Merge pull request godotengine#112573 from TokageItLab/fix-jacobian-gradient

Fix JacobianIK to apply gradient correctly

Author: Repiteo

doc/classes/JacobianIK3D.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="JacobianIK3D" inherits="IterateIK3D" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
 	<brief_description>
-		Pseudo inverse Jacobian matrix based inverse kinematics solver.
+		Jacobian transpose based inverse kinematics solver.
 	</brief_description>
 	<description>
 		[JacobianIK3D] calculates rotations for all joints simultaneously, producing natural and smooth movement. It is particularly suited for biological animations.

scene/3d/jacobian_ik_3d.cpp

@@ -54,7 +54,7 @@ void JacobianIK3D::_solve_iteration(double p_delta, Skeleton3D *p_skeleton, Iter
 			continue;
 		}
 
-		Quaternion to_rot = Quaternion(axis.normalized(), axis.length() / MAX(CMP_EPSILON, head_to_effector.length()));
+		Quaternion to_rot = Quaternion(axis.normalized(), MIN(axis.length() / MAX(CMP_EPSILON, head_to_effector.length_squared()), angular_delta_limit)); // Clip by angular_delta_limit for stability.
 
 		for (int j = TAIL; j < chain_size; j++) {
 			Vector3 to_tail = p_setting->chain[j] - current_head;