be reduced or completely eliminated, suggested by the software suppliers.However, there is no systematic investigation on the validity of 3D clothing simulation for fi t analysis, especially in view of the fabric property diversity.A sensory test was used to identify the deviation of virtual garments from real garments based on body shape, yet a nonmainstream 3D simulation was adopted.The eff ectiveness of a mainstream 3D simulation system for pants fi t evaluation was carried out by wear trial.It was found that the visual information of the silhouette of the overall pants was accurate, but not the information about fabrics [6].Further investigation is required to identify the range of validity for fabric simulation.Much research has been conducted for 3D garment design and simulation.Liu et al. [7] presented a survey on CAD methods in 3D garment design.Turquin et al. [8] introduced a technique that allows the users to sketch garment contours directly onto a 3D human model, then a 3D garment surface is generated by computing the distance fi eld around the human body.This method is mainly used to create a 3D garments for virtual characters, and it does not aim to generate patterns for real garment.Brouet et al. [9] studied for a 3D garment with complex features such as wrinkles, although a plausible 3D garment shape can be gotten, the shapes of the resulting 2D patterns tend to have somewhat wavy outlines, sub-optimal for actual manufacturing.Porterfi eld and Lamar [10] investigated how using 3D garment simulation to conduct fi ttings virtually might impact the interactive process of garment fi tting.Lee and Park [11] provided suggestions for areas of improvement in 3D virtual fi t simulation technology for increased adoption of the 3D technology for eff ective prototyping and quality assessment in the fashion industry.Lage and Ancutiene [12] investigated distance ease distribution between straight shape virtual dress and 3D body in respect to fabrics mechanical (tensile, bending, shear) properties using virtual try-on software Modaris 3D Fit (CAD Lectra).Kim and LaBat [13] researched was to examine consumer experience and satisfaction of using 3D virtual simulation technology, especially for online shopping, and consumers' willingness to use the technology in the future.Wu et al. [14] have an exploratory study to analyzed the accuracy of 3D cloth simulation system so as to examine its validity and eff ectiveness in garment fi t evaluation.Modeling virtual clothing where 2D and 3D digital technology is a modern tool is becoming a platform for the design, preparation and production of clothing.3D virtualized technology reduces the number of samples, creates effi cient production, and makes quick decisions, increases competitiveness, communication and e-sales [15].The aim of this paper is to make a 2D pattern and 3D simulation of men's shirt.First, the construction of the men's shirt model was made on a sketch-based, i.e. a 2D pattern is developed.Secondly, a 2D pattern is developed by fl attening 3D surface patches, then a 3D fi ne garment is formed directly based on the information of sewing relations and correspondence between 3D surfaces and 2D patterns.

EXPERIMENTAL PART
Figure 1 shows a technical sketch of a men's shirt.A computer construction of a men's shirt size 40 was made on the computer program Lectra Modaris.After that, with the Clo3D program 2D to 3D transformation was made, a simulation was made by sewing the parts, their fi tting form to the avatar with arrangement points in blue colors.Then using a strain map, a 3D human body is represented by a triangular mesh, places that show a problem with a pattern such as not fi t well, parts (front, back, sleeve or collar) are wide or tight or show some other deformation.

Figure 1: Technical sketch of men's shirt
Based on this data, determined by a strain map where they are shown in red color, a correction of these parts of the deformations can be made immediately on the avatar, and corrected clothing is obtained.The mesh is made of triangles that must be the same size for the clothes to fi t the avatar well, in the opposite would otherwise mean that something is not as it should be.

RESULTS AND DISCUSSION
Figure 2 shows the computer construction of a men's shirt on the Lectra Modaris program.
Based on a 3D human model, an initial 3D garment surface is automatically generated.Editable control curves are used to control the garment shape interactively and accurately, and the resulting garment can  [16] well fi t the underlying human body.A surface mapping technique is proposed to create a 3D fi ne garment model, which is constructed by automatically sewing fl attened 2D patterns using the information of sewing relations and correspondence between 3D surface patches and 2D patterns.Figure 3 shows the fl owchart of a 3D garment design [16].
The traditional process of creating a 3D virtual garment starts with the design of 2D patterns.The patterns are placed around a 3D human body and then stitched together, where cloth simulation is used to generate the fi nal 3D shape.
Figure 4 shows a correspondence between 3D surface patches and 2D patterns with an arrangement point.Arrangement points on the avatar in 3D denote points for positioning parts before sewing.It takes one piece at a time from 2D and is carried in 3D where it is placed at an arrangement point marked in blue color.
To design 2D patterns, fi rstly seam lines will be drawn on the base garment surface, then a 3D surface patch surrounding by seam lines will be searched and fl attened into a 2D mesh, and fi nally the boundary lines of the mesh are generated to form the fi nal pattern.Seam lines are used to defi ne the style of a garment and the shape of 2D patterns.Since seam lines are drawn on the base garment surface manually, and the shape of a 2D pattern is computed automatically by fl attening a 3D surface patch, the method provides a straightforward pattern design approach and alleviates the requirements of knowledge and experience for a pattern designer, shown in Figure 5, 6 and 7 (front, side and back).
Sewing information indicates adjacent relations of 2D patterns that are sewn together in 3D.Since 2D patterns are obtained by fl attening 3D surface patches, the information of adjacency between 2D patterns can be automatically achieved based on the relative positions of corresponding 3D surface patches.
However, two adjacent patterns in 3D space are not necessarily sewn together, so sometimes it is necessary to interactively adjust the automatically established sewing information.
The avatar in Figures 5, 6 and 7 is shown in diff erent postures in front, side and back.
After the transformation of the parts of the men's shirt from 2D to 3D, where the seams to be sewn are marked on the 2D surface, i.e. the fi nished shirt is obtained on the avatar, the model is checked for deformations in relation to the fi t.This is done using strain maps.
Strain Map -Garment's distortion rate due to external stress appears in percentage.In the case of the men's shirt, it can be seen that the red color appears in the area of the armhole sleeves on the front and back, (Figure 8).This may mean that the sleeve in that part is larger in width and does not fi t well, i.e. that it has more material than is needed in that part.So immediately go to the correction where this can be corrected, that is, reduce the armhole of the sleeve to 2D and then check it in 3D.Also, the red color of the mesh occurs at the hem of the sleeve, which could mean that the cuff is tight or wide.In this case, it can be seen that the cuff does not fi t well on the arm.Check and see what the problem is, if there is some distortion then fi xes it, and if there is no it can be ignored and not considered a problem.
On the whole, can see that the men's shirt fi ts well on the avatar, which shows us the strain map or mesh that we get is with equilateral triangles in blue color and there is a slight distortion in the armhole and the length of the cuff .In this way, has got a quick production of a men's shirt not only in 2D but also in 3D, where in that way the production time and sewing of clothes is shortened.Also, from the fi nal garment it can be immediately concluded whether the whole process of its production from construction to manufacture is done well and how the garment will behave on the human body.

CONCLUSION
The study of this paper is to make a 2D pattern and 3D simulation of men's shirt.First, the computer construction of the men's shirt model was made on a sketch-based, i.e. a 2D pattern is developed.Secondly, 2D pattern is developed by fl attening 3D surface patches, then a 3D fi ne garment is formed directly based on the information of sewing relations and correspondence between 3D surfaces and 2D patterns.
To cope with rapid fashion changes and also to reduce the costs, there is pressure from the retail sector to shorten product-development as much as possible and also to minimise the investment in physical prototyping.Virtual prototyping is off ered as a solution to this problem.Draping the 2D patterns onto a virtual human model to visualise the 3D appearance of the clothing, coupled with a realistic simulation of the material behaviour, provides the opportunity to check fi t and pattern fl aws so that the initial 2D pattern pieces might be refi ned.It is claimed by the software suppliers that such an approach will reduce the dependency on physical prototyping, and will shorten the product-development lead time and the associated costs when communicated over the internet platform.

Figure 2 :Figure 3 :
Figure 2: Construction on the basic pattern of the men's shirt

Figure 5 :
Figure 5: Sewing process on the avatar in 3D on front

Figure 6 :
Figure 6: Sewing process on the avatar in 3D on side

Figure 7 :
Figure 7: Sewing process on the avatar in 3D on back