Doc:Glossary/Axis

Axis

A reference line.

1) The geometry of Blender's world is defined by 3 orthogonal axes, x-axis, y-axis, and z-axis. They are shown as red, green, and blue lines, respectively, in the 3D Viewport. Their mutual intersection defines the position of the origin of the global coordinate system in Blender. In this Cartesian-derived system, a 3D position is defined in terms of its offset from these axes.

2) Each object (or simultaneously selected set of objects) has its own, local axes that are orthogonal to each other and to the sides of the object's bounding box. Local axes are invisible. If toggled on, the Transform Manipulator resides on the operational center of the object, and its arrows by default parallel the global axes. However, a Local mode can be selected from the Transform Orientation combo box on the 3D Viewport header. When in this mode, provided that any rotation of the object has occurred while in Object mode, the arrows of the Transform Manipulator will coincide with the local axes of the object. While in this mode, again providing that any rotations have been made in Object mode, manipulations in either Object of Edit mode will occur with respect to local object axes.

3) A set of small axes in the lower left corner of the 3D Viewport acts as an orientation monitor. Its arrows always parallel global axes, regardless of view and even in free-roaming view. The arrow heads point in the positive direction along each global axis.