ISPRS Workshop on Service and Application of Spatial Data Infrastructure, XXXVI (4/W6), Oct.14-16, Hangzhou, China 
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3D MODELING OF SMALL INDUSTRIAL PARTS BASED ON THE PROJECTOR- 
CAMERA SYSTEM 
Jun Tao a 
d Wuhan University, College of Remote Sensing and Information Engineering, 129 Luoyu Road, Wuhan, Hubei, 
P.R.China, martintao@tom.com 
KEY WORDS: 3D Modeling, Industrial Parts, Slide Projector, Calibration, Planar Grid, Digital Close-Range Photogrammetry 
ABSTRACT: 
3D modeling of industrial parts is the key foundation and preceding step of 3D inspection and measurement of industrial parts. The 
common characteristic of industrial parts is that its surface is sleeky, homogeneous and lack of the texture. So the key difficulties in 
3D modeling of industrial parts are the matching and the extraction of the suitable texture and the makeup of the 3D model. The 
paper proposes a flexible and practical method to three-dimensional model the small industrial parts based on the projector-camera 
system. The projector-camera system is composed of a slide projector, a digital camera, a control ground and a computer. After both 
calibrated respectively first, the projector-camera system is similar with the binocular vision system in the principle of 3D modeling. 
The 3D model of the target small industrial parts is acquired by connecting all neighbor space feature points and the real texture is 
rendered from relative images without the projected texture characteristic. The 3D modeling of small industrial parts is achieved 
finally. The method of 3D modeling is active and effective because the projected texture characteristic can be designed first on 
motivation. The 3D modeling method is non-touched so that it is remote and nondestructive. Because of little effect by the space 
factor or the time factor, the method of the small industrial parts 3D modeling is flexible and practical. The 3D modeling of small 
industrial parts proposed in the paper is confirmed to be correct and effective entirely by the results of the modeling experiments. 
1. INTRODUCTION 
1.1 3D Modeling 
3D modeling is referred as a process of the recovery of three- 
dimensional model from the two-dimensional digital camera 
images. During the image formation process of the camera, 
explicit 3D information about the scene or objects in the scene 
is lost. Therefore, 3D model or depth information has to be 
inferred implicitly from the 2D intensity images. The key of the 
traditional method lies in the matching of the corresponding 
features in the images. When there is no feature or lack of 
feature in the objects, or when the features cannot be matched 
correctly at all, the main problems appear in the process of the 
3D modelling. 
The paper provides a method to resolve the problems above. It 
is an ordinary slide projector that can supply any feature what 
you want to the target object. These features are easy to be 
controlled and to be extracted out, which has paved the 
convenient path for the matching of them. According to the 
demand and real condition, the features can be changed or 
adjusted. 
The paper explains clearly how to use the ordinary slide 
projector and how to apply it to the applications of the 3D 
modeling, too. 
1.2 3D Modeling of Industrial Parts 
3D modeling of object has become an important task and a 
current challenge of the digital close-range photogrammetry and 
computer vision. With the development of the photogrammetry 
and computer science, their theories and skills are applied to all 
kinds of the industry. 3D modeling of industrial parts is the key 
foundation and preceding step of 3D inspection and 
measurement of industrial parts. The common characteristic of 
industrial parts is that its surface is sleeky, homogeneous and 
lack of the texture. So the key difficulties in 3D modeling of 
industrial parts are the matching and the extraction of the 
suitable texture and the makeup of the 3D model. According to 
the above difficulties and troubles, the paper proposes a flexible 
and practical method to three-dimensional model the small 
industrial parts based on the projector-camera system. 
The projector-camera system is composed of a slide projector, a 
digital camera, a control ground and a computer. The slide 
projector can project the texture characteristic onto the surface 
of the small industrial parts. Hence, The problem of lacking of 
texture of industrial parts is solved entirely. The projected 
texture characteristic is designed to be stable and clear so that it 
is easy to be matched correctly and rapidly. The digital camera 
can take images as the foundational data for 3D modeling. The 
control ground is a rotating platform with panel of the planar 
grid. The planar grid supplies the space coordinate system and 
the rotating platform is convenient to rotate the industrial parts 
for taking images from the different orientations. Because of the 
size of the planar grid, the target industrial parts are relatively 
small. The computer controls the slide projector to project, the 
digital camera to take images and the rotating platform to rotate 
by any angle, lets the other three equipments working together 
automatically and efficiently. 
Before the small industrial parts are 3D modeled, the slide 
projector and the digital camera must be calibrated in advance. 
Because the results of the calibration of the slide projector and 
the digital camera are the necessary and required parameters for 
the next 3D modeling of the small industrial parts. The planar 
grid is also functioned as the control ground for the calibrations 
of the digital camera and the slide projector. The digital camera 
takes images of the planar grid from the different orientations