godot/modules/gltf/extensions/physics/gltf_document_extension_physics.cpp

/**************************************************************************/
/*  gltf_document_extension_physics.cpp                                   */
/**************************************************************************/
/*                         This file is part of:                          */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "gltf_document_extension_physics.h"

#include "scene/3d/physics/area_3d.h"
#include "scene/3d/physics/static_body_3d.h"

// Import process.
Error GLTFDocumentExtensionPhysics::import_preflight(Ref<GLTFState> p_state, Vector<String> p_extensions) {
	if (!p_extensions.has("OMI_collider") && !p_extensions.has("OMI_physics_body") && !p_extensions.has("OMI_physics_shape")) {
		return ERR_SKIP;
	}
	Dictionary state_json = p_state->get_json();
	if (state_json.has("extensions")) {
		Dictionary state_extensions = state_json["extensions"];
		if (state_extensions.has("OMI_physics_shape")) {
			Dictionary omi_physics_shape_ext = state_extensions["OMI_physics_shape"];
			if (omi_physics_shape_ext.has("shapes")) {
				Array state_shape_dicts = omi_physics_shape_ext["shapes"];
				if (state_shape_dicts.size() > 0) {
					Array state_shapes;
					for (int i = 0; i < state_shape_dicts.size(); i++) {
						state_shapes.push_back(GLTFPhysicsShape::from_dictionary(state_shape_dicts[i]));
					}
					p_state->set_additional_data(StringName("GLTFPhysicsShapes"), state_shapes);
				}
			}
#ifndef DISABLE_DEPRECATED
		} else if (state_extensions.has("OMI_collider")) {
			Dictionary omi_collider_ext = state_extensions["OMI_collider"];
			if (omi_collider_ext.has("colliders")) {
				Array state_collider_dicts = omi_collider_ext["colliders"];
				if (state_collider_dicts.size() > 0) {
					Array state_colliders;
					for (int i = 0; i < state_collider_dicts.size(); i++) {
						state_colliders.push_back(GLTFPhysicsShape::from_dictionary(state_collider_dicts[i]));
					}
					p_state->set_additional_data(StringName("GLTFPhysicsShapes"), state_colliders);
				}
			}
#endif // DISABLE_DEPRECATED
		}
	}
	return OK;
}

Vector<String> GLTFDocumentExtensionPhysics::get_supported_extensions() {
	Vector<String> ret;
	ret.push_back("OMI_collider");
	ret.push_back("OMI_physics_body");
	ret.push_back("OMI_physics_shape");
	return ret;
}

Error GLTFDocumentExtensionPhysics::parse_node_extensions(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Dictionary &p_extensions) {
#ifndef DISABLE_DEPRECATED
	if (p_extensions.has("OMI_collider")) {
		Dictionary node_collider_ext = p_extensions["OMI_collider"];
		if (node_collider_ext.has("collider")) {
			// "collider" is the index of the collider in the state colliders array.
			int node_collider_index = node_collider_ext["collider"];
			Array state_colliders = p_state->get_additional_data(StringName("GLTFPhysicsShapes"));
			ERR_FAIL_INDEX_V_MSG(node_collider_index, state_colliders.size(), Error::ERR_FILE_CORRUPT, "glTF Physics: On node " + p_gltf_node->get_name() + ", the collider index " + itos(node_collider_index) + " is not in the state colliders (size: " + itos(state_colliders.size()) + ").");
			p_gltf_node->set_additional_data(StringName("GLTFPhysicsShape"), state_colliders[node_collider_index]);
		} else {
			p_gltf_node->set_additional_data(StringName("GLTFPhysicsShape"), GLTFPhysicsShape::from_dictionary(node_collider_ext));
		}
	}
#endif // DISABLE_DEPRECATED
	if (p_extensions.has("OMI_physics_body")) {
		Dictionary physics_body_ext = p_extensions["OMI_physics_body"];
		if (physics_body_ext.has("collider")) {
			Dictionary node_collider = physics_body_ext["collider"];
			// "shape" is the index of the shape in the state shapes array.
			int node_shape_index = node_collider.get("shape", -1);
			if (node_shape_index != -1) {
				Array state_shapes = p_state->get_additional_data(StringName("GLTFPhysicsShapes"));
				ERR_FAIL_INDEX_V_MSG(node_shape_index, state_shapes.size(), Error::ERR_FILE_CORRUPT, "glTF Physics: On node " + p_gltf_node->get_name() + ", the shape index " + itos(node_shape_index) + " is not in the state shapes (size: " + itos(state_shapes.size()) + ").");
				p_gltf_node->set_additional_data(StringName("GLTFPhysicsColliderShape"), state_shapes[node_shape_index]);
			} else {
				// If this node is a collider but does not have a collider
				// shape, then it only serves to combine together shapes.
				p_gltf_node->set_additional_data(StringName("GLTFPhysicsCompoundCollider"), true);
			}
		}
		if (physics_body_ext.has("trigger")) {
			Dictionary node_trigger = physics_body_ext["trigger"];
			// "shape" is the index of the shape in the state shapes array.
			int node_shape_index = node_trigger.get("shape", -1);
			if (node_shape_index != -1) {
				Array state_shapes = p_state->get_additional_data(StringName("GLTFPhysicsShapes"));
				ERR_FAIL_INDEX_V_MSG(node_shape_index, state_shapes.size(), Error::ERR_FILE_CORRUPT, "glTF Physics: On node " + p_gltf_node->get_name() + ", the shape index " + itos(node_shape_index) + " is not in the state shapes (size: " + itos(state_shapes.size()) + ").");
				p_gltf_node->set_additional_data(StringName("GLTFPhysicsTriggerShape"), state_shapes[node_shape_index]);
			} else {
				// If this node is a trigger but does not have a trigger shape,
				// then it's a trigger body, what Godot calls an Area3D node.
				Ref<GLTFPhysicsBody> trigger_body;
				trigger_body.instantiate();
				trigger_body->set_body_type("trigger");
				p_gltf_node->set_additional_data(StringName("GLTFPhysicsBody"), trigger_body);
			}
			// If this node defines explicit member shape nodes, save this information.
			if (node_trigger.has("nodes")) {
				Array node_trigger_nodes = node_trigger["nodes"];
				p_gltf_node->set_additional_data(StringName("GLTFPhysicsCompoundTriggerNodes"), node_trigger_nodes);
			}
		}
		if (physics_body_ext.has("motion") || physics_body_ext.has("type")) {
			p_gltf_node->set_additional_data(StringName("GLTFPhysicsBody"), GLTFPhysicsBody::from_dictionary(physics_body_ext));
		}
	}
	return OK;
}

void _setup_shape_mesh_resource_from_index_if_needed(Ref<GLTFState> p_state, Ref<GLTFPhysicsShape> p_gltf_shape) {
	GLTFMeshIndex shape_mesh_index = p_gltf_shape->get_mesh_index();
	if (shape_mesh_index == -1) {
		return; // No mesh for this shape.
	}
	Ref<ImporterMesh> importer_mesh = p_gltf_shape->get_importer_mesh();
	if (importer_mesh.is_valid()) {
		return; // The mesh resource is already set up.
	}
	TypedArray<GLTFMesh> state_meshes = p_state->get_meshes();
	ERR_FAIL_INDEX_MSG(shape_mesh_index, state_meshes.size(), "glTF Physics: When importing '" + p_state->get_scene_name() + "', the shape mesh index " + itos(shape_mesh_index) + " is not in the state meshes (size: " + itos(state_meshes.size()) + ").");
	Ref<GLTFMesh> gltf_mesh = state_meshes[shape_mesh_index];
	ERR_FAIL_COND(gltf_mesh.is_null());
	importer_mesh = gltf_mesh->get_mesh();
	ERR_FAIL_COND(importer_mesh.is_null());
	p_gltf_shape->set_importer_mesh(importer_mesh);
}

#ifndef DISABLE_DEPRECATED
CollisionObject3D *_generate_shape_with_body(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Ref<GLTFPhysicsShape> p_physics_shape, Ref<GLTFPhysicsBody> p_physics_body) {
	print_verbose("glTF: Creating shape with body for: " + p_gltf_node->get_name());
	bool is_trigger = p_physics_shape->get_is_trigger();
	// This method is used for the case where we must generate a parent body.
	// This is can happen for multiple reasons. One possibility is that this
	// glTF file is using OMI_collider but not OMI_physics_body, or at least
	// this particular node is not using it. Another possibility is that the
	// physics body information is set up on the same glTF node, not a parent.
	CollisionObject3D *body;
	if (p_physics_body.is_valid()) {
		// This code is run when the physics body is on the same glTF node.
		body = p_physics_body->to_node();
		if (is_trigger && (p_physics_body->get_body_type() != "trigger")) {
			// Edge case: If the body's trigger and the collider's trigger
			// are in disagreement, we need to create another new body.
			CollisionObject3D *child = _generate_shape_with_body(p_state, p_gltf_node, p_physics_shape, nullptr);
			child->set_name(p_gltf_node->get_name() + (is_trigger ? String("Trigger") : String("Solid")));
			body->add_child(child);
			return body;
		}
	} else if (is_trigger) {
		body = memnew(Area3D);
	} else {
		body = memnew(StaticBody3D);
	}
	CollisionShape3D *shape = p_physics_shape->to_node();
	shape->set_name(p_gltf_node->get_name() + "Shape");
	body->add_child(shape);
	return body;
}
#endif // DISABLE_DEPRECATED

CollisionObject3D *_get_ancestor_collision_object(Node *p_scene_parent) {
	// Note: Despite the name of the method, at the moment this only checks
	// the direct parent. Only check more later if Godot adds support for it.
	if (p_scene_parent) {
		CollisionObject3D *co = Object::cast_to<CollisionObject3D>(p_scene_parent);
		if (likely(co)) {
			return co;
		}
	}
	return nullptr;
}

Node3D *_generate_shape_node_and_body_if_needed(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Ref<GLTFPhysicsShape> p_physics_shape, CollisionObject3D *p_col_object, bool p_is_trigger) {
	// If we need to generate a body node, do so.
	CollisionObject3D *body_node = nullptr;
	if (p_is_trigger || p_physics_shape->get_is_trigger()) {
		// If the shape wants to be a trigger but it doesn't
		// have an Area3D parent, we need to make one.
		if (!Object::cast_to<Area3D>(p_col_object)) {
			body_node = memnew(Area3D);
		}
	} else {
		if (!Object::cast_to<PhysicsBody3D>(p_col_object)) {
			body_node = memnew(StaticBody3D);
		}
	}
	// Generate the shape node.
	_setup_shape_mesh_resource_from_index_if_needed(p_state, p_physics_shape);
	CollisionShape3D *shape_node = p_physics_shape->to_node(true);
	if (body_node) {
		shape_node->set_name(p_gltf_node->get_name() + "Shape");
		body_node->add_child(shape_node);
		return body_node;
	}
	return shape_node;
}

// Either add the child to the parent, or return the child if there is no parent.
Node3D *_add_physics_node_to_given_node(Node3D *p_current_node, Node3D *p_child, Ref<GLTFNode> p_gltf_node) {
	if (!p_current_node) {
		return p_child;
	}
	String suffix;
	if (Object::cast_to<CollisionShape3D>(p_child)) {
		suffix = "Shape";
	} else if (Object::cast_to<Area3D>(p_child)) {
		suffix = "Trigger";
	} else {
		suffix = "Collider";
	}
	p_child->set_name(p_gltf_node->get_name() + suffix);
	p_current_node->add_child(p_child);
	return p_current_node;
}

Array _get_ancestor_compound_trigger_nodes(Ref<GLTFState> p_state, TypedArray<GLTFNode> p_state_nodes, CollisionObject3D *p_ancestor_col_obj) {
	GLTFNodeIndex ancestor_index = p_state->get_node_index(p_ancestor_col_obj);
	ERR_FAIL_INDEX_V(ancestor_index, p_state_nodes.size(), Array());
	Ref<GLTFNode> ancestor_gltf_node = p_state_nodes[ancestor_index];
	Variant compound_trigger_nodes = ancestor_gltf_node->get_additional_data(StringName("GLTFPhysicsCompoundTriggerNodes"));
	if (compound_trigger_nodes.is_array()) {
		return compound_trigger_nodes;
	}
	Array ret;
	ancestor_gltf_node->set_additional_data(StringName("GLTFPhysicsCompoundTriggerNodes"), ret);
	return ret;
}

Node3D *GLTFDocumentExtensionPhysics::generate_scene_node(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Node *p_scene_parent) {
	Ref<GLTFPhysicsBody> gltf_physics_body = p_gltf_node->get_additional_data(StringName("GLTFPhysicsBody"));
#ifndef DISABLE_DEPRECATED
	// This deprecated code handles OMI_collider (which we internally name "GLTFPhysicsShape").
	Ref<GLTFPhysicsShape> gltf_physics_shape = p_gltf_node->get_additional_data(StringName("GLTFPhysicsShape"));
	if (gltf_physics_shape.is_valid()) {
		_setup_shape_mesh_resource_from_index_if_needed(p_state, gltf_physics_shape);
		// If this glTF node specifies both a shape and a body, generate both.
		if (gltf_physics_body.is_valid()) {
			return _generate_shape_with_body(p_state, p_gltf_node, gltf_physics_shape, gltf_physics_body);
		}
		CollisionObject3D *ancestor_col_obj = _get_ancestor_collision_object(p_scene_parent);
		if (gltf_physics_shape->get_is_trigger()) {
			// If the shape wants to be a trigger and it already has a
			// trigger parent, we only need to make the shape node.
			if (Object::cast_to<Area3D>(ancestor_col_obj)) {
				return gltf_physics_shape->to_node(true);
			}
		} else if (ancestor_col_obj != nullptr) {
			// If the shape has a valid parent, only make the shape node.
			return gltf_physics_shape->to_node(true);
		}
		// Otherwise, we need to create a new body.
		return _generate_shape_with_body(p_state, p_gltf_node, gltf_physics_shape, nullptr);
	}
#endif // DISABLE_DEPRECATED
	Node3D *ret = nullptr;
	CollisionObject3D *ancestor_col_obj = nullptr;
	Ref<GLTFPhysicsShape> gltf_physics_collider_shape = p_gltf_node->get_additional_data(StringName("GLTFPhysicsColliderShape"));
	Ref<GLTFPhysicsShape> gltf_physics_trigger_shape = p_gltf_node->get_additional_data(StringName("GLTFPhysicsTriggerShape"));
	if (gltf_physics_body.is_valid()) {
		ancestor_col_obj = gltf_physics_body->to_node();
		ret = ancestor_col_obj;
	} else {
		ancestor_col_obj = _get_ancestor_collision_object(p_scene_parent);
		if (Object::cast_to<Area3D>(ancestor_col_obj) && gltf_physics_trigger_shape.is_valid()) {
			// At this point, we found an ancestor Area3D node. But do we want to use it for this trigger shape?
			TypedArray<GLTFNode> state_nodes = p_state->get_nodes();
			GLTFNodeIndex self_index = state_nodes.find(p_gltf_node);
			Array compound_trigger_nodes = _get_ancestor_compound_trigger_nodes(p_state, state_nodes, ancestor_col_obj);
			// Check if the ancestor specifies compound trigger nodes, and if this node is in there.
			// Remember that JSON does not have integers, only "number", aka double-precision floats.
			if (compound_trigger_nodes.size() > 0 && !compound_trigger_nodes.has(double(self_index))) {
				// If the compound trigger we found is not the intended user of
				// this shape node, then we need to create a new Area3D node.
				ancestor_col_obj = memnew(Area3D);
				ret = ancestor_col_obj;
			}
		} else if (!Object::cast_to<PhysicsBody3D>(ancestor_col_obj)) {
			if (p_gltf_node->get_additional_data(StringName("GLTFPhysicsCompoundCollider"))) {
				// If the glTF file wants this node to group solid shapes together,
				// and there is no parent body, we need to create a static body.
				ancestor_col_obj = memnew(StaticBody3D);
				ret = ancestor_col_obj;
			}
		}
	}
	// Add the shapes to the tree. When an ancestor body is present, use it.
	// If an explicit body was specified, it has already been generated and
	// set above. If there is no ancestor body, we will either generate an
	// Area3D or StaticBody3D implicitly, so prefer an Area3D as the base
	// node for best compatibility with signal connections to this node.
	bool is_ancestor_col_obj_solid = Object::cast_to<PhysicsBody3D>(ancestor_col_obj);
	if (is_ancestor_col_obj_solid && gltf_physics_collider_shape.is_valid()) {
		Node3D *child = _generate_shape_node_and_body_if_needed(p_state, p_gltf_node, gltf_physics_collider_shape, ancestor_col_obj, false);
		ret = _add_physics_node_to_given_node(ret, child, p_gltf_node);
	}
	if (gltf_physics_trigger_shape.is_valid()) {
		Node3D *child = _generate_shape_node_and_body_if_needed(p_state, p_gltf_node, gltf_physics_trigger_shape, ancestor_col_obj, true);
		ret = _add_physics_node_to_given_node(ret, child, p_gltf_node);
	}
	if (!is_ancestor_col_obj_solid && gltf_physics_collider_shape.is_valid()) {
		Node3D *child = _generate_shape_node_and_body_if_needed(p_state, p_gltf_node, gltf_physics_collider_shape, ancestor_col_obj, false);
		ret = _add_physics_node_to_given_node(ret, child, p_gltf_node);
	}
	return ret;
}

// Export process.
bool _are_all_faces_equal(const Vector<Face3> &p_a, const Vector<Face3> &p_b) {
	if (p_a.size() != p_b.size()) {
		return false;
	}
	for (int i = 0; i < p_a.size(); i++) {
		const Vector3 *a_vertices = p_a[i].vertex;
		const Vector3 *b_vertices = p_b[i].vertex;
		for (int j = 0; j < 3; j++) {
			if (!a_vertices[j].is_equal_approx(b_vertices[j])) {
				return false;
			}
		}
	}
	return true;
}

GLTFMeshIndex _get_or_insert_mesh_in_state(Ref<GLTFState> p_state, Ref<ImporterMesh> p_mesh) {
	ERR_FAIL_COND_V(p_mesh.is_null(), -1);
	TypedArray<GLTFMesh> state_meshes = p_state->get_meshes();
	Vector<Face3> mesh_faces = p_mesh->get_faces();
	// De-duplication: If the state already has the mesh we need, use that one.
	for (GLTFMeshIndex i = 0; i < state_meshes.size(); i++) {
		Ref<GLTFMesh> state_gltf_mesh = state_meshes[i];
		ERR_CONTINUE(state_gltf_mesh.is_null());
		Ref<ImporterMesh> state_importer_mesh = state_gltf_mesh->get_mesh();
		ERR_CONTINUE(state_importer_mesh.is_null());
		if (state_importer_mesh == p_mesh) {
			return i;
		}
		if (_are_all_faces_equal(state_importer_mesh->get_faces(), mesh_faces)) {
			return i;
		}
	}
	// After the loop, we have checked that the mesh is not equal to any of the
	// meshes in the state. So we insert a new mesh into the state mesh array.
	Ref<GLTFMesh> gltf_mesh;
	gltf_mesh.instantiate();
	gltf_mesh->set_mesh(p_mesh);
	GLTFMeshIndex mesh_index = state_meshes.size();
	state_meshes.push_back(gltf_mesh);
	p_state->set_meshes(state_meshes);
	return mesh_index;
}

void GLTFDocumentExtensionPhysics::convert_scene_node(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Node *p_scene_node) {
	if (cast_to<CollisionShape3D>(p_scene_node)) {
		CollisionShape3D *godot_shape = Object::cast_to<CollisionShape3D>(p_scene_node);
		Ref<GLTFPhysicsShape> gltf_shape = GLTFPhysicsShape::from_node(godot_shape);
		ERR_FAIL_COND_MSG(gltf_shape.is_null(), "glTF Physics: Could not convert CollisionShape3D to GLTFPhysicsShape. Does it have a valid Shape3D?");
		{
			Ref<ImporterMesh> importer_mesh = gltf_shape->get_importer_mesh();
			if (importer_mesh.is_valid()) {
				gltf_shape->set_mesh_index(_get_or_insert_mesh_in_state(p_state, importer_mesh));
			}
		}
		CollisionObject3D *ancestor_col_obj = _get_ancestor_collision_object(p_scene_node->get_parent());
		if (cast_to<Area3D>(ancestor_col_obj)) {
			p_gltf_node->set_additional_data(StringName("GLTFPhysicsTriggerShape"), gltf_shape);
			// Write explicit member shape nodes to the ancestor compound trigger node.
			TypedArray<GLTFNode> state_nodes = p_state->get_nodes();
			GLTFNodeIndex self_index = state_nodes.size(); // The current p_gltf_node will be inserted next.
			Array compound_trigger_nodes = _get_ancestor_compound_trigger_nodes(p_state, p_state->get_nodes(), ancestor_col_obj);
			compound_trigger_nodes.push_back(double(self_index));
		} else {
			p_gltf_node->set_additional_data(StringName("GLTFPhysicsColliderShape"), gltf_shape);
		}
	} else if (cast_to<CollisionObject3D>(p_scene_node)) {
		CollisionObject3D *godot_body = Object::cast_to<CollisionObject3D>(p_scene_node);
		p_gltf_node->set_additional_data(StringName("GLTFPhysicsBody"), GLTFPhysicsBody::from_node(godot_body));
	}
}

Array _get_or_create_state_shapes_in_state(Ref<GLTFState> p_state) {
	Dictionary state_json = p_state->get_json();
	Dictionary state_extensions;
	if (state_json.has("extensions")) {
		state_extensions = state_json["extensions"];
	} else {
		state_json["extensions"] = state_extensions;
	}
	Dictionary omi_physics_shape_ext;
	if (state_extensions.has("OMI_physics_shape")) {
		omi_physics_shape_ext = state_extensions["OMI_physics_shape"];
	} else {
		state_extensions["OMI_physics_shape"] = omi_physics_shape_ext;
		p_state->add_used_extension("OMI_physics_shape");
	}
	Array state_shapes;
	if (omi_physics_shape_ext.has("shapes")) {
		state_shapes = omi_physics_shape_ext["shapes"];
	} else {
		omi_physics_shape_ext["shapes"] = state_shapes;
	}
	return state_shapes;
}

Dictionary _export_node_shape(Ref<GLTFState> p_state, Ref<GLTFPhysicsShape> p_physics_shape) {
	Array state_shapes = _get_or_create_state_shapes_in_state(p_state);
	int size = state_shapes.size();
	Dictionary shape_property;
	Dictionary shape_dict = p_physics_shape->to_dictionary();
	for (int i = 0; i < size; i++) {
		Dictionary other = state_shapes[i];
		if (other == shape_dict) {
			// De-duplication: If we already have an identical shape,
			// set the shape index to the existing one and return.
			shape_property["shape"] = i;
			return shape_property;
		}
	}
	// If we don't have an identical shape, add it to the array.
	state_shapes.push_back(shape_dict);
	shape_property["shape"] = size;
	return shape_property;
}

Error GLTFDocumentExtensionPhysics::export_node(Ref<GLTFState> p_state, Ref<GLTFNode> p_gltf_node, Dictionary &r_node_json, Node *p_node) {
	Dictionary physics_body_ext;
	Ref<GLTFPhysicsBody> physics_body = p_gltf_node->get_additional_data(StringName("GLTFPhysicsBody"));
	if (physics_body.is_valid()) {
		physics_body_ext = physics_body->to_dictionary();
		Variant compound_trigger_nodes = p_gltf_node->get_additional_data(StringName("GLTFPhysicsCompoundTriggerNodes"));
		if (compound_trigger_nodes.is_array()) {
			Dictionary trigger_property = physics_body_ext.get_or_add("trigger", {});
			trigger_property["nodes"] = compound_trigger_nodes;
		}
	}
	Ref<GLTFPhysicsShape> collider_shape = p_gltf_node->get_additional_data(StringName("GLTFPhysicsColliderShape"));
	if (collider_shape.is_valid()) {
		physics_body_ext["collider"] = _export_node_shape(p_state, collider_shape);
	}
	Ref<GLTFPhysicsShape> trigger_shape = p_gltf_node->get_additional_data(StringName("GLTFPhysicsTriggerShape"));
	if (trigger_shape.is_valid()) {
		physics_body_ext["trigger"] = _export_node_shape(p_state, trigger_shape);
	}
	if (!physics_body_ext.is_empty()) {
		Dictionary node_extensions = r_node_json["extensions"];
		node_extensions["OMI_physics_body"] = physics_body_ext;
		p_state->add_used_extension("OMI_physics_body");
	}
	return OK;
}