3D Point Cloud Processing with PCL

"What's better than 2D?"

Three dimensional (3D) point cloud can be understood as a set of points in the Euclidean coordinate system, with every point has X-, Y-, and Z-coordinates. Combined with the corresponding normal vectors or normals, this set forms oriented points - providing 6 degrees of freedom (DOF). This article aims to briefly introduce readers to the 3D point cloud processing with an open source library called Point Cloud Library (PCL). Two examples of using PCL are given and visualized.

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A 3D point cloud can be acquired using range sensors such as Microsoft Kinect, ASUS Xtion, or laser scanners. These devices apply either triangulation or time-of-flight (TOF). Apart from that, using the autofocus system on conventional industrial cameras can also deliver 3D point clouds.

To process and visualize 3D point clouds, PCL offers various modules, e.g., filtering, segmentation, I/O, data structures, and visualization. The author has been tasked to implement several of these features in the open source application for image processing called MILAN. The implementations are available within one particular plug-in of MILAN. The following images are examples of using MILAN with PCL.

Figure 1 - The features of PCL in MILAN are accessible via a toolbox docked to the right side as seen above. This is also where the Kinect sensor can be used and controlled.

Figure 2: PCL Downsampling Filter, to reduce the size of an input cloud (left - 63792 vertices) to an output (right - 20462 vertices).

Figure 3: PCL Euclidean Cluster Segmentation, to segmentize spatially isolated point clouds.

Before using MILAN, the author has used the PCL tutorials and implemented them in separate Microsoft Visual Studio (MSVS) 2008 projects. The Service Packet 1 (SP 1) of this IDE needs to be installed, otherwise the developers can only code in Release mode.

Another alternative to MSVS is the Qt Creator. The author has covered this in one post on the app FingKinector 2.0. It was developed with Qt 4 along OpenCV 2.4.5. Without writing any .PRO file for the Qt project, the author used a CMakeLists.txt entirely to build this Qt project.

FingKinector - Interacting with the Kinect Motor

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The pivot which connects the Kinect sensor to its base is motorized. This post is about an app called 'FingKinector', which is developed to utilize that motorized pivot without having to rotate the Kinect sensor manually. This is tested only on the Kinect sensor for XBOX 360 and developed for Windows 7.

"K.I.S.S. = Keep It Stupid, Simple"

Image 1: Kinect Sensor for XBOX 360, equipped with a wide-angle lens.

To be able to control the Kinect sensor from a PC, you will need an AC-adapter for your Kinect. It costs around € 8.00 on the Amazon. It has 2 outputs: the orange plug connector is used to supply the Kinect with 12 V at 1 A, whereas the second output is a regular USB connector [1].

If your Kinect is connected to your PC for the first time, by default Windows will attempt to automatically download and install the driver for that Kinect, which comes from PrimeSense. PrimeSense is the developer of the range camera in the Kinect sensor and it is an Israeli 3D sensing technology. As of this time - PrimeSense has become a subsidiary of Apple Inc [2].

At the bottom of this post, the writer puts a link for you to download FingKinector.

FingKinector works in 2 options:

1. Single run
2. Sequential run

The following image shows the first mode (single run). It is known from [3] that the motor is allowed to be tilted to an angle between -27° and 27°.

Image 2: Single Run mode on FingKinector

The second mode, as seen in Image 3 below - the sequential run, uses a factor to divide the range [-27°,27°] up to 10 sectors. By default this mode will first turn the Kinect to the position of 0°, then starts the sequential movement from either top (at 27°) or bottom (at -27°).

Image 3: Sequential mode on FingKinector

The writer also took a liberty to record an amateur video to demonstrate the sequential mode. The Kinect here is seen with an extra hardware called Kinect Zoom Wide-Angle Lens by Nyko [4]. Its cost is around € 14.00.

Sources:

[1]: Kinect Adapter in Amazon.de

[2]: PrimeSense (Wikipedia)

[3]: Kinect Sensor - Microsoft Developer Network

[4]: Kinect Zoom Wide-Angle Lense by Nyko (Amazon.de)

REMINDER / WARNING:

1. For Windows only. (Linux version will be made available in the next development)
2. The writer is NOT liable for any damage.
3. Use at your own risk.

Have fun!

Download link:
Download link for FingKinector (Windows)