X,Y,Z – What are they?
X,Y & Z are the names given to the 3 axis used in 3d space that tells a piece of software where something is relative to either the origin or object pivot via a set of coordinates. These axis are used for scaling, rotation, and translation throughout the 3d space in relation to the origin (0,0,0) at the centre of the virtual world. This applies to modern game engines or 3d modelling software such as 3ds Max.
Modern software uses Cartesian coordinates, a system published in the 17th century by the French mathematician and philosopher René Descartes, however there is evidence of people using similar systems well before that, such as Nicole Oresme in the 14th century.
Everything in 3d revolves around its relation to the origin at the centre of the world. The origin is a pre-determined location set by the software as the centre of the scene, therefore everything you do will be in relation to this. For example, think of a cube at the centre of a scene. This cubes relative position is (0,0,0). However, if you move it forward or back you will be changing its value along the X axis (First number), moving it to the side will change its position along the Y axis (Second number), and moving it up or down will change its position along the Z axis (Third Number). Moving things in relation to the world origin is called global relativity. Trying to use global relativity to give a character a fedora at (5327,76533,144) will end in tears for many reasons – one being that it is unnecessarily complicated, but as the character moves, the fedora wont unless some logic is applied to it. That’s where Local relativity is a LOT more useful and convenient. Local relativity uses an object as the origin instead of the world space, meaning that as an objects global position changes, its local will not – allowing you to move 3,000 vertices, a top hat and a red pepper all at once. Think of it as a solar system, with the sun as the origin, the planets as objects in global space relative to the sun, and the moon in local space around the earth.
As a result, all objects have a location via coordinates. Therefore, large game worlds can tend to have inaccuracies further out from the origin because the game engine hates the big numbers it’s having to deal with.