Comparison of the production of three-dimensional drawings of grating plates

Summary

The three-dimensional printing of the grating board has the function of rendering three-dimensional, so that when the viewer can view the object, the angle of the viewing is different, and the change of the object can be seen, thereby obtaining the three-dimensional sense of the object. You must rely on manual shooting of objects at different angles, which is time-consuming and laborious to produce, and the results may not be satisfactory. The purpose of this article is to use the characteristics of the three-dimensional effect of the grating plate, and to use it for the three-dimensional printing of buildings, with the help of computer software, you can reduce the difficulties encountered during manual shooting and improve the results and consistency of the finished product. And improve processing efficiency.

I. Introduction

The common three-dimensional color image printing currently on the market generally refers to the three-dimensional printing of grating plates. At present, this three-dimensional imaging technology is mostly developed for commercial purposes, and combined with printing, art and technology to create finished products, it is widely used in packaging and decoration, merchandise Advertisements, interior decoration, postcards, etc., Nepal has also used this technology to produce three-dimensional stamps. Compared with traditional printing, three-dimensional printing has the following characteristics:

1. Three-dimensional printing can realistically reproduce the three-dimensional sense of objects, with rich layers and realistic images.

2. The three-dimensional printing manuscripts are mostly made by modeling design or scenery shooting. The printing materials are mostly coated paper and high temperature resistant ink, so the gloss is good and the colors are bright and not easy to fade.

3. The three-dimensional printing surface is covered with a layer of grating prisms like concave-convex columnar prisms, and the three-dimensional effect of the full-frame picture can be directly seen.

4. The stereoscopic display system that does not need to wear auxiliary equipment will not cause discomfort due to frequent wearing of auxiliary equipment: and can be watched by multiple people at the same time.

With the advent of computer-to-plate CTP technology, high-precision multi-color printing with FM dots is used. The application of UV technology continues to mature, and many equipment manufacturers have launched various types of UV offset printing machines. Heidelberg, Manroland, KBA, Komori and Ryobi have all launched rubber printing machines with this feature. Direct printing of plastic grating materials with rubber printers is no longer a problem. The quality of 3D printing is guaranteed, which makes the rapid development of 3D printing of grating plates. In recent years, domestic three-dimensional printing has made great progress. The printing factory began to use the three-dimensional printing technology of grating plate to produce more complex products. From labels, posters to packaging products, even plastic cups have examples of their application. Although the three-dimensional printing products of the grating board do not see the three-dimensional visual effect in the true sense, the three-dimensional printing of the grating is not just promotional materials or art products. Compared with the traditional three-dimensional photo production technology, it shows its unique advantages in terms of economy and flexibility of use. For example, raster board printing is applied to the production of three-dimensional maps. In addition to the advantages of portability and easy storage, it can also obtain the viewing effect of physical three-dimensional maps. If combined with aerial or satellite images, it can provide a rich landscape vision , Is conducive to the research and judgment of terrain and features.

The traditional three-dimensional printing of a single landscape or person photo can be produced using the principle of fake 3D stereo imaging of a single photo, but the distance of the objects in the photo content is subjectively determined by the production staff, and then the image processing is used according to this judgment result The software is layered by manual drawing. After the layering is completed, the raster board pre-processing software is used to make the original. The results of this processing method have changed the true height differences between the features. The manual layering process is also quite time-consuming and labor-intensive, and the production results vary from person to person and lack product consistency.

The plane three-dimensional map or image has coordinates, and can be fitted with the digital terrain model (Digital Terrain Model, DTM) that has been produced on this island, thus providing an objective basis for image layering. The purpose of this article is to use the characteristics of the grating plate to present the three-dimensional effect, and apply it to the production of flat three-dimensional maps. With the aid of numerical terrain models, design a layered method using geographic information system software to reduce manual judgment , Improve product consistency and objectivity, and improve processing efficiency Because the number of layers is too small, the stereoscopic model may be discontinuous or inconspicuous when viewing. Too many layers will increase the production time, so this article also uses different layering methods to compare the results to understand the suitable production the way.

2. Stereo imaging technology

The distance between two human eyes (eye distance) is about 6.3-6.9 cm, so that no matter which eye we use to see a close object, we will get different far backgrounds. The phenomenon of different images seen by the left and right eyes is called Binocular Parallax. When both eyes gaze at the same point, the line of sight of the two eyes intersect at this point to form an intersection angle, called the parallax angle. The smaller the parallax angle, the farther the object, and the larger the parallax angle, the larger the object (Wolf and Dewitt, 2001), as shown in Fig. 1, the brain nerve distinguishes the distance between these two points based on the difference between these two points of view, and merges into a visual image space in the brain. Therefore, three-dimensional images can be seen by looking at two consecutive images taken at two different shooting positions through both eyes.

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At present, the stereo imaging technology has the following methods

1. Two different pictures are put into two mirrors of two stereoscopic pictures (Stereoscopic Pictures), so that the two eyes see different images, and the two pictures are merged in the brain to form a stereoscopic image.

2. The red and blue glasses stereoscopic method (Anaglyph) uses the images of two colors of red and blue to merge with red and blue glasses to watch the stereoscopic imaging.

3. Parallax barrier stereo method (Parallax Barrier) as shown in Figure 2.

4. Random dot stereogram (SIRDS) superimposes a random dot stereogram and another hidden stereogram into a picture.

5. The three-dimensional printing of the grating board (Lenticular Printing) divides the two different images of AB into several parts, and then arranges the first parts of A and the first parts of B in the lens of the grating in order, as shown in FIG.

6. The three-dimensional moiré method (Hologravure) uses the effect of moiré to view the stereo.

7. The Integral Method puts the images after superimposing different images under the spherical lens to watch the stereoscopic imaging.

8. Holography uses laser light to transmit light to the observer through a beam splitter, baffle, mirror, and spatial filter to watch stereo imaging.

3. Three-dimensional printing of grating plate

(1) Structure and characteristics of grating plate

The grating plate is sequentially arranged by a series of cylindrical lenses, which are refracted and imaged by light, and the focal length, radius focal length, and viewing angle of the lens all affect the imaging effect.

The specific gravity, thermal deformation temperature, transparency, refractive index, etc. of the material of the grating plate will affect the stereoscopic production effect and post-processing. The grating plate is distinguished by the number of lenticular lenses (Lenticules-Per-Inch, LPl) per inch. Because each type of grating plate has different number of lines, material refractive index, thickness and viewing angle, the effect can be different. The materials of grating plate are PET (polyester), PP (polypropylene), PVC (polyvinyl chloride) ) And PS (polystyrene) and acrylic.

The selection of the number of grating lines (LPI) is also very important for the stereoscopic imaging obtained by printing. The number of lines of grating plates produced in the world currently ranges from 10LPI (about 3mm) to 200LPI (0.2mm), and most of their size specifications are 20 "x28" inches. Commonly used grating plate material specifications and uses are as follows (Wu Wenhe, 2005a):

1. The thickness of 0.25mm, line number 141 LPI PET (Poly Ethylene Terephthalate) grating board, which is used in mobile phone panels, stamps, DVD discs and other commodities.

2. A PET grating with a thickness of 0.35 mm and a line number of 100 LPI is used in high-quality packaging boxes, wine boxes, VCD discs, labels and other commodities.

3. The PET grating with a thickness of 0.46mm and a line number of 75LPI is used in cards, medicine boxes, credit cards, stationery, books and other commodities.

4. The PET grating with a thickness of 0.68mm and a line number of 62LPI is used in posters, display cards, hang tags, postcards and other commodities.

The grating plate also has different uses due to the difference in different viewing angles. A wide viewing angle is suitable for changing the image effect, and a narrow viewing angle is suitable for the stereoscopic effect. Decisions are usually made based on demand price, stereoscopic effect and application. [next]

(2) Stylistic effect of grating board and the production of three-dimensional map

The three-dimensional printing effect of raster plate is quite wide. Generally speaking, it can be divided into 3D three-dimensional effect, image change effect, enlargement and reduction effect, continuous dynamic effect, Morph (similar to the change of face effect in a gradual way), three-dimensional moiré effect Or a combination of the above effects (Wu Wenhe, 2005). The 3D stereo effect is a method that can be directly applied to the production of stereo maps. The 3D stereo effect is divided into two ways: false 3D (Layer 3D) and true 3D (True 3D). The fake 3D stereoscopic effect uses a single photo or image, judges the depth of field of the object according to the author's subjectively, separates the front and rear layers, and then uses the software to generate the displacement image, and then divides it into a usable grating plate to obtain a stereoscopic image: true 3D For stereo effect, use professional stereo camera to shoot images at different angles at the same time, or use 3D animation software to simulate multiple images at different angles, then use the professional stereo production software to synthesize the front and back displacement images, and print them on the raster plate to produce images with front and rear levels. effect. In the production of 3D maps, although aerial photos or image pairs that match the nature of 3D photography can be obtained, the geometric relationship may not be compatible with existing software, so it is more convenient to create a 3D map from a single photo or image combined with numerical terrain data .

(3) Principle of stereo imaging of grating plate

The principle of the three-dimensional imaging of the grating plate is to merge the images of different perspectives into the same image, and then use the characteristics of the geometric optical imaging of the cylindrical lens array to allow the left and right eyes to see the images of different perspectives, so as to achieve the stereoscopic imaging effect, as shown in Figure 4. Show. That is to say, the scenes in the plane image have different front and back positions, or the left and right eyes will have a displacement effect when viewing the objects. We use this effect to create image drafts and attach the processed image drafts to the lenticular lens array plate to produce a stereoscopic image with depth of field (Gottfried, 2001).

Taking FIG. 5 as an example, suppose that there are five objects arranged in a straight line, and the viewing positions of the human eye are at positions A, B, and C. The image seen will be different due to different parallax angles. Location image. The image seen at position A is arranged from right to left; the image seen at position C is arranged from left to right; position B is because it is exactly in the middle, so the images are all superimposed together.

When the images of each viewing position in FIG. 5 are restored to a plane, when object 3 is the center point, objects 1 and 2 are before the center point, and objects 4 and 5 are behind the center point, and observation position A moves to observation position C When the object is before the center point, it will move to the left, and the object after the center point will move to the right, as shown in Figure 6. Therefore, when making a plane stereoscopic image, in addition to the image at the center point, the foreground or background image needs to be appropriately displaced. For left or right displacement, the corresponding image of the lenticular lens array is required Place it.

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After the image manuscript has been displaced by computer software as shown in Figure 6, each image needs to be decomposed into multiple long images, and then combined according to the position of different images in order. In order to facilitate and see through the lenticular lens array, different viewing angle images can be seen at the same location (see Figure 7). Since the two eyes see the images in different positions, and according to the principle of parallax, the different images are combined into a stereo image through the brain after being measured by the optic nerve. The processing flow of dividing the image and attaching the grating plate is shown in Figure 8.

(4) Three-dimensional printing process of grating plate

The three-dimensional printing of the grating board is a kind of printing that uses a grating board (cylindrical lens array) with a lens imaging effect to produce a three-dimensional saltiness after the specially processed scene image according to the aforementioned principles and processing. This technology combines computer technology, printing technology and artistic aesthetic design, so that the columnar transparent grating plate shows different special effects. Its main production process is: design composition-three-dimensional photography or animation output and production of three-dimensional layers-professional software to produce synthetic three-dimensional drawings-color separation and plate making-grating plate materials-printing methods-post-processing-finished product packaging ( Wu Wenhe, 2005a).

The main difference applied to the production of 3D maps in the above process is the 3D photography step. Traditional three-dimensional printing manuscripts use stereo photography to establish the parallax relationship between conjugate image points. This relationship can be used to calculate the elevation difference between objects, that is, to understand the difference in depth of field of the object, so as to perform the layering and merge processing of images However, for the maps and images of a single image, it is necessary to use the numerical terrain model that has been measured in this area to understand the relationship between the elevation and depth of field between the features, and then perform layering and merge processing. This kind of treatment process has traditionally used manual drawing and layered treatment, which is very time-consuming and laborious.

4. Introduction of 3D Laser Digital Scanner

Optech ILRIS-3D (Intelligent Laser Ranging and lmaging System) used in this article, ILRIS-3D uses a fast way to convert the scanned data into the format used by CAD software for plane / elevation selection and fast design. All detailed information, such as poles, road centerlines, and roadside guardrails, will be recorded with detailed and accurate positioning. Some auxiliary data will also be collected together, such as vegetation type, canopy size and tent volume. ILRIS-3D is equipped with a digital camera with 6 million pixels and a large LCD display screen. ILRIS-3D has a simple operation interface similar to ordinary digital cameras. It collects a large amount of data at a high speed of 2000 points per second and a long distance of 3m-1500m. The range-finding capability makes field work extremely simple and economical in any measurement mode. The ability of 360% X360% omnidirectional vision is equipped with a set of bases that can be rotated and tilted. The bases and the scanner itself act as a whole and are controlled by the controller software.

Photo and module results comparison

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5. Modeling of 3D laser digital scanner

set up

This time using the 3D laser digital scanner can get 2000 points in one second, and now the instrument can get 120,000 points in one second. When the instrument is used, the instrument should be set up first. The shooting angle of the instrument is 20 degrees on the left and right, 15 degrees on the top and bottom. After the tripod is added, it can be rotated 360 degrees and 90 degrees up and down. The instrument can be switched to free mode. Select the angle to take the photographic image. After determining the shooting target, first make an environmental assessment, such as the driving route, whether there is a building shadow, the number of scanning stations, the use time of the instrument, determine the scanning range and scanning density, and determine the point cloud density according to the required accuracy. Before scanning, it is necessary to determine the installation position of the instrument. Several scanning stations are required. The scanned images of each station must overlap with each other to select feature points and combine point clouds. The scanned point cloud is filtered using Realwork Surveyn software. In addition to unnecessary noise, do point cloud cutting and point cloud combination to complete point output.

Convert point cloud data to X, Y, and Z files. Use Rapidform to read data, perform point cloud number reduction, surface analysis, mesh patching, polygon creation and editing, and point cloud data output. You can use other rotations to map, Retouching, such as 3DMAX or other 3D drawing software. A high-precision photo of the target object must be taken first, so that a beautiful image can be created when mapping, so as to facilitate the completion of modeling.

6. Experimental design

The three-dimensional printing of the grating board has a great relationship with the manuscript, because the photo of the object needs to be used, and the acquisition of the photo is particularly important. There are two methods to obtain the photo: (1) is to take various aspects of a still object, The resulting photos are processed by software to form a map. (2) Use a 3D laser scanner to capture the digital file format of the point cloud, and quickly process the point cloud through the reverse engineering software Rapidform and build a solid 3D model. The 3D solid model is completely retained by the relevant parameterized software, and digital data is built for editing. Through the establishment of the model, using the screenshot program to obtain pictures, you can complete the three-dimensional mapping of the grating board. Take a landmark as an example to introduce two methods.

(1) For the shooting of a landmark, you need to prepare the camera and the tripod, first find the location of the shooting, and then align the tripod, then set up the tripod, and gradually carry out the action of standing and shooting. This method will have the following problems.

1. To shoot gradually, you need to consider external factors, such as weather conditions and human factors. In poor weather, lighting and shooting results should be included in the thinking. After all, it is impossible to use the camera to shoot when it is raining. .

2. It takes a lot of time to shoot during the shooting, each time it takes time and effort.

3. When standing, there will be occasional errors and human errors in the highlands, which make the shooting heights very different, and the angle when changing the station will also produce the same thing, so when making stereoscopic images, there will be excessive displacement, not Both are interlaced with the highlands.

(2) Use a 3D laser scanner to capture the point cloud digital file format, and quickly process the point cloud through the reverse engineering software Rapidform and build a solid 3D model, and then the relevant parameterized software completely retains the 3D solid model and builds the digital Edit the data. Through the establishment of the model, the screenshot program is used to obtain the picture, and the use is completed here. This side can improve (1) cause 2 or 3 problems. However, due to the implementation of the 3D laser scanner, it can not be used in rainy days, and the internal processing is more complicated, so the working time will also increase. According to the advantages of the 3D laser scanner, a complete modeling on the ground can be established, and the modeling has X, Y, and Z coordinates, and the accuracy is high. We can use it to establish a complete and detailed modeling, freely choose what we want The modeling diagram of the software can use the rotation function of the software on the same axis, and there will be no manual shooting and the height difference will cause the image to be partially blurred. It can be combined with aerial photographs to construct a three-dimensional map with latitude and longitude coordinates when combined with GPS measurement points. [next]

Comparison of two approaches:

7. Conclusions and recommendations

In the actual measurement, repetitive work will occur, that is to stand and shoot, the traditional method will produce many errors, as well as many defects on the finished product, which is inevitable. The method is to reduce repetitive work and improve its results. It is a digital processing. Although some problems need to be solved and paid attention to, if it can be overcome, it will definitely improve the quality of the finished product. The following is encountered during actual operation. The problem:

(1) Scanning procedure

During the 3D laser scanning process, factors such as space, environment, climate and equipment need to be considered.

1. If there are too many target obscurities, it is necessary to mark important features and add photos to carry out subsequent repair modeling work.

2. The roof of the target is not easy to shoot and scan. You need to find a high place to shoot, and you need to consider that the distance will affect the accuracy.

3. Field time needs to take into account the power of the computer and scanner and the scanning time and number of stations.

4. The combination of point cloud to select at least three feature points can improve the accuracy of the point cloud. It can be combined with the three methods provided by the software to perform combined actions, including 2D, 3D and photo methods.

(2) Digital construction process

1. Rapidform v2006's built-in automatic surface creation function, if the 3D digital point cloud data is not complete, you need to manually create the surface.

2. The original density of the point cloud image will affect the precision of the digital model. Rapidform v2006's point cloud data density is not enough, which will affect the accuracy of surface analysis.

3. If the data of the point cloud of the building is not enough, there will be broken surface, which needs to be repaired manually.

4. Pay attention to the integrity of the surface, the integrity of the photo, and the conversion between the 2D and 3D surfaces. [next]

references

Lin Rongtang, 2005, Optimization of Stereoscopic Display Technology with Cylindrical Array Lens. Master's thesis, Department of Graphic Communication and Digital Publishing, Shixin University, Taipei, P25-P50.

Wu Wenhe, 2005a, Application of three-dimensional color pictures in packaging. Three-dimensional product briefing, Shanshui Color Printing Co., Ltd., P5-P7.

Wu Wenhe, 2005b, Research on Random Dot Stereo Imaging Technology and Its Application in Raster Stereo Printing. Master's thesis, Department of Graphic Communication and Digital Publishing, Shixin University, Taipei, P15-P27.

Tokyu Tokyu, 2003, 3D Magic Eye. Taiwan Kadokawa Bookstore, P25.

Gottfried (2001). Lenticular Image and Method. NO. 6,329,987 B1, United States Patent.

Jsselsteijn W. A. I, Seuntiens P. J. H. and Meesters L. M. J. (2002). State-of-the-Art in Human Factors and Quality Issues of Stereoscopic Broadcast Television. ATTEST, PP. 1-41.

Yang Wenbin, Zheng Hongming, You Zhengxian, Chen Minbin, Chen Changliang, Yan Yaning, 2008, A preliminary study on the procedures of digital technology in the preservation of cultural assets, University of Science and Technology of China, P35-P40.

About the Author

1. Jun-Ze Li is a student of the Department of Surveying and Mapping Engineering, Institute of Technology, National Defense University.

2. Zhuang? F Mao (Jun-Mao Zhuang) is a student of the Department of Surveying and Mapping Engineering, National Institute of Technology, National Defense University.

3. Shi-Wei Ye is a student of the Department of Surveying and Mapping Engineering, Institute of Technology, National Defense University.

4. Wen-Ho Wu (Wen-Ho Wu), Master of the Department of Graphic Communication and Digital Publishing, Shixin University, Director of Shanshui Printing Company.

5. Hsing-Wei Lee, Ph.D. from the University of Illinois, USA, is a civilian teacher in the Department of Environmental Science and Technology, National Defense University.

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