Surface::boundToFreeJacobian could also use FreeVector parameters

[andiwand]

It seems inconsistent to use BoundVector for Surface::boundToFreeJacobian and FreeVector for Surface::freeToBoundJacobian. One is basically the inverse of the other and could use the same parameters.

acts/Core/include/Acts/Surfaces/Surface.hpp

Lines 315 to 333 in f7106bc

	/// Calculate the jacobian from local to global which the surface knows best,
	/// hence the calculation is done here.
	///
	/// @note In principle, the input could also be a free parameters
	/// vector as it could be transformed to a bound parameters. But the transform
	/// might fail in case the parameters is not on surface. To avoid the check
	/// inside this function, it takes directly the bound parameters as input
	/// (then the check might be done where this function is called).
	///
	/// @todo this mixes track parameterisation and geometry
	/// should move to :
	/// "Acts/EventData/detail/coordinate_transformations.hpp"
	///
	/// @param gctx The current geometry context object, e.g. alignment
	/// @param boundParams is the bound parameters vector
	///
	/// @return Jacobian from local to global
	virtual BoundToFreeMatrix boundToFreeJacobian(
	const GeometryContext& gctx, const BoundVector& boundParams) const;

acts/Core/include/Acts/Surfaces/Surface.hpp

Lines 335 to 350 in f7106bc

	/// Calculate the jacobian from global to local which the surface knows best,
	/// hence the calculation is done here.
	///
	/// @note It assumes the input free parameters is on surface, hence no
	/// onSurface check is done inside this function.
	///
	/// @todo this mixes track parameterisation and geometry
	/// should move to :
	/// "Acts/EventData/detail/coordinate_transformations.hpp"
	///
	/// @param gctx The current geometry context object, e.g. alignment
	/// @param parameters is the free parameters
	///
	/// @return Jacobian from global to local
	virtual FreeToBoundMatrix freeToBoundJacobian(
	const GeometryContext& gctx, const FreeVector& parameters) const;

Internally we always calculate the free parameters and externally we seem to always have the free parameters at hand.

There is also an extreme example where we do the free to bound twice

acts/Core/src/Propagator/detail/CovarianceEngine.cpp

Lines 201 to 218 in f7106bc

	// Get the local position
	const Vector3 position = freeParameters.segment<3>(eFreePos0);
	const Vector3 direction = freeParameters.segment<3>(eFreeDir0);
	auto lpResult = surface.globalToLocal(geoContext, position, direction);
	if (!lpResult.ok()) {
	return lpResult.error();
	}
	// Transform from free to bound parameters
	Result<BoundVector> boundParameters = detail::transformFreeToBoundParameters(
	freeParameters, surface, geoContext);
	if (!boundParameters.ok()) {
	return boundParameters.error();
	}
	// Reset the jacobian from local to global
	boundToFreeJacobian =
	surface.boundToFreeJacobian(geoContext, *boundParameters);
	return Result<void>::success();
	}

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