BasePart

The Anchored property determines whether the part will be immovable by physics. When enabled, a part will never change position due to gravity, other part collisions, overlapping other parts, or any other physics-related causes. As a result, two anchored parts will never fire the Touched event on each other.

An anchored part may still be moved by changing its CFrame or Position, and it still may have a nonzero AssemblyLinearVelocity and AssemblyAngularVelocity.

Finally, if an unanchored part is joined with an anchored part through an object like a Weld, it too will act anchored. If such a joint breaks, the part may be affected by physics again. See Assemblies for more details.

Network ownership cannot be set on anchored parts. If a part's anchored status changes on the server, the network ownership of that part will be affected.

The angular velocity vector of this part's assembly. It's the rate of change of orientation in radians per second.

Angular velocity is the same at every point of the assembly.

Setting the velocity directly may lead to unrealistic motion. Using Torque or AngularVelocity constraint is preferred, or use ApplyAngularImpulse() if you want instantaneous change in velocity.

If the part is owned by the server, this property must be changed from a server Script (not from a LocalScript or a Script with RunContext set to RunContext.Client). If the part is owned by a client through automatic ownership, this property can be changed from either a client script or a server script; changing it from a client script for a server-owned part will have no effect.

A position calculated via the Mass and Position of all the parts in the assembly.

If the assembly has an anchored part, that part's center of mass will be the assembly's center of mass, and the assembly will have infinite mass.

Knowing the center of mass can help the assembly maintain stability. A force applied to the center of mass will not cause angular acceleration, only linear. An assembly with a low center of mass will have a better time staying upright under the effect of gravity.

The linear velocity vector of this part's assembly. It's the rate of change in position of AssemblyCenterOfMass in studs per second.

If you want to know the velocity at a point other than the assembly's center of mass, use GetVelocityAtPosition().

Setting the velocity directly may lead to unrealistic motion. Using a VectorForce constraint is preferred, or use ApplyImpulse() if you want instantaneous change in velocity.

If the part is owned by the server, this property must be changed from a server Script (not from a LocalScript or a Script with RunContext set to RunContext.Client). If the part is owned by a client through automatic ownership, this property can be changed from either a client script or a server script; changing it from a client script for a server-owned part will have no effect.

The sum of the mass of all the BaseParts in this part's assembly. Parts that are Massless and are not the assembly's root part will not contribute to the AssemblyMass.

If the assembly has an anchored part, the assembly's mass is considered infinite. Constraints and other physical interactions between unanchored assemblies with a large difference in mass may cause instabilities.

This property indicates the BasePart automatically chosen to represent the assembly's root part. If the part is not parented to the Workspace, this property will be nil.

The root part can be changed by changing the RootPriority of the parts in the assembly.

Parts that all share the same AssemblyRootPart are in the same assembly.

For more information on root parts, see Assemblies.

AudioCanCollide determines whether the part will physically interact with audio simulation, similar to CastShadow for lighting.

When disabled, audio passes through the part; it is not occluded or reflected.

The BackParamA property is relevant when a part's BasePart.BackSurface is set to Motor or SteppingMotor and BasePart.BackSurfaceInput is set to Sin. It determines the amplitude of the motor's rotational velocity.

The BackParamB property is relevant when a part's BasePart.BackSurface is set to Motor or SteppingMotor and BasePart.BackSurfaceInput is set to Constant or Sin. For Constant, it determines the constant rotational velocity of the motor. For Sin, it determines the frequency of the motor's rotational velocity.

The BackSurface property determines the type of surface used for the positive Z direction of a part. When two parts' faces are placed next to each other, they may create a joint between them.

The BackSurfaceInput property determines the kind of input provided to a part's BasePart.BackSurface. This is only relevant for Motor or SteppingMotor SurfaceTypes. This property determines how BasePart.BackParamA and BasePart.BackParamB are used. For brevity, these properties will be referred to as ParamA and ParamB, respectively.

• By default, this is set to NoInput. This stops the motor altogether.
• For Constant, the motor rotates at a constant velocity equal to ParamB.
• For Sin, the motor rotates at a velocity equal to ParamA * math.sin(workspace.DistributedGameTime * ParamB). See Workspace.DistributedGameTime.

The BottomParamA property is relevant when a part's BasePart.BottomSurface is set to Motor or SteppingMotor and BasePart.BottomSurfaceInput is set to Sin. It determines the amplitude of the motor's rotational velocity.

The BottomParamB property is relevant when a part's BasePart.BottomSurface is set to Motor or SteppingMotor and BasePart.BottomSurfaceInput is set to Constant or Sin. For Constant, it determines the constant rotational velocity of the motor. For Sin, it determines the frequency of the motor's rotational velocity.

The BottomSurface property determines the type of surface used for the negative Y direction of a part. When two parts' faces are placed next to each other, they may create a joint between them.

The BottomSurfaceInput property determines the kind of input provided to a part's BasePart.BottomSurface. This is only relevant for Motor or SteppingMotor SurfaceTypes. This property determines how BasePart.BottomParamA and BasePart.BottomParamB are used. For brevity, these properties will be referred to as ParamA and ParamB, respectively.

• By default, this is set to NoInput. This stops the motor altogether.
• For Constant, the motor rotates at a constant velocity equal to ParamB.
• For Sin, the motor rotates at a velocity equal to ParamA * math.sin(workspace.DistributedGameTime * ParamB). See Workspace.DistributedGameTime.

This property determines the color of a part. If the part has a Material, this also determines the color used when rendering the material texture. For more control over the color, the Color property can be used and this property will use the closest BrickColor.

Other visual properties of a part are determined by Transparency and Reflectance.

CanCollide determines whether a part will physically interact with other parts. When disabled, other parts can pass through the part uninterrupted. Parts used for decoration usually have CanCollide disabled, as they need not be considered by the physics engine.

If a part is not Anchored and has CanCollide disabled, it may fall out of the world to be eventually destroyed by Workspace.FallenPartsDestroyHeight.

When CanCollide is disabled, parts may still fire the Touched event (as well the other parts touching them). You can disable this with CanTouch.

For more information on collisions, see Collisions.

This property determines whether the part is considered during spatial query operations, such as GetPartBoundsInBox or Raycast. Note that CanCollide must be disabled for CanQuery to take effect, and spatial query functions will never include parts with CanQuery of false.

Beyond this property, it is also possible to exclude parts which are descendants of a given list of parts using an OverlapParams or RaycastParams object when calling the spatial query functions.

This property determines if Touched and TouchEnded events fire on the part. If true, other touching parts must also have CanTouch set to true for touch events to fire. If false, touch events cannot be set up for the part and attempting to do so will throw an error. Similarly, if the property is set to false after a touch event is connected, the event will be disconnected and the TouchTransmitter removed.

Note that this collision logic can be set to respect collision groups through the Workspace.TouchesUseCollisionGroups property. If true, parts in non-colliding groups will ignore both collisions and touch events, thereby making this property irrelevant.

Performance#

There is a small performance gain on parts that have both CanTouch and CanCollide set to false, as these parts will never need to compute any kind of part to part collisions. However, they can still be hit by Raycasts and OverlapParams queries.

Determines whether or not a part casts a shadow. Disabling this property for a given part can cause visual artifacts on the shadows cast upon that part.

This property is not designed for performance enhancement, but in complex scenes, strategically disabling it on certain parts can improve performance. Due to the possibility of visual artifacts, we recommend leaving it enabled on all parts in most situations.

The CenterOfMass property describes the local position of a part's center of mass. If this is a single part assembly, this is the AssemblyCenterOfMass converted from world space to local. On simple Parts, the center of mass is always (0, 0, 0), but it can vary for WedgePart or MeshPart.

The CFrame property determines both the position and orientation of the BasePart in the world. It acts as an arbitrary reference location on the geometry, but ExtentsCFrame represents the actual CFrame of its physical center.

When setting CFrame on a part, other joined parts are also moved relative to the part, but it is recommended that you use PVInstance:PivotTo() to move an entire model, such as when teleporting a player's character.

Unlike setting BasePart.Position, setting CFrame will always move the part to the exact given CFrame; in other words: no overlap checking is done and the physics solver will attempt to resolve any overlap unless both parts are Anchored.

For keeping track of positions relative to a part's CFrame, an Attachment may be useful.

The CollisionGroup property describes the name of the part's collision group (maximum of 100 characters). Parts start off in the default group whose name is "Default". This value cannot be empty.

Although this property itself is non-replicated, the engine internally replicates the value through another private property to solve backward compatibility issues.

The BasePart.CollisionGroupId property describes the ID number of the part's collision group. Parts start off in the "Default" group whose ID is 0. If a part is unregistered, the value becomes -1. This value cannot be less than -1 and it cannot exceed WorldRoot:GetMaxCollisionGroups(). Invalid IDs are clamped.

Although this property can be directly changed, it's recommended that you specify the collision group by setting BasePart.CollisionGroup to the collision group's name.

The Color property determines the color of a part. If the part has a Material, this also determines the color used when rendering the material texture.

If this property is set, BrickColor will use the closest match to this Color value.

Other visual properties of a part are determined by Transparency and Reflectance.

CurrentPhysicalProperties indicates the current physical properties of the part. You can set custom values for the physical properties per part, custom material, and material override. The Roblox engine prioritizes more granular definitions when determining the effective physical properties of a part. The values in the following list are in order from highest to lowest priority:

• Custom physical properties of the part
• Custom physical properties of the part's custom material
• Custom physical properties of the material override of the part's material
• Default physical properties of the part's material

CustomPhysicalProperties lets you customize various physical aspects of a part, such as its density, friction, and elasticity.

If enabled, this property let's you configure these physical properties. If disabled, these physical properties are determined by the Material of the part.

The Elasticity of a part is now determined by either its Material or its CustomPhysicalProperties.

When true, and when Workspace.FluidForces is enabled, causes the physics engine to compute aerodynamic forces on this BasePart.

The CFrame of the physical extents of the BasePart, representing its physical center.

The actual physical size of the BasePart as regarded by the physics engine, for example in collision detection.

Used to control the Friction of the part, but now it no longer does anything. The Friction of a part is now determined by either its Material or its CustomPhysicalProperties.

The FrontParamA property is relevant when a part's BasePart.FrontSurface is set to Motor or SteppingMotor and BasePart.FrontSurfaceInput is set to Sin. It determines the amplitude of the motor's rotational velocity.

The FrontParamB property is relevant when a part's BasePart.FrontSurface is set to Motor or SteppingMotor and BasePart.FrontSurfaceInput is set to Constant or Sin. For Constant, it determines the constant rotational velocity of the motor. For Sin, it determines the frequency of the motor's rotational velocity.

The FrontSurface property determines the type of surface used for the negative Z direction of a part. When two parts' faces are placed next to each other, they may create a joint between them.

The FrontSurfaceInput property determines the kind of input provided to a part's BasePart.FrontSurface. This is only relevant for Motor or SteppingMotor SurfaceTypes. This property determines how BasePart.FrontParamA and BasePart.FrontParamB are used. For brevity, these properties will be referred to as ParamA and ParamB, respectively.

• By default, this is set to NoInput. This stops the motor altogether.
• For Constant, the motor rotates at a constant velocity equal to ParamB.
• For Sin, the motor rotates at a velocity equal to ParamA * math.sin(workspace.DistributedGameTime * ParamB). See Workspace.DistributedGameTime.

The LeftParamA property is relevant when a part's BasePart.LeftSurface is set to Motor or SteppingMotor and BasePart.LeftSurfaceInput is set to Sin. It determines the amplitude of the motor's rotational velocity.

The LeftParamB property is relevant when a part's BasePart.LeftSurface is set to Motor or SteppingMotor and BasePart.LeftSurfaceInput is set to Constant or Sin. For Constant, it determines the constant rotational velocity of the motor. For Sin, it determines the frequency of the motor's rotational velocity.

The LeftSurface property determines the type of surface used for the negative X direction of a part. When two parts' faces are placed next to each other, they may create a joint between them.

The LeftSurfaceInput property determines the kind of input provided to a part's BasePart.LeftSurface. This is only relevant for Motor or SteppingMotor SurfaceTypes. This property determines how BasePart.LeftParamA and BasePart.LeftParamB are used. For brevity, these properties will be referred to as ParamA and ParamB, respectively.

• By default, this is set to NoInput. This stops the motor altogether.
• For Constant, the motor rotates at a constant velocity equal to ParamB.
• For Sin, the motor rotates at a velocity equal to ParamA * math.sin(workspace.DistributedGameTime * ParamB). See Workspace.DistributedGameTime.

The LocalTransparencyModifier property is a multiplier to Transparency that is only visible to the local client. It does not replicate from client to server and is useful for when a part should not render for a specific client, such as how the player does not see their character's body parts when they zoom into first person mode.

This property modifies the local part's transparency through the following formula, with resulting values clamped between 0 and 1.

1 - ((1 - Transparency) × (1 - LocalTransparencyModifier))

Class.BasePart.Transparency|Transparency	LocalTransparencyModifier	Server-Side	Client-Side
0.5	0	0.5	0.5
0.5	0.25	0.5	0.625
0.5	0.5	0.5	0.75
0.5	0.75	0.5	0.875
0.5	1	0.5	1