New database for improving virtual system “body-dress”

The aim of this exploration is to develop a new database of solid algorithms and relations between the dress fit and the fabric mechanical properties, the pattern block construction for improving the reality of virtual system “body-dress”. In virtual simulation, the system “body-clothing” sometimes shown distinct results with reality, especially when important changes in pattern block and fabrics were involved. In this research, to enhance the simulation process, diverse fit parameters were proposed: bottom height of dress, angle of front center contours, air volume and its distribution between dress and dummy. Measurements were done and optimized by ruler, camera, 3D body scanner image processing software and 3D modeling software. In the meantime, pattern block indexes were measured and fabric properties were tested by KES. Finally, the correlation and linear regression equations between indexes of fabric properties, pattern blocks and fit parameters were investigated. In this manner, new database could be extended in programming modules of virtual design for more realistic results.


Introduction
Due to its superiority of efficiency and convenience, virtual clothing simulation becomes very popular in apparel industry and garment research. The results in virtual simulation environment looked realistically in general, however, these results were hardly trustful for exact clothing shape forecasting and research [1] . The reason of its inaccuracy is that virtual environment lacks the essential database of clothing fit with the synergy effects of combining textile materials, pattern block construction, clothing style, etc [2,3] . A small change of these synergy effect elements will conduct distinct fit or misfit of clothes, designs of collar, shoulder, armhole, etc could be the factors of clothes misfit. In order to analyze and describe the fit, we proposed and created identical parameters by correlations and linear regression equations with textile material mechanical properties, pattern block indexes, with which virtual design could be improved with realistic fit and simulation appearances.
The aim of this research is to improve the existing virtual database used for designing of system "body-dress" by adding new algorithms and relations between dress construction, fabric mechanical properties, and pattern blocks. Figure 1 shows the framework of improving the reality of virtual system "body-dress" by means of developing new database.  1. The framework of improving virtual system "body-dress" with new database 2. Methods of research "Dress-body" was analyzed as a system because both elements -dress and body -influenced the final appearance and fit of dress. Three essential elements used to build this system were investigated: dress style, pattern block and textile material.

Dummy for experiment
Dummy 160/84A (A means difference between bust girth and waist girth are from 14 to 18 cm, bust girth = 84 cm, waist girth = 66 cm, hip girth = 88 cm, shoulder width = 12 cm, distance between bust and waist = 16.8 cm, distance between waist and hip = 18.5 cm) was chosen. It was used in the process of pattern making, dresses wearing and fit indexes measuring.

Pattern blocks of dresses in H-style and X-style
Derived from Japanese new cultural basic block [4] , through optimizing and sample wearing experiments, the basic pattern block was sketched as Figure 2. Basic pattern blocks of dress in H-style (PDH1) and in X-style (PDX1) shown as Figure 3. There were no darts around waist level on PDH1 while PDX1 has ones. As more important factor of clothes fit, shoulder's design will directly affect the whole shape of dress,the fit will be changed as well. Therefore, to get the misfit of dresses, the basic block was transformed by increasing and decreasing SP (shoulder point), SNP (shoulder neck point), FNP (Front neck point), ADP (armpit depth point) with other pattern indexes kept constant as shown in Figure 4. After these transformation, the shoulder sloping angles of transformed pattern blocks in H-style(PDH2, PDH3, PDH4, PDH5) and X-style (PDX2, PDX3, PDX4, PDX5) changed accordingly.

Textile material tested by KES
Five kinds of textile materials for dress making were selected: plain woven cotton thin calico (T1), plain woven polyester cloth (T2), plain woven cotton thick calico (T3), twill woven elastic denim cloth (T4), plain woven elastic polyester cloth (T5). Essential mechanical properties of these fabrics were tested by KES testers (KES-FB1, KES-FB2) four times. Then the interval of tensile, shearing and bending properties were calculated as shown in Table 1.

Dresses for experiment
With five kinds of distinct fabrics and 10 pieces of patterns, 50 pieces of dresses in H-style and X-style with different fit were made. After measuring of bottom heights and 3D scanning (see 3.2, 3.4),the front center seams of all dresses were dismantled and ironed, then photographed in the front projection (camera installation was exactly the same).

Fit indexes of system "body-dress"
In order to express the fit of system "body-dress", new indexes were proposed to be measured and analyzed.

Shoulder sloping parameter SS on dress pattern blocks
Shoulder slope is the angle between shoulder line and horizontal plane, which is one of the pivotal index to describe shoulder shape of a body or clothing. Considering that shoulder widths of all dresses were constant in this experiment, shoulder sloping of pattern blocks (SS) were expressed by the vertical difference between SP and SNP: Where: LFNB is the length from front waist line to back waist line across SNP, LFSB is the length from front waist line to back waistline across SP, as shown in Figure 5. The SS value (cm) of pattern blocks were respectively 7, 5.5, 1.8, 8.7, 9.9.

Bottom heights of dresses
On PDH and PDX patterns, the bottom lengths were designed constant, too. However, the height from bottom to the floor varied when the patterns and the fabrics were changed. Therefore, bottom heights to the floor in front (BHF), profile (BHP) and back (BHB) projection were measured. The differences between BHP and BHF, BHP and BHB were calculated as ΔBHF and ΔBHB.

Angels of front contours
With dresses dismantling of front center seams, the angels of front contours (AFH, AFX) were measured in Photoshop.

Air volume parameters
Dummy and all dresses were scanned by VITUIS Smart XXL 3D body scanner and exported as 3D format file (.obj). These 3D files were optimized, sliced and measured in 3DS MAX (3D modeling software) as Figure 6 shows. Dress segments over bust level were closely fitted with dummy so that only segments between bust and hip levels were investigated. Thus, air volume indexes were obtained: Where: AVF x,y and AVB x,y were respectively front and back air gap between dress samples and body. VSF x,y and VSB x,y were respectively front and back air volume of dress samples, VDF x,y and VDB x,y were respectively front and back air volume of dummy. AV x,y expressed the full air gap. RV x,y expresses the ratio proportion of front and back air volume (x is the pattern number, y is the fabric number).

Discussion about fit indexes
When SS = 7 -9.9 cm, the dresses in H-style shown horizontal bottom line in three projection, but when SS = 8.7 cm, the dresses in X-style were close to show horizontal bottom. And bottom heights of the dresses in H-style were inclined to be horizontal rather than the dresses in X-style.
In addition, the dresses from PDH2 and PDH3 (1.8 cm ≤ SS ≤ 5.5 cm) shown AFH as 0°, which indicated that the front center lines were vertical and dress shape would be immobile after front contours were seamed. Moreover, the dresses from PDH4 and PDH5 (8.7 cm ≤ SS ≤ 9.9 cm) shown bigger AFH, AFX (2.1° … 10.5°).

New algorithms of fabric properties, pattern block parameter and fit indexes
Based on fabric properties, the pattern block parameters and the fit indexes, the linear regression equations were obtained after linear regression analysis as: Where: B warp is bending stiffness in warp direction of fabrics. From equations (6) -(9), AFH and AFX were expressed with B warp and SS. With B warp increasing, fabrics were less flexible to bending, the front center lines were more inclined to keep vertical with the bending strength from shoulder part and back torso, the angles of front contours would be bigger. Furthermore, as SS increasing, the shoulder slope of dress changed accordingly, the supporting point of dress moved from SNP to SP, the dress shape changed, which led to bigger angle of front contours. Taking dresses in X-style as example, the bottom height variance in front and back projections were described as: Where: F warp is tensile strength in warp direction of fabrics. From equations (10) -(12), ΔBHF and ΔBHB were described with F warp and SS. With F warp and SS varied, the length and proportion of front and back dress were changed, therefor resulting in changes of ΔBHF and ΔBHB. Furthermore, ΔBHB were more inclined to vary with SS rather than ΔBHF. As figure 8 shows, with these algorithms of fabric properties, pattern block parameter and fit indexes, dress fit indexes were expressed by : Where: AF is the angle of front contours as Figure 7, ΔBH is the bottom height difference as Figure 8.
With AF and ΔBH, the fit of system "body-dress" were predicted as concrete indexes and values, which could be the convincible basic database for realistic virtual design.

Conclusion
The synergy effects of textile materials, pattern block and clothing styles distinctly influence clothing fit, which are expressed by special algorithms of fit indexes. Fit and misfit can be predicted when shaping factors in system "body-dress" are fixed. The new database of fit variation mechanism to these synergy effects should be extended to virtual system "body-dress" to improve the simulation results.
In the future, we are going to increase the number of factors that affects clothes fit and misfit, the total database of fit variation mechanism of system "body-dress" will be investigated and utilized in virtual environments.