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visual3d:documentation:modeling:segments:segment_geometry [2025/06/20 15:37] – General clean-up and adding links. wikisysopvisual3d:documentation:modeling:segments:segment_geometry [2026/06/12 17:25] (current) – Added See Also section. wikisysop
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 ====== Segment Geometry ====== ====== Segment Geometry ======
  
-Visual3D models segments as cones, cylinders, spheres, and ellipsoids and uses this geometry to inform several quantities relevant for kinetic analyses: +Visual3D models segments as cones, cylinders, spheres, and ellipsoids and uses this geometry to inform several quantities relevant for kinetic analyses. 
-  * For segments created using a [[Visual3D:Documentation:Modeling:Segments:Segment_Mass|valid default name]], the segmental weight is determined from the total body weight and [[https://deepblue.lib.umich.edu/handle/2027.42/4540|Dempster's regression equations]]. The user can use the MASS qualifier to override the default value or to specify the weight of a segment with a non-default name. The segmental weight should be entered in kilograms. + 
-  * The principle moments of inertia are determined from the segmental weight and geometry. The user can use the IXX, IYY and IZZ qualifiers to override the default values or specify the inertia of a segment with a non-default name. The moments of inertia should be entered kg*m 2. +===== Default Segments ===== 
-  * Each segment's centre of gravity location is determined from the segment geometry.+ 
 +For segments created using a [[visual3d:documentation:modeling:segments:segment_default_names|valid default name]], the [[Visual3D:Documentation:Modeling:Segments:Segment_Mass|segmental mass]] is determined from the total body mass and [[https://deepblue.lib.umich.edu/handle/2027.42/4540|Dempster's regression equations]]. The user can use the MASS qualifier to override the default value or to specify the mass of a segment with a non-default name. This segmental mass should be entered in [[visual3d:documentation:pipeline:model_based_data_commands:units_of_measurement|kilograms]]. 
 + 
 +The principle [[visual3d:documentation:modeling:segments:segment_inertia|moments of inertia]] are determined from the segmental mass and geometry. The user can use the IXX, IYY and IZZ qualifiers to override the default values or specify the inertia of a segment with a non-default name. The moments of inertia should be entered kg*m 2. 
 + 
 +Finally, each segment's centre of gravity location is determined from the segment geometry and expressed relative to the segment's proximal end. 
 + 
 +==== Defining Default Segments ====
  
 Although these segment types differ geometrically, they all require defined distal and proximal radii to define [[visual3d:documentation:kinematics_and_kinetics:joint|joints]] for [[visual3d:documentation:kinematics_and_kinetics:six_degrees_of_freedom|6DOF tracking]]. Although these segment types differ geometrically, they all require defined distal and proximal radii to define [[visual3d:documentation:kinematics_and_kinetics:joint|joints]] for [[visual3d:documentation:kinematics_and_kinetics:six_degrees_of_freedom|6DOF tracking]].
  
-===== Cones - Frusta of right cones =====+==== Cones - Frusta of right cones ====
  
 Segments modelled as frusta of right cones require both the proximal and distal segment radii. Segments modelled as frusta of right cones require both the proximal and distal segment radii.
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   * If only a single target is used at a segment end, then a qualifier, either DIST_RAD or PROX_RAD, must be used.   * If only a single target is used at a segment end, then a qualifier, either DIST_RAD or PROX_RAD, must be used.
  
-===== Cylinders - Right elliptical cylinders =====+==== Cylinders - Right elliptical cylinders ====
  
 Segments modelled as right elliptical cylinders require a proximal segment radius, a distal segment radius (major axis), and a segment depth (minor axis radius). Segments modelled as right elliptical cylinders require a proximal segment radius, a distal segment radius (major axis), and a segment depth (minor axis radius).
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   * The depth of cylindrical segments must always be specified. The cylindrical depth is equal to one-half the distance from anterior to posterior. The qualifier DEPTH is used to specify this distance.   * The depth of cylindrical segments must always be specified. The cylindrical depth is equal to one-half the distance from anterior to posterior. The qualifier DEPTH is used to specify this distance.
  
-===== Spheres =====+==== Spheres ====
  
 Segments modelled as spheres require a proximal segment radius and a distal segment radius. Segments modelled as spheres require a proximal segment radius and a distal segment radius.
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 **Note**: One notable difference arises when creating spherical segments as Visual3D expects the distal targets to be located at 50% of the distance between segment ends. This allows the distal radius to produce a realistic measure of the dimension of the sphere. **Note**: One notable difference arises when creating spherical segments as Visual3D expects the distal targets to be located at 50% of the distance between segment ends. This allows the distal radius to produce a realistic measure of the dimension of the sphere.
  
-===== Ellipsoids =====+==== Ellipsoids ====
  
 Segments modelled as ellipsoids require a proximal segment radius and a distal segment radius. Segments modelled as ellipsoids require a proximal segment radius and a distal segment radius.
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 ===== Custom Segments ===== ===== Custom Segments =====
  
-Custom segment may be created by selecting "CUSTOM_SEG" and directly modifying the segment properties. An example of this can be found [[Visual3D:Documentation:Modeling:Segments:Segment_Properties#Modify_Segment_Properties|here]].+Custom segment may be created by selecting "CUSTOM_SEG" and directly modifying the segment properties using the [[visual3d:documentation:pipeline:model_commands:set_segment_properties|Set_Segment_Properties]] pipeline command. 
 + 
 +===== See Also ===== 
 + 
 +Go back to the [[visual3d:documentation:modeling:segments:segment_overview|Segment Overview]] for more information about segments in Visual3D.
  
 ===== References ===== ===== References =====
visual3d/documentation/modeling/segments/segment_geometry.1750433851.txt.gz · Last modified: by wikisysop