A Case Study on Manufacturing Processes for Virtual Garment Sample

The real garment was produced in the following sequence: pattern preparing, cutting, and modeling(Fig. 3). Pattern preparing includes the elements of seaming, marking, and plotting. Pattern seaming is a process of making seams for sewing, marking is a process of placing pattern pieces for cutting the cloth, and plotting refers to a process for printing a pattern. The cutting process consists of unwrapping the fabric, spreading and controlling the fabric, setting patterns, scissoring off pieces, notching, controlling, and finishing pieces, marking in/out, naming, and interfacing. This step is important in the preparation for modeling, because it involves creating patterns out of fabrics. The modeling process consists of overlocking, sewing, and ironing each part of the garment. Overlocking is a type of seam finish, sewing is a stage for stitching the pattern pieces, and ironing is done to straighten and finish the seams.

Fig. 3.

Real garment sample making process.

In the modeling process, parts of the bodice, collar, sleeves, and scarf were respectively made and combined with the bodice. In the real garment making process, scissoring and ironing were done to organize the seams after sewing the seamlines. The traffic line was very complex for a worker conducting this process, and more time was spent moving from place to place than on actual work. In particular, for the characteristics of a chiffon blouse, the edges of the seam allowance were overlocked together, and the sewing machine and overlock machine were used repeatedly, leading to a longer period of time required for this work. In addition, as the collar and cuffs were made into two layers, the right side needed to be turned out after sewing, and this process was accompanied with manual work. The machines used in the real garment making process were typical sewing machines, an overlock machine, buttonhole machine, and iron. The worker utilized each machine by moving from one to the next, in accordance with the process required.

The process of making a virtual garment is done in the following sequence: preparing, modeling, and dressing(Fig. 4). The preparing process consists of exporting and importing the pattern, creating fabric, and editing fabric properties. Pattern placing includes the laying out of pieces for the front, sides, and back of the model shadow in a 2D pattern window.

Fig. 4.

Virtual garment sample making process.

In making a virtual garment, the process of preparing combines the steps of preparing and cutting in the making of a real garment. When compared to making a real garment, it can be seen that the preparation stage for a virtual garment is greatly simplified by staying in line with file exchanges and fabric properties. Not only the CLO program used in this study, but also most other forms of 3D garment simulation software, including Optitex and V-stitcher, use 2D CAD patterns in the dxf format.

The notches set in the 2D CAD pattern are the standards for matching the seamlines in the actual sewing process, and do not work in the 3D CAD. Therefore, when the outlines must be sewn with a notch as the standard, you must add a point on the position of the notch to divide the segments. You can easily complete the sewing just by clicking on the lines to be sewn. When selecting a pair of curves and creating seams, two lines make the same effect as actual sewing.

In the 3D CAD, the processes of finishing seams, turning the right side out, and ironing are not necessary, allowing users to easily complete their garments. However, in order to express the effects of folding the fabric, such as in pleats, tucks, and crease lines, the angle must be folded for the internal line or seamline. A hidden placket was used for the blouse in this experiment to apply the function of a folded angle(Fig. 5). You can create a button and buttonhole with just one click by using the button menu, and you can also select to fasten or unfasten a button. In CLO, a button and buttonhole do not exist as images but have actual opening and closing functions and are expressed in three-dimensional shapes(Fig. 6).

Fig. 5.

Fold angle.

Fig. 6.

Button & buttonhole.

Unlike with a real garment, a virtual garment is made as it is worn on a human body. The digital garment consists entirely of vertices and, as actual physical laws do not apply, the clothing can go through the human body if collision properties are not designated. If there is no collision with the human body, the original shape cannot be maintained, as the garment pieces are separated before they are sewn. Therefore, the dressing process on a digital model is essential in the process of completing a virtual garment, unlike in the making of a real garment.

In the 3D window, a pattern piece is placed near the digital human model. Because there is an arrangement point on the model, the pattern piece falls into placed when it is connected to this point. The position, offset, orientation, etc., of the pattern piece being placed can be changed by using the property editor. With this menu, the pattern piece is placed to provide a similar shape to when it is worn on an actual human body(Fig. 7).

Fig. 7.

Pattern arrangement, positioning and properties.

Simulation progresses in sequence with vertex calculation. Vertex calculation is a process for assembling the virtual garment onto the simulated human body(Fig. 8). A pattern piece is composed of a vertex, and the lines sewn in the 3D CAD combine the pieces through vertex calculation. This designates the seams to be sewn and has the same role as sewing in the manufacturing process for a real garment. For a smooth simulation, a sewing line is selectively activated and deactivated to freeze or omit part of the 3D garment.

Fig. 8.

Vertex.

Garments are basically made by supposing the bilateral symmetry of the human body. The front panel of the garment design realized for this study has differences in its left part and right part at the opening, while the back and sleeves for the left and right parts are equal to each other. Therefore, first, the left part of the garment is made, and the right pattern is created through a symmetric paste. The pattern made through the symmetric paste creates a perfect pair, and if the pattern is modified, the other pattern is also changed(Fig. 9). Through this process, the left and right parts of the back are separated from each other, and a sewing line is made in the center of the back, as well. However, two backs can be combined into one through symmetric merging(Fig. 10).

Fig. 9.

Left side.

Fig. 10.

Asymmetric paste.

The texture and color, as well as the physical properties of the materials, are determined by editing the fabric properties. You can express several hundred different designs by applying the various fabric properties to a piece of pattern(Fig. 11). The freeze and unfreeze menu is used in the simulation process for items separate from the garment, such as a scarf for a blouse, to allow the item to be simulated in turn. In a real garment, tying a scarf is very simple. However, in making a virtual garment, this process demands a considerable amount of time and skill, though it remains theoretically possible. Therefore, this study did not tie the scarf into the shape of a ribbon, but rather completed it in the shape of a tie.

Fig. 11.

Color and textile variation.

The real garment making process uses several sewing machines and irons, requiring a long traffic line for the worker and considerable time reserved for moving between the machines. However, this process can certainly be used to complete a real garment sample to be worn on a model for checking the fit and suitability for movement.

The virtual garment making process can be used to create a garment sample with a simple click of the mouse on a computer, and even fashion designers with limited experience in making samples can employ this method in the sample making process. This, however, does not result in a real garment sample being made, and no dressing can be done in this process. In order to settle the issue, the fit of a garment on an avatar is presented by suggesting a stress map, strain map, and fit map. Stress maps display the strength of the friction applied to the garment through color codes and numerical values, according to the fabric’s unit area. Strain maps show how the garment is affected by outer forces(pressure) in terms of percentages. Fit maps depict the tightness of a garment through colors(Fig. 12).

Fig. 12.

Texture display : (a) stress map, (b) strain map, and (c) fit map.