Recently, applying 3-D printing [1,2] in fashion has attracted attention but is limited to printing parts of body. This limitation has resulted in inadequate product size, and the printing price is higher than the clothes, which are being made traditionally. Particularly, in the sewing factory, they only can sew to international standard measurements. However, clothes are out of shape if the human shape is different from the standard measures.

Anthropometric surveys toward applications in the garment industry were conducted early by nations worldwide but were primarily performed by traditional hand measurement. Japan was the first country to undertake a large-scale countrywide survey using 3-D body scanners from 1992 to 1994. Other nations, in turn, performed anthropometric surveys and built their own body measuring systems utilizing 3-D body scanning technologies.

Many research groups have conducted building 3-D human models, from building a part of the human body (ears, human organs) to constructing the entire body to serve different needs such as health care, fashion, etc. Thanks to the quick growth of technology and skill, many methods of building 3-D human models have been improved. They are being applied in modern printing and scanning 3-D equipment to respond demands of building complete human models. Kieu et al. [3] applied regression and interpolation to build 3-D human model. They divided the model into parts, then used Hermite interpolation to interpolate each part of the model. Nguyen et al. [4] used Convolutional Neural Network to create a set of points of 3-D human model. This method used the diameter of a circle to create key slices of the model and used interpolation to create remaining slices. Zeng et al. [5] followed the anthropometric modeling approach. They proposed a local mapping technique based on new feature selection, allowing automatic anthropometric parameter modeling for each body aspect.

Point cloud learning has been gaining more attention recently due to its effectiveness in many applications such as computer vision, autonomous vehicles, and robotics. Deep learning has dramatically solved visual problems [6]. 3-D data can often be represented in various formats, including depth images, point clouds, meshes, and volumetric. As a commonly used format, the point cloud representation preserves the original geometry information in 3-D space without any changes.

In this study, we propose a new method based on deep learning and point cloud learning to conduct training of 3-D models. First, we convert the 3-D model into point clouds: Get the uniform point per slice with a probability proportional to the surface area, using the built-in function in the pytorch3D library. This step converts the input models into a set of model point clouds to form a complete mesh. Then, we move the input cloud points such that all of these points come close to the hand measurement data. Finally, we construct a 3-D model of the person corresponding to the data. We repeat those steps until all the cloud points have the lowest error compared to the hand-measured data.

We train our method on the 3-D model set and the model surface. Contrary to previous approaches, which need a lot of data and need to calculate the interpolation in detail, our point cloud learning method has a lower error and better control over input data and data when training the model. Also, our model has improved how to train the model on the whole 3-D model.

To build a 3-D human model, we deform a 3-D input model to create a target model according to hand measurements. To turn the input model into a target (according to the problem requirements) in each iteration, we move point in the set of points of the model from the original input model in order to build the output model so that the points of the input model get closer to the corresponding point of the output model . After finishing iterations, the distance between the points on the input model and the corresponding points on the output model will be reduced.

We set up an Algorithm 1 to make the meshes structure and algorithm 2 to build the train model. Based on Algorithm 1 and Algorithm 2, we create a 3-D model of the human body by Algorithm 3. In this article, we use deep learning to transform the original model. We choose two input 3-D models to apply the proposed method, including the 3-D sphere model (3.1) and 3-D standard humanmodel (3.2).

We trained the model using Python and Google Colab platform with graphics processing unit assistance to accelerate the training process. We executed the trained model on the personal computer with an Intel Core i5 7th Gen processor and 8GigaByte random access memory.

The initial data was gathered from two sources, emphasizing youthful and middle-aged persons of both sexes, including over 1000 human models (378 male models and more than 600 female models) provided by the garment research group at Hanoi University of Technology [14]. More than 3000 foreign human models (more than 1500 male models and 1500 female models) were gathered by Yipin Yang et al. [15].

The errors acquired from experimenting with the equipment as mentioned above, with 12500 data points and 5000 data points, are shown in Tab. 1.

From Tab. 1, we can see that the error rate depends on the data points, the more points, the lower the error rate.

After training the 3-D model with 10000 iterations, we found that the error rate significantly decreased in the first 1000 iterations, then slightly reduced. The difference between loops is minimal from the 6000 iterations onwards. Based on Fig. 4, we trained the 3-D model with 7000 iterations to save training time. The error of slices of 3-D models were calculated with the formula in [3], applied to Tabs. 2 and 3.

Moreover, as shown in Tab. 3, 3-D male and 3-D female models also have differences in error. Specifically, the chest error of 3-D female models was higher than that of 3-D male models because they differed from the body structure.

The more the number of data points, the more decrease in error, implying that the error rate is proportional to the number of points in the model. More data points lead to more comprehensive and precise results, increasing accuracy and lowering error.

To verify the effectiveness of the method compared with other methods, Tab. 4 shows the results of errors of the method compared with other methods. Our method has errors lower than other methods, including interpolation [3], CNN [4].

The proposed method reduces the computational step since we train on the surface (known as the skin) and the entire model synchronously, without dividing into main slices and separate parts (arms, legs, body, etc.) like interpolation [3] and CNN [4] approach. The interpolation approach [3] is calculated based on the 14 main slices of the garment standard, which leads to the joining of slices leading to differential errors in the joined parts. The CNN approach [4] is based on interpolation from circles to body slices. Although this approach is practical, it reduces the number of computations in slices and increases the number of iterations because each certain distance is calculated once. However, there is also a mistake in concatenating the rings together (like [4]).

As a result, in practical applications, particularly in clothing, it is essential to have a reasonably realistic human model in terms of shape and size without needing to be extremely specific about each part and minute detail. Then, in terms of both time and accuracy, building a model with 5000 data points is a viable alternative.

Machine learning, especially deep learning, has been used to develop a method for creating a 3-D model of the human body. This technique takes less time to execute and has fewer errors than prior approaches. However, this technique has several drawbacks, including that the resulting model has a rough surface and needs to add a smoothing step. Besides, the resulting model makes errors about shape, especially the wrist. There are drawbacks that we could not fix in research time. We will develop automatic smoothing algorithms while training 3-D models and improve 3-D model algorithms with more than data points to reduce error in the shape of the wrist in the future.