gtsam/python/gtsam/tests/test_DsfTrackGenerator.py

"""Unit tests for track generation using a Disjoint Set Forest data structure.

Authors: John Lambert
"""

import unittest
from typing import Dict, Tuple

import numpy as np
from gtsam.gtsfm import Keypoints
from gtsam.utils.test_case import GtsamTestCase

import gtsam
from gtsam import (IndexPair, KeypointsVector, MatchIndicesMap, Point2,
                   SfmMeasurementVector, SfmTrack2d)


class TestDsfTrackGenerator(GtsamTestCase):
    """Tests for DsfTrackGenerator."""

    def test_generate_tracks_from_pairwise_matches_nontransitive(
        self,
    ) -> None:
        """Tests DSF for non-transitive matches.

        Test will result in no tracks since nontransitive tracks are naively
        discarded by DSF.
        """
        keypoints = get_dummy_keypoints_list()
        nontransitive_matches = get_nontransitive_matches()

        # For each image pair (i1,i2), we provide a (K,2) matrix
        # of corresponding keypoint indices (k1,k2).
        matches = MatchIndicesMap()
        for (i1, i2), correspondences in nontransitive_matches.items():
            matches[IndexPair(i1, i2)] = correspondences

        tracks = gtsam.gtsfm.tracksFromPairwiseMatches(
            matches,
            keypoints,
            verbose=True,
        )
        self.assertEqual(len(tracks), 0, "Tracks not filtered correctly")

    def test_track_generation(self) -> None:
        """Ensures that DSF generates three tracks from measurements
        in 3 images (H=200,W=400)."""
        kps_i0 = Keypoints(np.array([[10.0, 20], [30, 40]]))
        kps_i1 = Keypoints(np.array([[50.0, 60], [70, 80], [90, 100]]))
        kps_i2 = Keypoints(np.array([[110.0, 120], [130, 140]]))

        keypoints = KeypointsVector()
        keypoints.append(kps_i0)
        keypoints.append(kps_i1)
        keypoints.append(kps_i2)

        # For each image pair (i1,i2), we provide a (K,2) matrix
        # of corresponding image indices (k1,k2).
        matches = MatchIndicesMap()
        matches[IndexPair(0, 1)] = np.array([[0, 0], [1, 1]])
        matches[IndexPair(1, 2)] = np.array([[2, 0], [1, 1]])

        tracks = gtsam.gtsfm.tracksFromPairwiseMatches(
            matches,
            keypoints,
            verbose=False,
        )
        assert len(tracks) == 3

        # Verify track 0.
        track0 = tracks[0]
        assert track0.numberMeasurements() == 2
        np.testing.assert_allclose(track0.measurements[0][1], Point2(10, 20))
        np.testing.assert_allclose(track0.measurements[1][1], Point2(50, 60))
        assert track0.measurements[0][0] == 0
        assert track0.measurements[1][0] == 1
        np.testing.assert_allclose(
            track0.measurementMatrix(),
            [
                [10, 20],
                [50, 60],
            ],
        )
        np.testing.assert_allclose(track0.indexVector(), [0, 1])

        # Verify track 1.
        track1 = tracks[1]
        np.testing.assert_allclose(
            track1.measurementMatrix(),
            [
                [30, 40],
                [70, 80],
                [130, 140],
            ],
        )
        np.testing.assert_allclose(track1.indexVector(), [0, 1, 2])

        # Verify track 2.
        track2 = tracks[2]
        np.testing.assert_allclose(
            track2.measurementMatrix(),
            [
                [90, 100],
                [110, 120],
            ],
        )
        np.testing.assert_allclose(track2.indexVector(), [1, 2])


class TestSfmTrack2d(GtsamTestCase):
    """Tests for SfmTrack2d."""

    def test_sfm_track_2d_constructor(self) -> None:
        """Test construction of 2D SfM track."""
        measurements = SfmMeasurementVector()
        measurements.append((0, Point2(10, 20)))
        track = SfmTrack2d(measurements=measurements)
        track.measurement(0)
        assert track.numberMeasurements() == 1


def get_dummy_keypoints_list() -> KeypointsVector:
    """Generate a list of dummy keypoints for testing."""
    img1_kp_coords = np.array([[1, 1], [2, 2], [3, 3.]])
    img2_kp_coords = np.array(
        [
            [1, 1.],
            [2, 2],
            [3, 3],
            [4, 4],
            [5, 5],
            [6, 6],
            [7, 7],
            [8, 8],
        ]
    )
    img3_kp_coords = np.array(
        [
            [1, 1.],
            [2, 2],
            [3, 3],
            [4, 4],
            [5, 5],
            [6, 6],
            [7, 7],
            [8, 8],
            [9, 9],
            [10, 10],
        ]
    )
    img4_kp_coords = np.array(
        [
            [1, 1.],
            [2, 2],
            [3, 3],
            [4, 4],
            [5, 5],
        ]
    )
    keypoints = KeypointsVector()
    keypoints.append(Keypoints(coordinates=img1_kp_coords))
    keypoints.append(Keypoints(coordinates=img2_kp_coords))
    keypoints.append(Keypoints(coordinates=img3_kp_coords))
    keypoints.append(Keypoints(coordinates=img4_kp_coords))
    return keypoints


def get_nontransitive_matches() -> Dict[Tuple[int, int], np.ndarray]:
    """Set up correspondences for each (i1,i2) pair that violates transitivity.

    (i=0, k=0)             (i=0, k=1)
         |    \\               |
         |     \\              |
    (i=1, k=2)--(i=2,k=3)--(i=3, k=4)

    Transitivity is violated due to the match between frames 0 and 3.
    """
    nontransitive_matches = {
        (0, 1): np.array([[0, 2]]),
        (1, 2): np.array([[2, 3]]),
        (0, 2): np.array([[0, 3]]),
        (0, 3): np.array([[1, 4]]),
        (2, 3): np.array([[3, 4]]),
    }
    return nontransitive_matches


if __name__ == "__main__":
    unittest.main()