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Archive for March, 2014|Monthly archive page

Creating 3D mesh models using Asus xtion with RGBDemo and Meshlab on Ubuntu 12.04

In Computer Vision, Kinect on March 12, 2014 at 5:15 pm

by Li Yang Ku (Gooly)

Big-Bang-Theory-Kinect-3D-Scanner

Creating 3D models simply by scanning an object using low cost sensors is something that sounds futuristic but isn’t. Although models scanned with a Kinect or Asus xtion aren’t as pretty as CAD models nor laser scanned models, they might actually be helpful in robotics research. A not so perfect model scanned by the same sensor on the robot is closer to what the robot perceives. In this post I’ll go through the steps on creating a polygon mesh model from scanning a coke can using the xtion sensor. The steps are consist of 3 parts: compiling RGBDemo, scanning the object, and converting scanned vertices to a polygon mesh in Meshlab.

RGBDemo

RGBDemo is a great piece of opensource software that can help you scan objects into a single ply file with the help of some AR-tags. If you are using a Windows machine, running the compiled binary should be the easiest way to get started. However if you are running on an Ubuntu machine, the following are the steps I did. (I had compile errors following the official instruction, but still might worth a try)

  1. Make sure you have OpenNI installed. I use the old version OpenNI instead of OpenNI2. See my previous post about installing OpenNI on Ubuntu if you haven’t.
  2. Make sure you have PCL and OpenCV installed. For PCL I use the one that comes with ROS (ros-fuerte-pcl) and for OpenCV I have libcv2.3 installed.
  3. Download RGBDemo from Github https://github.com/rgbdemo/rgbdemo.
    git clone --recursive https://github.com/rgbdemo/rgbdemo.git
  4. Modify the file linux_configure.sh under the rgbdemo folder. Add the following line among the other options so that it won’t use OpenNI2.
        
        -DCMAKE_VERBOSE_MAKEFILE=1 \
        -DNESTK_USE_OPENNI2=0 \
        $*
  5. Modify rgbdemo/scan-markers/ModelAcquisitionWindow.cpp. Comment out line 57 to 61. (For compile error: ‘const class ntk::RGBDImage’ has no member named ‘withDepthDataAndCalibrated’)
        
        void ModelAcquisitionWindow::on_saveMeshButton_clicked()
        {
            //if (!m_controller.modelAcquisitionController()->currentImage().withDepthDataAndCalibrated())
            //{
                //ntk_dbg(1) << "No image already processed.";
                //return;
            //}
    
            QString filename = QFileDialog::getSaveFileName
  6. cmake and build
    ./linux_configure.sh
    ./linux_build.sh
  7. The binary files should be built under build/bin/.

turtle mesh

To create a 3D mesh model, we first capture a model (PLY file) that only consists of vertices using RGBDemo.

  1. Print out the AR tags located in the folder ./scan-markers/data/, stick them on a flat board such that the numbers are close to each other. Put your target object on the center of the board.
  2. Run the binary ./build/bin/rgbd-scan-markers
  3. Two windows should pop out, RGB-D Capture and 3D View. Point the camera toward the object on the board and click “Add current frame” in the 3D view window. Move the camera around the object to fill the missing pieces of the model.
  4. Click on the RGB-D Capture window and click Capture->pause in the menu top of the screen. Click “Remove floor plane” in the 3D View Window to remove most of the board.
  5. Click “Save current mesh” to save the vertices into a ply file.

meshlab

The following steps convert the model captured from RGBDemo to a 3D mesh model in MeshLab (MeshLab can be installed through Ubuntu Software Center).

  1. Import the ply file created in the last section.
  2. Remove unwanted vertices in the model. (select and delete, let me know if you can’t figure out how to do this)
  3. Click on “Filters ->Point Set -> Surface Reconstruction: Poisson”. This will pop up a dialog, apply the default setting will generate a mesh that has an estimated surface. If you check “View -> show layer dialog” you should be able to see two layers, the original and the new constructed mesh.
  4. To transfer color to the new mesh click “Filters -> Sampling -> Vertex Attribute Transfer”. Select mesh.ply as source and poisson mesh as target. This should transfer the colors on the vertices to the mesh.
  5. Note that MeshLab has some problem when saving to the collada(dae) format.