#### Example
Adding two vectors.
```lua
local p1 = Vec3( 1, 0, 8)
local p2 = Vec3( -1, 2, 3)
local p3 = p1:add( p2)
```
Since `add()` is also used as `__add` of Vec3's metatable, you can
shorten the above example by using the `+` operator.
```lua
local p1 = Vec3( 1, 0, 8)
local p2 = Vec3( -1, 2, 3)
local p3 = p1 + p2
```
