Fix Curve3D::get_closest_point() broken

The problem is caused by calling adaptive tessellation baking function by mistake, which produce too few points for straight lines. Calling the even length tessellation fix the problem.

The code for `get_closest_point()` and `get_closest_offset()` are also updated. They used to assume bake interval to be exact, which is no longer true.

The out dated document for `get_closest_point()` is also updated.

2 files changed, 13 insertions, 11 deletions

diff --git a/doc/classes/Curve3D.xml b/doc/classes/Curve3D.xml
index 67e4e45e52..851996131f 100644
--- a/doc/classes/Curve3D.xml
+++ b/doc/classes/Curve3D.xml
@@ -64,7 +64,7 @@
 			<return type="Vector3" />
 			<param index="0" name="to_point" type="Vector3" />
 			<description>
-				Returns the closest baked point (in curve's local space) to [param to_point].
+				Returns the closest point on baked segments (in curve's local space) to [param to_point].
 				[param to_point] must be in this curve's local space.
 			</description>
 		</method>
diff --git a/scene/resources/curve.cpp b/scene/resources/curve.cpp
index 9289c5da4a..93c3d4f851 100644
--- a/scene/resources/curve.cpp
+++ b/scene/resources/curve.cpp
@@ -1407,15 +1407,15 @@ void Curve3D::_bake_segment3d_even_length(RBMap<real_t, Vector3> &r_bake, real_t
 	Vector3 beg = p_a.bezier_interpolate(p_a + p_out, p_b + p_in, p_b, p_begin);
 	Vector3 end = p_a.bezier_interpolate(p_a + p_out, p_b + p_in, p_b, p_end);
 
-	size_t length = beg.distance_to(end);
+	real_t length = beg.distance_to(end);
 
 	if (length > p_length && p_depth < p_max_depth) {
 		real_t mp = (p_begin + p_end) * 0.5;
 		Vector3 mid = p_a.bezier_interpolate(p_a + p_out, p_b + p_in, p_b, mp);
 		r_bake[mp] = mid;
 
-		_bake_segment3d(r_bake, p_begin, mp, p_a, p_out, p_b, p_in, p_depth + 1, p_max_depth, p_length);
-		_bake_segment3d(r_bake, mp, p_end, p_a, p_out, p_b, p_in, p_depth + 1, p_max_depth, p_length);
+		_bake_segment3d_even_length(r_bake, p_begin, mp, p_a, p_out, p_b, p_in, p_depth + 1, p_max_depth, p_length);
+		_bake_segment3d_even_length(r_bake, mp, p_end, p_a, p_out, p_b, p_in, p_depth + 1, p_max_depth, p_length);
 	}
 }
 
@@ -1839,10 +1839,11 @@ Vector3 Curve3D::get_closest_point(const Vector3 &p_to_point) const {
 	real_t nearest_dist = -1.0f;
 
 	for (int i = 0; i < pc - 1; i++) {
+		const real_t interval = baked_dist_cache[i + 1] - baked_dist_cache[i];
 		Vector3 origin = r[i];
-		Vector3 direction = (r[i + 1] - origin) / bake_interval;
+		Vector3 direction = (r[i + 1] - origin) / interval;
 
-		real_t d = CLAMP((p_to_point - origin).dot(direction), 0.0f, bake_interval);
+		real_t d = CLAMP((p_to_point - origin).dot(direction), 0.0f, interval);
 		Vector3 proj = origin + direction * d;
 
 		real_t dist = proj.distance_squared_to(p_to_point);
@@ -1875,13 +1876,16 @@ real_t Curve3D::get_closest_offset(const Vector3 &p_to_point) const {
 
 	real_t nearest = 0.0f;
 	real_t nearest_dist = -1.0f;
-	real_t offset = 0.0f;
+	real_t offset;
 
 	for (int i = 0; i < pc - 1; i++) {
+		offset = baked_dist_cache[i];
+
+		const real_t interval = baked_dist_cache[i + 1] - baked_dist_cache[i];
 		Vector3 origin = r[i];
-		Vector3 direction = (r[i + 1] - origin) / bake_interval;
+		Vector3 direction = (r[i + 1] - origin) / interval;
 
-		real_t d = CLAMP((p_to_point - origin).dot(direction), 0.0f, bake_interval);
+		real_t d = CLAMP((p_to_point - origin).dot(direction), 0.0f, interval);
 		Vector3 proj = origin + direction * d;
 
 		real_t dist = proj.distance_squared_to(p_to_point);
@@ -1890,8 +1894,6 @@ real_t Curve3D::get_closest_offset(const Vector3 &p_to_point) const {
 			nearest = offset + d;
 			nearest_dist = dist;
 		}
-
-		offset += bake_interval;
 	}
 
 	return nearest;