Add linear/cubic angle interpolation to Animation interpolation type

core/math/math_funcs.h

@@ -253,6 +253,35 @@ class Math {
 						(-p_pre + 3.0f * p_from - 3.0f * p_to + p_post) * (p_weight * p_weight * p_weight));
 	}
 
+	static _ALWAYS_INLINE_ double cubic_interpolate_angle(double p_from, double p_to, double p_pre, double p_post, double p_weight) {
+		double from_rot = fmod(p_from, Math_TAU);
+
+		double pre_diff = fmod(p_pre - from_rot, Math_TAU);
+		double pre_rot = from_rot + fmod(2.0 * pre_diff, Math_TAU) - pre_diff;
+
+		double to_diff = fmod(p_to - from_rot, Math_TAU);
+		double to_rot = from_rot + fmod(2.0 * to_diff, Math_TAU) - to_diff;
+
+		double post_diff = fmod(p_post - to_rot, Math_TAU);
+		double post_rot = to_rot + fmod(2.0 * post_diff, Math_TAU) - post_diff;
+
+		return cubic_interpolate(from_rot, to_rot, pre_rot, post_rot, p_weight);
+	}
+	static _ALWAYS_INLINE_ float cubic_interpolate_angle(float p_from, float p_to, float p_pre, float p_post, float p_weight) {
+		float from_rot = fmod(p_from, (float)Math_TAU);
+
+		float pre_diff = fmod(p_pre - from_rot, (float)Math_TAU);
+		float pre_rot = from_rot + fmod(2.0f * pre_diff, (float)Math_TAU) - pre_diff;
+
+		float to_diff = fmod(p_to - from_rot, (float)Math_TAU);
+		float to_rot = from_rot + fmod(2.0f * to_diff, (float)Math_TAU) - to_diff;
+
+		float post_diff = fmod(p_post - to_rot, (float)Math_TAU);
+		float post_rot = to_rot + fmod(2.0f * post_diff, (float)Math_TAU) - post_diff;
+
+		return cubic_interpolate(from_rot, to_rot, pre_rot, post_rot, p_weight);
+	}
+
 	static _ALWAYS_INLINE_ double cubic_interpolate_in_time(double p_from, double p_to, double p_pre, double p_post, double p_weight,
 			double p_to_t, double p_pre_t, double p_post_t) {
 		/* Barry-Goldman method */
@@ -276,6 +305,37 @@ class Math {
 		return Math::lerp(b1, b2, p_to_t == 0 ? 0.5f : t / p_to_t);
 	}
 
+	static _ALWAYS_INLINE_ double cubic_interpolate_angle_in_time(double p_from, double p_to, double p_pre, double p_post, double p_weight,
+			double p_to_t, double p_pre_t, double p_post_t) {
+		double from_rot = fmod(p_from, Math_TAU);
+
+		double pre_diff = fmod(p_pre - from_rot, Math_TAU);
+		double pre_rot = from_rot + fmod(2.0 * pre_diff, Math_TAU) - pre_diff;
+
+		double to_diff = fmod(p_to - from_rot, Math_TAU);
+		double to_rot = from_rot + fmod(2.0 * to_diff, Math_TAU) - to_diff;
+
+		double post_diff = fmod(p_post - to_rot, Math_TAU);
+		double post_rot = to_rot + fmod(2.0 * post_diff, Math_TAU) - post_diff;
+
+		return cubic_interpolate_in_time(from_rot, to_rot, pre_rot, post_rot, p_weight, p_to_t, p_pre_t, p_post_t);
+	}
+	static _ALWAYS_INLINE_ float cubic_interpolate_angle_in_time(float p_from, float p_to, float p_pre, float p_post, float p_weight,
+			float p_to_t, float p_pre_t, float p_post_t) {
+		float from_rot = fmod(p_from, (float)Math_TAU);
+
+		float pre_diff = fmod(p_pre - from_rot, (float)Math_TAU);
+		float pre_rot = from_rot + fmod(2.0f * pre_diff, (float)Math_TAU) - pre_diff;
+
+		float to_diff = fmod(p_to - from_rot, (float)Math_TAU);
+		float to_rot = from_rot + fmod(2.0f * to_diff, (float)Math_TAU) - to_diff;
+
+		float post_diff = fmod(p_post - to_rot, (float)Math_TAU);
+		float post_rot = to_rot + fmod(2.0f * post_diff, (float)Math_TAU) - post_diff;
+
+		return cubic_interpolate_in_time(from_rot, to_rot, pre_rot, post_rot, p_weight, p_to_t, p_pre_t, p_post_t);
+	}
+
 	static _ALWAYS_INLINE_ double bezier_interpolate(double p_start, double p_control_1, double p_control_2, double p_end, double p_t) {
 		/* Formula from Wikipedia article on Bezier curves. */
 		double omt = (1.0 - p_t);

core/variant/variant_utility.cpp

@@ -367,11 +367,20 @@ struct VariantUtilityFunctions {
 		return Math::cubic_interpolate(from, to, pre, post, weight);
 	}
 
+	static inline double cubic_interpolate_angle(double from, double to, double pre, double post, double weight) {
+		return Math::cubic_interpolate_angle(from, to, pre, post, weight);
+	}
+
 	static inline double cubic_interpolate_in_time(double from, double to, double pre, double post, double weight,
 			double to_t, double pre_t, double post_t) {
 		return Math::cubic_interpolate_in_time(from, to, pre, post, weight, to_t, pre_t, post_t);
 	}
 
+	static inline double cubic_interpolate_angle_in_time(double from, double to, double pre, double post, double weight,
+			double to_t, double pre_t, double post_t) {
+		return Math::cubic_interpolate_angle_in_time(from, to, pre, post, weight, to_t, pre_t, post_t);
+	}
+
 	static inline double bezier_interpolate(double p_start, double p_control_1, double p_control_2, double p_end, double p_t) {
 		return Math::bezier_interpolate(p_start, p_control_1, p_control_2, p_end, p_t);
 	}
@@ -1419,7 +1428,9 @@ void Variant::_register_variant_utility_functions() {
 	FUNCBINDVR3(lerp, sarray("from", "to", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(lerpf, sarray("from", "to", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(cubic_interpolate, sarray("from", "to", "pre", "post", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);
+	FUNCBINDR(cubic_interpolate_angle, sarray("from", "to", "pre", "post", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(cubic_interpolate_in_time, sarray("from", "to", "pre", "post", "weight", "to_t", "pre_t", "post_t"), Variant::UTILITY_FUNC_TYPE_MATH);
+	FUNCBINDR(cubic_interpolate_angle_in_time, sarray("from", "to", "pre", "post", "weight", "to_t", "pre_t", "post_t"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(bezier_interpolate, sarray("start", "control_1", "control_2", "end", "t"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(lerp_angle, sarray("from", "to", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);
 	FUNCBINDR(inverse_lerp, sarray("from", "to", "weight"), Variant::UTILITY_FUNC_TYPE_MATH);

doc/classes/@GlobalScope.xml

@@ -260,6 +260,32 @@
 				Cubic interpolates between two values by the factor defined in [param weight] with pre and post values.
 			</description>
 		</method>
+		<method name="cubic_interpolate_angle">
+			<return type="float" />
+			<param index="0" name="from" type="float" />
+			<param index="1" name="to" type="float" />
+			<param index="2" name="pre" type="float" />
+			<param index="3" name="post" type="float" />
+			<param index="4" name="weight" type="float" />
+			<description>
+				Cubic interpolates between two rotation values with shortest path by the factor defined in [param weight] with pre and post values. See also [method lerp_angle].
+			</description>
+		</method>
+		<method name="cubic_interpolate_angle_in_time">
+			<return type="float" />
+			<param index="0" name="from" type="float" />
+			<param index="1" name="to" type="float" />
+			<param index="2" name="pre" type="float" />
+			<param index="3" name="post" type="float" />
+			<param index="4" name="weight" type="float" />
+			<param index="5" name="to_t" type="float" />
+			<param index="6" name="pre_t" type="float" />
+			<param index="7" name="post_t" type="float" />
+			<description>
+				Cubic interpolates between two rotation values with shortest path by the factor defined in [param weight] with pre and post values. See also [method lerp_angle].
+				It can perform smoother interpolation than [code]cubic_interpolate()[/code] by the time values.
+			</description>
+		</method>
 		<method name="cubic_interpolate_in_time">
 			<return type="float" />
 			<param index="0" name="from" type="float" />

doc/classes/Animation.xml

@@ -600,6 +600,14 @@
 		<constant name="INTERPOLATION_CUBIC" value="2" enum="InterpolationType">
 			Cubic interpolation.
 		</constant>
+		<constant name="INTERPOLATION_LINEAR_ANGLE" value="3" enum="InterpolationType">
+			Linear interpolation with shortest path rotation.
+			[b]Note:[/b] The result value is always normalized and may not match the key value.
+		</constant>
+		<constant name="INTERPOLATION_CUBIC_ANGLE" value="4" enum="InterpolationType">
+			Cubic interpolation with shortest path rotation.
+			[b]Note:[/b] The result value is always normalized and may not match the key value.
+		</constant>
 		<constant name="UPDATE_CONTINUOUS" value="0" enum="UpdateMode">
 			Update between keyframes.
 		</constant>

editor/animation_track_editor.cpp

@@ -2122,10 +2122,12 @@ void AnimationTrackEdit::_notification(int p_what) {
 					get_theme_icon(SNAME("InterpWrapClamp"), SNAME("EditorIcons")),
 					get_theme_icon(SNAME("InterpWrapLoop"), SNAME("EditorIcons")),
 				};
-				Ref<Texture2D> interp_icon[3] = {
+				Ref<Texture2D> interp_icon[5] = {
 					get_theme_icon(SNAME("InterpRaw"), SNAME("EditorIcons")),
 					get_theme_icon(SNAME("InterpLinear"), SNAME("EditorIcons")),
 					get_theme_icon(SNAME("InterpCubic"), SNAME("EditorIcons")),
+					get_theme_icon(SNAME("InterpLinearAngle"), SNAME("EditorIcons")),
+					get_theme_icon(SNAME("InterpCubicAngle"), SNAME("EditorIcons")),
 				};
 				Ref<Texture2D> cont_icon[4] = {
 					get_theme_icon(SNAME("TrackContinuous"), SNAME("EditorIcons")),
@@ -2848,6 +2850,23 @@ void AnimationTrackEdit::gui_input(const Ref<InputEvent> &p_event) {
 				menu->add_icon_item(get_theme_icon(SNAME("InterpRaw"), SNAME("EditorIcons")), TTR("Nearest"), MENU_INTERPOLATION_NEAREST);
 				menu->add_icon_item(get_theme_icon(SNAME("InterpLinear"), SNAME("EditorIcons")), TTR("Linear"), MENU_INTERPOLATION_LINEAR);
 				menu->add_icon_item(get_theme_icon(SNAME("InterpCubic"), SNAME("EditorIcons")), TTR("Cubic"), MENU_INTERPOLATION_CUBIC);
+				// Check is angle property.
+				AnimationPlayerEditor *ape = AnimationPlayerEditor::get_singleton();
+				if (ape) {
+					AnimationPlayer *ap = ape->get_player();
+					if (ap) {
+						NodePath path = animation->track_get_path(track);
+						Node *nd = ap->get_node(ap->get_root())->get_node(NodePath(path.get_concatenated_names()));
+						StringName prop = path.get_concatenated_subnames();
+						PropertyInfo prop_info;
+						ClassDB::get_property_info(nd->get_class(), prop, &prop_info);
+						bool is_angle = prop_info.type == Variant::FLOAT && prop_info.hint_string.find("radians") != -1;
+						if (is_angle) {
+							menu->add_icon_item(get_theme_icon(SNAME("InterpLinearAngle"), SNAME("EditorIcons")), TTR("Linear Angle"), MENU_INTERPOLATION_LINEAR_ANGLE);
+							menu->add_icon_item(get_theme_icon(SNAME("InterpCubicAngle"), SNAME("EditorIcons")), TTR("Cubic Angle"), MENU_INTERPOLATION_CUBIC_ANGLE);
+						}
+					}
+				}
 				menu->reset_size();
 
 				Vector2 popup_pos = get_screen_position() + interp_mode_rect.position + Vector2(0, interp_mode_rect.size.height);
@@ -3188,7 +3207,9 @@ void AnimationTrackEdit::_menu_selected(int p_index) {
 		} break;
 		case MENU_INTERPOLATION_NEAREST:
 		case MENU_INTERPOLATION_LINEAR:
-		case MENU_INTERPOLATION_CUBIC: {
+		case MENU_INTERPOLATION_CUBIC:
+		case MENU_INTERPOLATION_LINEAR_ANGLE:
+		case MENU_INTERPOLATION_CUBIC_ANGLE: {
 			Animation::InterpolationType interp_mode = Animation::InterpolationType(p_index - MENU_INTERPOLATION_NEAREST);
 			undo_redo->create_action(TTR("Change Animation Interpolation Mode"));
 			undo_redo->add_do_method(animation.ptr(), "track_set_interpolation_type", track, interp_mode);
@@ -6042,6 +6063,9 @@ void AnimationTrackEditor::_edit_menu_pressed(int p_option) {
 				Vector<int> keys = E->value;
 				int len = keys.size() - 1;
 
+				// Special case for angle interpolation.
+				bool is_using_angle = animation->track_get_interpolation_type(track) == Animation::INTERPOLATION_LINEAR_ANGLE || animation->track_get_interpolation_type(track) == Animation::INTERPOLATION_CUBIC_ANGLE;
+
 				// Make insert queue.
 				Vector<Pair<double, Variant>> insert_queue;
 				for (int i = 0; i < len; i++) {
@@ -6051,6 +6075,12 @@ void AnimationTrackEditor::_edit_menu_pressed(int p_option) {
 						double to_t = animation->track_get_key_time(track, keys[i + 1]);
 						Variant from_v = animation->track_get_key_value(track, keys[i]);
 						Variant to_v = animation->track_get_key_value(track, keys[i + 1]);
+						if (is_using_angle) {
+							real_t a = from_v;
+							real_t b = to_v;
+							real_t to_diff = fmod(b - a, Math_TAU);
+							to_v = a + fmod(2.0 * to_diff, Math_TAU) - to_diff;
+						}
 						Variant delta_v;
 						Variant::sub(to_v, from_v, delta_v);
 						double duration = to_t - from_t;
@@ -6192,10 +6222,14 @@ void AnimationTrackEditor::_edit_menu_pressed(int p_option) {
 				do_bake |= b_bs && type == Animation::TYPE_BLEND_SHAPE;
 				do_bake |= b_v && type == Animation::TYPE_VALUE;
 				if (do_bake && !animation->track_is_compressed(i)) {
-					if (animation->track_get_interpolation_type(i) == Animation::INTERPOLATION_NEAREST) {
-						continue; // Nearest interpolation cannot be baked.
+					Animation::InterpolationType it = animation->track_get_interpolation_type(i);
+					if (it == Animation::INTERPOLATION_NEAREST) {
+						continue; // Nearest and Angle interpolation cannot be baked.
 					}
 
+					// Special case for angle interpolation.
+					bool is_using_angle = it == Animation::INTERPOLATION_LINEAR_ANGLE || it == Animation::INTERPOLATION_CUBIC_ANGLE;
+
 					// Make insert queue.
 					Vector<Pair<double, Variant>> insert_queue;
 
@@ -6259,7 +6293,7 @@ void AnimationTrackEditor::_edit_menu_pressed(int p_option) {
 					}
 
 					// Insert keys.
-					undo_redo->add_do_method(animation.ptr(), "track_set_interpolation_type", i, Animation::INTERPOLATION_LINEAR);
+					undo_redo->add_do_method(animation.ptr(), "track_set_interpolation_type", i, is_using_angle ? Animation::INTERPOLATION_LINEAR_ANGLE : Animation::INTERPOLATION_LINEAR);
 					for (int j = insert_queue.size() - 1; j >= 0; j--) {
 						undo_redo->add_do_method(animation.ptr(), "track_insert_key", i, insert_queue[j].first, insert_queue[j].second);
 						undo_redo->add_undo_method(animation.ptr(), "track_remove_key", i, j);

editor/animation_track_editor.h

@@ -144,6 +144,8 @@ class AnimationTrackEdit : public Control {
 		MENU_INTERPOLATION_NEAREST,
 		MENU_INTERPOLATION_LINEAR,
 		MENU_INTERPOLATION_CUBIC,
+		MENU_INTERPOLATION_LINEAR_ANGLE,
+		MENU_INTERPOLATION_CUBIC_ANGLE,
 		MENU_LOOP_WRAP,
 		MENU_LOOP_CLAMP,
 		MENU_KEY_INSERT,
@@ -500,7 +502,7 @@ class AnimationTrackEditor : public VBoxContainer {
 		NodePath full_path;
 		NodePath base_path;
 		Animation::TrackType track_type = Animation::TYPE_ANIMATION;
-		Animation::InterpolationType interp_type = Animation::INTERPOLATION_CUBIC;
+		Animation::InterpolationType interp_type = Animation::INTERPOLATION_CUBIC_ANGLE;
 		Animation::UpdateMode update_mode = Animation::UPDATE_CAPTURE;
 		Animation::LoopMode loop_mode = Animation::LOOP_PINGPONG;
 		bool loop_wrap = false;

scene/animation/animation_tree.cpp

@@ -602,6 +602,8 @@ bool AnimationTree::_update_caches(AnimationPlayer *player) {
 							track_value->object = child;
 						}
 
+						track_value->is_using_angle = anim->track_get_interpolation_type(i) == Animation::INTERPOLATION_LINEAR_ANGLE || anim->track_get_interpolation_type(i) == Animation::INTERPOLATION_CUBIC_ANGLE;
+
 						track_value->subpath = leftover_path;
 						track_value->object_id = track_value->object->get_instance_id();
 
@@ -804,6 +806,10 @@ bool AnimationTree::_update_caches(AnimationPlayer *player) {
 					default: {
 					}
 				}
+			} else if (track_cache_type == Animation::TYPE_VALUE) {
+				// If it has at least one angle interpolation, it also uses angle interpolation for blending.
+				TrackCacheValue *track_value = memnew(TrackCacheValue);
+				track_value->is_using_angle |= anim->track_get_interpolation_type(i) == Animation::INTERPOLATION_LINEAR_ANGLE || anim->track_get_interpolation_type(i) == Animation::INTERPOLATION_CUBIC_ANGLE;
 			}
 
 			track->setup_pass = setup_pass;
@@ -1353,8 +1359,28 @@ void AnimationTree::_process_graph(double p_delta) {
 								t->value = t->init_value;
 							}
 
-							Variant::sub(value, t->init_value, value);
-							Variant::blend(t->value, value, blend, t->value);
+							// Special case for angle interpolation.
+							if (t->is_using_angle) {
+								// For blending consistency, it prevents rotation of more than 180 degrees from init_value.
+								// This is the same as for Quaternion blends.
+								float rot_a = t->value;
+								float rot_b = value;
+								float rot_init = t->init_value;
+								rot_a = Math::fposmod(rot_a, (float)Math_TAU);
+								rot_b = Math::fposmod(rot_b, (float)Math_TAU);
+								rot_init = Math::fposmod(rot_init, (float)Math_TAU);
+								if (rot_init < Math_PI) {
+									rot_a = rot_a > rot_init + Math_PI ? rot_a - Math_TAU : rot_a;
+									rot_b = rot_b > rot_init + Math_PI ? rot_b - Math_TAU : rot_b;
+								} else {
+									rot_a = rot_a < rot_init - Math_PI ? rot_a + Math_TAU : rot_a;
+									rot_b = rot_b < rot_init - Math_PI ? rot_b + Math_TAU : rot_b;
+								}
+								t->value = Math::fposmod(rot_a + (rot_b - rot_init) * (float)blend, (float)Math_TAU);
+							} else {
+								Variant::sub(value, t->init_value, value);
+								Variant::blend(t->value, value, blend, t->value);
+							}
 						} else {
 							if (blend < CMP_EPSILON) {
 								continue; //nothing to blend

scene/animation/animation_tree.h

@@ -233,6 +233,7 @@ class AnimationTree : public Node {
 		Variant init_value;
 		Variant value;
 		Vector<StringName> subpath;
+		bool is_using_angle = false;
 		TrackCacheValue() { type = Animation::TYPE_VALUE; }
 	};