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WeldConstraint

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WeldConstraint

Show deprecated

WeldConstraints are used to attach two BasePart|parts together. The constraint makes sure that the parts stay in the same relative position and orientation to one another, meaning that if one part moves, the other will move the same amount. Even if the two parts are not touching one another, they can be welded together with a weld constraint.

The most common way to create a weld constraint is through the Studio Create menu in the Model tab (select Weld). This tool will act differently based on how many parts are selected when the tool is activated:

  • If no parts are selected when the Weld tool is clicked, the next two parts that are clicked on will be welded together. If the same part is clicked twice, no weld will be created.
  • If one part is selected when the Weld tool is clicked, the next part that is clicked on will be welded to the selected part.
  • If several parts are selected when the Weld tool is clicked, any parts in that selection that are touching or overlapping will be welded together.

Repositioning Welded Parts

Roblox handles moving a welded part differently depending on whether the part was moved using its BasePart/Position|Position or with its datatype/CFrame|CFrame.

If a welded part’s BasePart/Position|Position is updated, the part will move but none of the connected parts will move with it. The weld will recalculate the offset from the other part based on the part’s new position.

-- Create two parts and position them at the same height
local partA = Instance.new("Part")
local partB = Instance.new("Part")
partA.Position = Vector3.new(0, 10, 0)
partB.Position = Vector3.new(0, 10, 10)
partA.Parent = workspace
partB.Parent = workspace

-- Weld the two parts together
local weld = Instance.new("WeldConstraint")
weld.Parent = workspace
weld.Part0 = partA
weld.Part1 = partB

-- Update the position of the first part; the first part will move but the second will stay where it started
partA.Position = Vector3.new(0, 20, 0)

In contrast, if a part’s datatype/CFrame|CFrame is updated, that part will move and any part welded to that part will also move. These other parts will be moved to make sure they maintain the same offset as when the weld was created.

-- Create two parts and position them at the same height
local partA = Instance.new("Part")
local partB = Instance.new("Part")
partA.Position = Vector3.new(0, 10, 0)
partB.Position = Vector3.new(0, 10, 10)
partA.Parent = workspace
partB.Parent = workspace

-- Weld the two parts together
local weld = Instance.new("WeldConstraint")
weld.Parent = workspace
weld.Part0 = partA
weld.Part1 = partB

-- Update the CFrame of the first part; the second part will also move to maintain the offset of the weld
partA.CFrame = CFrame.new(0, 20, 0)

Properties

bool

Active

[ReadOnly] [NotReplicated]

Indicates if the WeldConstraint is currently active in the world

bool

Enabled

Toggles the constraint on and off.

BasePart

Part0

[NotReplicated]

The first part connected by the constraint.

BasePart

Part1

[NotReplicated]

The second part connected by the constraint.

Inherited from Instance: Show Hide

bool

Archivable

Determines if an Instance can be cloned using /Instance/Clone or saved to file.

string

ClassName

[ReadOnly] [NotReplicated]

A read-only string representing the class this Instance belongs to

int

DataCost

[ReadOnly] [NotReplicated] [Deprecated]

The cost of saving the instance using data persistence.

string

Name

A non-unique identifier of the Instance

Instance

Parent

Determines the hierarchical parent of the Instance

bool

RobloxLocked

If true, the Instance and its descendants cannot be indexed or edited by a Script or LocalScript and will throw an error if it is attempted

bool

archivable

[Hidden] [NotReplicated] [Deprecated]
string

className

[ReadOnly] [NotReplicated] [Deprecated]

Functions

Inherited from Instance: Show Hide

void

ClearAllChildren ( )

This function destroys all of an Instance's children.

Instance

Clone ( )

Create a deep copy of a Roblox instance and descendants where Archivable = true.

void

Destroy ( )

Sets the Instance/Parent property to nil, locks the Instance/Parent property, disconnects all connections and calls Destroy on all children.

Instance

FindFirstAncestor ( string name )

Returns the first ancestor of the Instance whose Instance/Name is equal to the given name.

Instance

FindFirstAncestorOfClass ( string className )

Returns the first ancestor of the Instance whose Instance/ClassName is equal to the given className.

Instance

FindFirstAncestorWhichIsA ( string className )

Returns the first ancestor of the Instance for whom Instance/IsA returns true for the given className.

Instance

FindFirstChild ( string name , bool recursive )

Returns the first child of the Instance found with the given name.

Instance

FindFirstChildOfClass ( string className )

Returns the first child of the Instance whose Instance/ClassName|ClassName is equal to the given className.

Instance

FindFirstChildWhichIsA ( string className , bool recursive )

Returns the first child of the Instance for whom Instance/IsA returns true for the given className.

Objects

GetChildren ( )

Returns an array containing all of the Instance's children.

string

GetDebugId ( int scopeLength )

[NotBrowsable]

Returns a coded string of the Instances DebugId used internally by Roblox.

Array

GetDescendants ( )

[CustomLuaState]

Returns an array containing all of the descendants of the instance

string

GetFullName ( )

Returns a string describing the Instance's ancestry.

RBXScriptSignal

GetPropertyChangedSignal ( string property )

Get an event that fires when a given property of an object changes.

bool

IsA ( string className )

[CustomLuaState]

Returns true if an Instance's class matches or inherits from a given class

bool

IsAncestorOf ( Instance descendant )

Returns true if an Instance is an ancestor of the given descendant.

bool

IsDescendantOf ( Instance ancestor )

Returns true if an Instance is a descendant of the given ancestor.

void

Remove ( )

[Deprecated]

Sets the object’s Parent to nil, and does the same for all its descendants.

Instance

WaitForChild ( string childName , double timeOut )

[CustomLuaState] [CanYield]

Returns the child of the Instance with the given name. If the child does not exist, it will yield the current thread until it does.

Objects

children ( )

[Deprecated]

Returns an array of the object’s children.

Instance

clone ( )

[Deprecated]
void

destroy ( )

[Deprecated]
Instance

findFirstChild ( string name , bool recursive )

[Deprecated]
Objects

getChildren ( )

[Deprecated]
bool

isA ( string className )

[Deprecated] [CustomLuaState]
bool

isDescendantOf ( Instance ancestor )

[Deprecated]
void

remove ( )

[Deprecated]

Events

Inherited from Instance: Show Hide

RBXScriptSignal

AncestryChanged ( Instance child , Instance parent )

Fires when the Instance/Parent property of the object or one of its ancestors is changed.

RBXScriptSignal

Changed ( string property )

Fired immediately after a property of an object changes.

RBXScriptSignal

ChildAdded ( Instance child )

Fires when an object is parented to this Instance.

RBXScriptSignal

ChildRemoved ( Instance child )

Fires when a child is removed from this Instance.

RBXScriptSignal

DescendantAdded ( Instance descendant )

Fires when a descendant is added to the Instance

RBXScriptSignal

DescendantRemoving ( Instance descendant )

Fires immediately before a descendant of the Instance is removed.

RBXScriptSignal

childAdded ( Instance child )

[Deprecated]