rotate: initial UNTESTED implementation

It doesn't have a chat command interface yet.

.....I REALLY need to learn Quaternions, but they don't currently make sense to me

worldeditadditions/lib/rotate.lua

@@ -0,0 +1,119 @@
+local weac = worldeditadditions_core
+local Vector3 = weac.Vector3
+
+-- ██████   ██████  ████████  █████  ████████ ███████
+-- ██   ██ ██    ██    ██    ██   ██    ██    ██     
+-- ██████  ██    ██    ██    ███████    ██    █████  
+-- ██   ██ ██    ██    ██    ██   ██    ██    ██     
+-- ██   ██  ██████     ██    ██   ██    ██    ███████
+
+--- Compiles a list of rotations into something we can iteratively pass to Vector3.rotate3d.
+-- TODO Learn Quaternions.
+-- @param	rotlist		table<{axis: string, rad: number}>	The list of rotations. Rotations will be processed in order. Each rotation is a table with a SINGLE axis as a string (x, y, z, -x, -y, or -z; the axis parameter), and an amount in radians to rotate by (the rad parameter.
+-- @returns	Vector3[]	The list of the compiled rotations, in a form that Vector3.rotate3d understands.
+local function __compile_rotlist(rotlist)
+	return weac.table.map(rotlist, function(rot)
+		--- 1: Construct a Vector3 to represent which axis we want to rotate on
+		local rotval = Vector3.new(0, 0, 0)
+		if rot.axis:find("x", 1, true) then rotval.x = 1
+		elseif rot.axis:find("y", 1, true) then rotval.y = 1
+		elseif rot.axis:find("z", 1, true) then rotval.z = 1 end
+		if rot.axis:sub(1, 1) == "-" then
+			rotval = rotval * -1
+		end
+		
+		--- 2: Rotate & apply amount of rotation to apply in radians
+		return rotval * rot.rad
+	end)
+end
+
+
+--- Rotates the given region around a given origin point using a set of rotations.
+-- TODO Learn quaternions and make this more effiient.
+-- @param	pos1	Vector3		Position 1 of the defined region to rotate.
+-- @param	pos2	Vector3		Position 2 of the defined region to rotate.
+-- @param	origin	Vector3		The coordinates of the origin point around which we should rotate the region defined by pos1..pos2.
+-- @param	rotlist		table<{axis: string, rad: number}>	The list of rotations. Rotations will be processed in order. Each rotation is a table with a SINGLE axis as a string (x, y, z, -x, -y, or -z; the axis parameter), and an amount in radians to rotate by (the rad parameter.
+-- @returns	bool,string|table<{changed: number}>	A success boolean (true == success; false == failure), followed by either an error message as a string if success == false or a table of statistics if success == true.
+-- 
+-- Currently the only parameter in the statistics table is changed, which is a number representing the number of nodes that were rotated.
+-- 
+-- This is NOT NECESSARILY the number of nodes in the target region..... since rotations and roundings mean the target area the source region was rotated into could have slightly more or less nodes than the source region.
+function worldeditadditions.rotate(pos1, pos2, origin, rotlist)
+	pos1, pos2 = Vector3.sort(pos1, pos2)
+	
+	--- 1: Compile the rotation list
+	local rotlist_c = __compile_rotlist(rotlist)
+	
+	
+	--- 2: Find the target area we will be rotating into
+	-- First, rotate the defined region to find the target region
+	local pos1_rot, pos2_rot = pos1:clone(), pos2:clone()
+	for i, rot in ipairs(rotlist_c) do
+		pos1_rot = Vector3.rotate3d(origin, pos1_rot, rot)
+		pos2_rot = Vector3.rotate3d(origin, pos2_rot, rot)
+	end
+	-- Then, align it to the world axis so we can grab a VoxelManipulator
+	-- We add 1 node either side for safety just in case of rounding errors when actually rotating
+	local pos1_dstvm, pos2_dstvm = Vector3.sort(pos1_rot, pos2_rot)
+	pos1_dstvm = pos1_dstvm:floor() - Vector3.new(1, 1, 1)
+	pos2_dstvm = pos2_dstvm:ceil() + Vector3.new(1, 1, 1)
+	
+	
+	--- 3: Check out a VoxelManipulator for the source and target regions
+	local manip_src, area_src = worldedit.manip_helpers.init(pos1, pos2)
+	local data_src = manip_src:get_data()
+	
+	local manip_dest, area_dest = worldedit.manip_helpers.init(pos1_dstvm, pos2_dstvm)
+	local data_dest = manip_dest:get_data()
+	-- TODO: Also carry param2 along for the ride
+	
+	
+	--- 4: Do the rotation operation
+	local count_rotated = 0
+	for z = pos2.z, pos1.z, -1 do
+		for y = pos2.y, pos1.y, -1 do
+			for x = pos2.x, pos1.x, -1 do
+				local cpos_src = Vector3.new(x, y, z)
+				local cpos_dest = cpos_src:clone()
+				
+				-- TODO: This is very inefficient. If we could use quaternions here to stack up the rotations, it would be much more efficient.
+				for i, rot in ipairs(rotlist) do
+					cpos_dest = Vector3.rotate3d(origin, cpos_dest, rot)
+				end
+				
+				cpos_dest = cpos_dest:round()
+				
+				local i_src = area_src:index(cpos_src.x, cpos_src.y, cpos_src.z)
+				local i_dest = area_dest:index(cpos_dest.x, cpos_dest.y, cpos_dest.z)
+				
+				data_dest[i_dest] = data_src[i_src]
+				count_rotated = count_rotated + 1
+			end
+		end
+	end
+	
+	--- 5: Wipe the source area & save it back to disk
+	local id_air = minetest.get_content_id("air")
+	for z = pos2.z, pos1.z, -1 do
+		for y = pos2.y, pos1.y, -1 do
+			for x = pos2.x, pos1.x, -1 do
+				data_src[area_src:index(x, y, z)] = id_air
+			end
+		end
+	end
+	worldedit.manip_helpers.finish(manip_src, data_src)
+	manip_src, area_src, data_src = nil, nil, nil
+	
+	
+	
+	--- 6: Save the destination back to disk
+	-- Note that this MUST be AFTER the source is saved to disk, since the rotated region needs to overwrite the WIPED source area to avoid leaving an unrotated copy behind
+	worldedit.manip_helpers.finish(manip_dest, data_dest)
+	
+	
+	--- 5: Return
+	return true, {
+		count_rotated = count_rotated
+	}
+end