From ecfbb0fd28946e5f7f60073e8fb4b84572e03bab Mon Sep 17 00:00:00 2001
From: asheraryam <asheraryam@gmail.com>
Date: Thu, 30 Apr 2020 09:41:22 +0300
Subject: [PATCH] Expose creating multiple-convex-collision static bodies to
 GDScript

---
 doc/classes/MeshInstance3D.xml |  7 +++++++
 scene/3d/mesh_instance_3d.cpp  | 37 ++++++++++++++++++++++++++++++++++
 scene/3d/mesh_instance_3d.h    |  3 +++
 3 files changed, 47 insertions(+)

diff --git a/doc/classes/MeshInstance3D.xml b/doc/classes/MeshInstance3D.xml
index e1a6cf44a74..b015a21d67c 100644
--- a/doc/classes/MeshInstance3D.xml
+++ b/doc/classes/MeshInstance3D.xml
@@ -20,6 +20,13 @@
 				This helper creates a [StaticBody3D] child node with a [ConvexPolygonShape3D] collision shape calculated from the mesh geometry. It's mainly used for testing.
 			</description>
 		</method>
+		<method name="create_multiple_convex_collisions">
+			<return type="void">
+			</return>
+			<description>
+				This helper creates a [StaticBody3D] child node with multiple [ConvexPolygonShape3D] collision shapes calculated from the mesh geometry via convex decomposition. It's mainly used for testing.
+			</description>
+		</method>
 		<method name="create_debug_tangents">
 			<return type="void">
 			</return>
diff --git a/scene/3d/mesh_instance_3d.cpp b/scene/3d/mesh_instance_3d.cpp
index 7623ede0fca..99fa8f1f3e7 100644
--- a/scene/3d/mesh_instance_3d.cpp
+++ b/scene/3d/mesh_instance_3d.cpp
@@ -271,6 +271,41 @@ void MeshInstance3D::create_convex_collision() {
 	}
 }
 
+Node *MeshInstance3D::create_multiple_convex_collisions_node() {
+	if (mesh.is_null()) {
+		return nullptr;
+	}
+
+	Vector<Ref<Shape3D>> shapes = mesh->convex_decompose();
+	if (!shapes.size()) {
+		return nullptr;
+	}
+
+	StaticBody3D *static_body = memnew(StaticBody3D);
+	for (int i = 0; i < shapes.size(); i++) {
+		CollisionShape3D *cshape = memnew(CollisionShape3D);
+		cshape->set_shape(shapes[i]);
+		static_body->add_child(cshape);
+	}
+	return static_body;
+}
+
+void MeshInstance3D::create_multiple_convex_collisions() {
+	StaticBody3D *static_body = Object::cast_to<StaticBody3D>(create_multiple_convex_collisions_node());
+	ERR_FAIL_COND(!static_body);
+	static_body->set_name(String(get_name()) + "_col");
+
+	add_child(static_body);
+	if (get_owner()) {
+		static_body->set_owner(get_owner());
+		int count = static_body->get_child_count();
+		for (int i = 0; i < count; i++) {
+			CollisionShape3D *cshape = Object::cast_to<CollisionShape3D>(static_body->get_child(i));
+			cshape->set_owner(get_owner());
+		}
+	}
+}
+
 void MeshInstance3D::_notification(int p_what) {
 	if (p_what == NOTIFICATION_ENTER_TREE) {
 		_resolve_skeleton_path();
@@ -417,6 +452,8 @@ void MeshInstance3D::_bind_methods() {
 	ClassDB::set_method_flags("MeshInstance3D", "create_trimesh_collision", METHOD_FLAGS_DEFAULT);
 	ClassDB::bind_method(D_METHOD("create_convex_collision"), &MeshInstance3D::create_convex_collision);
 	ClassDB::set_method_flags("MeshInstance3D", "create_convex_collision", METHOD_FLAGS_DEFAULT);
+	ClassDB::bind_method(D_METHOD("create_multiple_convex_collisions"), &MeshInstance3D::create_multiple_convex_collisions);
+	ClassDB::set_method_flags("MeshInstance3D", "create_multiple_convex_collisions", METHOD_FLAGS_DEFAULT);
 
 	ClassDB::bind_method(D_METHOD("create_debug_tangents"), &MeshInstance3D::create_debug_tangents);
 	ClassDB::set_method_flags("MeshInstance3D", "create_debug_tangents", METHOD_FLAGS_DEFAULT | METHOD_FLAG_EDITOR);
diff --git a/scene/3d/mesh_instance_3d.h b/scene/3d/mesh_instance_3d.h
index 8aec2273377..9dea5804e08 100644
--- a/scene/3d/mesh_instance_3d.h
+++ b/scene/3d/mesh_instance_3d.h
@@ -86,6 +86,9 @@ public:
 	Node *create_convex_collision_node();
 	void create_convex_collision();
 
+	Node *create_multiple_convex_collisions_node();
+	void create_multiple_convex_collisions();
+
 	void create_debug_tangents();
 
 	virtual AABB get_aabb() const override;