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Overview
The Converter class provides static utility functions for converting between different mathematical representations used in ORB-SLAM3: OpenCV matrices, Eigen matrices, g2o types, and Sophus types.
Header: include/Converter.h
Descriptor Conversion
toDescriptorVector
static std::vector<cv::Mat> toDescriptorVector(const cv::Mat &Descriptors)
Descriptors - Matrix where each row is a descriptor
Returns: Vector of descriptor rows
Used in: BoW database queries
SE3 Conversions
toSE3Quat (from cv::Mat)
static g2o::SE3Quat toSE3Quat(const cv::Mat &cvT)
cvT - 4x4 OpenCV transformation matrix (SE3)
Returns: g2o SE3 quaternion
toSE3Quat (from Sophus)
static g2o::SE3Quat toSE3Quat(const Sophus::SE3f &T)
T - Sophus SE3 transformation
Returns: g2o SE3 quaternion
toSE3Quat (from Sim3)
static g2o::SE3Quat toSE3Quat(const g2o::Sim3 &gSim3)
gSim3 - g2o Sim3 transformation
Returns: g2o SE3 quaternion (scale removed)
OpenCV Matrix Conversions
toCvMat (from SE3)
static cv::Mat toCvMat(const g2o::SE3Quat &SE3)
toCvMat (from Sim3)
static cv::Mat toCvMat(const g2o::Sim3 &Sim3)
Sim3 - g2o Sim3 transformation
Returns: 4x4 OpenCV Mat (CV_32F)
toCvMat (from Eigen 4x4 double)
static cv::Mat toCvMat(const Eigen::Matrix<double,4,4> &m)
m - Eigen 4x4 matrix (double)
Returns: 4x4 OpenCV Mat (CV_32F)
toCvMat (from Eigen 4x4 float)
static cv::Mat toCvMat(const Eigen::Matrix<float,4,4> &m)
m - Eigen 4x4 matrix (float)
Returns: 4x4 OpenCV Mat (CV_32F)
toCvMat (from Eigen 3x4)
static cv::Mat toCvMat(const Eigen::Matrix<float,3,4> &m)
m - Eigen 3x4 matrix (float)
Returns: 3x4 OpenCV Mat (CV_32F)
toCvMat (from Eigen 3x3 double)
static cv::Mat toCvMat(const Eigen::Matrix3d &m)
m - Eigen 3x3 matrix (double)
Returns: 3x3 OpenCV Mat (CV_32F)
toCvMat (from Eigen 3x3 float)
static cv::Mat toCvMat(const Eigen::Matrix<float,3,3> &m)
m - Eigen 3x3 matrix (float)
Returns: 3x3 OpenCV Mat (CV_32F)
toCvMat (from Eigen 3x1 double)
static cv::Mat toCvMat(const Eigen::Matrix<double,3,1> &m)
m - Eigen 3x1 vector (double)
Returns: 3x1 OpenCV Mat (CV_32F)
toCvMat (from Eigen 3x1 float)
static cv::Mat toCvMat(const Eigen::Matrix<float,3,1> &m)
m - Eigen 3x1 vector (float)
Returns: 3x1 OpenCV Mat (CV_32F)
toCvMat (from Eigen MatrixXf)
static cv::Mat toCvMat(const Eigen::MatrixXf &m)
m - Eigen dynamic matrix (float)
Returns: OpenCV Mat (CV_32F)
toCvMat (from Eigen MatrixXd)
static cv::Mat toCvMat(const Eigen::MatrixXd &m)
m - Eigen dynamic matrix (double)
Returns: OpenCV Mat (CV_32F)
Eigen Conversions
toVector3d (from cv::Mat)
static Eigen::Matrix<double,3,1> toVector3d(const cv::Mat &cvVector)
cvVector - 3x1 OpenCV Mat
Returns: Eigen 3D vector (double)
toVector3f (from cv::Mat)
static Eigen::Matrix<float,3,1> toVector3f(const cv::Mat &cvVector)
cvVector - 3x1 OpenCV Mat
Returns: Eigen 3D vector (float)
toVector3d (from cv::Point3f)
static Eigen::Matrix<double,3,1> toVector3d(const cv::Point3f &cvPoint)
toMatrix3d
static Eigen::Matrix<double,3,3> toMatrix3d(const cv::Mat &cvMat3)
toMatrix3f
static Eigen::Matrix<float,3,3> toMatrix3f(const cv::Mat &cvMat3)
toMatrix4d
static Eigen::Matrix<double,4,4> toMatrix4d(const cv::Mat &cvMat4)
toMatrix4f
static Eigen::Matrix<float,4,4> toMatrix4f(const cv::Mat &cvMat4)
Rotation Conversions
toQuaternion
static std::vector<float> toQuaternion(const cv::Mat &M)
M - 3x3 rotation matrix (OpenCV Mat)
Returns: Vector of 4 floats [x, y, z, w]
toEuler
static std::vector<float> toEuler(const cv::Mat &R)
R - 3x3 rotation matrix (OpenCV Mat)
Returns: Vector of 3 floats [roll, pitch, yaw]
isRotationMatrix
static bool isRotationMatrix(const cv::Mat &R)
- Checks if R^T * R = I
- Checks if det(R) = 1
toCvSE3
static cv::Mat toCvSE3(const Eigen::Matrix<double,3,3> &R,
const Eigen::Matrix<double,3,1> &t)
R - 3x3 rotation matrix (Eigen double)t - 3x1 translation vector (Eigen double)
Returns: 4x4 OpenCV Mat transformation
tocvSkewMatrix
static cv::Mat tocvSkewMatrix(const cv::Mat &v)
v - 3x1 vector (OpenCV Mat)
Returns: 3x3 skew-symmetric matrix
Details:
For vector [x, y, z], returns:
[ 0 -z y ]
[ z 0 -x ]
[ -y x 0 ]
Sophus Conversions
toSophus (from cv::Mat)
static Sophus::SE3<float> toSophus(const cv::Mat& T)
T - 4x4 transformation matrix (OpenCV Mat)
Returns: Sophus SE3 (float)
Note: Marked for future deprecation
toSophus (from g2o::Sim3)
static Sophus::Sim3f toSophus(const g2o::Sim3& S)
S - g2o Sim3 transformation
Returns: Sophus Sim3 (float)
Note: Marked for future deprecation
Usage Examples
Converting Poses
// Convert g2o SE3 to OpenCV matrix
g2o::SE3Quat g2oSE3 = pKF->GetPose();
cv::Mat Tcw = Converter::toCvMat(g2oSE3);
// Convert OpenCV matrix to Eigen
Eigen::Matrix4d Tcw_eigen = Converter::toMatrix4d(Tcw);
// Extract rotation and translation
Eigen::Matrix3d R = Tcw_eigen.block<3,3>(0,0);
Eigen::Vector3d t = Tcw_eigen.block<3,1>(0,3);
Descriptor Conversion
// Convert descriptors for BoW
cv::Mat descriptors = pKF->mDescriptors;
std::vector<cv::Mat> vDesc = Converter::toDescriptorVector(descriptors);
// Use for DBoW3 queries
DBoW2::BowVector bow;
mpORBVocabulary->transform(vDesc, bow);
Rotation Conversion
// Convert rotation to quaternion
cv::Mat R = Tcw.rowRange(0,3).colRange(0,3);
std::vector<float> quat = Converter::toQuaternion(R);
// Convert rotation to Euler angles
std::vector<float> euler = Converter::toEuler(R);
// Validate rotation matrix
bool valid = Converter::isRotationMatrix(R);
// Build SE3 from rotation and translation
Eigen::Matrix3d R = pKF->GetRotation();
Eigen::Vector3d t = pKF->GetTranslation();
cv::Mat Tcw = Converter::toCvSE3(R, t);
// Create skew-symmetric matrix
cv::Mat v = (cv::Mat_<float>(3,1) << 1.0, 2.0, 3.0);
cv::Mat skew = Converter::tocvSkewMatrix(v);
Type Compatibility
The Converter class handles conversions between:
- OpenCV - cv::Mat (used for images and camera operations)
- Eigen - Efficient linear algebra operations
- g2o - Graph optimization types (SE3, Sim3)
- Sophus - Lie group representations
Common Patterns
Storage to Computation
// Poses stored as cv::Mat
cv::Mat Tcw_storage = pKF->GetPose();
// Convert to Eigen for computation
Eigen::Matrix4d Tcw = Converter::toMatrix4d(Tcw_storage);
// Perform operations
Eigen::Matrix4d Twc = Tcw.inverse();
// Convert back for storage
cv::Mat Twc_storage = Converter::toCvMat(Twc);
Optimization Integration
// Convert pose to g2o for optimization
cv::Mat Tcw = pFrame->mTcw;
g2o::SE3Quat SE3quat = Converter::toSE3Quat(Tcw);
// Create g2o vertex
g2o::VertexSE3Expmap* vSE3 = new g2o::VertexSE3Expmap();
vSE3->setEstimate(SE3quat);
// After optimization, convert back
SE3quat = vSE3->estimate();
Tcw = Converter::toCvMat(SE3quat);
See Also
- Optimizer - Uses conversions for g2o optimization
- Frame - Stores poses as cv::Mat
- KeyFrame - Uses various pose representations
- MapPoint - Converts 3D coordinates
