Fixing 2D moving platform logic

Fixing by applying the movement in two steps, first the platform
movement, and then the body movement. Plus, add the platform movement
when we are on_wall.

10 files changed, 93 insertions, 50 deletions

diff --git a/doc/classes/PhysicsServer2D.xml b/doc/classes/PhysicsServer2D.xml
index 67b27b174f..b492ddaa25 100644
--- a/doc/classes/PhysicsServer2D.xml
+++ b/doc/classes/PhysicsServer2D.xml
@@ -820,6 +820,10 @@
 			</argument>
 			<argument index="5" name="result" type="PhysicsTestMotionResult2D" default="null">
 			</argument>
+			<argument index="6" name="exclude_raycast_shapes" type="bool" default="true">
+			</argument>
+			<argument index="7" name="exclude" type="Array" default="[]">
+			</argument>
 			<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. [PhysicsTestMotionResult2D] can be passed to return additional information in.
 			</description>
diff --git a/scene/2d/physics_body_2d.cpp b/scene/2d/physics_body_2d.cpp
index 80aa99bf5e..b68f0312fc 100644
--- a/scene/2d/physics_body_2d.cpp
+++ b/scene/2d/physics_body_2d.cpp
@@ -76,12 +76,12 @@ Ref<KinematicCollision2D> PhysicsBody2D::_move(const Vector2 &p_motion, bool p_i
 	return Ref<KinematicCollision2D>();
 }
 
-bool PhysicsBody2D::move_and_collide(const Vector2 &p_motion, bool p_infinite_inertia, PhysicsServer2D::MotionResult &r_result, real_t p_margin, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding) {
+bool PhysicsBody2D::move_and_collide(const Vector2 &p_motion, bool p_infinite_inertia, PhysicsServer2D::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) {
 	if (is_only_update_transform_changes_enabled()) {
 		ERR_PRINT("Move functions do not work together with 'sync to physics' option. Please read the documentation.");
 	}
 	Transform2D gt = get_global_transform();
-	bool colliding = PhysicsServer2D::get_singleton()->body_test_motion(get_rid(), gt, p_motion, p_infinite_inertia, p_margin, &r_result, p_exclude_raycast_shapes);
+	bool colliding = PhysicsServer2D::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,
@@ -960,11 +960,14 @@ void RigidBody2D::_reload_physics_characteristics() {
 
 void CharacterBody2D::move_and_slide() {
 	Vector2 body_velocity_normal = linear_velocity.normalized();
-
 	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();
+
 	Vector2 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
 		PhysicsDirectBodyState2D *bs = PhysicsServer2D::get_singleton()->body_get_direct_state(on_floor_body);
 		if (bs) {
@@ -972,20 +975,30 @@ void CharacterBody2D::move_and_slide() {
 		}
 	}
 
-	// Hack in order to work with calling from _process as well as from _physics_process; calling from thread is risky
-	Vector2 motion = (current_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 = Vector2();
 	floor_velocity = Vector2();
 
+	if (current_floor_velocity != Vector2()) {
+		PhysicsServer2D::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();
+	Vector2 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) {
 		PhysicsServer2D::MotionResult result;
 		bool found_collision = false;
@@ -1009,35 +1022,19 @@ void CharacterBody2D::move_and_slide() {
 				found_collision = true;
 
 				motion_results.push_back(result);
-
-				if (up_direction == Vector2()) {
-					//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) {
-								Transform2D gt = get_global_transform();
-								if (result.motion.length() > margin) {
-									gt.elements[2] -= result.motion.slide(up_direction);
-								} else {
-									gt.elements[2] -= result.motion;
-								}
-								set_global_transform(gt);
-								linear_velocity = Vector2();
-								return;
-							}
+				_set_collision_direction(result);
+
+				if (on_floor && stop_on_slope) {
+					if ((body_velocity_normal + up_direction).length() < 0.01) {
+						Transform2D gt = get_global_transform();
+						if (result.motion.length() > margin) {
+							gt.elements[2] -= result.motion.slide(up_direction);
+						} else {
+							gt.elements[2] -= 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 = Vector2();
+						return;
 					}
 				}
 
@@ -1057,6 +1054,11 @@ void CharacterBody2D::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 == Vector2()) {
 		return;
 	}
@@ -1093,6 +1095,29 @@ void CharacterBody2D::move_and_slide() {
 	}
 }
 
+void CharacterBody2D::_set_collision_direction(const PhysicsServer2D::MotionResult &p_result) {
+	on_floor = false;
+	on_ceiling = false;
+	on_wall = false;
+	if (up_direction == Vector2()) {
+		//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 CharacterBody2D::separate_raycast_shapes(PhysicsServer2D::MotionResult &r_result) {
 	PhysicsServer2D::SeparationResult sep_res[8]; //max 8 rays
 
diff --git a/scene/2d/physics_body_2d.h b/scene/2d/physics_body_2d.h
index 5a5417eaf3..52e432f005 100644
--- a/scene/2d/physics_body_2d.h
+++ b/scene/2d/physics_body_2d.h
@@ -50,7 +50,7 @@ protected:
 	Ref<KinematicCollision2D> _move(const Vector2 &p_motion, bool p_infinite_inertia = true, bool p_exclude_raycast_shapes = true, bool p_test_only = false, real_t p_margin = 0.08);
 
 public:
-	bool move_and_collide(const Vector2 &p_motion, bool p_infinite_inertia, PhysicsServer2D::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 Vector2 &p_motion, bool p_infinite_inertia, PhysicsServer2D::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 Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia = true, bool p_exclude_raycast_shapes = true, const Ref<KinematicCollision2D> &r_collision = Ref<KinematicCollision2D>(), real_t p_margin = 0.08);
 
 	TypedArray<PhysicsBody2D> get_collision_exceptions();
@@ -308,6 +308,7 @@ private:
 
 	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);
diff --git a/servers/physics_2d/physics_server_2d_sw.cpp b/servers/physics_2d/physics_server_2d_sw.cpp
index 155dda4394..467c664302 100644
--- a/servers/physics_2d/physics_server_2d_sw.cpp
+++ b/servers/physics_2d/physics_server_2d_sw.cpp
@@ -946,7 +946,7 @@ void PhysicsServer2DSW::body_set_pickable(RID p_body, bool p_pickable) {
 	body->set_pickable(p_pickable);
 }
 
-bool PhysicsServer2DSW::body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool PhysicsServer2DSW::body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude) {
 	Body2DSW *body = body_owner.getornull(p_body);
 	ERR_FAIL_COND_V(!body, false);
 	ERR_FAIL_COND_V(!body->get_space(), false);
@@ -954,7 +954,7 @@ bool PhysicsServer2DSW::body_test_motion(RID p_body, const Transform2D &p_from,
 
 	_update_shapes();
 
-	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, p_margin, r_result, p_exclude_raycast_shapes);
+	return body->get_space()->test_body_motion(body, p_from, p_motion, p_infinite_inertia, p_margin, r_result, p_exclude_raycast_shapes, p_exclude);
 }
 
 int PhysicsServer2DSW::body_test_ray_separation(RID p_body, const Transform2D &p_transform, bool p_infinite_inertia, Vector2 &r_recover_motion, SeparationResult *r_results, int p_result_max, real_t p_margin) {
diff --git a/servers/physics_2d/physics_server_2d_sw.h b/servers/physics_2d/physics_server_2d_sw.h
index 5002bf5fc8..f40b5a7c42 100644
--- a/servers/physics_2d/physics_server_2d_sw.h
+++ b/servers/physics_2d/physics_server_2d_sw.h
@@ -247,7 +247,7 @@ public:
 
 	virtual void body_set_pickable(RID p_body, bool p_pickable) override;
 
-	virtual bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true) override;
+	virtual bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, 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 Transform2D &p_transform, bool p_infinite_inertia, Vector2 &r_recover_motion, SeparationResult *r_results, int p_result_max, real_t p_margin = 0.08) override;
 
 	// this function only works on physics process, errors and returns null otherwise
diff --git a/servers/physics_2d/physics_server_2d_wrap_mt.h b/servers/physics_2d/physics_server_2d_wrap_mt.h
index a8f7ff3393..fb7235c031 100644
--- a/servers/physics_2d/physics_server_2d_wrap_mt.h
+++ b/servers/physics_2d/physics_server_2d_wrap_mt.h
@@ -253,9 +253,9 @@ public:
 
 	FUNC2(body_set_pickable, RID, bool);
 
-	bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true) override {
+	bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true, const Set<RID> &p_exclude = Set<RID>()) override {
 		ERR_FAIL_COND_V(main_thread != Thread::get_caller_id(), false);
-		return physics_2d_server->body_test_motion(p_body, p_from, p_motion, p_infinite_inertia, p_margin, r_result, p_exclude_raycast_shapes);
+		return physics_2d_server->body_test_motion(p_body, p_from, p_motion, p_infinite_inertia, p_margin, r_result, p_exclude_raycast_shapes, p_exclude);
 	}
 
 	int body_test_ray_separation(RID p_body, const Transform2D &p_transform, bool p_infinite_inertia, Vector2 &r_recover_motion, SeparationResult *r_results, int p_result_max, real_t p_margin = 0.08) override {
diff --git a/servers/physics_2d/space_2d_sw.cpp b/servers/physics_2d/space_2d_sw.cpp
index cbde7144b7..82da5774db 100644
--- a/servers/physics_2d/space_2d_sw.cpp
+++ b/servers/physics_2d/space_2d_sw.cpp
@@ -709,7 +709,7 @@ int Space2DSW::test_body_ray_separation(Body2DSW *p_body, const Transform2D &p_t
 	return rays_found;
 }
 
-bool Space2DSW::test_body_motion(Body2DSW *p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, PhysicsServer2D::MotionResult *r_result, bool p_exclude_raycast_shapes) {
+bool Space2DSW::test_body_motion(Body2DSW *p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, PhysicsServer2D::MotionResult *r_result, bool p_exclude_raycast_shapes, const Set<RID> &p_exclude) {
 	//give me back regular physics engine logic
 	//this is madness
 	//and most people using this function will think
@@ -801,6 +801,9 @@ bool Space2DSW::test_body_motion(Body2DSW *p_body, const Transform2D &p_from, co
 				Transform2D body_shape_xform = body_transform * p_body->get_shape_transform(j);
 				for (int i = 0; i < amount; i++) {
 					const CollisionObject2DSW *col_obj = intersection_query_results[i];
+					if (p_exclude.has(col_obj->get_self())) {
+						continue;
+					}
 					int shape_idx = intersection_query_subindex_results[i];
 
 					if (CollisionObject2DSW::TYPE_BODY == col_obj->get_type()) {
@@ -930,6 +933,9 @@ bool Space2DSW::test_body_motion(Body2DSW *p_body, const Transform2D &p_from, co
 
 			for (int i = 0; i < amount; i++) {
 				const CollisionObject2DSW *col_obj = intersection_query_results[i];
+				if (p_exclude.has(col_obj->get_self())) {
+					continue;
+				}
 				int col_shape_idx = intersection_query_subindex_results[i];
 				Shape2DSW *against_shape = col_obj->get_shape(col_shape_idx);
 
@@ -1086,6 +1092,9 @@ bool Space2DSW::test_body_motion(Body2DSW *p_body, const Transform2D &p_from, co
 
 			for (int i = 0; i < amount; i++) {
 				const CollisionObject2DSW *col_obj = intersection_query_results[i];
+				if (p_exclude.has(col_obj->get_self())) {
+					continue;
+				}
 				int shape_idx = intersection_query_subindex_results[i];
 
 				if (CollisionObject2DSW::TYPE_BODY == col_obj->get_type()) {
diff --git a/servers/physics_2d/space_2d_sw.h b/servers/physics_2d/space_2d_sw.h
index 4d737d622f..f7224e4661 100644
--- a/servers/physics_2d/space_2d_sw.h
+++ b/servers/physics_2d/space_2d_sw.h
@@ -183,7 +183,7 @@ public:
 
 	int get_collision_pairs() const { return collision_pairs; }
 
-	bool test_body_motion(Body2DSW *p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, PhysicsServer2D::MotionResult *r_result, bool p_exclude_raycast_shapes = true);
+	bool test_body_motion(Body2DSW *p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, PhysicsServer2D::MotionResult *r_result, bool p_exclude_raycast_shapes = true, const Set<RID> &p_exclude = Set<RID>());
 	int test_body_ray_separation(Body2DSW *p_body, const Transform2D &p_transform, bool p_infinite_inertia, Vector2 &r_recover_motion, PhysicsServer2D::SeparationResult *r_results, int p_result_max, real_t p_margin);
 
 	void set_debug_contacts(int p_amount) { contact_debug.resize(p_amount); }
diff --git a/servers/physics_server_2d.cpp b/servers/physics_server_2d.cpp
index ec0ff57a5e..e8272f377e 100644
--- a/servers/physics_server_2d.cpp
+++ b/servers/physics_server_2d.cpp
@@ -498,12 +498,16 @@ void PhysicsTestMotionResult2D::_bind_methods() {
 
 ///////////////////////////////////////
 
-bool PhysicsServer2D::_body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, const Ref<PhysicsTestMotionResult2D> &p_result) {
+bool PhysicsServer2D::_body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin, const Ref<PhysicsTestMotionResult2D> &p_result, bool p_exclude_raycast_shapes, const Vector<RID> &p_exclude) {
 	MotionResult *r = nullptr;
 	if (p_result.is_valid()) {
 		r = p_result->get_result_ptr();
 	}
-	return body_test_motion(p_body, p_from, p_motion, p_infinite_inertia, p_margin, r);
+	Set<RID> exclude;
+	for (int i = 0; i < p_exclude.size(); i++) {
+		exclude.insert(p_exclude[i]);
+	}
+	return body_test_motion(p_body, p_from, p_motion, p_infinite_inertia, p_margin, r, p_exclude_raycast_shapes, exclude);
 }
 
 void PhysicsServer2D::_bind_methods() {
@@ -630,7 +634,7 @@ void PhysicsServer2D::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("body_set_force_integration_callback", "body", "callable", "userdata"), &PhysicsServer2D::body_set_force_integration_callback, DEFVAL(Variant()));
 
-	ClassDB::bind_method(D_METHOD("body_test_motion", "body", "from", "motion", "infinite_inertia", "margin", "result"), &PhysicsServer2D::_body_test_motion, DEFVAL(0.08), DEFVAL(Variant()));
+	ClassDB::bind_method(D_METHOD("body_test_motion", "body", "from", "motion", "infinite_inertia", "margin", "result", "exclude_raycast_shapes", "exclude"), &PhysicsServer2D::_body_test_motion, DEFVAL(0.08), DEFVAL(Variant()), DEFVAL(true), DEFVAL(Array()));
 
 	ClassDB::bind_method(D_METHOD("body_get_direct_state", "body"), &PhysicsServer2D::body_get_direct_state);
 
diff --git a/servers/physics_server_2d.h b/servers/physics_server_2d.h
index e2bff2975e..8542b54838 100644
--- a/servers/physics_server_2d.h
+++ b/servers/physics_server_2d.h
@@ -208,7 +208,7 @@ class PhysicsServer2D : public Object {
 
 	static PhysicsServer2D *singleton;
 
-	virtual bool _body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, const Ref<PhysicsTestMotionResult2D> &p_result = Ref<PhysicsTestMotionResult2D>());
+	virtual bool _body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, const Ref<PhysicsTestMotionResult2D> &p_result = Ref<PhysicsTestMotionResult2D>(), bool p_exclude_raycast_shapes = true, const Vector<RID> &p_exclude = Vector<RID>());
 
 protected:
 	static void _bind_methods();
@@ -481,7 +481,7 @@ public:
 		Variant collider_metadata;
 	};
 
-	virtual bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true) = 0;
+	virtual bool body_test_motion(RID p_body, const Transform2D &p_from, const Vector2 &p_motion, bool p_infinite_inertia, real_t p_margin = 0.08, MotionResult *r_result = nullptr, bool p_exclude_raycast_shapes = true, const Set<RID> &p_exclude = Set<RID>()) = 0;
 
 	struct SeparationResult {
 		real_t collision_depth;