Collision object

Namespace: physics Language: Lua Type: Defold Lua File: physics_ddf.proto Source: engine/gamesys/proto/gamesys/physics_ddf.proto

Collision object physics API documentation

API

angular_damping

Type: PROPERTY The angular damping value for the collision object. Setting this value alters the damping of angular motion of the object (rotation). Valid values are between 0 (no damping) and 1 (full damping).

Examples

How to decrease a collision object component’s angular damping:

-- get angular damping from collision object "collisionobject" in gameobject "floater"
local target = "floater#collisionobject"
local damping = go.get(target, "angular_damping")
-- decrease it by 10%
go.set(target, "angular_damping", damping * 0.9)

angular_velocity

Type: PROPERTY The current angular velocity of the collision object component as a vector3. The velocity is measured as a rotation around the vector with a speed equivalent to the vector length in radians/s.

Replaces: request_velocity and velocity_response

Examples

How to query and modify a collision object component’s angular velocity:

-- get angular velocity from collision object "collisionobject" in gameobject "boulder"
local velocity = go.get("boulder#collisionobject", "angular_velocity")
-- do something interesting
if velocity.z < 0 then
    -- clockwise rotation
    ...
else
    -- counter clockwise rotation
    ...
end
-- decrease it by 10%
velocity.z = velocity.z * 0.9
go.set("boulder#collisionobject", "angular_velocity", velocity * 0.9)

apply_force

Type: MESSAGE Post this message to a collision-object-component to apply the specified force on the collision object. The collision object must be dynamic.

Parameters

• force (vector3) - the force to be applied on the collision object, measured in Newton
• position (vector3) - the position where the force should be applied

Examples

Assuming the instance of the script has a collision-object-component with id “co”:

-- apply a force of 1 Newton towards world-x at the center of the game object instance
msg.post("#co", "apply_force", {force = vmath.vector3(1, 0, 0), position = go.get_world_position()})

collision_event

Type: MESSAGE See physics.set_event_listener. This message is sent to a function specified in physics.set_event_listener when two collision objects collide. This message only reports that a collision has occurred and will be sent once per frame and per colliding pair. For more detailed information, check for the contact_point_event.

Parameters

• a (message.physics.collision_info) - collision information for object A
• b (message.physics.collision_info) - collision information for object B

Examples

How to take action when a collision occurs:

physics.set_event_listener(function(self, event, data)
  if event == hash("collision_event") then
      pprint(data)
      -- {
      --  a = {
      --          group = hash: [default],
      --          position = vmath.vector3(183, 666, 0),
      --          id = hash: [/go1]
      --      },
      --  b = {
      --          group = hash: [default],
      --          position = vmath.vector3(185, 704.05865478516, 0),
      --          id = hash: [/go2]
      --      }
      -- }
  end
end)

collision_response

Type: MESSAGE This message is broadcasted to every component of an instance that has a collision object, when the collision object collides with another collision object. For a script to take action when such a collision happens, it should check for this message in its on_message callback function. This message only reports that a collision actually happened and will only be sent once per colliding pair and frame. To retrieve more detailed information, check for the contact_point_response instead.

Parameters

• other_id (hash) - the id of the instance the collision object collided with
• other_position (vector3) - the world position of the instance the collision object collided with
• other_group (hash) - the collision group of the other collision object
• own_group (hash) - the collision group of the own collision object

Examples

How to take action when a collision occurs:

function on_message(self, message_id, message, sender)
    -- check for the message
    if message_id == hash("collision_response") then
        -- take action
    end
end

contact_point_event

Type: MESSAGE See physics.set_event_listener. This message is sent to a function specified in physics.set_event_listener when a collision object has contact points with another collision object. Since multiple contact points can occur for two colliding objects, this event can be sent multiple times in the same frame for the same two colliding objects. To only be notified once when the collision occurs, check for the collision_event event instead.

Parameters

• applied_impulse (number) - the impulse the contact resulted in
• distance (number) - the penetration distance between the objects, which is always positive
• a (message.physics.contact_point_info) - contact point information for object A
• b (message.physics.contact_point_info) - contact point information for object B

Examples

How to take action when a contact point occurs:

physics.set_event_listener(function(self, events)
  for _,event in ipairs(events) do
    if event['type'] == hash("contact_point_event") then
        pprint(event)
        -- {
        --  applied_impulse = 310.00769042969,
        --  distance = 0.0714111328125,
        --  a = {
        --      position = vmath.vector3(446, 371, 0),
        --      relative_velocity = vmath.vector3(1.1722083854693e-06, -20.667181015015, -0),
        --      mass = 0,
        --      group = hash: [default],
        --      id = hash: [/flat],
        --      normal = vmath.vector3(-0, -1, -0)
        --  },
        --  b = {
        --      position = vmath.vector3(185, 657.92858886719, 0),
        --      relative_velocity = vmath.vector3(-1.1722083854693e-06, 20.667181015015, 0),
        --      mass = 10,
        --      group = hash: [default],
        --      id = hash: [/go2],
        --      normal = vmath.vector3(0, 1, 0)
        --  },
        --  type = hash: [contact_point_event]
        -- }
     end
   end
end)

contact_point_response

Type: MESSAGE This message is broadcasted to every component of an instance that has a collision object, when the collision object has contact points with respect to another collision object. For a script to take action when such contact points occur, it should check for this message in its on_message callback function. Since multiple contact points can occur for two colliding objects, this message can be sent multiple times in the same frame for the same two colliding objects. To only be notified once when the collision occurs, check for the collision_response message instead.

Parameters

• position (vector3) - world position of the contact point
• normal (vector3) - normal in world space of the contact point, which points from the other object towards the current object
• relative_velocity (vector3) - the relative velocity of the collision object as observed from the other object
• distance (number) - the penetration distance between the objects, which is always positive
• applied_impulse (number) - the impulse the contact resulted in
• life_time (number) - life time of the contact, not currently used
• mass (number) - the mass of the current collision object in kg
• other_mass (number) - the mass of the other collision object in kg
• other_id (hash) - the id of the instance the collision object is in contact with
• other_position (vector3) - the world position of the other collision object
• other_group (hash) - the collision group of the other collision object
• own_group (hash) - the collision group of the own collision object

Examples

How to take action when a contact point occurs:

function on_message(self, message_id, message, sender)
    -- check for the message
    if message_id == hash("contact_point_response") then
        -- take action
    end
end

linear_damping

Type: PROPERTY The linear damping value for the collision object. Setting this value alters the damping of linear motion of the object. Valid values are between 0 (no damping) and 1 (full damping).

Examples

How to increase a collision object component’s linear damping:

-- get linear damping from collision object "collisionobject" in gameobject "floater"
local target = "floater#collisionobject"
local damping = go.get(target, "linear_damping")
-- increase it by 10% if it's below 0.9
if damping <= 0.9 then
    go.set(target, "linear_damping", damping * 1.1)
end

linear_velocity

Type: PROPERTY The current linear velocity of the collision object component as a vector3. The velocity is measured in units/s (pixels/s).

Replaces: request_velocity and velocity_response

Examples

How to query and modify a collision object component’s linear velocity:

-- get linear velocity from collision object "collisionobject" in gameobject "ship"
local source = "ship#collisionobject"
local velocity = go.get(source, "linear_velocity")
-- decrease it by 10%
go.set(source, "linear_velocity", velocity * 0.9)
-- apply the velocity on target game object "boulder"'s collision object as a force
local target = "boulder#collisionobject"
local pos = go.get_position(target)
msg.post(target, "apply_force", { force = velocity, position = pos })

mass

Type: PROPERTY READ ONLY Returns the defined physical mass of the collision object component as a number.

Examples

How to query a collision object component’s mass:

-- get mass from collision object component "boulder"
local mass = go.get("#boulder", "mass")
-- do something useful
assert(mass > 1)

message.physics.collision_info

Type: STRUCT collision object information

Members

• position (vector3) - object position in world space
• id (hash) - object identifier
• group (hash) - object collision group

message.physics.contact_point_info

Type: STRUCT contact-point object information

Members

• position (vector3) - contact point position in world space
• instance_position (vector3) - object position in world space
• normal (vector3) - contact normal pointing from the other object toward this object
• relative_velocity (vector3) - object velocity relative to the other object
• mass (number) - object mass in kilograms
• id (hash) - object identifier
• group (hash) - object collision group

message.physics.trigger_info

Type: STRUCT trigger interaction object information

Members

• id (hash) - object identifier
• group (hash) - object collision group

physics.create_joint

Type: FUNCTION Create a physics joint between two collision object components. Note: Currently only supported in 2D physics.

Parameters

• joint_type (physics.JOINT_TYPE) - the joint type

• collisionobject_a (string

  hash

  url) - first collision object

• joint_id (string

  hash) - id of the joint

• position_a (vector3) - local position where to attach the joint on the first collision object

• collisionobject_b (string

  hash

  url) - second collision object

• position_b (vector3) - local position where to attach the joint on the second collision object
• properties (physics.joint_properties) (optional) - optional joint-specific properties

physics.destroy_joint

Type: FUNCTION Destroy an already physics joint. The joint has to be created before a destroy can be issued. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - collision object where the joint exist

• joint_id (string

  hash) - id of the joint

physics.event

Type: TYPEDEF An event delivered to a physics world listener. Inspect its type field to determine which event-specific fields are available.

Parameters

• value (message.physics.contact_point_event

  message.physics.collision_event

  message.physics.trigger_event

  message.physics.ray_cast_response

  message.physics.ray_cast_missed) - physics event data

physics.get_gravity

Type: FUNCTION Get the gravity in runtime. The gravity returned is not global, it will return the gravity for the collection that the function is called from. Note: For 2D physics the z component will always be zero.

Returns

• gravity (vector3) - gravity vector of collection

Examples

function init(self)
    local gravity = physics.get_gravity()
    -- Inverse gravity!
    gravity = -gravity
    physics.set_gravity(gravity)
end

physics.get_group

Type: FUNCTION Returns the group name of a collision object as a hash.

Parameters

• url (string

  hash

  url) - the collision object to return the group of.

Returns

• group (hash) - hash value of the group.

Examples

local function check_is_enemy()
    local group = physics.get_group("#collisionobject")
    return group == hash("enemy")
end

physics.get_joint_properties

Type: FUNCTION Get a table for properties for a connected joint. The joint has to be created before properties can be retrieved. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - collision object where the joint exist

• joint_id (string

  hash) - id of the joint

Returns

• properties (physics.joint_properties_info) - joint properties

physics.get_joint_reaction_force

Type: FUNCTION Get the reaction force for a joint. The joint has to be created before the reaction force can be calculated. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - collision object where the joint exist

• joint_id (string

  hash) - id of the joint

Returns

• force (vector3) - reaction force for the joint

physics.get_joint_reaction_torque

Type: FUNCTION Get the reaction torque for a joint. The joint has to be created before the reaction torque can be calculated. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - collision object where the joint exist

• joint_id (string

  hash) - id of the joint

Returns

• torque (number) - the reaction torque on bodyB in N*m.

physics.get_maskbit

Type: FUNCTION Returns true if the specified group is set in the mask of a collision object, false otherwise.

Parameters

• url (string

  hash

  url) - the collision object to check the mask of.

• group (string) - the name of the group to check for.

Returns

• maskbit (boolean) - boolean value of the maskbit. ‘true’ if present, ‘false’ otherwise.

Examples

local function is_invincible()
    -- check if the collisionobject would collide with the "bullet" group
    local invincible = physics.get_maskbit("#collisionobject", "bullet")
    return invincible
end

physics.get_shape

Type: FUNCTION Gets collision shape data from a collision object

Parameters

• url (string

  hash

  url) - the collision object.

• shape (string

  hash) - the name of the shape to get data for.

Returns

• table (physics.shape_data) - collision shape data

Examples

local function get_shape_meta()
    local sphere = physics.get_shape("#collisionobject", "my_sphere_shape")
    -- returns a table with sphere.diameter
    return sphere
end

physics.joint_properties

Type: STRUCT The available fields depend on the joint type.

Members

• collide_connected? (boolean) - whether the connected objects should collide
• length? (number) - Natural spring length between the anchor points.
• frequency? (number) - Mass-spring-damper frequency in Hertz; zero disables softness.
• damping? (number) - Damping ratio, where zero is no damping and one is critical damping.
• max_length? (number) - Maximum fixed-joint rope length.
• local_axis_a? (vector3) - Local translation unit axis in the first body.
• reference_angle? (number) - Angle of the second body relative to the first body, in radians.
• lower_angle? (number) - Lower angular limit in radians.
• upper_angle? (number) - Upper angular limit in radians.
• lower_translation? (number) - Lower translation limit, usually in meters.
• upper_translation? (number) - Upper translation limit, usually in meters.
• max_motor_torque? (number) - Maximum motor torque used to reach the desired speed, usually in N-m.
• max_motor_force? (number) - Maximum motor force used to reach the desired speed.
• motor_speed? (number) - Desired motor speed.
• enable_limit? (boolean) - Whether joint limits are enabled.
• enable_motor? (boolean) - Whether the joint motor is enabled.

physics.joint_properties_info

Type: STRUCT The available optional fields depend on the joint type.

Members

• collide_connected (boolean) - whether the connected objects collide
• length? (number) - spring length
• frequency? (number) - spring frequency
• damping? (number) - damping ratio
• max_length? (number) - fixed-joint maximum length
• local_axis_a? (vector3) - local joint axis
• reference_angle? (number) - reference angle
• lower_angle? (number) - lower angular limit
• upper_angle? (number) - upper angular limit
• lower_translation? (number) - lower translation limit
• upper_translation? (number) - upper translation limit
• max_motor_torque? (number) - maximum motor torque
• max_motor_force? (number) - maximum motor force
• motor_speed? (number) - motor speed
• enable_limit? (boolean) - whether limits are enabled
• enable_motor? (boolean) - whether the motor is enabled
• joint_angle? (number) - Read-only current hinge angle in radians.
• joint_speed? (number) - Read-only current hinge angular speed or slider/wheel translation speed.
• joint_translation? (number) - Read-only current slider or wheel translation, usually in meters.

physics.JOINT_TYPE

Type: ENUM Joint types

Members

• physics.JOINT_TYPE_FIXED - Fixed joint; uses max_length from physics.joint_properties.
• physics.JOINT_TYPE_HINGE - Hinge joint; uses the angular-limit and motor fields from physics.joint_properties.
• physics.JOINT_TYPE_SLIDER - Slider joint; uses the translation-limit and motor fields from physics.joint_properties.
• physics.JOINT_TYPE_SPRING - Spring joint; uses length, frequency, and damping from physics.joint_properties.
• physics.JOINT_TYPE_WELD - Weld joint; uses reference_angle, frequency, and damping from physics.joint_properties.
• physics.JOINT_TYPE_WHEEL - Wheel joint; uses the axis, motor, frequency, and damping fields from physics.joint_properties.

physics.raycast

Type: FUNCTION Ray casts are used to test for intersections against collision objects in the physics world. Collision objects of types kinematic, dynamic and static are tested against. Trigger objects do not intersect with ray casts. Which collision objects to hit is filtered by their collision groups and can be configured through groups. NOTE: Ray casts will ignore collision objects that contain the starting point of the ray. This is a limitation in Box2D.

Parameters

• from (vector3) - the world position of the start of the ray
• to (vector3) - the world position of the end of the ray
• groups (hash[]) - a lua table containing the hashed groups for which to test collisions against
• options (physics.raycast_options) (optional) - optional ray-cast options

Returns

• result (message.physics.ray_cast_response[]

  message.physics.ray_cast_response

  nil) - It returns a list. If missed it returns nil. See ray_cast_response for details on the returned values.

Examples

How to perform a ray cast synchronously:

function init(self)
    self.groups = {hash("world"), hash("enemy")}
end

function update(self, dt)
    -- request ray cast
    local result = physics.raycast(from, to, self.groups, {all=true})
    if result ~= nil then
        -- act on the hit (see 'ray_cast_response')
        for _,result in ipairs(results) do
            handle_result(result)
        end
    end
end

physics.raycast_async

Type: FUNCTION Ray casts are used to test for intersections against collision objects in the physics world. Collision objects of types kinematic, dynamic and static are tested against. Trigger objects do not intersect with ray casts. Which collision objects to hit is filtered by their collision groups and can be configured through groups. The actual ray cast will be performed during the physics-update.

If an object is hit, the result will be reported via a ray_cast_response message. If there is no object hit, the result will be reported via a ray_cast_missed message.

NOTE: Ray casts will ignore collision objects that contain the starting point of the ray. This is a limitation in Box2D.

Parameters

• from (vector3) - the world position of the start of the ray
• to (vector3) - the world position of the end of the ray
• groups (hash[]) - a lua table containing the hashed groups for which to test collisions against
• request_id (integer) (optional) - a number in range [0,255]. It will be sent back in the response for identification, 0 by default

Examples

How to perform a ray cast asynchronously:

function init(self)
    self.my_groups = {hash("my_group1"), hash("my_group2")}
end

function update(self, dt)
    -- request ray cast
    physics.raycast_async(my_start, my_end, self.my_groups)
end

function on_message(self, message_id, message, sender)
    -- check for the response
    if message_id == hash("ray_cast_response") then
        -- act on the hit
    elseif message_id == hash("ray_cast_missed") then
        -- act on the miss
    end
end

physics.raycast_options

Type: STRUCT Ray-cast options

Members

• all? (boolean) - Return every hit instead of only the closest hit.

physics.set_event_listener

Type: FUNCTION Only one physics world event listener can be set at a time.

Parameters

• callback (fun(self:script_instance, events:physics.event[])

  nil) - A callback that receives information about all physics interactions in this physics world. Pass nil to remove the listener.

self:script_instance

The calling script instance</dd>

events:physics.event[]

An array of event tables. Each event table contains a type field with the hashed name of one of these messages, together with fields specific to that event type:</dd> </dl>

• contact_point_event
• collision_event
• trigger_event
• ray_cast_response
• ray_cast_missed

Examples

local function physics_world_listener(self, events)
  for _,event in ipairs(events) do
      local event_type = event["type"]
      if event_type == hash("contact_point_event") then
          pprint(event)
          -- {
          --  distance = 2.1490633487701,
          --  applied_impulse = 0
          --  a = { --[[0x113f7c6c0]]
          --    group = hash: [box],
          --    id = hash: [/box]
          --    mass = 0,
          --    normal = vmath.vector3(0.379, 0.925, -0),
          --    position = vmath.vector3(517.337, 235.068, 0),
          --    instance_position = vmath.vector3(480, 144, 0),
          --    relative_velocity = vmath.vector3(-0, -0, -0),
          --  },
          --  b = { --[[0x113f7c840]]
          --    group = hash: [circle],
          --    id = hash: [/circle]
          --    mass = 0,
          --    normal = vmath.vector3(-0.379, -0.925, 0),
          --    position = vmath.vector3(517.337, 235.068, 0),
          --    instance_position = vmath.vector3(-0.0021, 0, -0.0022),
          --    relative_velocity = vmath.vector3(0, 0, 0),
          --  },
          -- }
      elseif event_type == hash("collision_event") then
          pprint(event)
          -- {
          --  a = {
          --          group = hash: [default],
          --          position = vmath.vector3(183, 666, 0),
          --          id = hash: [/go1]
          --      },
          --  b = {
          --          group = hash: [default],
          --          position = vmath.vector3(185, 704.05865478516, 0),
          --          id = hash: [/go2]
          --      }
          -- }
      elseif event_type ==  hash("trigger_event") then
          pprint(event)
          -- {
          --  enter = true,
          --  b = {
          --      group = hash: [default],
          --      id = hash: [/go2]
          --  },
          --  a = {
          --      group = hash: [default],
          --      id = hash: [/go1]
          --  }
          -- },
      elseif event_type ==  hash("ray_cast_response") then
          pprint(event)
          --{
          --  group = hash: [default],
          --  request_id = 0,
          --  position = vmath.vector3(249.92222595215, 249.92222595215, 0),
          --  fraction = 0.68759721517563,
          --  normal = vmath.vector3(0, 1, 0),
          --  id = hash: [/go]
          -- }
      elseif event_type ==  hash("ray_cast_missed") then
          pprint(event)
          -- {
          --  request_id = 0
          --},
      end
end

function init(self)
    physics.set_event_listener(physics_world_listener)
end

physics.set_gravity

Type: FUNCTION Set the gravity in runtime. The gravity change is not global, it will only affect the collection that the function is called from. Note: For 2D physics the z component of the gravity vector will be ignored.

Parameters

• gravity (vector3) - the new gravity vector

Examples

function init(self)
    -- Set "upside down" gravity for this collection.
    physics.set_gravity(vmath.vector3(0, 10.0, 0))
end

physics.set_group

Type: FUNCTION Updates the group property of a collision object to the specified string value. The group name should exist i.e. have been used in a collision object in the editor.

Parameters

• url (string

  hash

  url) - the collision object affected.

• group (string) - the new group name to be assigned.

Examples

local function change_collision_group()
     physics.set_group("#collisionobject", "enemy")
end

physics.set_hflip

Type: FUNCTION Flips the collision shapes horizontally for a collision object

Parameters

• url (string

  hash

  url) - the collision object that should flip its shapes

• flip (boolean) - true if the collision object should flip its shapes, false if not

Examples

function init(self)
    self.fliph = true -- set on some condition
    physics.set_hflip("#collisionobject", self.fliph)
end

physics.set_joint_properties

Type: FUNCTION Updates the properties for an already connected joint. The joint has to be created before properties can be changed. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - collision object where the joint exist

• joint_id (string

  hash) - id of the joint

• properties (physics.joint_properties) - joint specific properties table Note: The collide_connected field cannot be updated/changed after a connection has been made.

physics.set_maskbit

Type: FUNCTION Sets or clears the masking of a group (maskbit) in a collision object.

Parameters

• url (string

  hash

  url) - the collision object to change the mask of.

• group (string) - the name of the group (maskbit) to modify in the mask.
• maskbit (boolean) - boolean value of the new maskbit. ‘true’ to enable, ‘false’ to disable.

Examples

local function make_invincible()
    -- no longer collide with the "bullet" group
    physics.set_maskbit("#collisionobject", "bullet", false)
end

physics.set_shape

Type: FUNCTION Sets collision shape data for a collision object. Please note that updating data in 3D can be quite costly for box and capsules. Because of the physics engine, the cost comes from having to recreate the shape objects when certain shapes needs to be updated.

Parameters

• url (string

  hash

  url) - the collision object.

• shape (string

  hash) - the name of the shape to get data for.

• table (physics.shape_data) - updated collision shape data Hull and mesh geometry cannot be changed with this function.

Examples

local function set_shape_data()
    -- set capsule shape data
    local data = {}
    data.type = physics.SHAPE_TYPE_CAPSULE
    data.diameter = 10
    data.height = 20
    physics.set_shape("#collisionobject", "my_capsule_shape", data)

    -- set sphere shape data
    data = {}
    data.type = physics.SHAPE_TYPE_SPHERE
    data.diameter = 10
    physics.set_shape("#collisionobject", "my_sphere_shape", data)

    -- set box shape data
    data = {}
    data.type = physics.SHAPE_TYPE_BOX
    data.dimensions = vmath.vector3(10, 10, 5)
    physics.set_shape("#collisionobject", "my_box_shape", data)
end

physics.set_vflip

Type: FUNCTION Flips the collision shapes vertically for a collision object

Parameters

• url (string

  hash

  url) - the collision object that should flip its shapes

• flip (boolean) - true if the collision object should flip its shapes, false if not

Examples

function init(self)
    self.flipv = true -- set on some condition
    physics.set_vflip("#collisionobject", self.flipv)
end

physics.shape_data

Type: STRUCT The available geometry fields depend on type.

Members

• type (physics.SHAPE_TYPE) - shape type
• diameter? (number) - sphere diameter or capsule pole diameter
• dimensions? (vector3) - box dimensions
• height? (number) - capsule height

physics.SHAPE_TYPE

Type: ENUM Shape types

Members

• physics.SHAPE_TYPE_BOX - Box shape.
• physics.SHAPE_TYPE_CAPSULE - Capsule shape; supported only by 3D physics.
• physics.SHAPE_TYPE_HULL - Convex hull shape.
• physics.SHAPE_TYPE_MESH - Triangle mesh shape; supported only by the Bullet 3D backend.
• physics.SHAPE_TYPE_SPHERE - Sphere shape.

physics.update_mass

Type: FUNCTION The function recalculates the density of each shape based on the total area of all shapes and the specified mass, then updates the mass of the body accordingly. Note: Currently only supported in 2D physics.

Parameters

• collisionobject (string

  hash

  url) - the collision object whose mass needs to be updated.

• mass (number) - the new mass value to set for the collision object.

Examples

 physics.update_mass("#collisionobject", 14)

physics.wakeup

Type: FUNCTION Collision objects tend to fall asleep when inactive for a small period of time for efficiency reasons. This function wakes them up.

Parameters

• url (string

  hash

  url) - the collision object to wake.

Examples

function on_input(self, action_id, action)
    if action_id == hash("test") and action.pressed then
        physics.wakeup("#collisionobject")
    end
end

ray_cast_missed

Type: MESSAGE This message is sent back to the sender of a ray_cast_request, or to the physics world listener if it is set (see physics.set_event_listener), if the ray didn’t hit any collision object. See physics.raycast_async for examples of how to use it.

Parameters

• request_id (integer) - id supplied when the ray cast was requested

ray_cast_response

Type: MESSAGE This message is sent back to the sender of a ray_cast_request, or to the physics world listener if it is set (see physics.set_event_listener), if the ray hits a collision object. See physics.raycast_async for examples of how to use it.

Parameters

• fraction (number) - the fraction of the hit measured along the ray, where 0 is the start of the ray and 1 is the end
• position (vector3) - the world position of the hit
• normal (vector3) - the normal of the surface of the collision object where it was hit
• id (hash) - the instance id of the hit collision object
• group (hash) - the collision group of the hit collision object as a hashed name
• request_id (integer) - id supplied when the ray cast was requested

trigger_event

Type: MESSAGE See physics.set_event_listener. This message is sent to a function specified in physics.set_event_listener when a collision object interacts with another collision object and one of them is a trigger. This message only reports that an interaction actually happened and will be sent once per colliding pair and frame. For more detailed information, check for the contact_point_event.

Parameters

• enter (boolean) - if the interaction was an entry or not
• a (message.physics.trigger_info) - interaction information for object A
• b (message.physics.trigger_info) - interaction information for object B

Examples

How to take action when a trigger interaction occurs:

physics.set_event_listener(function(self, event, data)
 if event ==  hash("trigger_event") then
     if data.enter then
        -- take action for entry
     else
        -- take action for exit
     end
     pprint(data)
     -- {
     --  enter = true,
     --  b = {
     --      group = hash: [default],
     --      id = hash: [/go2]
     --  },
     --  a = {
     --      group = hash: [default],
     --      id = hash: [/go1]
     --  }
     -- },
  end
end)

trigger_response

Type: MESSAGE This message is broadcasted to every component of an instance that has a collision object, when the collision object interacts with another collision object and one of them is a trigger. For a script to take action when such an interaction happens, it should check for this message in its on_message callback function. This message only reports that an interaction actually happened and will only be sent once per colliding pair and frame. To retrieve more detailed information, check for the contact_point_response instead.

Parameters

• other_id (hash) - the id of the instance the collision object collided with
• enter (boolean) - if the interaction was an entry or not
• other_group (hash) - the collision group of the triggering collision object
• own_group (hash) - the collision group of the own collision object

Examples

How to take action when a trigger interaction occurs:

function on_message(self, message_id, message, sender)
    -- check for the message
    if message_id == hash("trigger_response") then
        if message.enter then
            -- take action for entry
        else
            -- take action for exit
        end
    end
end