Grouping positions together

[Nostradamus]

I don't know if this is new, since it's too obvious, but I had an idea: why don't we use positions on a unix timestamp format or something like that?

We can use some convention like:

X
Y = 60X
Z = (60^2)X

So comparations between positions can be much easy.

Here it is an easy example of doing that with the memoize technique, to reuse the same table for the same ps.

local results = {}
setmetatable(results, {__mode = "v"}) -- make values weak
function mkPos(posX, posY, posZ)
    local key = posX + posY*60 + posZ*(60^2) 
    if (results[key]) then
        return results[key]
    else
        local newPos = {x = posX, y = posY, z = posZ}
        results[key] = newPos
        return newPos
    end
end

Also, we can even make this pos table locked, since we don't need to alter these values, using this function:

function table.lock(t)
    local lock = {}
    local mt = {
        __index = t,
        __newindex = function (t, k, v)
           error("Attempt to update a locked table")
        end
    }
    setmetatable(lock, mt)
    return lock
end

 

[Colandus]

Nice, but I don't see much use of it ^.-

You might give some examples of the usage

 

[hodleo]

i dont get it

 

[elf]

I would rather move bits for the position ->
posbit |= pos.z << 16;
posbit |= pos.y << 8;
posbit |= pos.x;

and to get real pos
pos.z = posbit >> 16;
pos.y = posbit >> 8 & 0xFF;
pos.x = posbit & 0xFF;

simplier, alot.

 

[slaw]

Found this some time ago.

(unknown author)

if(bit == nil) then
	error("Your server does not have bit libraries.")
end

function posToIndex(pos)
	if(pos.x == nil or pos.y == nil or pos.z == nil) then
		error("[posToIndex]: Argument is not a valid position!")
		return LUA_ERROR
	end

	-- ((x & 0xFFFF) << 24 | (y & 0xFFFF) << 8 | (z & 0xFF))
	local index = bit.bor( bit.lshift( bit.band(pos.x, 65535), 24 ), bit.lshift( bit.band(pos.y, 65535), 8), bit.band(pos.z, 255) )
	return index
end
 
function indexToPos(index)
	if(type(index) ~= "number") then
		error("[indexToPos]: Argument is not a valid index!")
		return LUA_ERROR
	end

	-- pos.x = ((index) >> 24) & 0xFFFF; pos.y = ((index) >> 8) & 0xFFFF; pos.z = ((index) & 0xFF);
	local x = bit.band(bit.rshift(index, 24), 65535)
	local y = bit.band(bit.rshift(index, 8), 65535)
	local z = bit.band(index, 255)
	return {x=x, y=y, z=z}
end

Usage is simple, fe. saving position in 1 storage:

local pos = getPlayerPosition(cid)
setPlayerStorageValue(cid, 666, posToIndex(pos))

and reusing it

local oldPos = indexToPos(getPlayerStorageValue(cid, 666))
doSendMagicEffect(oldPos, 40)

 

[Colandus]

@Up
Author is Pedro B. but he only converted code from POT to Lua.