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Example Luau scripts

Show a message when user touches an object

Here is a very simple script that shows a message to a user when they touch an object: 

--lua

function onUserTouchedObject(av : Avatar, ob : Object)
	showMessageToUser("Hi " .. av.name .. ", you touched the red cube!", av)
end

Which has this result in-world when you walk into the red cube:

Jump pad

When a user touches an object, it shoots the user into the air

--lua
function onUserTouchedObject(avatar : Avatar, ob : WorldObject)
	local v = avatar.linear_velocity
	local new_v = Vec3f(v.x, v.y, 10.0)
	avatar.linear_velocity = new_v

Change text when user enters parcel

This script should be applied to a text object. It changes the text to read 'User entered parcel' when the user enters the parcels the object is in, and to 'User exited parcel' when they leave the parcel. It also changes the text colour.

--lua 
 
function onUserEnteredParcel(user : User, ob : WorldObject, parcel : Parcel)
	ob.content = "User entered parcel"
	mat = ob:getMaterial(0)
	mat.colour = Vec3f(0,1,0)
end

function onUserExitedParcel(user : User, ob : WorldObject, parcel : Parcel)
	ob.content = "User exited parcel"
	mat = ob:getMaterial(0)
	mat.colour = Vec3f(1,0.1,0)
end

Change object colour when user enters/exits parcel

--lua 
  
function onUserEnteredParcel(user : User, ob : WorldObject, parcel : Parcel)
	mat = ob:getMaterial(0)
	mat.colour = Vec3f(1,0,0)
end

function onUserExitedParcel(user : User, ob : WorldObject, parcel : Parcel)
	mat = ob:getMaterial(0)
	mat.colour = Vec3f(0,1,0)
end

Object that moves towards nearby users

--lua

local near_user = nil
function onTimerEvent(ob : WorldObject)

	if(near_user) then
		local dx = near_user.pos.x - ob.pos.x
		local dy = near_user.pos.y - ob.pos.y
		local dz = (near_user.pos.z - 1.68) - ob.pos.z
		d = math.sqrt(dx*dx + dy*dy + dz*dz)
		if(d > 1.0) then
			dx /= d
			dy /= d	
			dz /= d
			step_dist = 0.4
			local newx = ob.pos.x + dx * step_dist
			local newy = ob.pos.y + dy * step_dist
			local newz = ob.pos.z + dz * step_dist
			ob.pos = {x=newx, y=newy, z=newz}
		end
	end
end

createTimer(onTimerEvent, 0.1, true)


function onUserMovedNearToObject(user : User, ob : WorldObject)
	print("onUserMovedNearToObject!!!")
	near_user = user
end

function onUserMovedAwayFromObject(user : User, ob : WorldObject)
	print("onUserMovedAwayFromObject!!!")
	near_user = nil
end

Showing information by updating text using an external HTTP API

This script shows how to fetch information from somewhere else on the web, using the doHTTPPostRequestAsync function. We will use it to get the current Ethereum gas price from Infura, and update a text object in substrata to show the current gas price.

This example uses parseJSON to convert JSON returned from the HTTP request to a Lua object, and getSecret to get infura_project_id, which is a private API key. 

--lua

function onDone(res)
	print("response_code: " .. tostring(res.response_code))
	print("response_message: " .. res.response_message)
	print("mime_type: " .. res.mime_type)
	print("body_data: " .. string.sub(buffer.tostring(res.body_data), 1, 100))

	local data = parseJSON(buffer.tostring(res.body_data))
	local price_num = tonumber(data.result)
	this_object.content = "Ethereum gas price: " .. string.format("%.2f", price_num * 1.0e-9) ..
		" Gwei"
end

function onError(res)
	print("error_code: " .. tostring(res.error_code))
	print("error_description: " .. res.error_description)
end

infura_project_id = getSecret('infura_project_id')
print("infura_project_id " .. tostring(infura_project_id))

function onTimerEvent()
	print("Fetching current gas price...")
	-- See https://docs.infura.io/api/networks/ethereum/json-rpc-methods/eth_gasprice

	doHTTPPostRequestAsync("https://mainnet.infura.io/v3/" .. infura_project_id,
		'{"jsonrpc":"2.0","method":"eth_gasPrice","params": [],"id":1}', -- post content
		"application/json", -- content type
 		{}, -- additional header lines
		onDone, onError)
end

if(IS_SERVER) then
	createTimer(onTimerEvent, 60.0, true) -- Call onTimerEvent every 60 seconds, repeatedly.
else
	print("running on client, not doing anything.")
end

Showing information by updating text using an external HTTP API (again)

This script shows how to fetch information from somewhere else on the web, using the doHTTPGetRequestAsync function. We will use it to get the current Eth/USD exchange rate from Coinbase, and update a text object in Substrata with it. 

--lua

function onDone(res)
	local json_data = parseJSON(buffer.tostring(res.body_data))
	local price_num = tonumber(json_data.data.rates.USD)
	this_object.content = "Eth price: " .. string.format("%d", price_num) .. " USD"
end

function onError(res)
	print("error_code: " .. tostring(res.error_code))
end

function onTimerEvent()
	print("Fetching current ETH/USD rate...")

	-- See https://docs.cdp.coinbase.com/coinbase-app/docs/api-exchange-rates

	doHTTPGetRequestAsync("https://api.coinbase.com/v2/exchange-rates?currency=ETH",
 		{}, -- additional header lines
		onDone, onError)
end

if(IS_SERVER) then
	createTimer(onTimerEvent, 60.0, true)
end

Race script

This is a complete race script for bicycle races, with a leaderboard.

To set it up, apply the script to an object. You will also need to create some waypoint sensor objects, then get their UIDs and edit the script to use the waypoint ids on the 'waypoint_uids' line.

scoreboard_text_ob_uid should be the UID of a text object which will show the high score list

This script uses objectstorage.setItem and objectstorage.getItem to store the high-score data persistently.

--lua
 
local race_info = {} -- A map from avatar UID to per-user race info.

local waypoint_uids = {587, 583, 584, 585, 587} -- UIDs of waypoint sensor objects.  The first object is the start line sensor, the last object is the finish line sensor.
local reset_ob_uid = 588 -- Touching this object will reset the race state.
local scoreboard_text_ob_uid = 589

local MAX_NUM_BEST_TIMES = 5
local best_times = nil -- An array of the top MAX_NUM_BEST_TIMES best times.  Each entry is a table { av_uid : UID, av_name : string, time : number }

best_times = objectstorage.getItem("best_times")
--print("Result of loading best_times from object storage: " .. tostring(best_times))
if best_times ~= nil then
	print("loaded " .. tostring(#best_times) .. " best times from object storage!")
else
	print("No best times found in object storage, starting with empty best times.")
	best_times = {}
end


print("best_times: ")
print(best_times)
print(tostring(best_times))

print("race_info: ")
print(race_info)
print(tostring(race_info))

function updateScoreboardText()
	local s = "---Best times---\n"
	for i = 1, #best_times do
		s = s .. tostring(i) .. ":  " .. best_times[i].av_name .. ":  " .. string.format("%.3f", best_times[i].time) .. " s\n"
	end
	getObjectForUID(scoreboard_text_ob_uid).content = s
end

function checkAddTimeToBestTimes(av : Avater, time_s : number)
	for i = 1 , #best_times do
		if(time_s < best_times[i].time) then -- If the new time was faster than time i:
			
			-- Move time i and other times to the right one place to the right
			-- Do this by starting at the rightmost index we want to move the time to, copy from the index to the left, and then iterate left.
			for z = math.min(#best_times + 1, MAX_NUM_BEST_TIMES), i+1, -1 do
				best_times[z] = best_times[z-1]
			end

			-- Set time i
			best_times[i] = { av_uid = av.uid, av_name = av.name, time = time_s }	

			-- Save updated best times to object storage
			objectstorage.setItem("best_times", best_times)
	
			updateScoreboardText()
			return
		end
	end
	-- If we got here the new time was not better than any of the existing times.
	-- If not all slots were occupied on scoreboard:
	if(#best_times < MAX_NUM_BEST_TIMES) then
		best_times[#best_times + 1] = { av_uid = av.uid, av_name = av.name, time = time_s } -- Add new time

		-- Save updated best times to object storage
		objectstorage.setItem("best_times", best_times)

		updateScoreboardText()
	end
end

function onUserTouchedObject(av : Avater, ob : Object)
	print("User touched object " .. tostring(ob.uid))

	-- Get or create per-user race information (user_race_info)
	local user_race_info = race_info[av.uid]
	if(not user_race_info) then
		print("Making new user_race_info...")
		user_race_info = {next_waypoint_index=1, valid=true}
		race_info[av.uid] = user_race_info
	end

	print("user_race_info.next_waypoint_index: " .. tostring(user_race_info.next_waypoint_index) .. ", valid: " .. tostring(user_race_info.valid))

	if(ob.uid == reset_ob_uid) then
		if((user_race_info.next_waypoint_index == 1) or not user_race_info.valid) then -- If user has not started race, or their race was invalid (went through wrong gates)
			-- Prepare to start/restart the race
			showMessageToUser("prepare to start race, move through start gate to start!", av)
			user_race_info.next_waypoint_index = 1
			user_race_info.valid = true
		end

		return
	end
	if(not user_race_info.valid) then
		showMessageToUser("Touch the restart object to restart the race.", av)
		return
	end
	
	if((user_race_info.next_waypoint_index >= 2) and (ob.uid == waypoint_uids[user_race_info.next_waypoint_index-1])) then
		-- User went through the same waypoint again
		showMessageToUser("You need to go through the next waypoint!", av)
	elseif(ob.uid == waypoint_uids[user_race_info.next_waypoint_index]) then -- If user went through correct waypoint:

		if(user_race_info.next_waypoint_index == 1) then -- If user went through the start gate:
			local vehicle = av.vehicle_inside
			if(not vehicle) then
				showMessageToUser("You must be in a vehicle!", av)
				user_race_info.valid = false
				return
			end

			if((vehicle.mass < 199.99) or (vehicle.mass > 200.01)) then
				showMessageToUser("You must be in a standard bike!", av)
				user_race_info.valid = false
				return
			end
	
			showMessageToUser("Race Started!", av)

			user_race_info.vehicle = vehicle

			-- Add event listener for the user exiting the vehicle, so we can disqualify them if they are racing.
			addEventListener("onUserExitedVehicle", vehicle.uid, onUserExitedVehicle)

			user_race_info.start_time = getCurrentTime()
			user_race_info.next_waypoint_index = user_race_info.next_waypoint_index + 1
		elseif(user_race_info.next_waypoint_index == #waypoint_uids) then -- If user went through the last gate (finish line):
			-- race completed!

			local user_time = getCurrentTime() - user_race_info.start_time
			showMessageToUser("Finish!  your time: " .. string.format("%.3f", user_time) .. " s", av)
			
			checkAddTimeToBestTimes(av, user_time)
			--if(user_time < best_time) then
			--	print("You set the best time..")
			--	best_time = user_time
			--	getObjectForUID(scoreboard_text_ob_uid).content = "Best time: " .. string.format("%.3f", user_time) .. " s by " .. av.name
			--end

			--user_race_info.next_waypoint_index = 1 -- restart
		
			-- Now that the race is completed, just mark it as invalid, so we won't get messages when exiting vehicle etc.
			user_race_info.valid = false
		else
			showMessageToUser("waypoint " .. tostring(user_race_info.next_waypoint_index - 1) .. "/" .. tostring(#waypoint_uids - 2) .. " done", av)
			user_race_info.next_waypoint_index = user_race_info.next_waypoint_index + 1
		end
			
	else -- else if user went through an incorrect gate (wrong order):

		showMessageToUser("You went through the wrong waypoint!", av)
		user_race_info.valid = false
	end
end

function onUserExitedVehicle(av : Avatar, vehicle : Object)
	print("onUserExitedVehicle")
	local user_race_info = race_info[av.uid]
	if(user_race_info and user_race_info.valid) then
		showMessageToUser("You exited your vehicle during the race and were disqualified!", av)
		user_race_info.valid = false
	end
end


-- Add event listeners for the onUserTouchedObject event on our waypoint sensor objects
for key, uid in waypoint_uids do
	addEventListener("onUserTouchedObject", uid, onUserTouchedObject)
end
addEventListener("onUserTouchedObject", reset_ob_uid, onUserTouchedObject)


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