Briefly stated, a space or a coordinate system is a way to interpret a set of (x, y, z), coordinates. By convention, the X value means “to the right”, Y means “up” and Z means “forward”. With relation to what? Well, that’s exactly what we have to always clearly state! If I tell you to “go two steps to the right”, your immediate question will be “my right or your right?” (ok, maybe it would be the second question, just after “why are you giving me orders?”).

A space is just a formalization of this. A space is just a notion of which way is right/up/forward and with relation to what:

The names we normally give to these arrows are:

• X axis – red arrow. This points to the right.
• Y axis – green arrow. This points up.
• Z axis – blue arrow. This points forward.

Look at the slime in this scene. The three arrows on it represent the slime’s actor space. That’s what the slime thinks of as “forward” (blue arrow), “right” (red arrow) and “up” (green arrow). Same thing with the lion: that’s the lion’s actor space. That’s what it thinks of as forward/right/up. It’s different than the slime’s notion. It’s a different space.

The third space or coordinate system in the picture (the one in the center) is what we call world space. It’s a global coordinate system that everyone agrees on. When something is given in world coordinates that’s the space that it’s represented on. So if I say “go two steps in the world forward direction”, everyone in the scene would agree about in which direction to go. World space is the same for everyone.

When we are talking about world space, instead of saying “forward”, “backward”, “right” and “left”, we tend to say north, south east and west instead, because that makes it more clear that we are talking about world space. So if I say “everyone, move two steps north”, everyone would go in the same direction regardless of where they are facing.

Note: if you have used other game engines and graphics programs before, you may have noticed that some of them like to think of Z as pointing “backward” instead of “forward”. We use forward because we think it’s more intuitive this way.