Fix 3D moving platform logic

Same thing that was already done in 2D, applies moving platform motion
by using a call to move_and_collide that excludes the platform itself,
instead of making it part of the body motion.

Helps with handling walls and slopes correctly when the character walks
on the moving platform.

Also made some minor adjustments to the 2D version and documentation.

Co-authored-by: fabriceci <fabricecipolla@gmail.com>

doc/classes/KinematicBody.xml

@@ -95,6 +95,7 @@
 				[code]floor_max_angle[/code] is the maximum angle (in radians) where a slope is still considered a floor (or a ceiling), rather than a wall. The default value equals 45 degrees.
 				If [code]infinite_inertia[/code] is [code]true[/code], body will be able to push [RigidBody] nodes, but it won't also detect any collisions with them. If [code]false[/code], it will interact with [RigidBody] nodes like with [StaticBody].
 				Returns the [code]linear_velocity[/code] vector, rotated and/or scaled if a slide collision occurred. To get detailed information about collisions that occurred, use [method get_slide_collision].
+				When the body touches a moving platform, the platform's velocity is automatically added to the body motion. If a collision occurs due to the platform's motion, it will always be first in the slide collisions.
 			</description>
 		</method>
 		<method name="move_and_slide_with_snap">

doc/classes/KinematicBody2D.xml

@@ -93,6 +93,7 @@
 				[code]floor_max_angle[/code] is the maximum angle (in radians) where a slope is still considered a floor (or a ceiling), rather than a wall. The default value equals 45 degrees.
 				If [code]infinite_inertia[/code] is [code]true[/code], body will be able to push [RigidBody2D] nodes, but it won't also detect any collisions with them. If [code]false[/code], it will interact with [RigidBody2D] nodes like with [StaticBody2D].
 				Returns the [code]linear_velocity[/code] vector, rotated and/or scaled if a slide collision occurred. To get detailed information about collisions that occurred, use [method get_slide_collision].
+				When the body touches a moving platform, the platform's velocity is automatically added to the body motion. If a collision occurs due to the platform's motion, it will always be first in the slide collisions.
 			</description>
 		</method>
 		<method name="move_and_slide_with_snap">

doc/classes/PhysicsServer.xml

@@ -602,6 +602,8 @@
 			<argument index="2" name="motion" type="Vector3" />
 			<argument index="3" name="infinite_inertia" type="bool" />
 			<argument index="4" name="result" type="PhysicsTestMotionResult" default="null" />
+			<argument index="5" name="exclude_raycast_shapes" type="bool" default="true" />
+			<argument index="6" name="exclude" type="Array" default="[  ]" />
 			<description>
 				Returns [code]true[/code] if a collision would result from moving in the given direction from a given point in space. [PhysicsTestMotionResult] can be passed to return additional information in.
 			</description>

modules/bullet/bullet_physics_server.cpp

@@ -856,12 +856,12 @@ PhysicsDirectBodyState *BulletPhysicsServer::body_get_direct_state(RID p_body) {
 	return BulletPhysicsDirectBodyState::get_singleton(body);
 }
 
-bool BulletPhysicsServer::body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool BulletPhysicsServer::body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude) {
 	RigidBodyBullet *body = rigid_body_owner.get(p_body);
 	ERR_FAIL_COND_V(!body, false);
 	ERR_FAIL_COND_V(!body->get_space(), false);
 
-	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, r_result, p_exclude_raycast_shapes);
+	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, r_result, p_exclude_raycast_shapes, p_exclude);
 }
 
 int BulletPhysicsServer::body_test_ray_separation(RID p_body, const Transform &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, SeparationResult *r_results, int p_result_max, float p_margin) {

modules/bullet/bullet_physics_server.h

@@ -254,7 +254,7 @@ class BulletPhysicsServer : public PhysicsServer {
 	// this function only works on physics process, errors and returns null otherwise
 	virtual PhysicsDirectBodyState *body_get_direct_state(RID p_body);
 
-	virtual bool body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true);
+	virtual bool body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true, const Set<RID> &p_exclude = Set<RID>());
 	virtual int body_test_ray_separation(RID p_body, const Transform &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, SeparationResult *r_results, int p_result_max, float p_margin = 0.001);
 
 	/* SOFT BODY API */

modules/bullet/godot_result_callbacks.cpp

@@ -142,6 +142,10 @@ bool GodotKinClosestConvexResultCallback::needsCollision(btBroadphaseProxy *prox
 			if (m_self_object->has_collision_exception(gObj) || gObj->has_collision_exception(m_self_object)) {
 				return false;
 			}
+
+			if (m_exclude->has(gObj->get_self())) {
+				return false;
+			}
 		}
 		return true;
 	} else {

modules/bullet/godot_result_callbacks.h

@@ -105,11 +105,13 @@ struct GodotAllConvexResultCallback : public btCollisionWorld::ConvexResultCallb
 struct GodotKinClosestConvexResultCallback : public btCollisionWorld::ClosestConvexResultCallback {
 public:
 	const RigidBodyBullet *m_self_object;
+	const Set<RID> *m_exclude;
 	const bool m_infinite_inertia;
 
-	GodotKinClosestConvexResultCallback(const btVector3 &convexFromWorld, const btVector3 &convexToWorld, const RigidBodyBullet *p_self_object, bool p_infinite_inertia) :
+	GodotKinClosestConvexResultCallback(const btVector3 &convexFromWorld, const btVector3 &convexToWorld, const RigidBodyBullet *p_self_object, bool p_infinite_inertia, const Set<RID> *p_exclude) :
 			btCollisionWorld::ClosestConvexResultCallback(convexFromWorld, convexToWorld),
 			m_self_object(p_self_object),
+			m_exclude(p_exclude),
 			m_infinite_inertia(p_infinite_inertia) {}
 
 	virtual bool needsCollision(btBroadphaseProxy *proxy0) const;

modules/bullet/space_bullet.cpp

@@ -928,7 +928,7 @@ static Ref<SpatialMaterial> red_mat;
 static Ref<SpatialMaterial> blue_mat;
 #endif
 
-bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer::MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer::MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude) {
 #if debug_test_motion
 	/// Yes I know this is not good, but I've used it as fast debugging hack.
 	/// I'm leaving it here just for speedup the other eventual debugs
@@ -968,7 +968,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform &p_f
 	btVector3 initial_recover_motion(0, 0, 0);
 	{ /// Phase one - multi shapes depenetration using margin
 		for (int t(RECOVERING_MOVEMENT_CYCLES); 0 < t; --t) {
-			if (!recover_from_penetration(p_body, body_transform, RECOVERING_MOVEMENT_SCALE, p_infinite_inertia, initial_recover_motion)) {
+			if (!recover_from_penetration(p_body, body_transform, RECOVERING_MOVEMENT_SCALE, p_infinite_inertia, initial_recover_motion, nullptr, p_exclude)) {
 				break;
 			}
 		}
@@ -1020,7 +1020,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform &p_f
 				break;
 			}
 
-			GodotKinClosestConvexResultCallback btResult(shape_world_from.getOrigin(), shape_world_to.getOrigin(), p_body, p_infinite_inertia);
+			GodotKinClosestConvexResultCallback btResult(shape_world_from.getOrigin(), shape_world_to.getOrigin(), p_body, p_infinite_inertia, &p_exclude);
 			btResult.m_collisionFilterGroup = p_body->get_collision_layer();
 			btResult.m_collisionFilterMask = p_body->get_collision_mask();
 
@@ -1043,7 +1043,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform &p_f
 		btVector3 __rec(0, 0, 0);
 		RecoverResult r_recover_result;
 
-		has_penetration = recover_from_penetration(p_body, body_transform, 1, p_infinite_inertia, __rec, &r_recover_result);
+		has_penetration = recover_from_penetration(p_body, body_transform, 1, p_infinite_inertia, __rec, &r_recover_result, p_exclude);
 
 		// Parse results
 		if (r_result) {
@@ -1195,7 +1195,7 @@ struct RecoverPenetrationBroadPhaseCallback : public btBroadphaseAabbCallback {
 	}
 };
 
-bool SpaceBullet::recover_from_penetration(RigidBodyBullet *p_body, const btTransform &p_body_position, btScalar p_recover_movement_scale, bool p_infinite_inertia, btVector3 &r_delta_recover_movement, RecoverResult *r_recover_result) {
+bool SpaceBullet::recover_from_penetration(RigidBodyBullet *p_body, const btTransform &p_body_position, btScalar p_recover_movement_scale, bool p_infinite_inertia, btVector3 &r_delta_recover_movement, RecoverResult *r_recover_result, const Set<RID> &p_exclude) {
 	// Calculate the cumulative AABB of all shapes of the kinematic body
 	btVector3 aabb_min, aabb_max;
 	bool shapes_found = false;
@@ -1264,6 +1264,12 @@ bool SpaceBullet::recover_from_penetration(RigidBodyBullet *p_body, const btTran
 
 		for (int i = recover_broad_result.results.size() - 1; 0 <= i; --i) {
 			btCollisionObject *otherObject = recover_broad_result.results[i].collision_object;
+
+			CollisionObjectBullet *gObj = static_cast<CollisionObjectBullet *>(otherObject->getUserPointer());
+			if (p_exclude.has(gObj->get_self())) {
+				continue;
+			}
+
 			if (p_infinite_inertia && !otherObject->isStaticOrKinematicObject()) {
 				otherObject->activate(); // Force activation of hitten rigid, soft body
 				continue;

modules/bullet/space_bullet.h

@@ -185,7 +185,7 @@ class SpaceBullet : public RIDBullet {
 	real_t get_linear_damp() const { return linear_damp; }
 	real_t get_angular_damp() const { return angular_damp; }
 
-	bool test_body_motion(RigidBodyBullet *p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer::MotionResult *r_result, bool p_exclude_raycast_shapes);
+	bool test_body_motion(RigidBodyBullet *p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer::MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude = Set<RID>());
 	int test_ray_separation(RigidBodyBullet *p_body, const Transform &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, PhysicsServer::SeparationResult *r_results, int p_result_max, float p_margin);
 
 private:
@@ -213,7 +213,7 @@ class SpaceBullet : public RIDBullet {
 				local_shape_most_recovered(0) {}
 	};
 
-	bool recover_from_penetration(RigidBodyBullet *p_body, const btTransform &p_body_position, btScalar p_recover_movement_scale, bool p_infinite_inertia, btVector3 &r_delta_recover_movement, RecoverResult *r_recover_result = nullptr);
+	bool recover_from_penetration(RigidBodyBullet *p_body, const btTransform &p_body_position, btScalar p_recover_movement_scale, bool p_infinite_inertia, btVector3 &r_delta_recover_movement, RecoverResult *r_recover_result = nullptr, const Set<RID> &p_exclude = Set<RID>());
 	/// This is an API that recover a kinematic object from penetration
 	/// This allow only Convex Convex test and it always use GJK algorithm, With this API we don't benefit of Bullet special accelerated functions
 	bool RFP_convex_convex_test(const btConvexShape *p_shapeA, const btConvexShape *p_shapeB, btCollisionObject *p_objectB, int p_shapeId_A, int p_shapeId_B, const btTransform &p_transformA, const btTransform &p_transformB, btScalar p_recover_movement_scale, btVector3 &r_delta_recover_movement, RecoverResult *r_recover_result = nullptr);

scene/2d/physics_body_2d.cpp

@@ -1128,7 +1128,7 @@ Vector2 KinematicBody2D::move_and_slide(const Vector2 &p_linear_velocity, const
 	floor_normal = Vector2();
 	floor_velocity = Vector2();
 
-	if (current_floor_velocity != Vector2()) {
+	if (current_floor_velocity != Vector2() && on_floor_body.is_valid()) {
 		Collision floor_collision;
 		Set<RID> exclude;
 		exclude.insert(on_floor_body);

scene/3d/physics_body.cpp

@@ -973,14 +973,14 @@ Ref<KinematicCollision> KinematicBody::_move(const Vector3 &p_motion, bool p_inf
 	return Ref<KinematicCollision>();
 }
 
-bool KinematicBody::move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, Collision &r_collision, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding) {
+bool KinematicBody::move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, Collision &r_collision, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding, const Set<RID> &p_exclude) {
 	if (sync_to_physics) {
 		ERR_PRINT("Functions move_and_slide and move_and_collide do not work together with 'sync to physics' option. Please read the documentation.");
 	}
 
 	Transform gt = get_global_transform();
 	PhysicsServer::MotionResult result;
-	bool colliding = PhysicsServer::get_singleton()->body_test_motion(get_rid(), gt, p_motion, p_infinite_inertia, &result, p_exclude_raycast_shapes);
+	bool colliding = PhysicsServer::get_singleton()->body_test_motion(get_rid(), gt, p_motion, p_infinite_inertia, &result, p_exclude_raycast_shapes, p_exclude);
 
 	// Restore direction of motion to be along original motion,
 	// in order to avoid sliding due to recovery,
@@ -1061,8 +1061,11 @@ Vector3 KinematicBody::move_and_slide(const Vector3 &p_linear_velocity, const Ve
 		}
 	}
 
+	// Hack in order to work with calling from _process as well as from _physics_process; calling from thread is risky
+	float delta = Engine::get_singleton()->is_in_physics_frame() ? get_physics_process_delta_time() : get_process_delta_time();
+
 	Vector3 current_floor_velocity = floor_velocity;
-	if (on_floor && on_floor_body.is_valid()) {
+	if ((on_floor || on_wall) && on_floor_body.is_valid()) {
 		// This approach makes sure there is less delay between the actual body velocity and the one we saved.
 		PhysicsDirectBodyState *bs = PhysicsServer::get_singleton()->body_get_direct_state(on_floor_body);
 		if (bs) {
@@ -1072,17 +1075,26 @@ Vector3 KinematicBody::move_and_slide(const Vector3 &p_linear_velocity, const Ve
 		}
 	}
 
-	// Hack in order to work with calling from _process as well as from _physics_process; calling from thread is risky
-	Vector3 motion = (current_floor_velocity + body_velocity) * (Engine::get_singleton()->is_in_physics_frame() ? get_physics_process_delta_time() : get_process_delta_time());
-
+	colliders.clear();
 	on_floor = false;
-	on_floor_body = RID();
 	on_ceiling = false;
 	on_wall = false;
-	colliders.clear();
 	floor_normal = Vector3();
 	floor_velocity = Vector3();
 
+	if (current_floor_velocity != Vector3() && on_floor_body.is_valid()) {
+		Collision floor_collision;
+		Set<RID> exclude;
+		exclude.insert(on_floor_body);
+		if (move_and_collide(current_floor_velocity * delta, p_infinite_inertia, floor_collision, true, false, false, exclude)) {
+			colliders.push_back(floor_collision);
+			_set_collision_direction(floor_collision, up_direction, p_floor_max_angle);
+		}
+	}
+
+	on_floor_body = RID();
+	Vector3 motion = body_velocity * delta;
+
 	// No sliding on first attempt to keep floor motion stable when possible,
 	// when stop on slope is enabled.
 	bool sliding_enabled = !p_stop_on_slope;
@@ -1110,33 +1122,18 @@ Vector3 KinematicBody::move_and_slide(const Vector3 &p_linear_velocity, const Ve
 
 				colliders.push_back(collision);
 
-				if (up_direction == Vector3()) {
-					//all is a wall
-					on_wall = true;
-				} else {
-					if (Math::acos(collision.normal.dot(up_direction)) <= p_floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //floor
-
-						on_floor = true;
-						floor_normal = collision.normal;
-						on_floor_body = collision.collider_rid;
-						floor_velocity = collision.collider_vel;
-
-						if (p_stop_on_slope) {
-							if ((body_velocity_normal + up_direction).length() < 0.01) {
-								Transform gt = get_global_transform();
-								if (collision.travel.length() > margin) {
-									gt.origin -= collision.travel.slide(up_direction);
-								} else {
-									gt.origin -= collision.travel;
-								}
-								set_global_transform(gt);
-								return Vector3();
-							}
+				_set_collision_direction(collision, up_direction, p_floor_max_angle);
+
+				if (on_floor && p_stop_on_slope) {
+					if ((body_velocity_normal + up_direction).length() < 0.01) {
+						Transform gt = get_global_transform();
+						if (collision.travel.length() > margin) {
+							gt.origin -= collision.travel.slide(up_direction);
+						} else {
+							gt.origin -= collision.travel;
 						}
-					} else if (Math::acos(collision.normal.dot(-up_direction)) <= p_floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //ceiling
-						on_ceiling = true;
-					} else {
-						on_wall = true;
+						set_global_transform(gt);
+						return Vector3();
 					}
 				}
 
@@ -1162,6 +1159,11 @@ Vector3 KinematicBody::move_and_slide(const Vector3 &p_linear_velocity, const Ve
 		}
 	}
 
+	if (!on_floor && !on_wall) {
+		// Add last platform velocity when just left a moving platform.
+		return body_velocity + current_floor_velocity;
+	}
+
 	return body_velocity;
 }
 
@@ -1207,6 +1209,29 @@ Vector3 KinematicBody::move_and_slide_with_snap(const Vector3 &p_linear_velocity
 	return ret;
 }
 
+void KinematicBody::_set_collision_direction(const Collision &p_collision, const Vector3 &p_up_direction, float p_floor_max_angle) {
+	on_floor = false;
+	on_ceiling = false;
+	on_wall = false;
+	if (p_up_direction == Vector3()) {
+		//all is a wall
+		on_wall = true;
+	} else {
+		if (Math::acos(p_collision.normal.dot(p_up_direction)) <= p_floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //floor
+			on_floor = true;
+			floor_normal = p_collision.normal;
+			on_floor_body = p_collision.collider_rid;
+			floor_velocity = p_collision.collider_vel;
+		} else if (Math::acos(p_collision.normal.dot(-p_up_direction)) <= p_floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //ceiling
+			on_ceiling = true;
+		} else {
+			on_wall = true;
+			on_floor_body = p_collision.collider_rid;
+			floor_velocity = p_collision.collider_vel;
+		}
+	}
+}
+
 bool KinematicBody::is_on_floor() const {
 	return on_floor;
 }

scene/3d/physics_body.h

@@ -300,13 +300,14 @@ class KinematicBody : public PhysicsBody {
 
 	Transform last_valid_transform;
 	void _direct_state_changed(Object *p_state);
+	void _set_collision_direction(const Collision &p_collision, const Vector3 &p_up_direction, float p_floor_max_angle);
 
 protected:
 	void _notification(int p_what);
 	static void _bind_methods();
 
 public:
-	bool move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, Collision &r_collision, bool p_exclude_raycast_shapes = true, bool p_test_only = false, bool p_cancel_sliding = true);
+	bool move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, Collision &r_collision, bool p_exclude_raycast_shapes = true, bool p_test_only = false, bool p_cancel_sliding = true, const Set<RID> &p_exclude = Set<RID>());
 	bool test_move(const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia);
 
 	bool separate_raycast_shapes(bool p_infinite_inertia, Collision &r_collision);

servers/physics/physics_server_sw.cpp

@@ -860,15 +860,15 @@ bool PhysicsServerSW::body_is_ray_pickable(RID p_body) const {
 	return body->is_ray_pickable();
 }
 
-bool PhysicsServerSW::body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool PhysicsServerSW::body_test_motion(RID p_body, const Transform &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude) {
 	BodySW *body = body_owner.get(p_body);
 	ERR_FAIL_COND_V(!body, false);
 	ERR_FAIL_COND_V(!body->get_space(), false);
 	ERR_FAIL_COND_V(body->get_space()->is_locked(), false);
 
 	_update_shapes();
 
-	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, body->get_kinematic_margin(), r_result, p_exclude_raycast_shapes);
+	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, body->get_kinematic_margin(), r_result, p_exclude_raycast_shapes, p_exclude);
 }
 
 int PhysicsServerSW::body_test_ray_separation(RID p_body, const Transform &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, SeparationResult *r_results, int p_result_max, float p_margin) {