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Matter.Body

Defined in: src/body/Body.js:1

The Matter.Body module contains methods for creating and manipulating body models. A Matter.Body is a rigid body that can be simulated by a Matter.Engine. Factories for commonly used body configurations (such as rectangles, circles and other polygons) can be found in the module Matter.Bodies.

See the included usage examples.

Methods

Matter.Body._initProperties

(body, [options])
private

Initialises body properties.

Parameters

Matter.Body._totalProperties

(body)
private

Returns the sums of the properties of all compound parts of the parent body.

Parameters

Returns

Matter.Body.applyForce

(body, position, force)

Applies a force to a body from a given world-space position, including resulting torque.

Parameters

Matter.Body.create

(options)
Body

Creates a new rigid body model. The options parameter is an object that specifies any properties you wish to override the defaults. All properties have default values, and many are pre-calculated automatically based on other properties. Vertices must be specified in clockwise order. See the properties section below for detailed information on what you can pass via the options object.

Parameters

Returns

Body

body

Matter.Body.nextCategory

()
Number

Returns the next unique category bitfield (starting after the initial default category 0x0001). There are 32 available. See body.collisionFilter for more information.

Returns

Number

Unique category bitfield

Matter.Body.nextGroup

([isNonColliding=false])
Number

Returns the next unique group index for which bodies will collide. If isNonColliding is true, returns the next unique group index for which bodies will not collide. See body.collisionFilter for more information.

Parameters

  • [isNonColliding=false] Bool optional

Returns

Number

Unique group index

Matter.Body.rotate

(body, rotation, [point])

Rotates a body by a given angle relative to its current angle, without imparting any angular velocity.

Parameters

Matter.Body.scale

(body, scaleX, scaleY, [point])

Scales the body, including updating physical properties (mass, area, axes, inertia), from a world-space point (default is body centre).

Parameters

Matter.Body.set

(body, settings, value)

Given a property and a value (or map of), sets the property(s) on the body, using the appropriate setter functions if they exist. Prefer to use the actual setter functions in performance critical situations.

Parameters

  • body Body
  • settings Object

    A property name (or map of properties and values) to set on the body.

  • value Object

    The value to set if settings is a single property name.

Matter.Body.setAngle

(body, angle)

Sets the angle of the body instantly. Angular velocity, position, force etc. are unchanged.

Parameters

Matter.Body.setAngularVelocity

(body, velocity)

Sets the angular velocity of the body instantly. Position, angle, force etc. are unchanged. See also Body.applyForce.

Parameters

Matter.Body.setDensity

(body, density)

Sets the density of the body. Mass is automatically updated to reflect the change.

Parameters

Matter.Body.setInertia

(body, inertia)

Sets the moment of inertia (i.e. second moment of area) of the body of the body. Inverse inertia is automatically updated to reflect the change. Mass is not changed.

Parameters

Matter.Body.setMass

(body, mass)

Sets the mass of the body. Inverse mass and density are automatically updated to reflect the change.

Parameters

Matter.Body.setParts

(body, [body], [autoHull=true])

Sets the parts of the body and updates mass, inertia and centroid. Each part will have its parent set to body. By default the convex hull will be automatically computed and set on body, unless autoHull is set to false. Note that this method will ensure that the first part in body.parts will always be the body.

Parameters

  • body Body
  • [body] Object optional

    parts

  • [autoHull=true] Bool optional

Matter.Body.setPosition

(body, position)

Sets the position of the body instantly. Velocity, angle, force etc. are unchanged.

Parameters

Matter.Body.setStatic

(body, isStatic)

Sets the body as static, including isStatic flag and setting mass and inertia to Infinity.

Parameters

  • body Body
  • isStatic Bool

Matter.Body.setVelocity

(body, velocity)

Sets the linear velocity of the body instantly. Position, angle, force etc. are unchanged. See also Body.applyForce.

Parameters

Matter.Body.setVertices

(body, vertices)

Sets the body's vertices and updates body properties accordingly, including inertia, area and mass (with respect to body.density). Vertices will be automatically transformed to be orientated around their centre of mass as the origin. They are then automatically translated to world space based on body.position.

The vertices argument should be passed as an array of Matter.Vector points (or a Matter.Vertices array). Vertices must form a convex hull, concave hulls are not supported.

Parameters

Matter.Body.translate

(body, translation)

Moves a body by a given vector relative to its current position, without imparting any velocity.

Parameters

Matter.Body.update

(body, deltaTime, timeScale, correction)

Performs a simulation step for the given body, including updating position and angle using Verlet integration.

Parameters

Properties

The following properties are specified for objects created by Matter.Body.create and for objects passed to it via the options argument.

A Number specifying the angle of the body, in radians.

Default: 0

A Number that measures the current angular speed of the body after the last Body.update. It is read-only and always positive (it's the magnitude of body.angularVelocity).

Default: 0

A Number that measures the current angular velocity of the body after the last Body.update. It is read-only. If you need to modify a body's angular velocity directly, you should apply a torque or simply change the body's angle (as the engine uses position-Verlet integration).

Default: 0

A Number that measures the area of the body's convex hull, calculated at creation by Body.create.

An array of unique axis vectors (edge normals) used for collision detection. These are automatically calculated from the given convex hull (vertices array) in Body.create. They are constantly updated by Body.update during the simulation.

A Bounds object that defines the AABB region for the body. It is automatically calculated from the given convex hull (vertices array) in Body.create and constantly updated by Body.update during simulation.

An Object that specifies the collision filtering properties of this body.

Collisions between two bodies will obey the following rules:

  • If the two bodies have the same non-zero value of collisionFilter.group, they will always collide if the value is positive, and they will never collide if the value is negative.
  • If the two bodies have different values of collisionFilter.group or if one (or both) of the bodies has a value of 0, then the category/mask rules apply as follows:

Each body belongs to a collision category, given by collisionFilter.category. This value is used as a bit field and the category should have only one bit set, meaning that the value of this property is a power of two in the range [1, 2^31]. Thus, there are 32 different collision categories available.

Each body also defines a collision bitmask, given by collisionFilter.mask which specifies the categories it collides with (the value is the bitwise AND value of all these categories).

Using the category/mask rules, two bodies A and B collide if each includes the other's category in its mask, i.e. (categoryA & maskB) !== 0 and (categoryB & maskA) !== 0 are both true.

A bit field that specifies the collision category this body belongs to. The category value should have only one bit set, for example 0x0001. This means there are up to 32 unique collision categories available. See body.collisionFilter for more information.

Default: 1

An Integer Number, that specifies the collision group this body belongs to. See body.collisionFilter for more information.

Default: 0

A bit mask that specifies the collision categories this body may collide with. See body.collisionFilter for more information.

Default: -1

A Number that defines the density of the body, that is its mass per unit area. If you pass the density via Body.create the mass property is automatically calculated for you based on the size (area) of the object. This is generally preferable to simply setting mass and allows for more intuitive definition of materials (e.g. rock has a higher density than wood).

Default: 0.001

A Vector that specifies the force to apply in the current step. It is zeroed after every Body.update. See also Body.applyForce.

Default: { x: 0, y: 0 }

A Number that defines the friction of the body. The value is always positive and is in the range (0, 1). A value of 0 means that the body may slide indefinitely. A value of 1 means the body may come to a stop almost instantly after a force is applied.

The effects of the value may be non-linear. High values may be unstable depending on the body. The engine uses a Coulomb friction model including static and kinetic friction. Note that collision response is based on pairs of bodies, and that friction values are combined with the following formula:

Math.min(bodyA.friction, bodyB.friction)

Default: 0.1

A Number that defines the air friction of the body (air resistance). A value of 0 means the body will never slow as it moves through space. The higher the value, the faster a body slows when moving through space. The effects of the value are non-linear.

Default: 0.01

A Number that defines the static friction of the body (in the Coulomb friction model). A value of 0 means the body will never 'stick' when it is nearly stationary and only dynamic friction is used. The higher the value (e.g. 10), the more force it will take to initially get the body moving when nearly stationary. This value is multiplied with the friction property to make it easier to change friction and maintain an appropriate amount of static friction.

Default: 0.5

An integer Number uniquely identifying number generated in Body.create by Common.nextId.

A Number that defines the moment of inertia (i.e. second moment of area) of the body. It is automatically calculated from the given convex hull (vertices array) and density in Body.create. If you modify this value, you must also modify the body.inverseInertia property (1 / inertia).

A Number that defines the inverse moment of inertia of the body (1 / inertia). If you modify this value, you must also modify the body.inertia property.

A Number that defines the inverse mass of the body (1 / mass). If you modify this value, you must also modify the body.mass property.

A flag that indicates whether a body is a sensor. Sensor triggers collision events, but doesn't react with colliding body physically.

Default: false

A flag that indicates whether the body is considered sleeping. A sleeping body acts similar to a static body, except it is only temporary and can be awoken. If you need to set a body as sleeping, you should use Sleeping.set as this requires more than just setting this flag.

Default: false

A flag that indicates whether a body is considered static. A static body can never change position or angle and is completely fixed. If you need to set a body as static after its creation, you should use Body.setStatic as this requires more than just setting this flag.

Default: false

An arbitrary String name to help the user identify and manage bodies.

Default: "Body"

A Number that defines the mass of the body, although it may be more appropriate to specify the density property instead. If you modify this value, you must also modify the body.inverseMass property (1 / mass).

A Number that measures the amount of movement a body currently has (a combination of speed and angularSpeed). It is read-only and always positive. It is used and updated by the Matter.Sleeping module during simulation to decide if a body has come to rest.

Default: 0

A self reference if the body is not a part of another body. Otherwise this is a reference to the body that this is a part of. See body.parts.

An array of bodies that make up this body. The first body in the array must always be a self reference to the current body instance. All bodies in the parts array together form a single rigid compound body. Parts are allowed to overlap, have gaps or holes or even form concave bodies. Parts themselves should never be added to a World, only the parent body should be. Use Body.setParts when setting parts to ensure correct updates of all properties.

Body.plugin

An object reserved for storing plugin-specific properties.

A Vector that specifies the current world-space position of the body.

Default: { x: 0, y: 0 }

An Object that defines the rendering properties to be consumed by the module Matter.Render.

A String that defines the fill style to use when rendering the body (if a sprite is not defined). It is the same as when using a canvas, so it accepts CSS style property values.

Default: a random colour

A Number that defines the line width to use when rendering the body outline (if a sprite is not defined). A value of 0 means no outline will be rendered.

Default: 0

Sets the opacity to use when rendering.

Default: 1

An Object that defines the sprite properties to use when rendering, if any.

An String that defines the path to the image to use as the sprite texture, if any.

A Number that defines the offset in the x-axis for the sprite (normalised by texture width).

Default: 0

A Number that defines the scaling in the x-axis for the sprite, if any.

Default: 1

A Number that defines the offset in the y-axis for the sprite (normalised by texture height).

Default: 0

A Number that defines the scaling in the y-axis for the sprite, if any.

Default: 1

A String that defines the stroke style to use when rendering the body outline (if a sprite is not defined). It is the same as when using a canvas, so it accepts CSS style property values.

Default: a random colour

A flag that indicates if the body should be rendered.

Default: true

A Number that defines the restitution (elasticity) of the body. The value is always positive and is in the range (0, 1). A value of 0 means collisions may be perfectly inelastic and no bouncing may occur. A value of 0.8 means the body may bounce back with approximately 80% of its kinetic energy. Note that collision response is based on pairs of bodies, and that restitution values are combined with the following formula:

Math.max(bodyA.restitution, bodyB.restitution)

Default: 0

A Number that defines the number of updates in which this body must have near-zero velocity before it is set as sleeping by the Matter.Sleeping module (if sleeping is enabled by the engine).

Default: 60

A Number that specifies a tolerance on how far a body is allowed to 'sink' or rotate into other bodies. Avoid changing this value unless you understand the purpose of slop in physics engines. The default should generally suffice, although very large bodies may require larger values for stable stacking.

Default: 0.05

A Number that measures the current speed of the body after the last Body.update. It is read-only and always positive (it's the magnitude of body.velocity).

Default: 0

A Number that allows per-body time scaling, e.g. a force-field where bodies inside are in slow-motion, while others are at full speed.

Default: 1

A Number that specifies the torque (turning force) to apply in the current step. It is zeroed after every Body.update.

Default: 0

A String denoting the type of object.

Default: "body"

A Vector that measures the current velocity of the body after the last Body.update. It is read-only. If you need to modify a body's velocity directly, you should either apply a force or simply change the body's position (as the engine uses position-Verlet integration).

Default: { x: 0, y: 0 }

An array of Vector objects that specify the convex hull of the rigid body. These should be provided about the origin (0, 0). E.g.

[{ x: 0, y: 0 }, { x: 25, y: 50 }, { x: 50, y: 0 }]
                                            

When passed via Body.create, the vertices are translated relative to body.position (i.e. world-space, and constantly updated by Body.update during simulation). The Vector objects are also augmented with additional properties required for efficient collision detection.

Other properties such as inertia and bounds are automatically calculated from the passed vertices (unless provided via options). Concave hulls are not currently supported. The module Matter.Vertices contains useful methods for working with vertices.

Events

The following events are emitted by objects created by <span class="prefix">Matter.</span>Body.create to objects that have subscribed using Matter.Events.on.

Events.on(Body, "sleepEnd", callback)

Fired when a body ends sleeping (where this is the body).

Event Payload:

  • event Object

    An event object

    • source

      The source object of the event

    • name

      The name of the event

Events.on(Body, "sleepStart", callback)

Fired when a body starts sleeping (where this is the body).

Event Payload:

  • event Object

    An event object

    • source

      The source object of the event

    • name

      The name of the event

0.13.0