Most structure from motion or monocular SLAM algorithms use some kind of feature tracking and then estimate a dense reconstruction after they optimize the locat

Most structure from motion or monocular SLAM algorithms use some kind of feature tracking and then estimate a dense reconstruction after they optimize the locations of all the cameras and all the features. But it's not the only way. There's one notable alternative method, which is LSD-SLAM: https://github.com/tum-vision/lsd_slam https://github.com/tum-vision/lsd_slam In general, it's extremely hard to get good quality models from a cellphone camera. Believe me, thousands of innovative researchers are trying their best to make it better.