added (optional) support for 6d facedir in dir_to_facedir and added facedir_to_dir

builtin/item.lua

@@ -34,8 +34,45 @@ function minetest.get_pointed_thing_position(pointed_thing, above)
 	end
 end
 
-function minetest.dir_to_facedir(dir)
-	if math.abs(dir.x) > math.abs(dir.z) then
+function minetest.dir_to_facedir(dir, is6d)
+	--account for y if requested
+	if is6d and math.abs(dir.y) > math.abs(dir.x) and math.abs(dir.y) > math.abs(dir.z) then
+
+		--from above
+		if dir.y < 0 then
+			if math.abs(dir.x) > math.abs(dir.z) then
+				if dir.x < 0 then
+					return 19
+				else
+					return 13
+				end
+			else
+				if dir.z < 0 then
+					return 10
+				else
+					return 4
+				end
+			end
+
+		--from below
+		else
+			if math.abs(dir.x) > math.abs(dir.z) then
+				if dir.x < 0 then
+					return 15
+				else
+					return 17
+				end
+			else
+				if dir.z < 0 then
+					return 6
+				else
+					return 8
+				end
+			end
+		end
+
+	--otherwise, place horizontally
+	elseif math.abs(dir.x) > math.abs(dir.z) then
 		if dir.x < 0 then
 			return 3
 		else
@@ -50,6 +87,27 @@ function minetest.dir_to_facedir(dir)
 	end
 end
 
+function minetest.facedir_to_dir(facedir)
+	--a table of possible dirs
+	return ({{x=0, y=0, z=1},
+					{x=1, y=0, z=0},
+					{x=0, y=0, z=-1},
+					{x=-1, y=0, z=0},
+					{x=0, y=-1, z=0},
+					{x=0, y=1, z=0}})
+
+					--indexed into by a table of correlating facedirs
+					[({[0]=1, 2, 3, 4, 
+						5, 2, 6, 4,
+						6, 2, 5, 4,
+						1, 5, 3, 6,
+						1, 6, 3, 5,
+						1, 4, 3, 2})
+
+						--indexed into by the facedir in question
+						[facedir]]
+end
+
 function minetest.dir_to_wallmounted(dir)
 	if math.abs(dir.y) > math.max(math.abs(dir.x), math.abs(dir.z)) then
 		if dir.y < 0 then

doc/lua_api.txt

@@ -1270,8 +1270,10 @@ minetest.inventorycube(img1, img2, img3)
 ^ Returns a string for making an image of a cube (useful as an item image)
 minetest.get_pointed_thing_position(pointed_thing, above)
 ^ Get position of a pointed_thing (that you can get from somewhere)
-minetest.dir_to_facedir(dir)
-^ Convert a vector to a facedir value, used in param2 for paramtype2="facedir"
+minetest.dir_to_facedir(dir, is6d)
+^ Convert a vector to a facedir value, used in param2 for paramtype2="facedir"; passing something non-nil/false for the optional second parameter causes it to take the y component into account
+minetest.facedir_to_dir(facedir)
+^ Convert a facedir back into a vector aimed directly out the "back" of a node
 minetest.dir_to_wallmounted(dir)
 ^ Convert a vector to a wallmounted value, used for paramtype2="wallmounted"
 minetest.get_node_drops(nodename, toolname)