Godot Rapier Physics

https://godot.rapier.rs/docs
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Godot Rapier Physics provides a 2D and 3D physics engine for the Godot game engine, leveraging the...
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### Set and get joint extra parameters

Source: https://godot.rapier.rs/docs/reference/physics-server

Shows how to set and get extra parameters on a joint using joint_set_extra_param and joint_get_extra_param. The parameter is selected by constants like JOINT_TYPE.

```gdscript
RapierPhysicsServer2D.joint_set_extra_param(joint, param, value)  
RapierPhysicsServer2D.joint_get_extra_param(joint, param)  

```

--------------------------------

### Manual stepping example script (GDScript)

Source: https://godot.rapier.rs/docs/documentation/determinism

Disables auto-stepping for the 2D physics space and manually steps it 10 times with the project's fixed delta, then flushes queries. Uses RapierPhysicsServer2D.space_step and space_flush_queries.

```gdscript
extends Node2D  
  
func _ready() -> void:  
	var space := get_viewport().world_2d.space  
	PhysicsServer2D.space_set_active(space, false)  
  
func _on_button_pressed() -> void:  
	var space := get_viewport().world_2d.space  
	var fixed_delta = 1.0 / ProjectSettings.get_setting("physics/common/physics_ticks_per_second")  
	for i in 10:  
		RapierPhysicsServer2D.space_step(space, fixed_delta)  
	RapierPhysicsServer2D.space_flush_queries(space)  
```

--------------------------------

### body_get_contact_force_threshold

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the contact force threshold for a body.

```APIDOC
## body_get_contact_force_threshold

### Description
Gets the contact force threshold for a body.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_contact_force_threshold(body)

### Parameters
#### Path Parameters
- **body** (RID) - Required - The RID of the physics body.

### Request Example
```
var threshold = RapierPhysicsServer2D.body_get_contact_force_threshold(rid)
```

### Response
#### Success Response (200)
- **threshold** (float) - The current contact force threshold.

#### Response Example
```
10.0
```
```

--------------------------------

### body_get_total_contact_impulse

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the total contact impulse on the body this step, as a vector.

```APIDOC
## body_get_total_contact_impulse

### Description
Gets the total contact impulse on the body this step, as a vector.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_total_contact_impulse(body)

### Parameters
#### Path Parameters
- **body** (RID) - Required - The RID of the physics body.

### Request Example
```
var impulse = RapierPhysicsServer2D.body_get_total_contact_impulse(rid)
```

### Response
#### Success Response (200)
- **impulse** (Vector2/Vector3) - The total contact impulse vector.

#### Response Example
```
Vector2(1.0, 2.0)
```
```

--------------------------------

### body_get_total_friction_impulse

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the total friction impulse magnitude this step.

```APIDOC
## body_get_total_friction_impulse

### Description
Gets the total friction impulse magnitude this step.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_total_friction_impulse(body)

### Parameters
#### Path Parameters
- **body** (RID) - Required - The RID of the physics body.

### Request Example
```
var friction_impulse = RapierPhysicsServer2D.body_get_total_friction_impulse(rid)
```

### Response
#### Success Response (200)
- **friction_impulse** (float) - The total friction impulse magnitude.

#### Response Example
```
3.0
```
```

--------------------------------

### Get active body transforms (2D and 3D)

Source: https://godot.rapier.rs/docs/documentation/performance

Use these functions to retrieve the transforms of all active bodies after disabling state_sync_callback. The 2D version returns Transform2D, the 3D version returns Transform3D.

```GDScript
var body_rids: Array = RapierPhysicsServer2D.space_get_active_bodies(space_rid)  
var body_transforms: Array[Transform2D] = RapierPhysicsServer2D.space_get_bodies_transform(body_rids)  
#or  
var body_rids: Array = RapierPhysicsServer3D.space_get_active_bodies(space_rid)  
var body_transforms: Array[Transform3D] = RapierPhysicsServer3D.space_get_bodies_transform(body_rids)  
```

--------------------------------

### Get default space RID

Source: https://godot.rapier.rs/docs/documentation/serialization

Obtains the RID of the default physics space for the current viewport, either 2D or 3D. Use this RID when calling export_state or import_state on a RapierStateManager2D/3D node.

```gdscript
var space_2d_rid = get_viewport().world_2d.space  
# or  
var space_3d_rid = get_viewport().world_3d.space  
```

--------------------------------

### Joint Parameters

Source: https://godot.rapier.rs/docs/reference/physics-server

Functions to set and get extra joint parameters, including joint type.

```APIDOC
## RapierPhysicsServer2D.joint_set_extra_param(joint, param, value)

### Description
Sets an extra parameter on a joint, such as the joint type.

### Method
Function

### Parameters
- **joint** (RID) - Required - The joint to configure.
- **param** (int) - Required - The parameter identifier (e.g., JOINT_TYPE).
- **value** (int) - Required - The value to set.
```

```APIDOC
## RapierPhysicsServer2D.joint_get_extra_param(joint, param)

### Description
Gets an extra parameter from a joint.

### Method
Function

### Parameters
- **joint** (RID) - Required - The joint to query.
- **param** (int) - Required - The parameter identifier.

### Returns
- **int** - The current value of the parameter.
```

--------------------------------

### Manual physics stepping with PhysicsServer2D.Call

Source: https://godot.rapier.rs/docs/documentation/dotnet

Shows how to manually step the physics space from C# by calling RapierPhysicsServer2D methods through the PhysicsServer2D singleton. Disables the automatic space processing in _Ready and then steps the space ten times plus flushes queries when a button is pressed.

```csharp
public partial class ManualPhysicsStepper : Node2D  
{  
    public override void _Ready()  
    {  
        Rid space = GetViewport().World2D.Space;  
        PhysicsServer3D.SpaceSetActive(space, false);  
    }  
    public void OnButtonPressed()  
    {  
        Rid space = GetViewport().World2D.Space;  
        float fixedDelta = 1f / ProjectSettings.GetSetting("physics/common/physics_ticks_per_second").AsSingle();  
        for(int i = 0; i < 10; i++)  
        {  
            PhysicsServer2D.Singleton.Call("space_step", space, fixedDelta);  
        }  
        PhysicsServer2D.Singleton.Call("space_flush_queries", space);  
    }  
}  
```

--------------------------------

### Create rope and fixed joints with RapierPhysicsServer2D

Source: https://godot.rapier.rs/docs/reference/physics-server

Shows how to create a rope joint (bodies move freely while closer than max_distance) and a fixed joint (locks all relative motion) using RapierPhysicsServer2D. Anchors are in world space.

```gdscript
# Rope: bodies move freely while closer than max_distance.  
RapierPhysicsServer2D.joint_make_rope(joint, anchor_a, anchor_b, max_distance, body_a, body_b)  
  
# Fixed: locks all relative motion.  
RapierPhysicsServer2D.joint_make_fixed(joint, anchor, body_a, body_b)  

```

--------------------------------

### body_get_contact_tangent_impulse

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the friction impulse at one reported contact.

```APIDOC
## body_get_contact_tangent_impulse

### Description
Gets the friction impulse at one reported contact.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_contact_tangent_impulse(body, contact_idx)

### Parameters
#### Path Parameters
- **body** (RID) - Required - The RID of the physics body.

#### Query Parameters
- **contact_idx** (int) - Required - The index of the contact.

### Request Example
```
var tangent_impulse = RapierPhysicsServer2D.body_get_contact_tangent_impulse(rid, 0)
```

### Response
#### Success Response (200)
- **tangent_impulse** (float) - The friction impulse at the specified contact.

#### Response Example
```
1.5
```
```

--------------------------------

### Load physics state from a file

Source: https://godot.rapier.rs/docs/tutorial/save-and-load-state

Reads the saved state and imports it back. The scene tree must contain the same physics nodes as when saving; import restores state, not creates nodes. Format is detected automatically on import.

```GDScript
func load_game() -> void:  
	var file := FileAccess.open("user://physics_save.bin", FileAccess.READ)  
	state_manager.import_state(get_world_2d().space, file.get_var())  
```

--------------------------------

### bodies_get_contact_impulse

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the impulse that body_a receives from body_b specifically.

```APIDOC
## bodies_get_contact_impulse

### Description
Gets the impulse that body_a receives from body_b specifically.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.bodies_get_contact_impulse(body_a, body_b)

### Parameters
#### Path Parameters
- **body_a** (RID) - Required - The RID of the first body.
- **body_b** (RID) - Required - The RID of the second body.

### Request Example
```
var impulse = RapierPhysicsServer2D.bodies_get_contact_impulse(rid_a, rid_b)
```

### Response
#### Success Response (200)
- **impulse** (Vector2/Vector3) - The impulse vector received by body_a from body_b.

#### Response Example
```
Vector2(0.5, 0.0)
```
```

--------------------------------

### Render active bodies with MultiMeshInstance3D

Source: https://godot.rapier.rs/docs/documentation/performance

In _process, fetch active bodies and their transforms, then update a MultiMeshInstance3D to render them. This avoids per-body Godot node updates and improves performance.

```GDScript
extends MultiMeshInstance3D  
  
func _process(delta: float) -> void:  
	var bodies := RapierPhysicsServer3D.space_get_active_bodies(get_viewport().world_3d.space)  
	var transforms := RapierPhysicsServer3D.space_get_bodies_transform(get_viewport().world_3d.space, bodies)  
	multimesh.instance_count = transforms.size()  
	var idx = 0  
	for transform in transforms:  
		multimesh.set_instance_transform(idx, transform)  
		idx += 1  
```

--------------------------------

### Save physics state to a file

Source: https://godot.rapier.rs/docs/tutorial/save-and-load-state

Exports the space's state and writes it to disk. Uses RustBincode format for speed; use Json while debugging for readability. Requires a RapierStateManager2D node in the scene.

```GDScript
@onready var state_manager: RapierStateManager2D = $RapierStateManager2D  

func save_game() -> void:  
	var state: Variant = state_manager.export_state(get_world_2d().space, "RustBincode")  
	var file := FileAccess.open("user://physics_save.bin", FileAccess.WRITE)  
	file.store_var(state)  
```

--------------------------------

### body_get_max_contact_impulse

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the strongest single contact impulse magnitude this step.

```APIDOC
## body_get_max_contact_impulse

### Description
Gets the strongest single contact impulse magnitude this step.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_max_contact_impulse(body)

### Parameters
#### Path Parameters
- **body** (RID) - Required - The RID of the physics body.

### Request Example
```
var max_impulse = RapierPhysicsServer2D.body_get_max_contact_impulse(rid)
```

### Response
#### Success Response (200)
- **max_impulse** (float) - The maximum contact impulse magnitude.

#### Response Example
```
5.0
```
```

--------------------------------

### Render active bodies with MultiMeshInstance2D

Source: https://godot.rapier.rs/docs/documentation/performance

In _process, fetch active bodies and their transforms, then update a MultiMeshInstance2D to render them. This avoids per-body Godot node updates and improves performance.

```GDScript
extends MultiMeshInstance2D  
  
func _process(delta: float) -> void:  
	var bodies := RapierPhysicsServer2D.space_get_active_bodies(get_viewport().world_2d.space)  
	var transforms := RapierPhysicsServer2D.space_get_bodies_transform(get_viewport().world_2d.space, bodies)  
	multimesh.instance_count = transforms.size()  
	var idx = 0  
	for transform in transforms:  
		multimesh.set_instance_transform_2d(idx, transform)  
		idx += 1  
```

--------------------------------

### Fluid and Space API

Source: https://godot.rapier.rs/docs/reference/physics-server

API documentation for the fluid and space functions in the Godot Rapier physics server.

```APIDOC
## fluid_create()

### Description
Creates a fluid and returns its RID.

### Method
Function

### Parameters
None

### Returns
- **RID** - The RID of the newly created fluid.
```

```APIDOC
## fluid_set_space(fluid, space)

### Description
Puts the fluid in a space.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **space** (RID) - Required - The space RID.
```

```APIDOC
## fluid_set_density(fluid, density)

### Description
Sets the density of the fluid.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **density** (float) - Required - The density value.
```

```APIDOC
## fluid_set_effects(fluid, effects)

### Description
Sets effect resources (viscosity, elasticity, surface tension).

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **effects** (Array) - Required - The effect resources.
```

```APIDOC
## fluid_set_points(fluid, points)

### Description
Replaces all particles.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **points** (Array) - Required - The particle positions.
```

```APIDOC
## fluid_set_points_and_velocities(fluid, points, velocities)

### Description
Replaces particles and velocities.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **points** (Array) - Required - The particle positions.
- **velocities** (Array) - Required - The particle velocities.
```

```APIDOC
## fluid_add_points_and_velocities(fluid, points, velocities)

### Description
Adds particles.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **points** (Array) - Required - The particle positions.
- **velocities** (Array) - Required - The particle velocities.
```

```APIDOC
## fluid_delete_points(fluid, indices)

### Description
Removes particles by index.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **indices** (Array) - Required - The indices of particles to remove.
```

```APIDOC
## fluid_get_points(fluid)

### Description
Returns the particle positions.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.

### Returns
- **Array** - The particle positions.
```

```APIDOC
## fluid_get_velocities(fluid)

### Description
Returns the particle velocities.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.

### Returns
- **Array** - The particle velocities.
```

```APIDOC
## fluid_get_accelerations(fluid)

### Description
Returns the particle accelerations.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.

### Returns
- **Array** - The particle accelerations.
```

```APIDOC
## fluid_get_particles_in_aabb(fluid, aabb)

### Description
Returns the indices of particles inside a box.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **aabb** (AABB) - Required - The axis-aligned bounding box.

### Returns
- **Array** - The indices of particles inside the box.
```

```APIDOC
## fluid_get_particles_in_ball(fluid, center, radius)

### Description
Returns the indices of particles inside a sphere.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **center** (Vector3) - Required - The center of the sphere.
- **radius** (float) - Required - The radius of the sphere.

### Returns
- **Array** - The indices of particles inside the sphere.
```

```APIDOC
## fluid_set_collision_masks(fluid, mask, layer)

### Description
Sets the interaction groups.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.
- **mask** (int) - Required - The collision mask.
- **layer** (int) - Required - The collision layer.
```

```APIDOC
## fluid_get_collision_mask(fluid)

### Description
Reads back the collision mask.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.

### Returns
- **int** - The collision mask.
```

```APIDOC
## fluid_get_collision_layer(fluid)

### Description
Reads back the collision layer.

### Method
Function

### Parameters
- **fluid** (RID) - Required - The fluid RID.

### Returns
- **int** - The collision layer.
```

```APIDOC
## space_step(space, delta)

### Description
Steps one space manually. Requires disabling automatic stepping.

### Method
Function

### Parameters
- **space** (RID) - Required - The space RID.
- **delta** (float) - Required - The time step.
```

```APIDOC
## space_flush_queries(space)

### Description
Flushes queued callbacks after `space_step`.

### Method
Function

### Parameters
- **space** (RID) - Required - The space RID.
```

```APIDOC
## space_get_active_bodies(space)

### Description
Returns the RIDs of the active bodies.

### Method
Function

### Parameters
- **space** (RID) - Required - The space RID.

### Returns
- **Array** - The RIDs of the active bodies.
```

```APIDOC
## space_get_bodies_transform(space, bodies)

### Description
Returns the transforms for a list of bodies.

### Method
Function

### Parameters
- **space** (RID) - Required - The space RID.
- **bodies** (Array) - Required - The list of body RIDs.

### Returns
- **Array** - The transforms for the given bodies.
```

--------------------------------

### body_get_extra_param

Source: https://godot.rapier.rs/docs/reference/physics-server

Gets the value of an extra body parameter previously set on a physics body.

```APIDOC
## body_get_extra_param

### Description
Gets the value of an extra body parameter previously set on a physics body.

### Method
Static method

### Endpoint
RapierPhysicsServer2D.body_get_extra_param(rid, param)

### Parameters
#### Path Parameters
- **rid** (RID) - Required - The RID of the physics body.

#### Query Parameters
- **param** (int) - Required - The body parameter to get. Use one of the BODY_PARAM_* constants.

### Request Example
```
var value = RapierPhysicsServer2D.body_get_extra_param(rid, BODY_PARAM_CONTACT_SKIN)
```

### Response
#### Success Response (200)
- **value** (Variant) - The current value of the parameter.

#### Response Example
```
0.1
```
```

--------------------------------

### Checkpoint and retry with in-memory cache

Source: https://godot.rapier.rs/docs/tutorial/save-and-load-state

For rapid restores (checkpoint retries, rollback), keep snapshots in memory instead of files. Uses cache_state, ordered_cache_tags, and load_cached_state methods.

```GDScript
func checkpoint() -> void:  
	state_manager.cache_state(get_world_2d().space, "checkpoint")  

func retry() -> void:  
	var index: int = state_manager.ordered_cache_tags().find("checkpoint")  
	state_manager.load_cached_state(get_world_2d().space, index)  
```

--------------------------------

### Body State Methods

Source: https://godot.rapier.rs/docs/reference/physics-server

Methods to query body state, including kinetic energy and CCD activity.

```APIDOC
## body_get_kinetic_energy(body)

### Description
Returns the kinetic energy of a body, combining both linear and angular motion.

### Method
Function

### Parameters
- **body** (RID) - Required - The body to query.

### Returns
- **float** - Kinetic energy combining linear and angular motion.
```

```APIDOC
## body_is_ccd_active(body)

### Description
Returns whether continuous collision detection actually ran for this body during the last physics step.

### Method
Function

### Parameters
- **body** (RID) - Required - The body to query.

### Returns
- **bool** - Whether continuous collision detection actually ran for this body last step.
```

--------------------------------

### Set additional solver iterations via RapierPhysicsServer2D

Source: https://godot.rapier.rs/docs/reference/bodies

Sets the additional solver iterations parameter on a plain Godot body via the Rapier physics server. Use this when you need to configure a body without using the custom Rapier body nodes.

```gdscript
RapierPhysicsServer2D.body_set_extra_param(
    body.get_rid(), RapierPhysicsServer2D.BODY_PARAM_ADDITIONAL_SOLVER_ITERATIONS, 4)

```
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