Lightweight 3x3 matrix and 3D vector helpers used during PETSIRD geometry analysis. More...

Functions
Mat3	transpose (const Mat3 &mat)
	Transpose a 3x3 matrix.
Mat3	subtract (const Mat3 &A, const Mat3 &B)
	Subtract two 3x3 matrices (A - B).
Vec3	getAxisFromSkew (const Mat3 &S)
	Extract rotation axis from the skew-symmetric matrix S = R - R^T.

Detailed Description

Lightweight 3x3 matrix and 3D vector helpers used during PETSIRD geometry analysis.

Provides utilities to:

Mat3: std::array<std::array<float,3>,3> for compact fixed-size storage.
Vec3: std::array<float,3> for simple 3D vectors.
getAxisFromSkew(): Given S = R - R^T (skew-symmetric part of a rotation matrix R), returns the axis proportional to: (S_z,y - S_y,z)/2, (S_x,z - S_z,x)/2, (S_y,x - S_x,y)/2. For a pure rotation, S encodes the axis direction.
These helpers assume small numerical noise; thresholds are handled by callers.
No external dependencies; intended for quick geometric inference (e.g., rotation axis detection).

Might worth it to use stir::Arrays here. I started a bit of this work but lots pending. See the test_petsird_info_helpers.cxx for some of the work done so far.
The function are moved in ArrayFunctions

Function Documentation

Mat3 matrix::transpose ( const Mat3 & mat )

inline

Transpose a 3x3 matrix.

Parameters

mat	Input matrix.

References transpose().

Referenced by transpose().

Mat3 matrix::subtract	(	const Mat3 &	A,
		const Mat3 &	B )

inline

Subtract two 3x3 matrices (A - B).

Parameters

A	Left-hand matrix.
B	Right-hand matrix.

References subtract().

Referenced by subtract().

Vec3 matrix::getAxisFromSkew ( const Mat3 & S )

inline

Extract rotation axis from the skew-symmetric matrix S = R - R^T.

Parameters

S	Skew-symmetric matrix.