How to Structure from Motion

A self reliant tutorial on Structure from Motion (SFM).

In this repository, we provide

• Self-reliant tutorial on SFM
• SFM Python Script
• Associated Booklet

1. Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

1.1. Prerequisites

To run tutorials, you need to have following libraries installed:

Numpy >= 1.13.1
OpenCV 3
Meshlab

Furthermore, to run SFM python script, you also need:

OpenCV Contrib

1.2. Data

Please download the standard data benchmarks from here

After downloading, you should have the following directory structure

data/
    fountain-P11/ 
        images/
            0001.jpg
            ...
            0011.jpg
        gt_dense_cameras/
            0000.jpg.camera
            ...
            0011.jpg.camera
    Herz-Jesus-P8/
        ...
    Castle-P19/
        ...
    ...

2. Demo/Quick Start

2.1. Tutorial Notebook

Tutorials are in tutorial/ directory. Furthermore, they're divided in following sections

1. Chapter 1: Prerequisites
2. Chapter 2: Epipolar Geometry
3. Chapter 3: 3D Scene Estimations
4. Chapter 4: Putting It Together: Part I

2.2. SFM Script

1. Go to script/ directory

   cd script
   

2. Run featmatch.py to generate feature keypoints, descriptors and matches

   python featmatch.py
   

   All arguments are shown below:

   usage: featmatch.py [-h] [--data_dir DATA_DIR] [--ext EXT] [--out_dir OUT_DIR]
                       [--features FEATURES] [--print_every PRINT_EVERY]
                       [--save_results SAVE_RESULTS]
   
   optional arguments:
   -h, --help            show this help message and exit
   
   --data_dir  directory containing images (default: ../data/fountain-P11/images/)
   --ext   comma seperated string of allowed image extensions (default: jpg,png)
   --out_dir   root directory to store results in (default: ../data/fountain-P11)
   
   --features  [SIFT|SURF] Feature algorithm to use (default: SURF)
   --matcher   [BFMatcher|FlannBasedMatcher] Matching algorithm to use (default: BFMatcher)
   --cross_check   [True|False] Whether to cross check feature matching or not (default: True)
   
   --print_every   [1,+inf] print progress every print_every seconds, -1 to disable (default: 1)
   --save_results  [True|False] whether to save images with keypoints drawn on them (default: False)
   

3. Run sfm.py to generate point cloud:

   python sfm.py --data-dir <path-to-data-directory>
   

   All arguments are shown below

   usage: sfm.py [-h] [--data_dir DATA_DIR] [--dataset DATASET] [--ext EXT]
             [--out_dir OUT_DIR] [--features FEATURES] [--matcher MATCHER]
             [--cross_check CROSS_CHECK] [--calibration_mat CALIBRATION_MAT]
             [--fund_method FUND_METHOD] [--outlier_thres OUTLIER_THRES]
             [--fund_prob FUND_PROB] [--pnp_method PNP_METHOD]
             [--pnp_prob PNP_PROB] [--allow_duplicates ALLOW_DUPLICATES]
             [--color_policy COLOR_POLICY] [--plot_error PLOT_ERROR]
             [--verbose VERBOSE]
   
   optional arguments:
   -h, --help            show this help message and exit
   
   --data_dir  root directory containing input data (default: ../data/)
   --dataset   name of dataset (default: fountain-P11)
   --ext   comma seperated string of allowed image extensions (default: jpg,png)
   --out_dir   root directory to store results in (default: ../results/)
   
   --features  [SIFT|SURF] Feature algorithm to use (default: SURF)
   --matcher   [BFMatcher|FlannBasedMatcher] Matching algorithm to use (default: BFMatcher)
   --calibration_mat   [benchmark|lg_g3] Type of intrinsic camera to use (default: benchmark)
   
   --fund_method   [FM_RANSAC | FM_8POINT] Method to estimate fundamental matrix (default: FM_RANSAC)
   --outlier_thres     Threshold value of outlier to be used in fundamental matrix estimation (default: 0.9)
   --fund_prob     [0, 1] Confidence in fundamental matrix estimation required(default: 0.9)
   
   --pnp_method    [SOLVEPNP_DLS | SOLVEPNP_EPNP | ...] Method used for PnP estimation (default: SOLVEPNP_DLS)
   --pnp_prob  [0, 1] Confidence in PnP estimation required (default: 0.99)
   

3. Results

3.1. Fountain P11

3.2. Herz Jesus P8

3.3. Entry P10

Authors

• Muneeb Aadil
• Sibt ul Hussain