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visual3d:documentation:kinematics_and_kinetics:pose_estimation [2024/06/18 13:28] – sgrangervisual3d:documentation:kinematics_and_kinetics:pose_estimation [2025/04/08 14:04] (current) – wikisysop
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 +====== Pose Estimation ======
 +
 Visual3D has two distinctive approaches to computing the position and orientation of a segment. The first approach is the Six Degrees of Freedom method, which determines the position and orientation of segments independently from one another based solely upon measurements of that segment. The second approach is the Inverse Kinematics method, where segments form a hierarchical linked chain with joint properties that define the "connection" between segments. Visual3D has two distinctive approaches to computing the position and orientation of a segment. The first approach is the Six Degrees of Freedom method, which determines the position and orientation of segments independently from one another based solely upon measurements of that segment. The second approach is the Inverse Kinematics method, where segments form a hierarchical linked chain with joint properties that define the "connection" between segments.
  
-===== Six Degrees of Freedom =====+==== Six Degrees of Freedom ====
  
 The [[Visual3D:Documentation:Kinematics_and_Kinetics:Six_Degrees_of_Freedom|Six Degrees of Freedom]] method (6 DOF) is also referred to as Segment Optimization, since segment positions and orientations are solved for on a per-segment basis. The [[Visual3D:Documentation:Kinematics_and_Kinetics:Six_Degrees_of_Freedom|Six Degrees of Freedom]] method (6 DOF) is also referred to as Segment Optimization, since segment positions and orientations are solved for on a per-segment basis.
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 The method's name refers to the fact that each segment (or each joint) is considered to have 6 variables that describe its pose (3 variable describe the position of the origin, 3 variables describe the rotation about each of the principal axes of the segment) The method's name refers to the fact that each segment (or each joint) is considered to have 6 variables that describe its pose (3 variable describe the position of the origin, 3 variables describe the rotation about each of the principal axes of the segment)
  
-===== Inverse Kinematics =====+==== Inverse Kinematics ====
  
 An alternative to the 6 DOF solution is to define joints (e.g. explicitly state which segments are connected by a joint) and to specify the properties of all joints. Because the targets used to track the segments are often subject to measurement error and soft tissue artifact, motion about some of the degrees of freedom maybe much larger than the motion that would be realistically possible. An alternative to the 6 DOF solution is to define joints (e.g. explicitly state which segments are connected by a joint) and to specify the properties of all joints. Because the targets used to track the segments are often subject to measurement error and soft tissue artifact, motion about some of the degrees of freedom maybe much larger than the motion that would be realistically possible.
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 Lu and O’Connor (1999) described a global optimization process where physically realistic joint constraints can be added to the model to minimize the effect of the soft tissue and measurement error. Lu and O’Connor termed this process Global Optimization while other inside the biomechanics community prefer the term "Inverse Kinematics." Visual3D uses the term Inverse Kinematics but the underlying calculations are based upon the Lu and O’Connor technique.) Lu and O’Connor (1999) described a global optimization process where physically realistic joint constraints can be added to the model to minimize the effect of the soft tissue and measurement error. Lu and O’Connor termed this process Global Optimization while other inside the biomechanics community prefer the term "Inverse Kinematics." Visual3D uses the term Inverse Kinematics but the underlying calculations are based upon the Lu and O’Connor technique.)
  
-===== Choosing between 6 DOF and IK =====+==== Choosing between 6 DOF and IK ====
  
 Many practitioners are interested in the questions: **How close are the 6 DOF and IK methods in terms of data and which one is correct?** Many practitioners are interested in the questions: **How close are the 6 DOF and IK methods in terms of data and which one is correct?**
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 In general I find that a visual inspection of the data in Visual3D will give you a good clue of whether IK is useful or not. If looking at the data in Visual3D you see a lot of joints disarticulating then IK will generally be a good idea. (For example I have looked at the upper extremities in baseball pitching and golf and you often see the elbow blow apart and IK helps this sort of data considerably.) In general I find that a visual inspection of the data in Visual3D will give you a good clue of whether IK is useful or not. If looking at the data in Visual3D you see a lot of joints disarticulating then IK will generally be a good idea. (For example I have looked at the upper extremities in baseball pitching and golf and you often see the elbow blow apart and IK helps this sort of data considerably.)
  
-===== Lecture Notes =====+==== Lecture Notes ====
  
-[[[https://www.has-motion.com/download/examples/POSE_Estimation.pptx|Lecture notes on pose estimation]]], including 6 DOF and Inverse Kinematics (e.g. Segment Optimization and Global Optimization).+[[https://www.has-motion.com/download/examples/POSE_Estimation.pptx|Lecture notes on pose estimation]], including 6 DOF and Inverse Kinematics (e.g. Segment Optimization and Global Optimization).
  
-===== Marker Sets and Pose Estimation =====+==== Marker Sets and Pose Estimation ====
  
-[[[https://drive.google.com/drive/folders/0BwthwD-r-QOUNnBIWENsakxfcFk|Allan Carman]]] has prepared an interesting expose on marker sets and pose estimation algorithms.+[[https://drive.google.com/drive/folders/0BwthwD-r-QOUNnBIWENsakxfcFk|Allan Carman]] has prepared an interesting expose on marker sets and pose estimation algorithms.
  
 While these opinions are Allan's, not ours, we highly recommend reading the information. While these opinions are Allan's, not ours, we highly recommend reading the information.
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 If you have any questions related to Allan's document and how things are implemented in Visual3D, you will probably find it in our wiki or text book chapters, but feel free to contact us about specific issues. If you have any questions related to Allan's document and how things are implemented in Visual3D, you will probably find it in our wiki or text book chapters, but feel free to contact us about specific issues.
  
-===== Further Reading =====+==== Further Reading ====
  
 Leardini A, Belvedere C, Nardini F, Sancisi N, Conconi M, Parenti-Castelli V (2017) Kinematic models of lower limb joints for musculo-skeletal modelling and optimization in gait analysis. J Biomech. 2017 Sep 6;62:77-86. doi: 10.1016/j.jbiomech.2017.04.029. Epub 2017 May 22. Leardini A, Belvedere C, Nardini F, Sancisi N, Conconi M, Parenti-Castelli V (2017) Kinematic models of lower limb joints for musculo-skeletal modelling and optimization in gait analysis. J Biomech. 2017 Sep 6;62:77-86. doi: 10.1016/j.jbiomech.2017.04.029. Epub 2017 May 22.
visual3d/documentation/kinematics_and_kinetics/pose_estimation.1718717287.txt.gz · Last modified: 2024/06/18 13:28 by sgranger