coordsys_cutoff

namespace nin {
    template <coordsys_traits CT>
    class coordsys_cutoff : public coordsys<CT>;
}

coordsys_cutoff accelerates transformation generation by short-circuiting kinematic tree traversal.

When mapCS() builds a coord_tf, it composes the tf_to_WCS() of the source with the tf_from_WCS() of the target. Each of those traverses the full chain of parents up to WCS, which can be expensive when the tree is deep or when backends along the way make remote calls (e.g. querying a physics engine or a network service).

If two coordinate systems are known to share a common subtree root, a coordsys_cutoff can be placed at that root and locked. While locked, offset() returns the identity transformation, so traversal stops at the cutoff instead of continuing to WCS. Both sides of a mapCS() call see the same cutoff and their common prefix cancels out, giving the correct relative transformation at lower cost.

A lock guard pattern is typical:

cutoff.lock();
coord_tf tf = mapCS(cs_a, cs_b);  // traversal stops at cutoff
cutoff.unlock();

Member functions

(Constructor)

`coordsys_cutoff()`	(1)
`coordsys_cutoff(coordsys_cutoff const& copy)`	(2)
`coordsys_cutoff(coordsys_cutoff && move)`	(3)
`explicit coordsys_cutoff(coordsys<CT> parent)`	(4)
`explicit coordsys_cutoff(WCS_t)`	(5)

(1) Default constructor.
(2) Deep copy.
(3) Move constructor.
(4)-(5) Constructs with a parent coordinate system.

lock
unlock

control tree traversal

void lock()

(1)

void unlock()

(2)

(1) Locks the cutoff. While locked, offset() returns a default-constructed transformation (identity), stopping traversal at this point.
(2) Unlocks the cutoff. Traversal resumes through the parent as normal.

parent

access the parent coordinate system

coordsys<CT> const& parent() const

(1)

Returns the parent coordinate system.

set_parent

change the parent coordinate system

void set_parent(coordsys<CT> parent)

(1)

Sets a new parent coordinate system.