1/* ----------------------------------------------------------------------------
2
3 * GTSAM Copyright 2010, Georgia Tech Research Corporation,
4 * Atlanta, Georgia 30332-0415
5 * All Rights Reserved
6 * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
7
8 * See LICENSE for the license information
9
10 * -------------------------------------------------------------------------- */
11
12/**
13 * @file SFMExampleExpressions.cpp
14 * @brief A structure-from-motion example done with Expressions
15 * @author Frank Dellaert
16 * @author Duy-Nguyen Ta
17 * @date October 1, 2014
18 */
19
20/**
21 * This is the Expression version of SFMExample
22 * See detailed description of headers there, this focuses on explaining the AD part
23 */
24
25// The two new headers that allow using our Automatic Differentiation Expression framework
26#include <gtsam/slam/expressions.h>
27#include <gtsam/nonlinear/ExpressionFactorGraph.h>
28
29// Header order is close to far
30#include "SFMdata.h"
31#include <gtsam/geometry/Point2.h>
32#include <gtsam/nonlinear/DoglegOptimizer.h>
33#include <gtsam/nonlinear/Values.h>
34#include <gtsam/inference/Symbol.h>
35
36#include <vector>
37
38using namespace std;
39using namespace gtsam;
40using namespace noiseModel;
41
42/* ************************************************************************* */
43int main(int argc, char* argv[]) {
44
45 Cal3_S2 K(50.0, 50.0, 0.0, 50.0, 50.0);
46 Isotropic::shared_ptr measurementNoise = Isotropic::Sigma(dim: 2, sigma: 1.0); // one pixel in u and v
47
48 // Create the set of ground-truth landmarks and poses
49 vector<Point3> points = createPoints();
50 vector<Pose3> poses = createPoses();
51
52 // Create a factor graph
53 ExpressionFactorGraph graph;
54
55 // Specify uncertainty on first pose prior
56 Vector6 sigmas; sigmas << Vector3(0.3,0.3,0.3), Vector3(0.1,0.1,0.1);
57 Diagonal::shared_ptr poseNoise = Diagonal::Sigmas(sigmas);
58
59 // Here we don't use a PriorFactor but directly the ExpressionFactor class
60 // x0 is an Expression, and we create a factor wanting it to be equal to poses[0]
61 Pose3_ x0('x',0);
62 graph.addExpressionFactor(h: x0, z: poses[0], R: poseNoise);
63
64 // We create a constant Expression for the calibration here
65 Cal3_S2_ cK(K);
66
67 // Simulated measurements from each camera pose, adding them to the factor graph
68 for (size_t i = 0; i < poses.size(); ++i) {
69 Pose3_ x('x', i);
70 PinholeCamera<Cal3_S2> camera(poses[i], K);
71 for (size_t j = 0; j < points.size(); ++j) {
72 Point2 measurement = camera.project(pw: points[j]);
73 // Below an expression for the prediction of the measurement:
74 Point3_ p('l', j);
75 Point2_ prediction = uncalibrate(K: cK, xy_hat: project(p_cam: transformTo(x, p)));
76 // Again, here we use an ExpressionFactor
77 graph.addExpressionFactor(h: prediction, z: measurement, R: measurementNoise);
78 }
79 }
80
81 // Add prior on first point to constrain scale, again with ExpressionFactor
82 Isotropic::shared_ptr pointNoise = Isotropic::Sigma(dim: 3, sigma: 0.1);
83 graph.addExpressionFactor(h: Point3_('l', 0), z: points[0], R: pointNoise);
84
85 // Create perturbed initial
86 Values initial;
87 Pose3 delta(Rot3::Rodrigues(wx: -0.1, wy: 0.2, wz: 0.25), Point3(0.05, -0.10, 0.20));
88 for (size_t i = 0; i < poses.size(); ++i)
89 initial.insert(j: Symbol('x', i), val: poses[i].compose(g: delta));
90 for (size_t j = 0; j < points.size(); ++j)
91 initial.insert<Point3>(j: Symbol('l', j), val: points[j] + Point3(-0.25, 0.20, 0.15));
92 cout << "initial error = " << graph.error(values: initial) << endl;
93
94 /* Optimize the graph and print results */
95 Values result = DoglegOptimizer(graph, initial).optimize();
96 cout << "final error = " << graph.error(values: result) << endl;
97
98 return 0;
99}
100/* ************************************************************************* */
101
102