Parts and objects

A part's properties

Member	Type	What it is
position	vec3	Where its middle is
rotation	vec3	Its turn in degrees (X, Y, Z)
transform	transform	Position and turn together
size	vec3	Units along its own X, Y, Z
color	colour	rgb(...) or hsv(...)
transparency	number	0 solid to 1 invisible
anchored	boolean	Stays where it is; unanchored parts fall and can be pushed
canCollide	boolean	Off: characters and parts go through it
shape	string	"Block", "Ball", "Cylinder", "Wedge"
material	string	"Plastic", "Smooth", "Neon", "Glass", "Metal", "Wood", "Grass", "Brick", "Concrete", "Sand", "Rock", "Water", "Leaves"...
velocity	vec3	Units a second
group	string	Its collision group ("Default") - see Physics and joints
mesh	string	The model a MeshPart shows
touched, touchEnded	event	Something started / stopped touching it

local part = world.Platform
part.position = vec3(0, 10, 0)
part.rotation = vec3(0, 45, 0)
part.color = rgb(80, 160, 255)
part.material = "Neon"
part.transparency = 0.3

A material changes a part's weight, grip and bounce too, not only its look: Metal is heavy, Wood light, Smooth slippery.

Every object

Parts, Models, Folders, objects on parts, UI - everything shares these:

Member	What it does
name, className, parent	Its name, its class, what it is inside
find(name)	A child by name, or nil
waitFor(name, timeout?)	A child by name, waiting until it exists (nil after timeout)
findByClass(className)	The first child of a class
children()	A list of its children
isA(className)	Whether it is of that class
clone()	A copy, with everything inside it (scripts inside are not copied)
destroy(), destroyAfter(seconds)	Removes it and everything inside
tween(goals, time or options)	Moves its properties smoothly

And children by name, as members: world.House.Door.

for _, child in world.Coins:children() do
    if child:isA("Part") then child.color = rgb(255, 215, 0) end
end

Making and removing

local crate = new("Part", world)       -- the parent as the second argument
crate.name = "Crate"
crate.size = vec3(3, 3, 3)
crate.material = "Wood"
crate.anchored = false
crate.position = vec3(0, 30, 0)

local tree = shared.Tree:clone()       -- a copy of a Model kept in ReplicationService
tree.parent = world

crate:destroyAfter(10)

A Model groups parts that move and copy as one. new("Model") makes one; put parts inside with part.parent = model.

Keep templates out of the world

Models you clone - enemies, coins, projectiles - are best kept in ReplicationService (shared) or StorageService (server only), so they aren't in the world until you clone them.

Server and client changes

A server Script's change to a part reaches every player. A ClientScript's change stays on that player's screen. Moving a door from a ClientScript moves it for one player only - and the server, which owns collisions, still has it closed. See Server and client.

Tweens

local lift = world.Lift
local bottom = lift.position

local tween = lift:tween({position = bottom + vec3(0, 20, 0)}, {
    time = 3,
    style = "Sine",
    direction = "InOut",
    repeats = -1,     -- forever
    reverses = true,  -- there and back
})
-- tween:cancel() stops it; tween.completed fires when it ends

Anything numeric or a value type tweens: position, size, color, transparency, rotation, transform...

Raycasts

world:raycast(origin, direction) finds the first part along a line:

local hit = world:raycast(vec3(0, 50, 0), vec3(0, -100, 0))   -- straight down, 100 units
if hit then
    print(hit.part.name, hit.position, hit.normal, hit.distance)
end

Objects on parts

Many objects work by being put inside a part:

Object	What it adds
Clickable	Players can click the part
Prompt	"[E] Open" near the part
Billboard	Text floating over the part
Sign	Writing on one face of the part
Sound	A sound heard around the part
Light	The part gives off light
ParticleEmitter	Sparks, smoke, fire...
Decal, Texture	A picture on a face
Highlight	An outline, even through walls
Trail, Beam	A streak behind it, a band to another part
Zone	The part is an area that knows who is inside
Hinge, Slider, BallJoint, Spring, Rope	Joins it to another part
Mover, Spinner, Thruster	Push a loose part
Teleporter, Hazard, Checkpoint, Pickup, Boost, Motion, Spawner, Seat	Gameplay with no code

Put them in in KHIM Engine, or from a script: new("Light", part). A script reaches one by its name: script.parent.Light.brightness = 3.

See Touch, prompts and zones, Sounds, lights and effects and Classes.

Values

IntValue, NumberValue, StringValue, BoolValue, ObjectValue, Vector3Value, Color3Value hold one value for scripts to read - a price on a shop item, a door's speed - set in the Inspector:

local price = script.parent.Price.value
script.parent.Price.changed:connect(function(new) print("now", new) end)

Attributes do the same job without an extra object.

Between scripts on the same side

A BindableEvent lets scripts tell each other something happened; a BindableFunction lets one ask another a question:

-- one Script
local roundOver = shared.RoundOver   -- a BindableEvent
roundOver:fire("Red")

-- another Script
shared.RoundOver.event:connect(function(winner) print(winner .. " won") end)

local getScore = shared.GetScore     -- a BindableFunction
getScore.onInvoke = function(player) return player.stats.Coins end
print(getScore:invoke(somePlayer))

To cross between the server and players, use net instead.