Colmap implements 3D reconstruction steps

1. Feature extraction
2. Feature matching
3. SFM+ triangulation to establish sparse point cloud, bundle adjustment (Bundle Adjustment)
4. Dense reconstruction
5. Undistrotion to remove distortion
6. Stereo dense matching
7. Fusion depth map fusion to generate dense point cloud
8. Possion Poisson surface reconstruction/Delaunay Delaunay triangular network reconstruction