Kyunghi Hong

3D pattern construction and its application to tight-fitting garments for comfortable pressure sensation

Tight-fitting clothing pattern reflecting the accurate information of the 3D body shape has been one of the challenges for garment industry, however, fitting problems still exist. The objectives of the paper is to develop a 2D pattern which fits tightly to the 3D human scan data for sports suits that need comfort and function for maximum performance. In this study, the user graphic interface application software for the semi-automatic garment pattern generation has been implemented using the triangle simplification scheme together with 2D projections of free-falling of 3D surface polygons keeping the original 3D surface area preservation. A typical application of the developed pattern to the functional body suits is presented and verification of the proposed method is also provided.

Validating a cloth simulator for measuring tight-fit clothing pressure

Tight-fit cloth pressure provides important clue on how well a cloth fits to a body and thus on how comfortable the wearer feels with the cloth. Traditionally-used pressure sensor devices are expensive, sensitive to the experimental environment, and difficult to reproduce. In this paper, a physically-based cloth simulator has been tested for its usability as to measuring the cloth pressure, in order to replace physical measurement of cloth pressure that requires careful operation of pressure sensors. We use existing cloth simulator based on a particle system and measure spring forces exerted on each particle along its normal direction, divided by the summed area of triangles adjacent to that particle. To quantitatively validate the pressure values from the simulator, we have conducted comparative analysis on a set of thin-shell cylindrical tubes --- clothing pressure values have been measured by theoretical estimation and physical experiments using pressure sensors, and compared with those measured by the simulation. While their absolute pressure values differ from each other they exhibit a consistent tendency. From these comparative studies we concluded that cloth simulator can actually be used to measure tight-fit cloth pressure, and further conducted the clothing pressure measure on 3D human body models using the simulator.

A breast modeler based on analysis of breast scans

The advent of 3D scanning technology has allowed effective measurement and analysis of breast size and shape, attracting interests by plastic surgeons, brassier designers, etc. Much work remains, however, before 3D scanning systems can be successfully used in automated analysis and synthesis of the breast—filtering noise, filling holes, and, in case a statistical analysis is desired, finding correspondence among each scan data. Moreover, analysis of a sagged breast is difficult to obtain, due to occlusions. In this paper, we address the problems and specific issues of using 3D scan data for the analysis and synthesis of breast models. The goal of our work is to build a breast modeler which can help both surgeons and garment designers in analyzing breast volume and surface measurements. Given enough samples of scanned breasts, our modeler can generate highly realistic breast shape, with some expected and consistent variability. Copyright

Development of 2D Patterns for Cycling Pants using 3D Data of Human Movement and Stretch Fabric

With recent advances in 3D scanning technology, three-dimensional (3D) patternmaking is becoming a powerful way to develop garments pattern. This technology is now applicable to the made to measure (MTM) system of both ordinary and tightly fitting garments. Although the pattern of fitted clothing has been developed using 3D human data, it is still interesting to develop cycling pants by considering while-cycling body posture and fabric elasticity. This study adopted the Garlands triangle simplification method in order to simplify data without distorting the original 3D scan. Next, the Runge-Kutta method (2C-AN program) was used to develop a 2D pattern from the triangular pixels in the 3D scanned data. The 3D scanned data of four male, university students aged from 21 to 25, was obtained using Whole body scanner (Model WB4, Cyberware, Inc., USA). Results showed the average error of measurement was (0.19%) for area and 0~0.61cm for the length between the 3D body scanned data and the 2D developed pattern data. This is an acceptable range of error for garment manufacture. Additionally, the 2D pattern developed, based on the 3D body scanned data, did not need ease for comfort or ease of movement when cycling. This study thus provides insights into how garment patterns may be developed for ergonomic comfort in certain special environments.

3D skin length deformation of lower body during knee joint flexion for the practical application of functional sportswear

With the advent of 3D technology in the design process, a tremendous amount of scanned data is available. However, it is difficult to trace the quantitative skin deformation of a designated location on the 3D body surface data during movement. Without identical landmarks or reflective markers, tracing the same reference points on the different body postures is not easy because of the complex shape change of the body. To find the least deformed location on the body, which is regarded as the optimal position of seams for the various lengths of functional compression pants, landmarks were directly marked on the skin of six subjects and scanned during knee joint flexion. Lines of non-extension (LoNE) and maximum stretch (LoMS) were searched for, both by tracing landmarks and newly drawn guidelines based on ratio division in various directions. Considering the waist as the anchoring position of the pants, holistic changes were quantified and visualized from the waistline in lengthwise and curvilinear deformation along the dermatomes of the lower body for various lengths of pants. Widthwise and unit area skin deformation data of the skin were also provided as guidelines for further use such as streamlined pants or design of other local wearing devices.

Ergonomic mapping of skin deformation in dynamic postures to provide fundamental data for functional design lines of outdoor pants

Outdoor brands often use streamlined cutting lines to design high-performance outdoor pants. Inappropriate design lines combined with the accompanying sewing lines can cause discomfort or even restrict body movement. To reduce such discomfort, we need to find the appropriate location for cutting lines that do not interfere with body movement. In this research, we conducted ergonomic mapping of skin deformation in dynamic postures to provide fundamental data for selecting functional design lines of pants that will not hinder various movements. To analyze the lower body skin deformation depending on the posture, we marked dots at 3 cm intervals on the leg. We then measured the change in length between the points for three different postures using a three-dimensional scanner and the Rapidform program. The results were shown as a skin deformation map; this is expected to be used as reference data for the functional design lines of streamlined outdoor pants.

Development of indirect method for clothing pressure measurement using three-dimensional imaging

A direct measurement method using an air-pack-type pressure sensor has been used widely to obtain clothing pressure, but this method still has many limitations. For instance, it gives only pointwise information and is inherently inconvenient and error-prone. Therefore, we suggest an indirect method for measuring the clothing pressure of various positions at once without touching the subject by using three-dimensional (3D) deformations of a reference shape (i.e., a circle grid) printed on clothing. The clothing pressure can be obtained with a simple analysis of tensile stress and the curvature data extracted from the 3D deformation of circle grids on the clothing surface. Specifically, the tensile stress of the fabric was obtained from a tensile tester and the direction of the principal stress and the radius of curvature in the principal direction were measured from 3D imaging data to obtain an accurate value. The clothing pressure from the indirect method was verified by comparing the results from direct pressure measurements using an air-pack-type pressure sensor. The indirect method was found to successfully estimate the clothing pressure.

Technical note: Estimating dynamic skin tension lines in vivo using 3D scans

Skin tension lines, defined as the lines of maximal tension, often provide guidelines for surgical incisions and pattern design of tight-fit, functional clothing. In this work, we are interested in developing methods for finding personalized, dynamic skin tension lines (DSTL) in a non-invasive manner. We base our study on the kinematic analysis of point markers that are colored on the skin. By tracking the motion-induced displacement of point markers, we locally analyze the skin deformation and numerically compute the maximum tension directions. Then, finding DSTL is transformed to the problem of finding continuous, interpolating locally computed lines of the maximum tension directions. Compared to existing methods, our method involves less invasive measurement on the skin, and is equipped with computational methods for identifying dynamic skin tension automatically. Consequently, our method is convenient to carry out, less prone to erroneous measurement, and repeatable. Our experiments have been successfully carried out on, though not limited to, lower body skins of male subjects.

Development and Performance Evaluation of Body Armor for Wear Comfort Enhancement

This study helps develop a cool body armor that maintains a tight-fit configuration to the body surface and evaluates the performance of newly developed body armor in a wear test. Three types of body armor were used for evaluation. One was a tight fitting body armor that was constructed to improve the degree of fit and ease of movement for Korean soldier using 3D technology. Another was ventilating body armor with attached spacers on the shoulder to reduce the thermal stress on the soldier. The third was a prevail- ing body armor produced by a Korean body armor company. In order to evaluate the performance of the body armor, a human wear test, a thermal mannequin test, and computational fluid dynamics (CFD) were executed. Five subjects participated in the wear test. Subjective wear sensation, total amount of sweat and dynamic change of clothing microclimate were observed during and after exercise on a treadmill; subse- quently, it was found that subjects rated tight fitting body armor and ventilating body armor lighter, drier, and easier to move than the conventional body armor (p<.05). Total amount of sweat was the least in the case of ventilating body armor. The thermal resistance and vapor resistance of the ventilating body armor were improved remarkably. In addition, the skin temperature of the ventilating body armor with spacers was lower than the tight fitting body armor by at least 1 o C in the CFD result. It is noted that thermal-wet comfort of the 3D body armor with ventilating feature is superior to the conventional body armor, espe- cially when the ventilating channel is not closed due to a backpack.

Use of three-dimensional technology to construct ergonomic patterns for a well-fitting life jacket of heterogeneous thickness

To produce a life jacket that fits users both comfortably and stably, we developed a life jacket pattern based on the three-dimensional (3D) shape of the human body, with foam flotation material of different thicknesses used in different sections to achieve the required buoyancy and facilitate movement. We created a nonstandard life jacket for water sports that can adopt free design for canoeing and kayaking. Engineering design process and 3D technology were used to create the ergonomic 3D life jacket, which comprised an inner pattern, a polyethylene (PE) foam pattern for proper buoyancy in water, and the outer pattern. We developed a layering method for achieving the heterogeneous thickness of the life jacket and its outer pattern considering the ergonomic aspects of the 3D human body curvature and movability. The pattern expansion length was calculated to enlarge the outer pattern of each panel covering the varying thicknesses of life jacket and spacing for torso flexion. The calculation formula for this length was useful in increasing or decreasing the life jacket’s buoyancy, which was affected by the PE-foam thickness. Human-subject wear tests were performed in air and water to evaluate the developed life jacket. The developed life jacket had improved functionality. Significant differences (P ≤ 0.01) existed between the newly developed and conventional life jackets in air, in terms of the overall comfort, freedom of rowing movement, and fits in the chest and waist areas. Significant differences (P ≤ 0.05) also existed in water in terms of the overall fit and prevention of separation from the shoulder due to buoyancy.