coordsys_bridge_traits

namespace nin {
    template <typename Br>
    concept coordsys_bridge_traits;
}

Any coordinate system bridge must satisfy the coordsys_bridge_traits concept. A bridge connects two coordinate systems that live in different spaces — for example, linking a 2D planar (R2) coordinate system with a 3D spatial (R3) one.

Requirements

A type Br satisfies coordsys_bridge_traits if:

Requirement Description

Br::coordsys_traits_A

The first coordinate system traits type. Must satisfy coordsys_traits.

Br::coordsys_traits_B

The second coordinate system traits type. Must satisfy coordsys_traits.

Inherits coordsys<coordsys_traits_A>

The bridge is itself a coordinate system in space A.

Inherits coordsys<coordsys_traits_B>

The bridge is also a coordinate system in space B.

br.convert(A::quantity_type) → B::quantity_type

Converts a coordinate from space A to space B.

br.convert(B::quantity_type) → A::quantity_type

Converts a coordinate from space B to space A.

Because a bridge inherits from coordsys on both sides, it occupies a position in the kinematic tree of both spaces simultaneously. This is what allows mapCS() to traverse from a coordinate system in space A, through the bridge, and into space B.

The concept additionally constrains the bridge’s layout: sizeof(Br) == sizeof(coordsys<coordsys_traits_A>) + sizeof(coordsys<coordsys_traits_B>). A bridge type must therefore add no data members of its own beyond the two coordsys subobjects it inherits. State that varies at runtime (per-bridge offsets, calibration data) belongs in one of those coordsys subobjects' backends, not in the bridge type itself.

Usage with mapCS

Bridges appear as intermediate arguments to mapCS():

coord_tf tf = mapCS(cs_2d, bridge, cs_3d);

Multiple bridges can be chained to cross several spaces in a single call. The convert() functions define how coordinate values change representation at each crossing point.

See also

For a step-by-step recipe on writing your own bridge, see How to define a bridge between two coordinate spaces.