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Udacity Sensor Fusion Nanodegree Course

This contains my homework assignments and quiz solutions for the programming portions of this nanodegree. They will be partitioned into separate directories, one for each course. Each course will have separate build instructions. Please note that I have also included the YOLOv3 weights from the Camera course as part of this repo. You will need Git LFS to download the weights. Please visit https://github.com/git-lfs/git-lfs/wiki/Installation to install Git LFS. Once you do, clone the repo and in the repo directory please use the following to download the YOLOv3 weights.

$ cd <path to this repo>
$ git lfs fetch

The weights will appear in SFND_Camera/detect_objects/dat/yolo/yolov3.weights

Please note that the Radar section of this course uses MATLAB so you will need to have this software available to run the code for this part of the course. This was not explicitly mentioned in the official overview of the course which alludes to only knowing C++. However, MATLAB is only required for one part of the Radar section and it isn't explicitly required to complete the course. Therefore, you can run most of the code in this section with Octave. The final project can run in either MATLAB or Octave.

There is also a portion of the course that uses Python to give a brief introduction to Kalman Filter principles, but the knowledge required is very basic and does not use any external dependencies. This also was not mentioned as part of the requirements in this course. Any version of Python 3 should work. The original code was originally in Python 2 which I have changed to Python 3 for longevity.

Instructions for building and running

LiDAR Obstacle Detection Course

This can be found in the SFND_Lidar_Obstacle_Detection directory in this repo. This was initially a fork from https://github.com/udacity/SFND_Lidar_Obstacle_Detection, but I made significant changes to the formatting, fixed some bugs that were seen on the Issues page of the original repo and diverged away a bit from the original specifications for submitting the project. However, the directory essentially contains the completed project and does fulfill the guidelines required to gain a successful pass.

If you'd like to see the commit history of how the project progressed from the beginning until completion, please see my fork: https://github.com/rayryeng/SFND_Lidar_Obstacle_Detection

Please note that it is assumed that you have all of the dependencies installed for this to build successfully. For instructions on getting these dependencies, please refer to the original repo or my fork from the links above. However, you should only need to install PCL as the extra dependency, which will tie in all of the other dependencies required upon installation (Boost in particular).

To build this project, there are three submodules.

Main environment

The main environment for the detection is for taking in a stream of PCD files and showing the object detection for cars / obstacles in 3D in real-time. This can be built navigating to the SFND_Lidar_Obstacle_Detection directory and using the CMakeLists.txt file in that directory:

$ cd SFND_Lidar_Obstacle_Detection
$ mkdir build && cd build
$ cmake ..
$ make

You can then run the environment by just doing:

$ ./environment

I have modified the executable so that we can switch between the different datasets that is part of this assessment. The datasets can be found in the src/sensors/data/pcd in the SFND_Lidar_Obstacle_Detection directory. Just running environment will run the data_1 dataset located in this directory. You can additionally specify a string to choose between the different datasets in this directory:

$ ./environment data_1

or

$ ./environment data_2

Mac OS X Modifications as of August 30, 2021

Due to recent updates to Qt from Homebrew, Qt version 6 is the latest version that is released. The LiDAR Obstacle Detection project requires Qt version 5 or else the project does not build successfully. Therefore, if you are using Mac OS to run this project, please make sure you uninstall Qt version 6, install Qt version 5 and establish the correct symlinks to allow the code to configure and build.

In your terminal, please do the following:

$ brew uninstall qt
$ brew install qt@5
$ sudo ln -s /usr/local/Cellar/qt@5/5.15.2/mkspecs /usr/local/mkspecs
$ sudo ln -s /usr/local/Cellar/qt@5/5.15.2/plugins /usr/local/plugins

The symlinks point the Qt version 5 libraries so that the project can find them. Please modify the path to Qt version 5 so that it points to the correct mkspecs and plugins directories.

In addition, I had to additionally add #include <boost/filesystem.hpp> to processPointClouds.h for the code to finally compile.

RANSAC quiz

The portion of the course that tests the implementation of 3D plane estimation using RANSAC can be built navigating to the SFND_Lidar_Obstacle_Detection/src/quiz/ransac directory and using the CMakeLists.txt file in that directory:

$ cd SFND_Lidar_Obstacle_Detection/src/quiz/ransac
$ mkdir build && cd build
$ cmake ..
$ make

You can then run the clustering quiz by:

$ ./quizRansac

Cluster quiz

The portion of the course that tests the implementation of Euclidean clustering can be built navigating to the SFND_Lidar_Obstacle_Detection/src/quiz/cluster directory and using the CMakeLists.txt file in that directory:

$ cd SFND_Lidar_Obstacle_Detection/src/quiz/cluster
$ mkdir build && cd build
$ cmake ..
$ make

You can then run the clustering quiz by:

$ ./quizCluster

Camera Course

OpenCV must be installed on your system prior to building. On Linux, you can simply follow: https://www.learnopencv.com/install-opencv-4-on-ubuntu-16-04/. On Mac OS, you can install OpenCV through Homebrew https://formulae.brew.sh/formula/opencv, specifically with brew install opencv. On Windows, you can download pre-compiled binaries from the official website: https://opencv.org/releases/

Navigate to the SFND_Camera/ directory to access the exercises and projects for this course.

Intro to OpenCV Exercises

Navigate to the SFND_Camera/intro_to_opencv_exercises/OpenCV_exercises directory, then build it:

$ cd SFND_Camera/intro_to_opencv_exercises/OpenCV_exercises
$ mkdir build && cd build
$ cmake ..
$ make

This will create five executables that reflect the different tutorials exercises. Additionally, there are solutions from the instructor in SFND_Camera/intro_to_opencv_exercises/solutions that can be accessed.

Intro to Time to Collision (TTC) Exercises

For the camera-based solution, navigate to the SFND_Camera/TTC_Camera/TTC_camera directory, then build it:

$ cd SFND_Camera/TTC_Camera/TTC_camera
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/TTC_Camera/solution that can be accessed.

Note: My solution and the provided solution crash due to out of bounds errors. This is because the provided source code to parse the data files to get the keypoints does not function properly, thus resulting in negative indices for accessing a std::vector thus causing the crash.

For the LiDAR-based solution, navigate to the SFND_Camera/TTC_lidar directory, then build it:

$ cd SFND_Camera/TTC_lidar
$ mkdir build && cd build
$ cmake ..
$ make

Intensity Gradient and Filtering Exercise

Navigate to the SFND_Camera/intensity_gradient_filtering/gradient_filtering directory, then build it:

$ cd SFND_Camera/intensity_gradient_filtering/gradient_filtering
$ mkdir build && cd build
$ cmake ..
$ make

This will create three executables for you to run. Additionally, there are solutions from the instructor in SFND_Camera/intensity_gradient_filtering/solutions that can be accessed.

Note: The instructor used double for loops for some of the solutions where I opted to use built-in OpenCV methods and operations (such as computing the gradient magnitude). Built-in operations using the cv::Mat class are faster as they are designed to operate on these datatypes and are multi-threaded when applicable.

Harris Corner Detector Exercise

Navigate to the SFND_Camera/harris_corner_nms/cornerness_harris directory then build it:

$ cd SFND_Camera/harris_corner_nms/cornerness_harris
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/harris_corner_nms/cornerness_harris/solution that can be accessed.

Note: The instructor's solution use the cv::KeyPoint::overlap() method to perform non-maximum suppression. In particular, keypoints can only exist if the particular keypoint within a finite window have the strongest response over all points that overlap with said keypoint. I approached this differently where within a finite window, we search for the largest response and the centre of the window should have this response. If and only if the largest response in the centre of this window is the largest do we keep this keypoint. This amounts to the same principle, but I felt that I approached it more sanely.

Detect Keypoints Exercise

Navigate to the SFND_Camera/detect_keypoints/detect_keypoints directory then build it:

$ cd SFND_Camera/detect_keypoints/detect_keypoints
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/detect_keypoints/detect_keypoints/solution that can be accessed.

Describe Keypoints Exercise

Navigate to the SFND_Camera/describe_keypoints/describe_keypoints directory then build it:

$ cd SFND_Camera/describe_keypoints/describe_keypoints
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/describe_keypoints/describe_keypoints/solution that can be accessed.

Descriptor Keypoint Matching Exercise

Navigate to the SFND_Camera/descriptor_matching/descriptor_matching directory then build it:

$ cd SFND_Camera/descriptor_matching/descriptor_matching
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/descriptor_matching/descriptor_matching/solution that can be accessed.

Midterm Project

In order to track commits (unlike the first project where I forked the project and just put everything in as one commit), I've cloned the original midterm project repo from here: https://github.com/udacity/SFND_2D_Feature_Tracking. Please ensure that you have the right dependencies installed by looking at this repo prior to building. Navigate to the SFND_Camera/SFND_2D_Feature_Matching directory then build it:

$ cd SFND_Camera/SFND_2D_Feature_Matching
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. This executable takes in command-line arguments. Please review the midterm report README for more details in SFND_Camera/SFND_2D_Feature_Matching/README_Midterm_Report.md.

LiDAR to Camera Exercise

Navigate to the SFND_Camera/lidar_to_camera/lidar_to_camera directory then build it:

$ cd SFND_Camera/lidar_to_camera/lidar_to_camera
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. Additionally, there are solutions from the instructor in SFND_Camera/lidar_to_camera/solution that can be accessed.

Detect Objects Exercise

Navigate to the SFND_Camera/detect_objects directory then build it:

$ cd SFND_Camera/detect_objects
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run.

Cluster with ROI Exercise

Navigate to the SFND_Camera/cluster_with_roi directory then build it:

$ cd SFND_Camera/cluster_with_roi
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run.

Final Project

In order to track commits, I've cloned the original final project repo from here: https://github.com/udacity/SFND_3D_Object_Tracking. Please ensure that you have the right dependencies installed by looking at this repo prior to building. Navigate to the SFND_Camera/SFND_3D_Object_Tracking/ directory then build it:

$ cd SFND_Camera/SFND_3D_Object_Tracking
$ mkdir build && cd build
$ cmake ..
$ make

This will create an executable for you to run. This executable takes in command-line arguments. Please review the final project report README for more details in SFND_Camera/SFND_3D_Object_Tracking/README_Final_Report.md. You can also have a look at the Jupyter Notebook located in SFND_Camera/SFND_3D_Object_Tracking/TTC_Camera_Plots.ipynb to take a look at the TTC performance graphs for different combinations of detectors and descriptors, but they're included in the final report for self-completeness.

Radar Course

Lesson 2 - Radar Principles

This section of the course talks about the maximum range a Radar can have for detecting objects. In SFND_Radar/Lesson2_Radar_Range_Equation, a MATLAB exercise is provided to calculate this quantity given the requirements of the Radar device in question. Just run the script in this directory to see the final output value.

Lesson 3 - Range-Doppler Estimation

This section of the course discusses the Doppler effect and how to simultaneously estimate the velocity and position of an object. In SFND_Radar/Lesson3 are various exercises to estimate the range (distance from the ego vehicle), the velocity (via the Doppler effect) and understanding how the Fast Fourier Transform (FFT) works, specifically on how it applies to simultaneous range and velocity estimation of objects with respect to the ego vehicle. Just run each script individually to see what the relevant outputs are.

Lesson 4 - Constant False Alarm Rate (CFAR)

This section of the course studies the Constant False Alarm Rate (CFAR) technique on how to adaptively threshold the frequency spectrum obtained by a radar signal to detect obstacles in the environment. I have implemented both the original non-efficient version using loops and one using convolution. In SFND_Radar/Lesson4, a MATLAB exercise is provided to demonstrate how to find peaks in a frequency spectrum. Just run the script to see what the relevant outputs are.

Lesson 5 - Clustering and Tracking

This section of the course introduces clustering and tracking using the Kalman Filter. The MATLAB code found in SFND_Radar/Lesson5 is the demonstration script that was used for this section. You can run it to simulate a driving scenario with vehicles and full sensor readings. Please note that you will need MATLAB's Automated Driving Toolbox to run this code. However, it is not essential for the completion of this course.

Final Project

This project dealt with generating an artificial moving target by assuming it is moving with the constant velocity model, creating a transmitted and received signal as what would be done in a radar module, then calculating a Range-Doppler Map (RDM) to ascertain the position and velocity of the target. Because the RDM is inherently noisy due to radar clutter, the CFAR is calculated in 2D in this RDM to finally detect where the object is and its speed. In the lecture videos, pow2db and db2pow are used to convert between unitless magnitude and dB. These functions are in the Signal Processing Toolbox in MATLAB. To ensure Octave compatibility, those functions have been implemented as anonymous functions in the code that can be called instead of using the ones from the Signal Processing Toolbox. Simply navigate to SFND_Radar/FinalProject to run the code. The README file in the same directory addresses how the 2D CFAR was implemented, as well as discussing the choice of the hyperparameters and handling other nuances in the method.

Kalman Filter Course

Review

In one section of the course, we use Python to implement a basic Kalman filter as well as answer some quiz questions. The answers to those questions as well as the basic Kalman filter implementation can be found in the SFND_Kalman_Filter/Review_Python directory. Any version of Python 3 should work for this as there are external dependencies. The same exercise in C++ can be found in SFND_Kalman_Filter/Review_CPP/tracking_1d which uses the Eigen library to perform matrix computations. Make sure Eigen is installed on your computer first prior to building. Eigen is a header-only library, so you can either download it or you can use package installers. Please go here to download it: http://eigen.tuxfamily.org/index.php?title=Main_Page#Download. You can also install it through Homebrew on Mac OS by a simple brew install eigen or through apt-get on Debian flavoured Unix distros (see https://askubuntu.com/questions/860207/how-to-install-eigen-3-3-in-ubuntu-14-04). Assuming you have installed Eigen, you can navigate to the aforementioned directory, then use the following to build:

$ cd SFND_Kalman_Filter/Review_CPP/tracking_1d
$ mkdir build && cd build
$ cmake ..
$ make

This will make an executable for you to run and you can run it.

2D Kalman Filter - Tracking Pedestrian Position using LiDAR

In this exercise, we are using a 2D Kalman Filter to predict the position of a pedestrian using LiDAR measurements. This code has been modified to run locally. In particular, I have made the necessary CMake files for this to run locally. Simply go to SFND_Kalman_Filter/EKF_Prep/tracking_2d, configure and build the project:

$ cd SFND_Kalman_Filter/EKF_Prep/tracking_2d
$ mkdir build && cd build
$ cmake ..
$ make

There will be an executable for you to run.

Jacobian Matrix

The measurement update step for the radar sensor is non-linear, so the need to linearise the measurement update functions is required. The Jacobian matrix help us do this. This exercise implements the Jacobian for measuring radar measurements and transferring those to updating the position and velocity states. Simply go to SFND_Kalman_Filter/EKF_Prep/jacobian_matrix, configure and build the project:

$ cd SFND_Kalman_Filter/EKF_Prep/jacobian_matrix
$ mkdir build && cd build
$ cmake ..
$ make

There will be an executable for you to run.

RMSE

A simple program for calculating the RMSE between vectors can be found in SFND_Kalman_Filter/EKF_Prep/rmse. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/EKF_Prep/rmse
$ mkdir build && cd build
$ cmake ..
$ make

Generating Sigma Points

This exercise is the first step for implementing the Unscented Kalman Filter. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/generating_sigma_points
$ mkdir build && cd build
$ cmake ..
$ make

UKF Augmentation - LiDAR

This exercise implements augmenting the state vector to observe the noise distributions of the acceleration and yaw acceleration. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/ukf_augmentation
$ mkdir build && cd build
$ cmake ..
$ make

UKF Augmentation: Predict - LiDAR

This exercise implements estimating the new augmented state vector from the previous observations. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/ukf_augmentation_predict
$ mkdir build && cd build
$ cmake ..
$ make

UKF Augmentation: Estimate new mean and covariance - LiDAR

This exercise implements estimating the mean and covariance of the augmented state vector. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/ukf_augmentation_mean_covariance
$ mkdir build && cd build
$ cmake ..
$ make

UKF Measurement Predict - Radar

This exercise implements estimating the measurement vector from the previous observations. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/ukf_predict_radar
$ mkdir build && cd build
$ cmake ..
$ make

UKF Update - Radar

This exercise implements updating the state vector and covariance. Configure and build, then run the executable found here:

$ cd SFND_Kalman_Filter/UKF_Prep/ukf_update
$ mkdir build && cd build
$ cmake ..
$ make

Unscented Kalman Filter Project

Please navigate to the SFND_Kalman_Filter/SFND_Unscented_Kalman_Filter directory to find the implementation of the Unscented Kalman Filter project. Please note that this is a clone of the official repo found here: https://github.com/udacity/SFND_Unscented_Kalman_Filter. However, there have been two crucial changes:

  1. This repo came with a local version of Eigen which I have removed to reduce space.
  2. The README file had some redundancies which I have removed.

To build this project, simply configure and build it:

$ cd SFND_Kalman_Filter/SFND_Unscented_Kalman_Filter
$ mkdir build && cd build
$ cmake ..
$ make

There will be an executable for you to run.

Note: I've had some difficulty building this on Mac OS - in particular, the way Eigen and PCL interact on my system causes some build errors with the cmath header. As a workaround, I had to specifically point to where my Xcode command-line tools were when I configured the project:

$ cd SFND_Kalman_Filter/SFND_Unscented_Kalman_Filter
$ mkdir build && cd build
$ cmake -DCMAKE_OSX_SYSROOT="/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk" ..
$ make

Note that the above CMake variable CMAKE_OSX_SYSROOT should be modified so that it points directly to the Xcode command-line tools SDK that is installed on your system. You can find this out by doing:

$ xcrun --show-sdk-path

Source: PointCloudLibrary/pcl#2601

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