Vector3: add rotate3d.

Thanks to GitHub Copilot for the implementation, it just needed
improving around the edges to make it work perfectly.
For the record, copilot generated it in JS, and then
I manually ported it to Lua.
If the Copilot code looks sufficiently similar to your own source,
get in touch and I will give you full credit.

worldeditadditions_core/utils/vector3.lua

@@ -125,6 +125,15 @@ function Vector3.round(a)
 	return Vector3.new(math.floor(a.x+0.5), math.floor(a.y+0.5), math.floor(a.z+0.5))
 end
 
+--- Rounds the components of this vector to the specified number of decimal places.
+-- @param	a		Vector3	The vector to round.
+-- @param	dp		number	The number of decimal places to round to.
+-- @returns	Vector3	A new instance with the components rounded to the specified number of decimal places.
+function Vector3.round_dp(a, dp)
+	local power = 10^dp
+	return (a * power):round() / power
+end
+
 
 --- Snaps this Vector3 to an imaginary square grid with the specified sized
 -- squares.
@@ -401,6 +410,43 @@ function Vector3.fromBearing(angle_x, angle_y, length)
 	)
 end
 
+--- Rotate a given point around an origin point in 3d space.
+-- Consider 3 axes (X, Y, and Z) that are centred on origin. This function
+-- rotates point around these axes in the aforementioned order.
+-- NOTE: This function is not as intuitive as it sounds.
+-- A whiteboard and a head for mathematics is recommended before using this
+-- function. Either that, or Blender 3 (https://blender.org/) is quite useful to visualise what's going on.
+-- @source	GitHub Copilot, generated 2023-01-17
+-- @warning	Not completely tested! Pending a thorough evaluation. Seems to basically work, after some tweaks to the fluff around the edges?
+-- @param	{Vector3}	origin	The origin point to rotate around
+-- @param	{Vector3}	point	The point to rotate.
+-- @param	{Vector3}	rotate	Rotate this much around the 3 different axes, x, y, and z. Axial rotations are handled in this order: X→Y→Z.
+-- @param	{Number}	x	Rotate this much around the X axis (yz plane), in radians.
+-- @param	{Number}	y	Rotate this much around the Y axis (xz plane), in radians.
+-- @param	{Number}	z	Rotate this much around the Z axis (xy plane), in radians.
+-- @return	{Vector3}	The rotated point.
+function Vector3.rotate3d(origin, point, rotate)
+	local point_norm = point - origin
+
+	-- rotate around x
+	local x1 = point_norm.x
+	local y1 = point_norm.y * math.cos(rotate.x) - point_norm.z * math.sin(rotate.x)
+	local z1 = point_norm.y * math.sin(rotate.x) + point_norm.z * math.cos(rotate.x)
+
+	-- rotate around y
+	local x2 = x1 * math.cos(rotate.y) + z1 * math.sin(rotate.y)
+	local y2 = y1
+	local z2 = -x1 * math.sin(rotate.y) + z1 * math.cos(rotate.y)
+
+	-- rotate around z
+	local x3 = x2 * math.cos(rotate.z) - y2 * math.sin(rotate.z)
+	local y3 = x2 * math.sin(rotate.z) + y2 * math.cos(rotate.z)
+	local z3 = z2
+
+	return Vector3.new(x3, y3, z3) + origin
+	-- return [x3+origin[0], y3+origin[1], z3+origin[2]];
+end
+
 
 --  ██████  ██████  ███████ ██████   █████  ████████  ██████  ██████
 -- ██    ██ ██   ██ ██      ██   ██ ██   ██    ██    ██    ██ ██   ██