121 lines
3.7 KiB
Python
121 lines
3.7 KiB
Python
"""
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GTSAM Copyright 2010, Georgia Tech Research Corporation,
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Atlanta, Georgia 30332-0415
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All Rights Reserved
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Authors: Frank Dellaert, et al. (see THANKS for the full author list)
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See LICENSE for the license information
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Solve a structure-from-motion problem from a "Bundle Adjustment in the Large" file
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Author: Frank Dellaert (Python: Akshay Krishnan, John Lambert)
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"""
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import argparse
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import logging
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import sys
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import matplotlib.pyplot as plt
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import numpy as np
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import gtsam
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from gtsam import (
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GeneralSFMFactorCal3Bundler,
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PinholeCameraCal3Bundler,
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PriorFactorPinholeCameraCal3Bundler,
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readBal,
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symbol_shorthand
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)
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C = symbol_shorthand.C
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P = symbol_shorthand.P
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logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)
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def run(args):
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""" Run LM optimization with BAL input data and report resulting error """
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input_file = gtsam.findExampleDataFile(args.input_file)
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# # Load the SfM data from file
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scene_data = readBal(input_file)
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logging.info(f"read {scene_data.number_tracks()} tracks on {scene_data.number_cameras()} cameras\n")
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# # Create a factor graph
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graph = gtsam.NonlinearFactorGraph()
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# # We share *one* noiseModel between all projection factors
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noise = gtsam.noiseModel.Isotropic.Sigma(2, 1.0) # one pixel in u and v
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# Add measurements to the factor graph
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j = 0
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for t_idx in range(scene_data.number_tracks()):
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track = scene_data.track(t_idx) # SfmTrack
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# retrieve the SfmMeasurement objects
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for m_idx in range(track.number_measurements()):
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# i represents the camera index, and uv is the 2d measurement
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i, uv = track.measurement(m_idx)
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# note use of shorthand symbols C and P
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graph.add(GeneralSFMFactorCal3Bundler(uv, noise, C(i), P(j)))
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j += 1
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# Add a prior on pose x1. This indirectly specifies where the origin is.
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graph.push_back(
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gtsam.PriorFactorPinholeCameraCal3Bundler(
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C(0), scene_data.camera(0), gtsam.noiseModel.Isotropic.Sigma(9, 0.1)
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)
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)
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# Also add a prior on the position of the first landmark to fix the scale
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graph.push_back(
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gtsam.PriorFactorPoint3(
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P(0), scene_data.track(0).point3(), gtsam.noiseModel.Isotropic.Sigma(3, 0.1)
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)
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)
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# # Create initial estimate
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initial = gtsam.Values()
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i = 0
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# add each PinholeCameraCal3Bundler
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for cam_idx in range(scene_data.number_cameras()):
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camera = scene_data.camera(cam_idx)
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initial.insert(C(i), camera)
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i += 1
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j = 0
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# add each SfmTrack
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for t_idx in range(scene_data.number_tracks()):
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track = scene_data.track(t_idx)
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initial.insert(P(j), track.point3())
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j += 1
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# Optimize the graph and print results
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try:
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params = gtsam.LevenbergMarquardtParams()
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params.setVerbosityLM("ERROR")
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lm = gtsam.LevenbergMarquardtOptimizer(graph, initial, params)
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result = lm.optimize()
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except Exception as e:
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logging.exception("LM Optimization failed")
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return
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# Error drops from 2764.22 to 0.046
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logging.info(f"final error: {graph.error(result)}")
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if __name__ == "__main__":
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parser = argparse.ArgumentParser()
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parser.add_argument(
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'-i',
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'--input_file',
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type=str,
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default="dubrovnik-3-7-pre",
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help='Read SFM data from the specified BAL file'
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'The data format is described here: https://grail.cs.washington.edu/projects/bal/.'
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'BAL files contain (nrPoses, nrPoints, nrObservations), followed by (i,j,u,v) tuples, '
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'then (wx,wy,wz,tx,ty,tz,f,k1,k1) as Bundler camera calibrations w/ Rodrigues vector'
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'and (x,y,z) 3d point initializations.'
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)
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run(parser.parse_args())
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