Merge pull request #64212 from xiongyaohua/curve3d_baking_refactor

Move rotation interpolation to Curve3d and refactor baking

doc/classes/Curve3D.xml

@@ -132,6 +132,15 @@
 				If the curve has no up vectors, the function sends an error to the console, and returns [code](0, 1, 0)[/code].
 			</description>
 		</method>
+		<method name="sample_baked_with_rotation" qualifiers="const">
+			<return type="Transform3D" />
+			<param index="0" name="offset" type="float" />
+			<param index="1" name="cubic" type="bool" default="false" />
+			<param index="2" name="apply_tilt" type="bool" default="false" />
+			<description>
+				Similar with [code]interpolate_baked()[/code]. The the return value is [code]Transform3D[/code], with [code]origin[/code] as point position, [code]basis.x[/code] as sideway vector, [code]basis.y[/code] as up vector, [code]basis.z[/code] as forward vector. When the curve length is 0, there is no reasonable way to caculate the rotation, all vectors aligned with global space axes.
+			</description>
+		</method>
 		<method name="samplef" qualifiers="const">
 			<return type="Vector3" />
 			<param index="0" name="fofs" type="float" />

doc/classes/PathFollow3D.xml

@@ -9,6 +9,16 @@
 	</description>
 	<tutorials>
 	</tutorials>
+	<methods>
+		<method name="correct_posture" qualifiers="static">
+			<return type="Transform3D" />
+			<param index="0" name="transform" type="Transform3D" />
+			<param index="1" name="rotation_mode" type="int" enum="PathFollow3D.RotationMode" />
+			<description>
+				Correct the [code]transform[/code]. [code]rotation_mode[/code] implicitly specifies how posture (forward, up and sideway direction) is caculated.
+			</description>
+		</method>
+	</methods>
 	<members>
 		<member name="cubic_interp" type="bool" setter="set_cubic_interpolation" getter="get_cubic_interpolation" default="true">
 			If [code]true[/code], the position between two cached points is interpolated cubically, and linearly otherwise.
@@ -30,6 +40,9 @@
 		<member name="rotation_mode" type="int" setter="set_rotation_mode" getter="get_rotation_mode" enum="PathFollow3D.RotationMode" default="3">
 			Allows or forbids rotation on one or more axes, depending on the [enum RotationMode] constants being used.
 		</member>
+		<member name="tilt_enabled" type="bool" setter="set_tilt_enabled" getter="is_tilt_enabled" default="true">
+			If [code]true[/code], the tilt property of [Curve3D] takes effect.
+		</member>
 		<member name="v_offset" type="float" setter="set_v_offset" getter="get_v_offset" default="0.0">
 			The node's offset perpendicular to the curve.
 		</member>

scene/3d/path_3d.cpp

@@ -182,125 +182,31 @@ void PathFollow3D::_update_transform(bool p_update_xyz_rot) {
 	if (bl == 0.0) {
 		return;
 	}
-	real_t bi = c->get_bake_interval();
-	real_t o_next = progress + bi;
-	real_t o_prev = progress - bi;
-
-	if (loop) {
-		o_next = Math::fposmod(o_next, bl);
-		o_prev = Math::fposmod(o_prev, bl);
-	} else if (rotation_mode == ROTATION_ORIENTED) {
-		if (o_next >= bl) {
-			o_next = bl;
-		}
-		if (o_prev <= 0) {
-			o_prev = 0;
-		}
-	}
-
-	Vector3 pos = c->sample_baked(progress, cubic);
-	Transform3D t = get_transform();
-	// Vector3 pos_offset = Vector3(h_offset, v_offset, 0); not used in all cases
-	// will be replaced by "Vector3(h_offset, v_offset, 0)" where it was formerly used
-
-	if (rotation_mode == ROTATION_ORIENTED) {
-		Vector3 forward = c->sample_baked(o_next, cubic) - pos;
-
-		// Try with the previous position
-		if (forward.length_squared() < CMP_EPSILON2) {
-			forward = pos - c->sample_baked(o_prev, cubic);
-		}
-
-		if (forward.length_squared() < CMP_EPSILON2) {
-			forward = Vector3(0, 0, 1);
-		} else {
-			forward.normalize();
-		}
-
-		Vector3 up = c->sample_baked_up_vector(progress, true);
 
-		if (o_next < progress) {
-			Vector3 up1 = c->sample_baked_up_vector(o_next, true);
-			Vector3 axis = up.cross(up1);
-
-			if (axis.length_squared() < CMP_EPSILON2) {
-				axis = forward;
-			} else {
-				axis.normalize();
-			}
-
-			up.rotate(axis, up.angle_to(up1) * 0.5f);
-		}
-
-		Vector3 scale = t.basis.get_scale();
-		Vector3 sideways = up.cross(forward).normalized();
-		up = forward.cross(sideways).normalized();
-
-		t.basis.set_columns(sideways, up, forward);
-		t.basis.scale_local(scale);
-
-		t.origin = pos + sideways * h_offset + up * v_offset;
-	} else if (rotation_mode != ROTATION_NONE) {
-		// perform parallel transport
-		//
-		// see C. Dougan, The Parallel Transport Frame, Game Programming Gems 2 for example
-		// for a discussion about why not Frenet frame.
+	Transform3D t;
 
+	if (rotation_mode == ROTATION_NONE) {
+		Vector3 pos = c->sample_baked(progress, cubic);
 		t.origin = pos;
-		if (p_update_xyz_rot && prev_offset != progress) { // Only update rotation if some parameter has changed - i.e. not on addition to scene tree.
-			real_t sample_distance = bi * 0.01;
-			Vector3 t_prev_pos_a = c->sample_baked(prev_offset - sample_distance, cubic);
-			Vector3 t_prev_pos_b = c->sample_baked(prev_offset + sample_distance, cubic);
-			Vector3 t_cur_pos_a = c->sample_baked(progress - sample_distance, cubic);
-			Vector3 t_cur_pos_b = c->sample_baked(progress + sample_distance, cubic);
-			Vector3 t_prev = (t_prev_pos_a - t_prev_pos_b).normalized();
-			Vector3 t_cur = (t_cur_pos_a - t_cur_pos_b).normalized();
-
-			Vector3 axis = t_prev.cross(t_cur);
-			real_t dot = t_prev.dot(t_cur);
-			real_t angle = Math::acos(CLAMP(dot, -1, 1));
-
-			if (likely(!Math::is_zero_approx(angle))) {
-				if (rotation_mode == ROTATION_Y) {
-					// assuming we're referring to global Y-axis. is this correct?
-					axis.x = 0;
-					axis.z = 0;
-				} else if (rotation_mode == ROTATION_XY) {
-					axis.z = 0;
-				} else if (rotation_mode == ROTATION_XYZ) {
-					// all components are allowed
-				}
+	} else {
+		t = c->sample_baked_with_rotation(progress, cubic, false);
+		Vector3 forward = t.basis.get_column(2); // Retain tangent for applying tilt
+		t = PathFollow3D::correct_posture(t, rotation_mode);
 
-				if (likely(!Math::is_zero_approx(axis.length()))) {
-					t.rotate_basis(axis.normalized(), angle);
-				}
-			}
+		// Apply tilt *after* correct_posture
+		if (tilt_enabled) {
+			const real_t tilt = c->sample_baked_tilt(progress);
 
-			// do the additional tilting
-			real_t tilt_angle = c->sample_baked_tilt(progress);
-			Vector3 tilt_axis = t_cur; // not sure what tilt is supposed to do, is this correct??
-
-			if (likely(!Math::is_zero_approx(Math::abs(tilt_angle)))) {
-				if (rotation_mode == ROTATION_Y) {
-					tilt_axis.x = 0;
-					tilt_axis.z = 0;
-				} else if (rotation_mode == ROTATION_XY) {
-					tilt_axis.z = 0;
-				} else if (rotation_mode == ROTATION_XYZ) {
-					// all components are allowed
-				}
-
-				if (likely(!Math::is_zero_approx(tilt_axis.length()))) {
-					t.rotate_basis(tilt_axis.normalized(), tilt_angle);
-				}
-			}
+			const Basis twist(forward, tilt);
+			t.basis = twist * t.basis;
 		}
-
-		t.translate_local(Vector3(h_offset, v_offset, 0));
-	} else {
-		t.origin = pos + Vector3(h_offset, v_offset, 0);
 	}
 
+	Vector3 scale = get_transform().basis.get_scale();
+
+	t.translate_local(Vector3(h_offset, v_offset, 0));
+	t.basis.scale_local(scale);
+
 	set_transform(t);
 }
 
@@ -358,6 +264,38 @@ PackedStringArray PathFollow3D::get_configuration_warnings() const {
 	return warnings;
 }
 
+Transform3D PathFollow3D::correct_posture(Transform3D p_transform, PathFollow3D::RotationMode p_rotation_mode) {
+	Transform3D t = p_transform;
+
+	// Modify frame according to rotation mode.
+	if (p_rotation_mode == PathFollow3D::ROTATION_NONE) {
+		// Clear rotation.
+		t.basis = Basis();
+	} else if (p_rotation_mode == PathFollow3D::ROTATION_ORIENTED) {
+		// Y-axis always straight up.
+		Vector3 up(0.0, 1.0, 0.0);
+		Vector3 forward = t.basis.get_column(2);
+
+		t.basis = Basis::looking_at(-forward, up);
+	} else {
+		// Lock some euler axes.
+		Vector3 euler = t.basis.get_euler_normalized(EulerOrder::YXZ);
+		if (p_rotation_mode == PathFollow3D::ROTATION_Y) {
+			// Only Y-axis allowed.
+			euler[0] = 0;
+			euler[2] = 0;
+		} else if (p_rotation_mode == PathFollow3D::ROTATION_XY) {
+			// XY allowed.
+			euler[2] = 0;
+		}
+
+		Basis locked = Basis::from_euler(euler, EulerOrder::YXZ);
+		t.basis = locked;
+	}
+
+	return t;
+}
+
 void PathFollow3D::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_progress", "progress"), &PathFollow3D::set_progress);
 	ClassDB::bind_method(D_METHOD("get_progress"), &PathFollow3D::get_progress);
@@ -380,6 +318,11 @@ void PathFollow3D::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_loop", "loop"), &PathFollow3D::set_loop);
 	ClassDB::bind_method(D_METHOD("has_loop"), &PathFollow3D::has_loop);
 
+	ClassDB::bind_method(D_METHOD("set_tilt_enabled", "enabled"), &PathFollow3D::set_tilt_enabled);
+	ClassDB::bind_method(D_METHOD("is_tilt_enabled"), &PathFollow3D::is_tilt_enabled);
+
+	ClassDB::bind_static_method("PathFollow3D", D_METHOD("correct_posture", "transform", "rotation_mode"), &PathFollow3D::correct_posture);
+
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "progress", PROPERTY_HINT_RANGE, "0,10000,0.01,or_less,or_greater,suffix:m"), "set_progress", "get_progress");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "progress_ratio", PROPERTY_HINT_RANGE, "0,1,0.0001,or_less,or_greater", PROPERTY_USAGE_EDITOR), "set_progress_ratio", "get_progress_ratio");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "h_offset", PROPERTY_HINT_NONE, "suffix:m"), "set_h_offset", "get_h_offset");
@@ -387,6 +330,7 @@ void PathFollow3D::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "rotation_mode", PROPERTY_HINT_ENUM, "None,Y,XY,XYZ,Oriented"), "set_rotation_mode", "get_rotation_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "cubic_interp"), "set_cubic_interpolation", "get_cubic_interpolation");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "loop"), "set_loop", "has_loop");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "tilt_enabled"), "set_tilt_enabled", "is_tilt_enabled");
 
 	BIND_ENUM_CONSTANT(ROTATION_NONE);
 	BIND_ENUM_CONSTANT(ROTATION_Y);
@@ -397,7 +341,6 @@ void PathFollow3D::_bind_methods() {
 
 void PathFollow3D::set_progress(real_t p_progress) {
 	ERR_FAIL_COND(!isfinite(p_progress));
-	prev_offset = progress;
 	progress = p_progress;
 
 	if (path) {
@@ -409,8 +352,6 @@ void PathFollow3D::set_progress(real_t p_progress) {
 				if (!Math::is_zero_approx(p_progress) && Math::is_zero_approx(progress)) {
 					progress = path_length;
 				}
-			} else {
-				progress = CLAMP(progress, 0, path_length);
 			}
 		}
 
@@ -476,3 +417,11 @@ void PathFollow3D::set_loop(bool p_loop) {
 bool PathFollow3D::has_loop() const {
 	return loop;
 }
+
+void PathFollow3D::set_tilt_enabled(bool p_enable) {
+	tilt_enabled = p_enable;
+}
+
+bool PathFollow3D::is_tilt_enabled() const {
+	return tilt_enabled;
+}

scene/3d/path_3d.h

@@ -72,14 +72,16 @@ public:
 		ROTATION_ORIENTED
 	};
 
+	static Transform3D correct_posture(Transform3D p_transform, PathFollow3D::RotationMode p_rotation_mode);
+
 private:
 	Path3D *path = nullptr;
-	real_t prev_offset = 0.0; // Offset during the last _update_transform.
 	real_t progress = 0.0;
 	real_t h_offset = 0.0;
 	real_t v_offset = 0.0;
 	bool cubic = true;
 	bool loop = true;
+	bool tilt_enabled = true;
 	RotationMode rotation_mode = ROTATION_XYZ;
 
 	void _update_transform(bool p_update_xyz_rot = true);
@@ -106,6 +108,9 @@ public:
 	void set_loop(bool p_loop);
 	bool has_loop() const;
 
+	void set_tilt_enabled(bool p_enable);
+	bool is_tilt_enabled() const;
+
 	void set_rotation_mode(RotationMode p_rotation_mode);
 	RotationMode get_rotation_mode() const;
 

scene/resources/curve.cpp

@@ -31,6 +31,7 @@
 #include "curve.h"
 
 #include "core/core_string_names.h"
+#include "core/math/math_funcs.h"
 
 const char *Curve::SIGNAL_RANGE_CHANGED = "range_changed";
 
@@ -1413,8 +1414,9 @@ void Curve3D::_bake() const {
 	if (points.size() == 0) {
 		baked_point_cache.clear();
 		baked_tilt_cache.clear();
-		baked_up_vector_cache.clear();
 		baked_dist_cache.clear();
+
+		baked_up_vector_cache.clear();
 		return;
 	}
 
@@ -1438,15 +1440,16 @@ void Curve3D::_bake() const {
 
 	Vector3 position = points[0].position;
 	real_t dist = 0.0;
-	List<Plane> pointlist;
+	List<Plane> pointlist; // Abuse Plane for (position, dist)
 	List<real_t> distlist;
 
 	// Start always from origin.
 	pointlist.push_back(Plane(position, points[0].tilt));
 	distlist.push_back(0.0);
 
+	// Step 1: Sample points
+	const real_t step = 0.1; // At least 10 substeps ought to be enough?
 	for (int i = 0; i < points.size() - 1; i++) {
-		real_t step = 0.1; // at least 10 substeps ought to be enough?
 		real_t p = 0.0;
 
 		while (p < 1.0) {
@@ -1461,7 +1464,7 @@ void Curve3D::_bake() const {
 			if (d > bake_interval) {
 				// OK! between P and NP there _has_ to be Something, let's go searching!
 
-				int iterations = 10; //lots of detail!
+				const int iterations = 10; // Lots of detail!
 
 				real_t low = p;
 				real_t hi = np;
@@ -1496,76 +1499,135 @@ void Curve3D::_bake() const {
 		Vector3 npp = points[i + 1].position;
 		real_t d = position.distance_to(npp);
 
-		position = npp;
-		Plane post;
-		post.normal = position;
-		post.d = points[i + 1].tilt;
+		if (d > CMP_EPSILON) { // Avoid the degenerate case of two very close points.
+			position = npp;
+			Plane post;
+			post.normal = position;
+			post.d = points[i + 1].tilt;
 
-		dist += d;
+			dist += d;
 
-		pointlist.push_back(post);
-		distlist.push_back(dist);
+			pointlist.push_back(post);
+			distlist.push_back(dist);
+		}
 	}
 
 	baked_max_ofs = dist;
 
-	baked_point_cache.resize(pointlist.size());
-	Vector3 *w = baked_point_cache.ptrw();
-	int idx = 0;
+	const int point_count = pointlist.size();
+	{
+		baked_point_cache.resize(point_count);
+		Vector3 *w = baked_point_cache.ptrw();
 
-	baked_tilt_cache.resize(pointlist.size());
-	real_t *wt = baked_tilt_cache.ptrw();
+		baked_tilt_cache.resize(point_count);
+		real_t *wt = baked_tilt_cache.ptrw();
 
-	baked_up_vector_cache.resize(up_vector_enabled ? pointlist.size() : 0);
-	Vector3 *up_write = baked_up_vector_cache.ptrw();
+		baked_dist_cache.resize(point_count);
+		real_t *wd = baked_dist_cache.ptrw();
 
-	baked_dist_cache.resize(pointlist.size());
-	real_t *wd = baked_dist_cache.ptrw();
+		int idx = 0;
+		for (const Plane &E : pointlist) {
+			w[idx] = E.normal;
+			wt[idx] = E.d;
+			wd[idx] = distlist[idx];
 
-	Vector3 sideways;
-	Vector3 up;
-	Vector3 forward;
+			idx++;
+		}
+	}
+
+	if (!up_vector_enabled) {
+		baked_up_vector_cache.resize(0);
+		return;
+	}
 
-	Vector3 prev_sideways = Vector3(1, 0, 0);
-	Vector3 prev_up = Vector3(0, 1, 0);
-	Vector3 prev_forward = Vector3(0, 0, 1);
+	// Step 2: Calculate the up vectors and the whole local reference frame
+	//
+	// See Dougan, Carl. "The parallel transport frame." Game Programming Gems 2 (2001): 215-219.
+	// for an example discussing about why not the Frenet frame.
+	{
+		PackedVector3Array forward_vectors;
 
-	for (const Plane &E : pointlist) {
-		w[idx] = E.normal;
-		wt[idx] = E.d;
-		wd[idx] = distlist[idx];
+		baked_up_vector_cache.resize(point_count);
+		forward_vectors.resize(point_count);
 
-		if (!up_vector_enabled) {
-			idx++;
-			continue;
+		Vector3 *up_write = baked_up_vector_cache.ptrw();
+		Vector3 *forward_write = forward_vectors.ptrw();
+
+		const Vector3 *points_ptr = baked_point_cache.ptr();
+
+		Basis frame; // X-right, Y-up, Z-forward.
+		Basis frame_prev;
+
+		// Set the initial frame based on Y-up rule.
+		{
+			Vector3 up(0, 1, 0);
+			Vector3 forward = (points_ptr[1] - points_ptr[0]).normalized();
+			if (forward.is_equal_approx(Vector3())) {
+				forward = Vector3(1, 0, 0);
+			}
+
+			if (abs(forward.dot(up)) > 1.0 - UNIT_EPSILON) {
+				frame_prev = Basis::looking_at(-forward, up);
+			} else {
+				frame_prev = Basis::looking_at(-forward, Vector3(1, 0, 0));
+			}
+
+			up_write[0] = frame_prev.get_column(1);
+			forward_write[0] = frame_prev.get_column(2);
 		}
 
-		forward = idx > 0 ? (w[idx] - w[idx - 1]).normalized() : prev_forward;
+		// Calculate the Parallel Transport Frame.
+		for (int idx = 1; idx < point_count; idx++) {
+			Vector3 forward = (points_ptr[idx] - points_ptr[idx - 1]).normalized();
+			if (forward.is_equal_approx(Vector3())) {
+				forward = frame_prev.get_column(2);
+			}
 
-		real_t y_dot = prev_up.dot(forward);
+			Basis rotate;
+			rotate.rotate_to_align(frame_prev.get_column(2), forward);
+			frame = rotate * frame_prev;
+			frame.orthonormalize(); // guard against float error accumulation
 
-		if (y_dot > (1.0f - CMP_EPSILON)) {
-			sideways = prev_sideways;
-			up = -prev_forward;
-		} else if (y_dot < -(1.0f - CMP_EPSILON)) {
-			sideways = prev_sideways;
-			up = prev_forward;
-		} else {
-			sideways = prev_up.cross(forward).normalized();
-			up = forward.cross(sideways).normalized();
+			up_write[idx] = frame.get_column(1);
+			forward_write[idx] = frame.get_column(2);
+
+			frame_prev = frame;
 		}
 
-		if (idx == 1) {
-			up_write[0] = up;
+		bool is_loop = true;
+		// Loop smoothing only applies when the curve is a loop, which means two ends meet, and share forward directions.
+		{
+			if (!points_ptr[0].is_equal_approx(points_ptr[point_count - 1])) {
+				is_loop = false;
+			}
+
+			real_t dot = forward_write[0].dot(forward_write[point_count - 1]);
+			if (dot < 1.0 - 0.01) { // Alignment should not be too tight, or it dosen't work for coarse bake interval
+				is_loop = false;
+			}
 		}
 
-		up_write[idx] = up;
+		// Twist up vectors, so that they align at two ends of the curve.
+		if (is_loop) {
+			const Vector3 up_start = up_write[0];
+			const Vector3 up_end = up_write[point_count - 1];
+
+			real_t sign = SIGN(up_end.cross(up_start).dot(forward_write[0]));
+			real_t full_angle = Quaternion(up_end, up_start).get_angle();
 
-		prev_sideways = sideways;
-		prev_up = up;
-		prev_forward = forward;
+			if (abs(full_angle) < UNIT_EPSILON) {
+				return;
+			} else {
+				const real_t *dists = baked_dist_cache.ptr();
+				for (int idx = 1; idx < point_count; idx++) {
+					const real_t frac = dists[idx] / baked_max_ofs;
+					const real_t angle = Math::lerp((real_t)0.0, full_angle, frac);
+					Basis twist(forward_write[idx] * sign, angle);
 
-		idx++;
+					up_write[idx] = twist.xform(up_write[idx]);
+				}
+			}
+		}
 	}
 }
 
@@ -1577,27 +1639,15 @@ real_t Curve3D::get_baked_length() const {
 	return baked_max_ofs;
 }
 
-Vector3 Curve3D::sample_baked(real_t p_offset, bool p_cubic) const {
-	if (baked_cache_dirty) {
-		_bake();
-	}
+Curve3D::Interval Curve3D::_find_interval(real_t p_offset) const {
+	Interval interval = {
+		-1,
+		0.0
+	};
+	ERR_FAIL_COND_V_MSG(baked_cache_dirty, interval, "Backed cache is dirty");
 
-	// Validate: Curve may not have baked points.
 	int pc = baked_point_cache.size();
-	ERR_FAIL_COND_V_MSG(pc == 0, Vector3(), "No points in Curve3D.");
-
-	if (pc == 1) {
-		return baked_point_cache.get(0);
-	}
-
-	const Vector3 *r = baked_point_cache.ptr();
-
-	if (p_offset < 0) {
-		return r[0];
-	}
-	if (p_offset >= baked_max_ofs) {
-		return r[pc - 1];
-	}
+	ERR_FAIL_COND_V_MSG(pc < 2, interval, "Less than two points in cache");
 
 	int start = 0;
 	int end = pc;
@@ -1617,9 +1667,27 @@ Vector3 Curve3D::sample_baked(real_t p_offset, bool p_cubic) const {
 	real_t offset_end = baked_dist_cache[idx + 1];
 
 	real_t idx_interval = offset_end - offset_begin;
-	ERR_FAIL_COND_V_MSG(p_offset < offset_begin || p_offset > offset_end, Vector3(), "Couldn't find baked segment.");
+	ERR_FAIL_COND_V_MSG(p_offset < offset_begin || p_offset > offset_end, interval, "Offset out of range.");
 
-	real_t frac = (p_offset - offset_begin) / idx_interval;
+	interval.idx = idx;
+	if (idx_interval < FLT_EPSILON) {
+		interval.frac = 0.5; // For a very short interval, 0.5 is a reasonable choice.
+		ERR_FAIL_V_MSG(interval, "Zero length interval.");
+	}
+
+	interval.frac = (p_offset - offset_begin) / idx_interval;
+	return interval;
+}
+
+Vector3 Curve3D::_sample_baked(Interval p_interval, bool p_cubic) const {
+	// Assuming p_interval is valid.
+	ERR_FAIL_INDEX_V_MSG(p_interval.idx, baked_point_cache.size(), Vector3(), "Invalid interval");
+
+	int idx = p_interval.idx;
+	real_t frac = p_interval.frac;
+
+	const Vector3 *r = baked_point_cache.ptr();
+	int pc = baked_point_cache.size();
 
 	if (p_cubic) {
 		Vector3 pre = idx > 0 ? r[idx - 1] : r[idx];
@@ -1630,114 +1698,150 @@ Vector3 Curve3D::sample_baked(real_t p_offset, bool p_cubic) const {
 	}
 }
 
-real_t Curve3D::sample_baked_tilt(real_t p_offset) const {
-	if (baked_cache_dirty) {
-		_bake();
-	}
-
-	// Validate: Curve may not have baked tilts.
-	int pc = baked_tilt_cache.size();
-	ERR_FAIL_COND_V_MSG(pc == 0, 0, "No tilts in Curve3D.");
+real_t Curve3D::_sample_baked_tilt(Interval p_interval) const {
+	// Assuming that p_interval is valid.
+	ERR_FAIL_INDEX_V_MSG(p_interval.idx, baked_tilt_cache.size(), 0.0, "Invalid interval");
 
-	if (pc == 1) {
-		return baked_tilt_cache.get(0);
-	}
+	int idx = p_interval.idx;
+	real_t frac = p_interval.frac;
 
 	const real_t *r = baked_tilt_cache.ptr();
 
-	if (p_offset < 0) {
-		return r[0];
+	return Math::lerp(r[idx], r[idx + 1], frac);
+}
+
+Basis Curve3D::_sample_posture(Interval p_interval, bool p_apply_tilt) const {
+	// Assuming that p_interval is valid.
+	ERR_FAIL_INDEX_V_MSG(p_interval.idx, baked_point_cache.size(), Basis(), "Invalid interval");
+	if (up_vector_enabled) {
+		ERR_FAIL_INDEX_V_MSG(p_interval.idx, baked_up_vector_cache.size(), Basis(), "Invalid interval");
 	}
-	if (p_offset >= baked_max_ofs) {
-		return r[pc - 1];
+
+	int idx = p_interval.idx;
+	real_t frac = p_interval.frac;
+
+	Vector3 forward_begin;
+	Vector3 forward_end;
+	if (idx == 0) {
+		forward_begin = (baked_point_cache[1] - baked_point_cache[0]).normalized();
+		forward_end = (baked_point_cache[1] - baked_point_cache[0]).normalized();
+	} else {
+		forward_begin = (baked_point_cache[idx] - baked_point_cache[idx - 1]).normalized();
+		forward_end = (baked_point_cache[idx + 1] - baked_point_cache[idx]).normalized();
 	}
 
-	int start = 0;
-	int end = pc;
-	int idx = (end + start) / 2;
-	// Binary search to find baked points.
-	while (start < idx) {
-		real_t offset = baked_dist_cache[idx];
-		if (p_offset <= offset) {
-			end = idx;
-		} else {
-			start = idx;
-		}
-		idx = (end + start) / 2;
+	Vector3 up_begin;
+	Vector3 up_end;
+	if (up_vector_enabled) {
+		const Vector3 *up_ptr = baked_up_vector_cache.ptr();
+		up_begin = up_ptr[idx];
+		up_end = up_ptr[idx + 1];
+	} else {
+		up_begin = Vector3(0.0, 1.0, 0.0);
+		up_end = Vector3(0.0, 1.0, 0.0);
 	}
 
-	real_t offset_begin = baked_dist_cache[idx];
-	real_t offset_end = baked_dist_cache[idx + 1];
+	// Build frames at both ends of the interval, then interpolate.
+	const Basis frame_begin = Basis::looking_at(-forward_begin, up_begin);
+	const Basis frame_end = Basis::looking_at(-forward_end, up_end);
+	const Basis frame = frame_begin.slerp(frame_end, frac).orthonormalized();
 
-	real_t idx_interval = offset_end - offset_begin;
-	ERR_FAIL_COND_V_MSG(p_offset < offset_begin || p_offset > offset_end, 0, "Couldn't find baked segment.");
+	if (!p_apply_tilt) {
+		return frame;
+	}
 
-	real_t frac = (p_offset - offset_begin) / idx_interval;
+	// Applying tilt.
+	const real_t tilt = _sample_baked_tilt(p_interval);
+	Vector3 forward = frame.get_column(2);
 
-	return Math::lerp(r[idx], r[idx + 1], (real_t)frac);
+	const Basis twist(forward, tilt);
+	return twist * frame;
 }
 
-Vector3 Curve3D::sample_baked_up_vector(real_t p_offset, bool p_apply_tilt) const {
+Vector3 Curve3D::sample_baked(real_t p_offset, bool p_cubic) const {
 	if (baked_cache_dirty) {
 		_bake();
 	}
 
-	// Validate: Curve may not have baked up vectors.
-	int count = baked_up_vector_cache.size();
-	ERR_FAIL_COND_V_MSG(count == 0, Vector3(0, 1, 0), "No up vectors in Curve3D.");
+	// Validate: Curve may not have baked points.
+	int pc = baked_point_cache.size();
+	ERR_FAIL_COND_V_MSG(pc == 0, Vector3(), "No points in Curve3D.");
 
-	if (count == 1) {
-		return baked_up_vector_cache.get(0);
+	if (pc == 1) {
+		return baked_point_cache[0];
 	}
 
-	const Vector3 *r = baked_up_vector_cache.ptr();
-	const Vector3 *rp = baked_point_cache.ptr();
-	const real_t *rt = baked_tilt_cache.ptr();
+	p_offset = CLAMP(p_offset, 0.0, get_baked_length()); // PathFollower implement wrapping logic.
 
-	int start = 0;
-	int end = count;
-	int idx = (end + start) / 2;
-	// Binary search to find baked points.
-	while (start < idx) {
-		real_t offset = baked_dist_cache[idx];
-		if (p_offset <= offset) {
-			end = idx;
-		} else {
-			start = idx;
-		}
-		idx = (end + start) / 2;
+	Curve3D::Interval interval = _find_interval(p_offset);
+	return _sample_baked(interval, p_cubic);
+}
+
+Transform3D Curve3D::sample_baked_with_rotation(real_t p_offset, bool p_cubic, bool p_apply_tilt) const {
+	if (baked_cache_dirty) {
+		_bake();
 	}
 
-	if (idx == count - 1) {
-		return p_apply_tilt ? r[idx].rotated((rp[idx] - rp[idx - 1]).normalized(), rt[idx]) : r[idx];
+	// Validate: Curve may not have baked points.
+	const int point_count = baked_point_cache.size();
+	ERR_FAIL_COND_V_MSG(point_count == 0, Transform3D(), "No points in Curve3D.");
+
+	if (point_count == 1) {
+		Transform3D t;
+		t.origin = baked_point_cache.get(0);
+		ERR_FAIL_V_MSG(t, "Only 1 point in Curve3D.");
 	}
 
-	real_t offset_begin = baked_dist_cache[idx];
-	real_t offset_end = baked_dist_cache[idx + 1];
+	p_offset = CLAMP(p_offset, 0.0, get_baked_length()); // PathFollower implement wrapping logic.
 
-	real_t idx_interval = offset_end - offset_begin;
-	ERR_FAIL_COND_V_MSG(p_offset < offset_begin || p_offset > offset_end, Vector3(0, 1, 0), "Couldn't find baked segment.");
+	// 0. Find interval for all sampling steps.
+	Curve3D::Interval interval = _find_interval(p_offset);
 
-	real_t frac = (p_offset - offset_begin) / idx_interval;
+	// 1. Sample position.
+	Vector3 pos = _sample_baked(interval, p_cubic);
+
+	// 2. Sample rotation frame.
+	Basis frame = _sample_posture(interval, p_apply_tilt);
+
+	return Transform3D(frame, pos);
+}
+
+real_t Curve3D::sample_baked_tilt(real_t p_offset) const {
+	if (baked_cache_dirty) {
+		_bake();
+	}
 
-	Vector3 forward = (rp[idx + 1] - rp[idx]).normalized();
-	Vector3 up = r[idx];
-	Vector3 up1 = r[idx + 1];
+	// Validate: Curve may not have baked tilts.
+	int pc = baked_tilt_cache.size();
+	ERR_FAIL_COND_V_MSG(pc == 0, 0, "No tilts in Curve3D.");
 
-	if (p_apply_tilt) {
-		up.rotate(forward, rt[idx]);
-		up1.rotate(idx + 2 >= count ? forward : (rp[idx + 2] - rp[idx + 1]).normalized(), rt[idx + 1]);
+	if (pc == 1) {
+		return baked_tilt_cache.get(0);
 	}
 
-	Vector3 axis = up.cross(up1);
+	p_offset = CLAMP(p_offset, 0.0, get_baked_length()); // PathFollower implement wrapping logic
 
-	if (axis.length_squared() < CMP_EPSILON2) {
-		axis = forward;
-	} else {
-		axis.normalize();
+	Curve3D::Interval interval = _find_interval(p_offset);
+	return _sample_baked_tilt(interval);
+}
+
+Vector3 Curve3D::sample_baked_up_vector(real_t p_offset, bool p_apply_tilt) const {
+	if (baked_cache_dirty) {
+		_bake();
+	}
+
+	// Validate: Curve may not have baked up vectors.
+	ERR_FAIL_COND_V_MSG(!up_vector_enabled, Vector3(0, 1, 0), "No up vectors in Curve3D.");
+
+	int count = baked_up_vector_cache.size();
+	if (count == 1) {
+		return baked_up_vector_cache.get(0);
 	}
 
-	return up.rotated(axis, up.angle_to(up1) * frac);
+	p_offset = CLAMP(p_offset, 0.0, get_baked_length()); // PathFollower implement wrapping logic.
+
+	Curve3D::Interval interval = _find_interval(p_offset);
+	return _sample_posture(interval, p_apply_tilt).get_column(1);
 }
 
 PackedVector3Array Curve3D::get_baked_points() const {
@@ -2034,6 +2138,7 @@ void Curve3D::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("get_baked_length"), &Curve3D::get_baked_length);
 	ClassDB::bind_method(D_METHOD("sample_baked", "offset", "cubic"), &Curve3D::sample_baked, DEFVAL(false));
+	ClassDB::bind_method(D_METHOD("sample_baked_with_rotation", "offset", "cubic", "apply_tilt"), &Curve3D::sample_baked_with_rotation, DEFVAL(false), DEFVAL(false));
 	ClassDB::bind_method(D_METHOD("sample_baked_up_vector", "offset", "apply_tilt"), &Curve3D::sample_baked_up_vector, DEFVAL(false));
 	ClassDB::bind_method(D_METHOD("get_baked_points"), &Curve3D::get_baked_points);
 	ClassDB::bind_method(D_METHOD("get_baked_tilts"), &Curve3D::get_baked_tilts);

scene/resources/curve.h

@@ -238,11 +238,6 @@ class Curve3D : public Resource {
 
 	Vector<Point> points;
 
-	struct BakedPoint {
-		real_t ofs = 0.0;
-		Vector3 point;
-	};
-
 	mutable bool baked_cache_dirty = false;
 	mutable PackedVector3Array baked_point_cache;
 	mutable Vector<real_t> baked_tilt_cache;
@@ -254,6 +249,15 @@ class Curve3D : public Resource {
 
 	void _bake() const;
 
+	struct Interval {
+		int idx;
+		real_t frac;
+	};
+	Interval _find_interval(real_t p_offset) const;
+	Vector3 _sample_baked(Interval p_interval, bool p_cubic) const;
+	real_t _sample_baked_tilt(Interval p_interval) const;
+	Basis _sample_posture(Interval p_interval, bool p_apply_tilt = false) const;
+
 	real_t bake_interval = 0.2;
 	bool up_vector_enabled = true;
 
@@ -296,9 +300,10 @@ public:
 
 	real_t get_baked_length() const;
 	Vector3 sample_baked(real_t p_offset, bool p_cubic = false) const;
+	Transform3D sample_baked_with_rotation(real_t p_offset, bool p_cubic = false, bool p_apply_tilt = false) const;
 	real_t sample_baked_tilt(real_t p_offset) const;
 	Vector3 sample_baked_up_vector(real_t p_offset, bool p_apply_tilt = false) const;
-	PackedVector3Array get_baked_points() const; //useful for going through
+	PackedVector3Array get_baked_points() const; // Useful for going through.
 	Vector<real_t> get_baked_tilts() const; //useful for going through
 	PackedVector3Array get_baked_up_vectors() const;
 	Vector3 get_closest_point(const Vector3 &p_to_point) const;