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Axes and coordinate frames.
An Axis is a point and a direction. A Frame is a full local
coordinate system: an origin plus three mutually perpendicular directions
plus a handedness.
Frames are how every piece of analytic geometry in the kernel is positioned. A cylinder is a radius and a frame; a circle is a radius and a frame; the parameterization of each is defined relative to its frame, which is what makes “the seam of this cylinder” a well-defined place rather than an accident of how the surface was built.
Unlike the conventional design, which splits right-handed and
possibly-left-handed frames into two separate types, there is one Frame
carrying a Handedness. The split buys nothing and costs a conversion at
every boundary between them.
Structs§
- Axis
- A point and a direction: an oriented line through space.
- Axis2
- A point and a direction in the plane.
- Frame
- A local coordinate system in space.
- Frame2
- A local coordinate system in the plane.
Enums§
- Handedness
- Whether a frame’s third direction follows the right-hand rule.