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--- visual3d:documentation:third-party:xsens:xsens [2024/07/17 15:46] – created sgranger
+++ visual3d:documentation:third-party:xsens:xsens [2024/10/24 14:25] (current) – wikisysop
@@ Line 1: / Line 1: @@
 ====== XSens ======
-\\
 For more information about Xsens, visit the [[https://www.xsens.com/|Xsens Website]].\\
+[[https://www.xsens.com/|Xsens]] uses IMU's to track motion, and processes the information in MVN, resulting in an MVNX file or a C3D file.
+Visual3D can directly read either the C3D or the MVNX file.
+Please note that raw data from Xsens or any IMU's is not useful for biomechanics without post-processing to generate POSE information.
-===== Introduction =====
+The legacy implementation of the mvnx model was released in Visual3D v5.02.24.
+If using Visual3D versions prior to this to process your data, please follow the instructions [[Visual3D:Documentation:Third-Party:XSens:XSens_v5|here]].
+A more flexible implementation of the mvnx model was released in Visual3D 2024.05.2
-[[https://www.xsens.com/|Xsens]] uses IMU's to track motion, and processes the information in MVN, resulting in an MVNX file or a C3D file. Visual3D can directly read either the C3D or the MVNX file. Please note that raw data from Xsens or any IMU's is not useful for biomechanics without post-processing to generate POSE information.
+Typically, Visual3D reads data in the C3D file format which contains target locations from a motion capture system.
+Although Xsens can export C3D files, there is more information in an MVNX file that Visual3D can use to create a model automatically.
+Visual3D compatible Xsens .mvnx files should contain the following variables for each segment : \\
+orientation, position, velocity, acceleration, angularVelocity, angularAcceleration. (See "Exporting from MVN Studio" below)
-This feature was released in Visual3D v5.02.24. If using version 5 to process your data, please follow the instructions [[Visual3D:Documentation:Third-Party:XSens:XSens_v5|here]].
+===== Opening MVNX Files =====
-=== Background ===
+MVNX files can be opened by going to File -> Open in Visual3D.
-Typically, Visual3D reads data in the C3D file format which contains target locations from a motion capture system. Although Xsens can export C3D files, there are reasons why a user may prefer to export Xsens data as an MVNX file. Visual3D compatible Xsens .mvnx files should contain the following variables for each segment : orientation, position, velocity, acceleration, angularVelocity, angularAcceleration. (See "Exporting from MVN Studio" below)
+They can also be opened using the File_Open pipeline command.
-\\
-**Model Pose (position and orientation):**
-Visual computes the model Pose using a "Link Model" that matches the Xsens link model. The model's root, which is the pelvis, has both an orientation and a position (all 6 degrees of freedom). Visual3D then work through model's chain (assuming a ball and socket at all joints) using the .mvnx segment orienation variables to compute the joint angles. This give us the position and orientation (POSE) of the entire model.
+=====Model Pose=====
+Model Pose (position and orientation) of the multi-body model
+Visual computes the model Pose using a "Link Model" that matches the Xsens link model.
+As of Visual3D version 2024.05.2, the user can choose one of two implementations of a model based on the mvnx file.
+There are two implementations of a Visual3D model for mvnx data. As users will likely want to use the same implementation each time an mvnx file is loaded,
+the selection of models can be made in the Program Options, which will save the selection to the registry
+{{FileOpenOptions.png}}
+=====Legacy Implementation=====
+When the file is opened, the user will be prompted for all the necessary model metrics to create the model.
+The model's root, which is the pelvis, has both an orientation and a position (all 6 degrees of freedom). Visual3D then work through model's chain (assuming a ball and socket at all joints) using the .mvnx segment orienation variables to compute the joint angles. This give us the position and orientation (POSE) of the entire model.
 **Segment Kinematics:**
@@ Line 36: / Line 58: @@
 If you take the first derivative of the ProxEndPos KINETIC_KINEMATIC variable it will not exactly equal the ProxEndVel KINETIC_KINEMATIC variable which come from the .mvnx Translational Velocity of the Origin. The idea is to use the Xsens data for velocity, acceleration and kinetic calculations even if it is slightly inconsistent with the derivative of the Pose data. (This data is assumed to be more accurate measure of velocity and acceleration then taking the derivatives of which amplifies noise.)
-=== Download Files ===
+==== Prop Sensors ====
+Visual3Dv2020.## supports reading MVNX files with one prop sensor. The sensor will be loaded automatically as a segment (ex. PR1). If more props are required to process your data, please contact C-Motion. When using an Xsens prop in Visual3D, all information is loaded automatically and no further steps are required. A sample MVNX file with a prop can be downloaded **[[https://www.has-motion.com/download/examples/Xsens/Xsens_Prop_Example.zip|here]].**\\
+[[Visual3D:Documentation:Third-Party:XSens:XSens_Prop|This tutorial explains how to adjust the location of the prop segment and assign a graphics object to the prop using a script]].\\
+=====Flexible Implementation=====
+Unlike the legacy implementation when the file is opened, the user will not be prompted for the anthropometric data (i.e. mass and moment of inertia).
+Instead default values are used, which can later be modified by the user.
+Our thinking was that users that are only interested in kinematics do not want to be prompted for unnecessary information every time a file is loaded.
+In this implementation, the information in the mvnx file is used to create 4x4 ROTATION signals similar to the output from markerless tracking systems like Theia3D, and Kinatrax,
+and is consistent with the ROTATION signals created from bvh files (Fujitsu implementation of bvh).
+Using model based information in the mvnx file, a model is created automatically from the ROTATION signals.
+In this implementation the Kinetic_Kinematic variables are created consistently with the other ROTATION based models.
+Unlike the legacy implementation the segment pose is explicitly defined.
+==== Prop Sensors ====
+If a prop sensor exists in the mvnx file, a ROTATION matrix is created form the prop pose.
+The user can create/modify a segment definition using this pose
+==== Download Files ====
   * [[https://www.has-motion.com/download/examples/Xsens/MVNX_Files.zip|Sample MVNX files]]
@@ Line 66: / Line 119: @@
-===== Opening MVNX Files =====
-As of Visual3Dv6, MVNX files can be opened by going to File -> Open in Visual3D.
-They can also be opened using the File_Open pipeline command. When the file is opened, the user will be prompted for all the necessary model metrics to create the model.
-===== Processing Xsens Data =====
-==== Trunk Graphic ====
-The default Xsens model points to the [[https://www.has-motion.com/download/examples/Xsens/Trunk_No_Neck.zip|thoraciccerviclet12toacromium_noneck.obj]] graphic.
-This means if the graphic does not appear in your model, you can download the graphic [[https://www.has-motion.com/download/examples/Xsens/Trunk_No_Neck.zip|here]], unzip the files (obj and mtl), and place them in your default graphics folder. Once the graphic file is placed in the models folder, you may need to close and re-open Visual3D. Instructions to find your models folder can be found [[Visual3D:Tutorials:Modeling:Fun_With_Graphics#Finding_your_Graphics_Folder|here]].
-==== Prop Sensors ====
-\\
-Visual3Dv2020.## supports reading MVNX files with one prop sensor. The sensor will be loaded automatically as a segment (ex. PR1). If more props are required to process your data, please contact C-Motion. When using an Xsens prop in Visual3D, all information is loaded automatically and no further steps are required. A sample MVNX file with a prop can be downloaded **[[https://www.has-motion.com/download/examples/Xsens/Xsens_Prop_Example.zip|here]].**\\
-\\
-[[Visual3D:Documentation:Third-Party:XSens:XSens_Prop|This tutorial explains how to adjust the location of the prop segment and assign a graphics object to the prop using a script]].\\