Merge pull request #48332 from TokageItLab/implement-ping-pong

4 files changed, 380 insertions, 197 deletions

diff --git a/scene/resources/animation.cpp b/scene/resources/animation.cpp
index b4eec2530b..4382674470 100644
--- a/scene/resources/animation.cpp
+++ b/scene/resources/animation.cpp
@@ -309,8 +309,8 @@ bool Animation::_get(const StringName &p_name, Variant &r_ret) const {
 
 	if (name == "length") {
 		r_ret = length;
-	} else if (name == "loop") {
-		r_ret = loop;
+	} else if (name == "loop_mode") {
+		r_ret = loop_mode;
 	} else if (name == "step") {
 		r_ret = step;
 	} else if (name.begins_with("tracks/")) {
@@ -1413,7 +1413,7 @@ void Animation::track_set_key_transition(int p_track, int p_key_idx, real_t p_tr
 }
 
 template <class K>
-int Animation::_find(const Vector<K> &p_keys, double p_time) const {
+int Animation::_find(const Vector<K> &p_keys, double p_time, bool p_backward) const {
 	int len = p_keys.size();
 	if (len == 0) {
 		return -2;
@@ -1443,8 +1443,14 @@ int Animation::_find(const Vector<K> &p_keys, double p_time) const {
 		}
 	}
 
-	if (keys[middle].time > p_time) {
-		middle--;
+	if (!p_backward) {
+		if (keys[middle].time > p_time) {
+			middle--;
+		}
+	} else {
+		if (keys[middle].time < p_time) {
+			middle++;
+		}
 	}
 
 	return middle;
@@ -1585,7 +1591,7 @@ real_t Animation::_cubic_interpolate(const real_t &p_pre_a, const real_t &p_a, c
 }
 
 template <class T>
-T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, InterpolationType p_interp, bool p_loop_wrap, bool *p_ok) const {
+T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, InterpolationType p_interp, bool p_loop_wrap, bool *p_ok, bool p_backward) const {
 	int len = _find(p_keys, length) + 1; // try to find last key (there may be more past the end)
 
 	if (len <= 0) {
@@ -1603,7 +1609,7 @@ T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, Interpol
 		return p_keys[0].value;
 	}
 
-	int idx = _find(p_keys, p_time);
+	int idx = _find(p_keys, p_time, p_backward);
 
 	ERR_FAIL_COND_V(idx == -2, T());
 
@@ -1612,24 +1618,42 @@ T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, Interpol
 	real_t c = 0.0;
 	// prepare for all cases of interpolation
 
-	if (loop && p_loop_wrap) {
+	if ((loop_mode == LOOP_LINEAR || loop_mode == LOOP_PINGPONG) && p_loop_wrap) {
 		// loop
-		if (idx >= 0) {
-			if ((idx + 1) < len) {
-				next = idx + 1;
-				real_t delta = p_keys[next].time - p_keys[idx].time;
-				real_t from = p_time - p_keys[idx].time;
-
-				if (Math::is_zero_approx(delta)) {
-					c = 0;
+		if (!p_backward) {
+			// no backward
+			if (idx >= 0) {
+				if (idx < len - 1) {
+					next = idx + 1;
+					real_t delta = p_keys[next].time - p_keys[idx].time;
+					real_t from = p_time - p_keys[idx].time;
+
+					if (Math::is_zero_approx(delta)) {
+						c = 0;
+					} else {
+						c = from / delta;
+					}
 				} else {
-					c = from / delta;
+					next = 0;
+					real_t delta = (length - p_keys[idx].time) + p_keys[next].time;
+					real_t from = p_time - p_keys[idx].time;
+
+					if (Math::is_zero_approx(delta)) {
+						c = 0;
+					} else {
+						c = from / delta;
+					}
 				}
-
 			} else {
+				// on loop, behind first key
+				idx = len - 1;
 				next = 0;
-				real_t delta = (length - p_keys[idx].time) + p_keys[next].time;
-				real_t from = p_time - p_keys[idx].time;
+				real_t endtime = (length - p_keys[idx].time);
+				if (endtime < 0) { // may be keys past the end
+					endtime = 0;
+				}
+				real_t delta = endtime + p_keys[next].time;
+				real_t from = endtime + p_time;
 
 				if (Math::is_zero_approx(delta)) {
 					c = 0;
@@ -1637,49 +1661,81 @@ T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, Interpol
 					c = from / delta;
 				}
 			}
-
 		} else {
-			// on loop, behind first key
-			idx = len - 1;
-			next = 0;
-			real_t endtime = (length - p_keys[idx].time);
-			if (endtime < 0) { // may be keys past the end
-				endtime = 0;
-			}
-			real_t delta = endtime + p_keys[next].time;
-			real_t from = endtime + p_time;
-
-			if (Math::is_zero_approx(delta)) {
-				c = 0;
+			// backward
+			if (idx <= len - 1) {
+				if (idx > 0) {
+					next = idx - 1;
+					real_t delta = (length - p_keys[next].time) - (length - p_keys[idx].time);
+					real_t from = (length - p_time) - (length - p_keys[idx].time);
+
+					if (Math::is_zero_approx(delta))
+						c = 0;
+					else
+						c = from / delta;
+				} else {
+					next = len - 1;
+					real_t delta = p_keys[idx].time + (length - p_keys[next].time);
+					real_t from = (length - p_time) - (length - p_keys[idx].time);
+
+					if (Math::is_zero_approx(delta))
+						c = 0;
+					else
+						c = from / delta;
+				}
 			} else {
-				c = from / delta;
+				// on loop, in front of last key
+				idx = 0;
+				next = len - 1;
+				real_t endtime = p_keys[idx].time;
+				if (endtime > length) // may be keys past the end
+					endtime = length;
+				real_t delta = p_keys[next].time - endtime;
+				real_t from = p_time - endtime;
+
+				if (Math::is_zero_approx(delta))
+					c = 0;
+				else
+					c = from / delta;
 			}
 		}
-
 	} else { // no loop
-
-		if (idx >= 0) {
-			if ((idx + 1) < len) {
-				next = idx + 1;
-				real_t delta = p_keys[next].time - p_keys[idx].time;
-				real_t from = p_time - p_keys[idx].time;
-
-				if (Math::is_zero_approx(delta)) {
-					c = 0;
+		if (!p_backward) {
+			if (idx >= 0) {
+				if (idx < len - 1) {
+					next = idx + 1;
+					real_t delta = p_keys[next].time - p_keys[idx].time;
+					real_t from = p_time - p_keys[idx].time;
+
+					if (Math::is_zero_approx(delta)) {
+						c = 0;
+					} else {
+						c = from / delta;
+					}
 				} else {
-					c = from / delta;
+					next = idx;
 				}
-
 			} else {
-				next = idx;
+				idx = next = 0;
 			}
-
 		} else {
-			// only allow extending first key to anim start if looping
-			if (loop) {
-				idx = next = 0;
+			if (idx <= len - 1) {
+				if (idx > 0) {
+					next = idx - 1;
+					real_t delta = (length - p_keys[next].time) - (length - p_keys[idx].time);
+					real_t from = (length - p_time) - (length - p_keys[idx].time);
+
+					if (Math::is_zero_approx(delta)) {
+						c = 0;
+					} else {
+						c = from / delta;
+					}
+
+				} else {
+					next = idx;
+				}
 			} else {
-				result = false;
+				idx = next = len - 1;
 			}
 		}
 	}
@@ -1729,7 +1785,7 @@ T Animation::_interpolate(const Vector<TKey<T>> &p_keys, double p_time, Interpol
 	// do a barrel roll
 }
 
-Error Animation::transform_track_interpolate(int p_track, double p_time, Vector3 *r_loc, Quaternion *r_rot, Vector3 *r_scale) const {
+Error Animation::transform_track_interpolate(int p_track, double p_time, Vector3 *r_loc, Quaternion *r_rot, Vector3 *r_scale, bool p_backward) const {
 	ERR_FAIL_INDEX_V(p_track, tracks.size(), ERR_INVALID_PARAMETER);
 	Track *t = tracks[p_track];
 	ERR_FAIL_COND_V(t->type != TYPE_TRANSFORM3D, ERR_INVALID_PARAMETER);
@@ -1738,7 +1794,7 @@ Error Animation::transform_track_interpolate(int p_track, double p_time, Vector3
 
 	bool ok = false;
 
-	TransformKey tk = _interpolate(tt->transforms, p_time, tt->interpolation, tt->loop_wrap, &ok);
+	TransformKey tk = _interpolate(tt->transforms, p_time, tt->interpolation, tt->loop_wrap, &ok, p_backward);
 
 	if (!ok) {
 		return ERR_UNAVAILABLE;
@@ -1813,7 +1869,7 @@ void Animation::_value_track_get_key_indices_in_range(const ValueTrack *vt, doub
 	}
 }
 
-void Animation::value_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices) const {
+void Animation::value_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged) const {
 	ERR_FAIL_INDEX(p_track, tracks.size());
 	Track *t = tracks[p_track];
 	ERR_FAIL_COND(t->type != TYPE_VALUE);
@@ -1827,30 +1883,50 @@ void Animation::value_track_get_key_indices(int p_track, double p_time, double p
 		SWAP(from_time, to_time);
 	}
 
-	if (loop) {
-		from_time = Math::fposmod(from_time, length);
-		to_time = Math::fposmod(to_time, length);
+	switch (loop_mode) {
+		case LOOP_NONE: {
+			if (from_time < 0) {
+				from_time = 0;
+			}
+			if (from_time > length) {
+				from_time = length;
+			}
 
-		if (from_time > to_time) {
-			// handle loop by splitting
-			_value_track_get_key_indices_in_range(vt, from_time, length, p_indices);
-			_value_track_get_key_indices_in_range(vt, 0, to_time, p_indices);
-			return;
-		}
-	} else {
-		if (from_time < 0) {
-			from_time = 0;
-		}
-		if (from_time > length) {
-			from_time = length;
-		}
+			if (to_time < 0) {
+				to_time = 0;
+			}
+			if (to_time > length) {
+				to_time = length;
+			}
+		} break;
+		case LOOP_LINEAR: {
+			from_time = Math::fposmod(from_time, length);
+			to_time = Math::fposmod(to_time, length);
 
-		if (to_time < 0) {
-			to_time = 0;
-		}
-		if (to_time > length) {
-			to_time = length;
-		}
+			if (from_time > to_time) {
+				// handle loop by splitting
+				_value_track_get_key_indices_in_range(vt, from_time, length, p_indices);
+				_value_track_get_key_indices_in_range(vt, 0, to_time, p_indices);
+				return;
+			}
+		} break;
+		case LOOP_PINGPONG: {
+			from_time = Math::pingpong(from_time, length);
+			to_time = Math::pingpong(to_time, length);
+
+			if (p_pingponged == -1) {
+				// handle loop by splitting
+				_value_track_get_key_indices_in_range(vt, 0, from_time, p_indices);
+				_value_track_get_key_indices_in_range(vt, 0, to_time, p_indices);
+				return;
+			}
+			if (p_pingponged == 1) {
+				// handle loop by splitting
+				_value_track_get_key_indices_in_range(vt, from_time, length, p_indices);
+				_value_track_get_key_indices_in_range(vt, to_time, length, p_indices);
+				return;
+			}
+		} break;
 	}
 
 	_value_track_get_key_indices_in_range(vt, from_time, to_time, p_indices);
@@ -1909,7 +1985,7 @@ void Animation::_track_get_key_indices_in_range(const Vector<T> &p_array, double
 	}
 }
 
-void Animation::track_get_key_indices_in_range(int p_track, double p_time, double p_delta, List<int> *p_indices) const {
+void Animation::track_get_key_indices_in_range(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged) const {
 	ERR_FAIL_INDEX(p_track, tracks.size());
 	const Track *t = tracks[p_track];
 
@@ -1920,104 +1996,176 @@ void Animation::track_get_key_indices_in_range(int p_track, double p_time, doubl
 		SWAP(from_time, to_time);
 	}
 
-	if (loop) {
-		if (from_time > length || from_time < 0) {
-			from_time = Math::fposmod(from_time, length);
-		}
+	switch (loop_mode) {
+		case LOOP_NONE: {
+			if (from_time < 0) {
+				from_time = 0;
+			}
+			if (from_time > length) {
+				from_time = length;
+			}
 
-		if (to_time > length || to_time < 0) {
-			to_time = Math::fposmod(to_time, length);
-		}
+			if (to_time < 0) {
+				to_time = 0;
+			}
+			if (to_time > length) {
+				to_time = length;
+			}
+		} break;
+		case LOOP_LINEAR: {
+			if (from_time > length || from_time < 0) {
+				from_time = Math::fposmod(from_time, length);
+			}
+			if (to_time > length || to_time < 0) {
+				to_time = Math::fposmod(to_time, length);
+			}
 
-		if (from_time > to_time) {
-			// handle loop by splitting
-
-			switch (t->type) {
-				case TYPE_TRANSFORM3D: {
-					const TransformTrack *tt = static_cast<const TransformTrack *>(t);
-					_track_get_key_indices_in_range(tt->transforms, from_time, length, p_indices);
-					_track_get_key_indices_in_range(tt->transforms, 0, to_time, p_indices);
-
-				} break;
-				case TYPE_VALUE: {
-					const ValueTrack *vt = static_cast<const ValueTrack *>(t);
-					_track_get_key_indices_in_range(vt->values, from_time, length, p_indices);
-					_track_get_key_indices_in_range(vt->values, 0, to_time, p_indices);
-
-				} break;
-				case TYPE_METHOD: {
-					const MethodTrack *mt = static_cast<const MethodTrack *>(t);
-					_track_get_key_indices_in_range(mt->methods, from_time, length, p_indices);
-					_track_get_key_indices_in_range(mt->methods, 0, to_time, p_indices);
-
-				} break;
-				case TYPE_BEZIER: {
-					const BezierTrack *bz = static_cast<const BezierTrack *>(t);
-					_track_get_key_indices_in_range(bz->values, from_time, length, p_indices);
-					_track_get_key_indices_in_range(bz->values, 0, to_time, p_indices);
-
-				} break;
-				case TYPE_AUDIO: {
-					const AudioTrack *ad = static_cast<const AudioTrack *>(t);
-					_track_get_key_indices_in_range(ad->values, from_time, length, p_indices);
-					_track_get_key_indices_in_range(ad->values, 0, to_time, p_indices);
-
-				} break;
-				case TYPE_ANIMATION: {
-					const AnimationTrack *an = static_cast<const AnimationTrack *>(t);
-					_track_get_key_indices_in_range(an->values, from_time, length, p_indices);
-					_track_get_key_indices_in_range(an->values, 0, to_time, p_indices);
-
-				} break;
+			if (from_time > to_time) {
+				// handle loop by splitting
+				switch (t->type) {
+					case TYPE_TRANSFORM3D: {
+						const TransformTrack *tt = static_cast<const TransformTrack *>(t);
+						_track_get_key_indices_in_range(tt->transforms, from_time, length, p_indices);
+						_track_get_key_indices_in_range(tt->transforms, 0, to_time, p_indices);
+					} break;
+					case TYPE_VALUE: {
+						const ValueTrack *vt = static_cast<const ValueTrack *>(t);
+						_track_get_key_indices_in_range(vt->values, from_time, length, p_indices);
+						_track_get_key_indices_in_range(vt->values, 0, to_time, p_indices);
+					} break;
+					case TYPE_METHOD: {
+						const MethodTrack *mt = static_cast<const MethodTrack *>(t);
+						_track_get_key_indices_in_range(mt->methods, from_time, length, p_indices);
+						_track_get_key_indices_in_range(mt->methods, 0, to_time, p_indices);
+					} break;
+					case TYPE_BEZIER: {
+						const BezierTrack *bz = static_cast<const BezierTrack *>(t);
+						_track_get_key_indices_in_range(bz->values, from_time, length, p_indices);
+						_track_get_key_indices_in_range(bz->values, 0, to_time, p_indices);
+					} break;
+					case TYPE_AUDIO: {
+						const AudioTrack *ad = static_cast<const AudioTrack *>(t);
+						_track_get_key_indices_in_range(ad->values, from_time, length, p_indices);
+						_track_get_key_indices_in_range(ad->values, 0, to_time, p_indices);
+					} break;
+					case TYPE_ANIMATION: {
+						const AnimationTrack *an = static_cast<const AnimationTrack *>(t);
+						_track_get_key_indices_in_range(an->values, from_time, length, p_indices);
+						_track_get_key_indices_in_range(an->values, 0, to_time, p_indices);
+					} break;
+				}
+				return;
+			}
+		} break;
+		case LOOP_PINGPONG: {
+			if (from_time > length || from_time < 0) {
+				from_time = Math::pingpong(from_time, length);
+			}
+			if (to_time > length || to_time < 0) {
+				to_time = Math::pingpong(to_time, length);
 			}
-			return;
-		}
-	} else {
-		if (from_time < 0) {
-			from_time = 0;
-		}
-		if (from_time > length) {
-			from_time = length;
-		}
 
-		if (to_time < 0) {
-			to_time = 0;
-		}
-		if (to_time > length) {
-			to_time = length;
-		}
+			if ((int)Math::floor(abs(p_delta) / length) % 2 == 0) {
+				if (p_pingponged == -1) {
+					// handle loop by splitting
+					switch (t->type) {
+						case TYPE_TRANSFORM3D: {
+							const TransformTrack *tt = static_cast<const TransformTrack *>(t);
+							_track_get_key_indices_in_range(tt->transforms, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(tt->transforms, 0, to_time, p_indices);
+						} break;
+						case TYPE_VALUE: {
+							const ValueTrack *vt = static_cast<const ValueTrack *>(t);
+							_track_get_key_indices_in_range(vt->values, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(vt->values, 0, to_time, p_indices);
+						} break;
+						case TYPE_METHOD: {
+							const MethodTrack *mt = static_cast<const MethodTrack *>(t);
+							_track_get_key_indices_in_range(mt->methods, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(mt->methods, 0, to_time, p_indices);
+						} break;
+						case TYPE_BEZIER: {
+							const BezierTrack *bz = static_cast<const BezierTrack *>(t);
+							_track_get_key_indices_in_range(bz->values, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(bz->values, 0, to_time, p_indices);
+						} break;
+						case TYPE_AUDIO: {
+							const AudioTrack *ad = static_cast<const AudioTrack *>(t);
+							_track_get_key_indices_in_range(ad->values, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(ad->values, 0, to_time, p_indices);
+						} break;
+						case TYPE_ANIMATION: {
+							const AnimationTrack *an = static_cast<const AnimationTrack *>(t);
+							_track_get_key_indices_in_range(an->values, 0, from_time, p_indices);
+							_track_get_key_indices_in_range(an->values, 0, to_time, p_indices);
+						} break;
+					}
+					return;
+				}
+				if (p_pingponged == 1) {
+					// handle loop by splitting
+					switch (t->type) {
+						case TYPE_TRANSFORM3D: {
+							const TransformTrack *tt = static_cast<const TransformTrack *>(t);
+							_track_get_key_indices_in_range(tt->transforms, from_time, length, p_indices);
+							_track_get_key_indices_in_range(tt->transforms, to_time, length, p_indices);
+						} break;
+						case TYPE_VALUE: {
+							const ValueTrack *vt = static_cast<const ValueTrack *>(t);
+							_track_get_key_indices_in_range(vt->values, from_time, length, p_indices);
+							_track_get_key_indices_in_range(vt->values, to_time, length, p_indices);
+						} break;
+						case TYPE_METHOD: {
+							const MethodTrack *mt = static_cast<const MethodTrack *>(t);
+							_track_get_key_indices_in_range(mt->methods, from_time, length, p_indices);
+							_track_get_key_indices_in_range(mt->methods, to_time, length, p_indices);
+						} break;
+						case TYPE_BEZIER: {
+							const BezierTrack *bz = static_cast<const BezierTrack *>(t);
+							_track_get_key_indices_in_range(bz->values, from_time, length, p_indices);
+							_track_get_key_indices_in_range(bz->values, to_time, length, p_indices);
+						} break;
+						case TYPE_AUDIO: {
+							const AudioTrack *ad = static_cast<const AudioTrack *>(t);
+							_track_get_key_indices_in_range(ad->values, from_time, length, p_indices);
+							_track_get_key_indices_in_range(ad->values, to_time, length, p_indices);
+						} break;
+						case TYPE_ANIMATION: {
+							const AnimationTrack *an = static_cast<const AnimationTrack *>(t);
+							_track_get_key_indices_in_range(an->values, from_time, length, p_indices);
+							_track_get_key_indices_in_range(an->values, to_time, length, p_indices);
+						} break;
+					}
+					return;
+				}
+			}
+		} break;
 	}
 
 	switch (t->type) {
 		case TYPE_TRANSFORM3D: {
 			const TransformTrack *tt = static_cast<const TransformTrack *>(t);
 			_track_get_key_indices_in_range(tt->transforms, from_time, to_time, p_indices);
-
 		} break;
 		case TYPE_VALUE: {
 			const ValueTrack *vt = static_cast<const ValueTrack *>(t);
 			_track_get_key_indices_in_range(vt->values, from_time, to_time, p_indices);
-
 		} break;
 		case TYPE_METHOD: {
 			const MethodTrack *mt = static_cast<const MethodTrack *>(t);
 			_track_get_key_indices_in_range(mt->methods, from_time, to_time, p_indices);
-
 		} break;
 		case TYPE_BEZIER: {
 			const BezierTrack *bz = static_cast<const BezierTrack *>(t);
 			_track_get_key_indices_in_range(bz->values, from_time, to_time, p_indices);
-
 		} break;
 		case TYPE_AUDIO: {
 			const AudioTrack *ad = static_cast<const AudioTrack *>(t);
 			_track_get_key_indices_in_range(ad->values, from_time, to_time, p_indices);
-
 		} break;
 		case TYPE_ANIMATION: {
 			const AnimationTrack *an = static_cast<const AnimationTrack *>(t);
 			_track_get_key_indices_in_range(an->values, from_time, to_time, p_indices);
-
 		} break;
 	}
 }
@@ -2055,7 +2203,7 @@ void Animation::_method_track_get_key_indices_in_range(const MethodTrack *mt, do
 	}
 }
 
-void Animation::method_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices) const {
+void Animation::method_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged) const {
 	ERR_FAIL_INDEX(p_track, tracks.size());
 	Track *t = tracks[p_track];
 	ERR_FAIL_COND(t->type != TYPE_METHOD);
@@ -2069,35 +2217,58 @@ void Animation::method_track_get_key_indices(int p_track, double p_time, double
 		SWAP(from_time, to_time);
 	}
 
-	if (loop) {
-		if (from_time > length || from_time < 0) {
-			from_time = Math::fposmod(from_time, length);
-		}
+	switch (loop_mode) {
+		case LOOP_NONE: {
+			if (from_time < 0) {
+				from_time = 0;
+			}
+			if (from_time > length) {
+				from_time = length;
+			}
 
-		if (to_time > length || to_time < 0) {
-			to_time = Math::fposmod(to_time, length);
-		}
+			if (to_time < 0) {
+				to_time = 0;
+			}
+			if (to_time > length) {
+				to_time = length;
+			}
+		} break;
+		case LOOP_LINEAR: {
+			if (from_time > length || from_time < 0) {
+				from_time = Math::fposmod(from_time, length);
+			}
+			if (to_time > length || to_time < 0) {
+				to_time = Math::fposmod(to_time, length);
+			}
 
-		if (from_time > to_time) {
-			// handle loop by splitting
-			_method_track_get_key_indices_in_range(mt, from_time, length, p_indices);
-			_method_track_get_key_indices_in_range(mt, 0, to_time, p_indices);
-			return;
-		}
-	} else {
-		if (from_time < 0) {
-			from_time = 0;
-		}
-		if (from_time > length) {
-			from_time = length;
-		}
+			if (from_time > to_time) {
+				// handle loop by splitting
+				_method_track_get_key_indices_in_range(mt, from_time, length, p_indices);
+				_method_track_get_key_indices_in_range(mt, 0, to_time, p_indices);
+				return;
+			}
+		} break;
+		case LOOP_PINGPONG: {
+			if (from_time > length || from_time < 0) {
+				from_time = Math::pingpong(from_time, length);
+			}
+			if (to_time > length || to_time < 0) {
+				to_time = Math::pingpong(to_time, length);
+			}
 
-		if (to_time < 0) {
-			to_time = 0;
-		}
-		if (to_time > length) {
-			to_time = length;
-		}
+			if (p_pingponged == -1) {
+				_method_track_get_key_indices_in_range(mt, 0, from_time, p_indices);
+				_method_track_get_key_indices_in_range(mt, 0, to_time, p_indices);
+				return;
+			}
+			if (p_pingponged == 1) {
+				_method_track_get_key_indices_in_range(mt, from_time, length, p_indices);
+				_method_track_get_key_indices_in_range(mt, to_time, length, p_indices);
+				return;
+			}
+		} break;
+		default:
+			break;
 	}
 
 	_method_track_get_key_indices_in_range(mt, from_time, to_time, p_indices);
@@ -2483,13 +2654,13 @@ real_t Animation::get_length() const {
 	return length;
 }
 
-void Animation::set_loop(bool p_enabled) {
-	loop = p_enabled;
+void Animation::set_loop_mode(Animation::LoopMode p_loop_mode) {
+	loop_mode = p_loop_mode;
 	emit_changed();
 }
 
-bool Animation::has_loop() const {
-	return loop;
+Animation::LoopMode Animation::get_loop_mode() const {
+	return loop_mode;
 }
 
 void Animation::track_set_imported(int p_track, bool p_imported) {
@@ -2628,7 +2799,7 @@ void Animation::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("track_set_interpolation_loop_wrap", "track_idx", "interpolation"), &Animation::track_set_interpolation_loop_wrap);
 	ClassDB::bind_method(D_METHOD("track_get_interpolation_loop_wrap", "track_idx"), &Animation::track_get_interpolation_loop_wrap);
 
-	ClassDB::bind_method(D_METHOD("transform_track_interpolate", "track_idx", "time_sec"), &Animation::_transform_track_interpolate);
+	ClassDB::bind_method(D_METHOD("transform_track_interpolate", "track_idx", "time_sec", "is_backward"), &Animation::_transform_track_interpolate, DEFVAL(false));
 	ClassDB::bind_method(D_METHOD("value_track_set_update_mode", "track_idx", "mode"), &Animation::value_track_set_update_mode);
 	ClassDB::bind_method(D_METHOD("value_track_get_update_mode", "track_idx"), &Animation::value_track_get_update_mode);
 
@@ -2666,8 +2837,8 @@ void Animation::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_length", "time_sec"), &Animation::set_length);
 	ClassDB::bind_method(D_METHOD("get_length"), &Animation::get_length);
 
-	ClassDB::bind_method(D_METHOD("set_loop", "enabled"), &Animation::set_loop);
-	ClassDB::bind_method(D_METHOD("has_loop"), &Animation::has_loop);
+	ClassDB::bind_method(D_METHOD("set_loop_mode", "loop_mode"), &Animation::set_loop_mode);
+	ClassDB::bind_method(D_METHOD("get_loop_mode"), &Animation::get_loop_mode);
 
 	ClassDB::bind_method(D_METHOD("set_step", "size_sec"), &Animation::set_step);
 	ClassDB::bind_method(D_METHOD("get_step"), &Animation::get_step);
@@ -2676,7 +2847,7 @@ void Animation::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("copy_track", "track_idx", "to_animation"), &Animation::copy_track);
 
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "length", PROPERTY_HINT_RANGE, "0.001,99999,0.001"), "set_length", "get_length");
-	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "loop"), "set_loop", "has_loop");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "loop_mode"), "set_loop_mode", "get_loop_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "step", PROPERTY_HINT_RANGE, "0,4096,0.001"), "set_step", "get_step");
 
 	ADD_SIGNAL(MethodInfo("tracks_changed"));
@@ -2696,6 +2867,10 @@ void Animation::_bind_methods() {
 	BIND_ENUM_CONSTANT(UPDATE_DISCRETE);
 	BIND_ENUM_CONSTANT(UPDATE_TRIGGER);
 	BIND_ENUM_CONSTANT(UPDATE_CAPTURE);
+
+	BIND_ENUM_CONSTANT(LOOP_NONE);
+	BIND_ENUM_CONSTANT(LOOP_LINEAR);
+	BIND_ENUM_CONSTANT(LOOP_PINGPONG);
 }
 
 void Animation::clear() {
@@ -2703,7 +2878,7 @@ void Animation::clear() {
 		memdelete(tracks[i]);
 	}
 	tracks.clear();
-	loop = false;
+	loop_mode = LOOP_NONE;
 	length = 1;
 	emit_changed();
 	emit_signal(SceneStringNames::get_singleton()->tracks_changed);
diff --git a/scene/resources/animation.h b/scene/resources/animation.h
index 9a410bd566..032b1a9277 100644
--- a/scene/resources/animation.h
+++ b/scene/resources/animation.h
@@ -60,7 +60,12 @@ public:
 		UPDATE_DISCRETE,
 		UPDATE_TRIGGER,
 		UPDATE_CAPTURE,
+	};
 
+	enum LoopMode {
+		LOOP_NONE,
+		LOOP_LINEAR,
+		LOOP_PINGPONG,
 	};
 
 private:
@@ -184,7 +189,8 @@ private:
 	int _insert(double p_time, T &p_keys, const V &p_value);
 
 	template <class K>
-	inline int _find(const Vector<K> &p_keys, double p_time) const;
+
+	inline int _find(const Vector<K> &p_keys, double p_time, bool p_backward = false) const;
 
 	_FORCE_INLINE_ Animation::TransformKey _interpolate(const Animation::TransformKey &p_a, const Animation::TransformKey &p_b, real_t p_c) const;
 
@@ -200,7 +206,7 @@ private:
 	_FORCE_INLINE_ real_t _cubic_interpolate(const real_t &p_pre_a, const real_t &p_a, const real_t &p_b, const real_t &p_post_b, real_t p_c) const;
 
 	template <class T>
-	_FORCE_INLINE_ T _interpolate(const Vector<TKey<T>> &p_keys, double p_time, InterpolationType p_interp, bool p_loop_wrap, bool *p_ok) const;
+	_FORCE_INLINE_ T _interpolate(const Vector<TKey<T>> &p_keys, double p_time, InterpolationType p_interp, bool p_loop_wrap, bool *p_ok, bool p_backward = false) const;
 
 	template <class T>
 	_FORCE_INLINE_ void _track_get_key_indices_in_range(const Vector<T> &p_array, double from_time, double to_time, List<int> *p_indices) const;
@@ -210,15 +216,16 @@ private:
 
 	double length = 1.0;
 	real_t step = 0.1;
-	bool loop = false;
+	LoopMode loop_mode = LOOP_NONE;
+	int pingponged = 0;
 
 	// bind helpers
 private:
-	Array _transform_track_interpolate(int p_track, double p_time) const {
+	Array _transform_track_interpolate(int p_track, double p_time, bool p_backward = false) const {
 		Vector3 loc;
 		Quaternion rot;
 		Vector3 scale;
-		transform_track_interpolate(p_track, p_time, &loc, &rot, &scale);
+		transform_track_interpolate(p_track, p_time, &loc, &rot, &scale, p_backward);
 		Array ret;
 		ret.push_back(loc);
 		ret.push_back(rot);
@@ -324,26 +331,26 @@ public:
 	void track_set_interpolation_loop_wrap(int p_track, bool p_enable);
 	bool track_get_interpolation_loop_wrap(int p_track) const;
 
-	Error transform_track_interpolate(int p_track, double p_time, Vector3 *r_loc, Quaternion *r_rot, Vector3 *r_scale) const;
+	Error transform_track_interpolate(int p_track, double p_time, Vector3 *r_loc, Quaternion *r_rot, Vector3 *r_scale, bool p_backward = false) const;
 
 	Variant value_track_interpolate(int p_track, double p_time) const;
-	void value_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices) const;
+	void value_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged = 0) const;
 	void value_track_set_update_mode(int p_track, UpdateMode p_mode);
 	UpdateMode value_track_get_update_mode(int p_track) const;
 
-	void method_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices) const;
+	void method_track_get_key_indices(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged = 0) const;
 	Vector<Variant> method_track_get_params(int p_track, int p_key_idx) const;
 	StringName method_track_get_name(int p_track, int p_key_idx) const;
 
 	void copy_track(int p_track, Ref<Animation> p_to_animation);
 
-	void track_get_key_indices_in_range(int p_track, double p_time, double p_delta, List<int> *p_indices) const;
+	void track_get_key_indices_in_range(int p_track, double p_time, double p_delta, List<int> *p_indices, int p_pingponged = 0) const;
 
 	void set_length(real_t p_length);
 	real_t get_length() const;
 
-	void set_loop(bool p_enabled);
-	bool has_loop() const;
+	void set_loop_mode(LoopMode p_loop_mode);
+	LoopMode get_loop_mode() const;
 
 	void set_step(real_t p_step);
 	real_t get_step() const;
@@ -359,5 +366,6 @@ public:
 VARIANT_ENUM_CAST(Animation::TrackType);
 VARIANT_ENUM_CAST(Animation::InterpolationType);
 VARIANT_ENUM_CAST(Animation::UpdateMode);
+VARIANT_ENUM_CAST(Animation::LoopMode);
 
 #endif
diff --git a/scene/resources/audio_stream_sample.cpp b/scene/resources/audio_stream_sample.cpp
index d018103e64..c8a10e1c2a 100644
--- a/scene/resources/audio_stream_sample.cpp
+++ b/scene/resources/audio_stream_sample.cpp
@@ -299,7 +299,7 @@ int AudioStreamPlaybackSample::mix(AudioFrame *p_buffer, float p_rate_scale, int
 
 			if (loop_format != AudioStreamSample::LOOP_DISABLED && offset < loop_begin_fp) {
 				/* loopstart reached */
-				if (loop_format == AudioStreamSample::LOOP_PING_PONG) {
+				if (loop_format == AudioStreamSample::LOOP_PINGPONG) {
 					/* bounce ping pong */
 					offset = loop_begin_fp + (loop_begin_fp - offset);
 					increment = -increment;
@@ -320,7 +320,7 @@ int AudioStreamPlaybackSample::mix(AudioFrame *p_buffer, float p_rate_scale, int
 			if (loop_format != AudioStreamSample::LOOP_DISABLED && offset >= loop_end_fp) {
 				/* loopend reached */
 
-				if (loop_format == AudioStreamSample::LOOP_PING_PONG) {
+				if (loop_format == AudioStreamSample::LOOP_PINGPONG) {
 					/* bounce ping pong */
 					offset = loop_end_fp - (offset - loop_end_fp);
 					increment = -increment;
@@ -650,7 +650,7 @@ void AudioStreamSample::_bind_methods() {
 
 	BIND_ENUM_CONSTANT(LOOP_DISABLED);
 	BIND_ENUM_CONSTANT(LOOP_FORWARD);
-	BIND_ENUM_CONSTANT(LOOP_PING_PONG);
+	BIND_ENUM_CONSTANT(LOOP_PINGPONG);
 	BIND_ENUM_CONSTANT(LOOP_BACKWARD);
 }
 
diff --git a/scene/resources/audio_stream_sample.h b/scene/resources/audio_stream_sample.h
index 24198e3c98..0eb34be9bf 100644
--- a/scene/resources/audio_stream_sample.h
+++ b/scene/resources/audio_stream_sample.h
@@ -92,7 +92,7 @@ public:
 	enum LoopMode {
 		LOOP_DISABLED,
 		LOOP_FORWARD,
-		LOOP_PING_PONG,
+		LOOP_PINGPONG,
 		LOOP_BACKWARD
 	};