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Serialization

Since this addon is written in the Rust language, it is fairly easy to save and load the state of it at any time. For this there are some helper methods, directly accessible from the RapierPhysicsServer2D or RapierPhysicsServer3D singletons. You can export and import to both json or binary.

RapierPhysicsServer.export_binary(rid)
RapierPhysicsServer.export_json(rid)

Space​

All the physics objects are grouped inside spaces (eg. a space contains all objects). Even if you don't create a space, a default space exists and can be obtained from:

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

If you want the physics simulation to happen inside another space and not interact with the default space, you can create a new space by creating a new SubViewport. These come with new world_2d and/or world_3d instances. If you do this, you also have to render the new viewport using SubViewportContainer.

Next, all you have to do is call the export function from the RapierPhysicsServer.

var exported_binary: String = RapierPhysicsServer.export_binary(space_rid)
note

Every export function has both json and binary variants. The binary one is going to be faster and result in less size, while the json one is going to be better for debugging.

Next, you can either print the result:

print(exported_binary)

Or store it to a file as binary:

var file = FileAccess.open("user://space.bin", FileAccess.WRITE)
file.store_buffer(exported_binary)

Collision Object Serialization​

A Collision Object inside the wrapper refers to either a:

  • RigidBody
  • Area
  • StaticBody
  • CharacterBody

This serializes the data a RigidBody structure has in Godot. This does not save the actual RigidBody Rapier uses, that is stored in the Space serialization. This just stores a handle to that.

var exported_json: String = RapierPhysicsServer.export_binary(body_rid)

In order to get the body_rid, call the get_rid() method on the Collision Object.

Joint Serialization​

Similar to other physics objects, get the rid and serialize the joint

var exported_json: String = RapierPhysicsServer.export_binary(joint_rid)

Shape Serialization​

Not all shapes can be serialized right now, some simply don't export the rid property. For those that do (eg. CollisionShape2D) do, use the get_shape_owners property of CollisionObject3D to get the shape owners and use that to get the shape_rid.

for owner_id in node.get_shape_owners():
    for owner_shape_id in node.shape_owner_get_shape_count(owner_id):
        var shape_rid = node.shape_owner_get_shape(owner_id, owner_shape_id).get_rid()

Then you can do:

var exported_json: String = RapierPhysicsServer.export_binary(shape_rid)