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/CharacterBody2D.xml

@@ -79,6 +79,7 @@
 				Moves the body based on [member linear_velocity]. If the body collides with another, it will slide along the other body rather than stop immediately. If the other body is a [CharacterBody2D] or [RigidBody2D], it will also be affected by the motion of the other body. You can use this to make moving and rotating platforms, or to make nodes push other nodes.
 				This method should be used in [method Node._physics_process] (or in a method called by [method Node._physics_process]), as it uses the physics step's [code]delta[/code] value automatically in calculations. Otherwise, the simulation will run at an incorrect speed.
 				Modifies [member linear_velocity] 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>
 	</methods>

doc/classes/CharacterBody3D.xml

@@ -65,6 +65,7 @@
 				Moves the body based on [member linear_velocity]. If the body collides with another, it will slide along the other body rather than stop immediately. If the other body is a [CharacterBody3D] or [RigidBody3D], it will also be affected by the motion of the other body. You can use this to make moving and rotating platforms, or to make nodes push other nodes.
 				This method should be used in [method Node._physics_process] (or in a method called by [method Node._physics_process]), as it uses the physics step's [code]delta[/code] value automatically in calculations. Otherwise, the simulation will run at an incorrect speed.
 				Modifies [member linear_velocity] 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>
 	</methods>

doc/classes/PhysicsServer3D.xml

@@ -572,6 +572,8 @@
 			<argument index="3" name="infinite_inertia" type="bool" />
 			<argument index="4" name="margin" type="float" default="0.001" />
 			<argument index="5" name="result" type="PhysicsTestMotionResult3D" default="null" />
+			<argument index="6" name="exclude_raycast_shapes" type="bool" default="true" />
+			<argument index="7" 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. Margin increases the size of the shapes involved in the collision detection. [PhysicsTestMotionResult3D] can be passed to return additional information in.
 			</description>

modules/bullet/bullet_physics_server.cpp

@@ -842,12 +842,12 @@ PhysicsDirectBodyState3D *BulletPhysicsServer3D::body_get_direct_state(RID p_bod
 	return BulletPhysicsDirectBodyState3D::get_singleton(body);
 }
 
-bool BulletPhysicsServer3D::body_test_motion(RID p_body, const Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool BulletPhysicsServer3D::body_test_motion(RID p_body, const Transform3D &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.getornull(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 BulletPhysicsServer3D::body_test_ray_separation(RID p_body, const Transform3D &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, SeparationResult *r_results, int p_result_max, real_t p_margin) {

modules/bullet/bullet_physics_server.h

@@ -253,7 +253,7 @@ class BulletPhysicsServer3D : public PhysicsServer3D {
 	// this function only works on physics process, errors and returns null otherwise
 	virtual PhysicsDirectBodyState3D *body_get_direct_state(RID p_body) override;
 
-	virtual bool body_test_motion(RID p_body, const Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true) override;
+	virtual bool body_test_motion(RID p_body, const Transform3D &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>()) override;
 	virtual int body_test_ray_separation(RID p_body, const Transform3D &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, SeparationResult *r_results, int p_result_max, real_t p_margin = 0.001) override;
 
 	/* SOFT BODY API */

modules/bullet/godot_result_callbacks.cpp

@@ -135,6 +135,10 @@ 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

@@ -100,11 +100,13 @@ 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

@@ -908,7 +908,7 @@ static Ref<StandardMaterial3D> red_mat;
 static Ref<StandardMaterial3D> blue_mat;
 #endif
 
-bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::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
@@ -948,7 +948,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform3D &p
 	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;
 			}
 		}
@@ -1000,7 +1000,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform3D &p
 				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();
 
@@ -1023,7 +1023,7 @@ bool SpaceBullet::test_body_motion(RigidBodyBullet *p_body, const Transform3D &p
 		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) {
@@ -1173,7 +1173,7 @@ 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;
@@ -1242,6 +1242,12 @@ 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

@@ -188,7 +188,7 @@ 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 Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult *r_result, bool p_exclude_raycast_shapes);
+	bool test_body_motion(RigidBodyBullet *p_body, const Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude = Set<RID>());
 	int test_ray_separation(RigidBodyBullet *p_body, const Transform3D &p_transform, bool p_infinite_inertia, Vector3 &r_recover_motion, PhysicsServer3D::SeparationResult *r_results, int p_result_max, real_t p_margin);
 
 private:
@@ -209,7 +209,7 @@ class SpaceBullet : public RIDBullet {
 		RecoverResult() {}
 	};
 
-	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

@@ -1075,7 +1075,7 @@ void CharacterBody2D::move_and_slide() {
 	floor_normal = Vector2();
 	floor_velocity = Vector2();
 
-	if (current_floor_velocity != Vector2()) {
+	if (current_floor_velocity != Vector2() && on_floor_body.is_valid()) {
 		PhysicsServer2D::MotionResult floor_result;
 		Set<RID> exclude;
 		exclude.insert(on_floor_body);

scene/2d/physics_body_2d.h

@@ -292,6 +292,8 @@ class CharacterBody2D : public PhysicsBody2D {
 
 	Ref<KinematicCollision2D> _get_slide_collision(int p_bounce);
 
+	void _set_collision_direction(const PhysicsServer2D::MotionResult &p_result);
+
 	bool separate_raycast_shapes(PhysicsServer2D::MotionResult &r_result);
 
 	void set_safe_margin(real_t p_margin);
@@ -314,7 +316,6 @@ class CharacterBody2D : public PhysicsBody2D {
 
 	const Vector2 &get_up_direction() const;
 	void set_up_direction(const Vector2 &p_up_direction);
-	void _set_collision_direction(const PhysicsServer2D::MotionResult &p_result);
 
 protected:
 	void _notification(int p_what);

scene/3d/physics_body_3d.cpp

@@ -117,9 +117,9 @@ Ref<KinematicCollision3D> PhysicsBody3D::_move(const Vector3 &p_motion, bool p_i
 	return Ref<KinematicCollision3D>();
 }
 
-bool PhysicsBody3D::move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult &r_result, real_t p_margin, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding) {
+bool PhysicsBody3D::move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult &r_result, real_t p_margin, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding, const Set<RID> &p_exclude) {
 	Transform3D gt = get_global_transform();
-	bool colliding = PhysicsServer3D::get_singleton()->body_test_motion(get_rid(), gt, p_motion, p_infinite_inertia, p_margin, &r_result, p_exclude_raycast_shapes);
+	bool colliding = PhysicsServer3D::get_singleton()->body_test_motion(get_rid(), gt, p_motion, p_infinite_inertia, p_margin, &r_result, p_exclude_raycast_shapes, p_exclude);
 
 	// Restore direction of motion to be along original motion,
 	// in order to avoid sliding due to recovery,
@@ -1090,14 +1090,17 @@ void CharacterBody3D::move_and_slide() {
 
 	bool was_on_floor = on_floor;
 
+	// 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();
+
 	for (int i = 0; i < 3; i++) {
 		if (locked_axis & (1 << i)) {
 			linear_velocity[i] = 0.0;
 		}
 	}
 
 	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
 		PhysicsDirectBodyState3D *bs = PhysicsServer3D::get_singleton()->body_get_direct_state(on_floor_body);
 		if (bs) {
@@ -1107,20 +1110,30 @@ void CharacterBody3D::move_and_slide() {
 		}
 	}
 
-	// Hack in order to work with calling from _process as well as from _physics_process; calling from thread is risky
-	Vector3 motion = (floor_velocity + linear_velocity) * (Engine::get_singleton()->is_in_physics_frame() ? get_physics_process_delta_time() : get_process_delta_time());
-
+	motion_results.clear();
 	on_floor = false;
-	on_floor_body = RID();
 	on_ceiling = false;
 	on_wall = false;
-	motion_results.clear();
 	floor_normal = Vector3();
 	floor_velocity = Vector3();
 
+	if (current_floor_velocity != Vector3() && on_floor_body.is_valid()) {
+		PhysicsServer3D::MotionResult floor_result;
+		Set<RID> exclude;
+		exclude.insert(on_floor_body);
+		if (move_and_collide(current_floor_velocity * delta, infinite_inertia, floor_result, true, false, false, false, exclude)) {
+			motion_results.push_back(floor_result);
+			_set_collision_direction(floor_result);
+		}
+	}
+
+	on_floor_body = RID();
+	Vector3 motion = linear_velocity * delta;
+
 	// No sliding on first attempt to keep floor motion stable when possible,
 	// when stop on slope is enabled.
 	bool sliding_enabled = !stop_on_slope;
+
 	for (int iteration = 0; iteration < max_slides; ++iteration) {
 		PhysicsServer3D::MotionResult result;
 		bool found_collision = false;
@@ -1144,35 +1157,19 @@ void CharacterBody3D::move_and_slide() {
 				found_collision = true;
 
 				motion_results.push_back(result);
-
-				if (up_direction == Vector3()) {
-					//all is a wall
-					on_wall = true;
-				} else {
-					if (Math::acos(result.collision_normal.dot(up_direction)) <= floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //floor
-
-						on_floor = true;
-						floor_normal = result.collision_normal;
-						on_floor_body = result.collider;
-						floor_velocity = result.collider_velocity;
-
-						if (stop_on_slope) {
-							if ((body_velocity_normal + up_direction).length() < 0.01) {
-								Transform3D gt = get_global_transform();
-								if (result.motion.length() > margin) {
-									gt.origin -= result.motion.slide(up_direction);
-								} else {
-									gt.origin -= result.motion;
-								}
-								set_global_transform(gt);
-								linear_velocity = Vector3();
-								return;
-							}
+				_set_collision_direction(result);
+
+				if (on_floor && stop_on_slope) {
+					if ((body_velocity_normal + up_direction).length() < 0.01) {
+						Transform3D gt = get_global_transform();
+						if (result.motion.length() > margin) {
+							gt.origin -= result.motion.slide(up_direction);
+						} else {
+							gt.origin -= result.motion;
 						}
-					} else if (Math::acos(result.collision_normal.dot(-up_direction)) <= floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //ceiling
-						on_ceiling = true;
-					} else {
-						on_wall = true;
+						set_global_transform(gt);
+						linear_velocity = Vector3();
+						return;
 					}
 				}
 
@@ -1198,6 +1195,11 @@ void CharacterBody3D::move_and_slide() {
 		}
 	}
 
+	if (!on_floor && !on_wall) {
+		// Add last platform velocity when just left a moving platform.
+		linear_velocity += current_floor_velocity;
+	}
+
 	if (!was_on_floor || snap == Vector3()) {
 		return;
 	}
@@ -1233,6 +1235,29 @@ void CharacterBody3D::move_and_slide() {
 	}
 }
 
+void CharacterBody3D::_set_collision_direction(const PhysicsServer3D::MotionResult &p_result) {
+	on_floor = false;
+	on_ceiling = false;
+	on_wall = false;
+	if (up_direction == Vector3()) {
+		//all is a wall
+		on_wall = true;
+	} else {
+		if (Math::acos(p_result.collision_normal.dot(up_direction)) <= floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //floor
+			on_floor = true;
+			floor_normal = p_result.collision_normal;
+			on_floor_body = p_result.collider;
+			floor_velocity = p_result.collider_velocity;
+		} else if (Math::acos(p_result.collision_normal.dot(-up_direction)) <= floor_max_angle + FLOOR_ANGLE_THRESHOLD) { //ceiling
+			on_ceiling = true;
+		} else {
+			on_wall = true;
+			on_floor_body = p_result.collider;
+			floor_velocity = p_result.collider_velocity;
+		}
+	}
+}
+
 bool CharacterBody3D::separate_raycast_shapes(PhysicsServer3D::MotionResult &r_result) {
 	PhysicsServer3D::SeparationResult sep_res[8]; //max 8 rays
 

scene/3d/physics_body_3d.h

@@ -53,7 +53,7 @@ class PhysicsBody3D : public CollisionObject3D {
 	Ref<KinematicCollision3D> _move(const Vector3 &p_motion, bool p_infinite_inertia = true, bool p_exclude_raycast_shapes = true, bool p_test_only = false, real_t p_margin = 0.001);
 
 public:
-	bool move_and_collide(const Vector3 &p_motion, bool p_infinite_inertia, PhysicsServer3D::MotionResult &r_result, real_t p_margin, 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, PhysicsServer3D::MotionResult &r_result, real_t p_margin, 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 Transform3D &p_from, const Vector3 &p_motion, bool p_infinite_inertia = true, bool p_exclude_raycast_shapes = true, const Ref<KinematicCollision3D> &r_collision = Ref<KinematicCollision3D>(), real_t p_margin = 0.001);
 
 	void set_axis_lock(PhysicsServer3D::BodyAxis p_axis, bool p_lock);
@@ -298,6 +298,8 @@ class CharacterBody3D : public PhysicsBody3D {
 
 	Ref<KinematicCollision3D> _get_slide_collision(int p_bounce);
 
+	void _set_collision_direction(const PhysicsServer3D::MotionResult &p_result);
+
 	bool separate_raycast_shapes(PhysicsServer3D::MotionResult &r_result);
 
 	void set_safe_margin(real_t p_margin);