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visual3d:documentation:modeling:marker_sets:marker_sets_overview [2024/06/19 13:57] – created sgrangervisual3d:documentation:modeling:marker_sets:marker_sets_overview [2024/07/17 15:45] (current) – created sgranger
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 +====== Marker Sets Overview ======
 +
 Visual3D supports almost any marker set, including 6 Degree of Freedom, Helen Hayes/Newinton (e.g." Convential Gait Model"), CODA, and many laboratory in-house systems. Place tracking markers on the segments in strategic and geometrically relevant positions that move only minimally with skin movement. Random placement of markers may result in unusable data You will need two types of markers: calibration markers (for defining the segments) and tracking markers (for computing the movements). Calibration markers can be used for tracking, but be aware that markers placed near the ends of segments (e.g. the lateral knee) are especially susceptible to skin movement artifacts. Visual3D supports almost any marker set, including 6 Degree of Freedom, Helen Hayes/Newinton (e.g." Convential Gait Model"), CODA, and many laboratory in-house systems. Place tracking markers on the segments in strategic and geometrically relevant positions that move only minimally with skin movement. Random placement of markers may result in unusable data You will need two types of markers: calibration markers (for defining the segments) and tracking markers (for computing the movements). Calibration markers can be used for tracking, but be aware that markers placed near the ends of segments (e.g. the lateral knee) are especially susceptible to skin movement artifacts.
  
-{{LowerBody6DOF.gif}}\\+{{:LowerBody6DOF.gif}}\\
  
  
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 Therefore, in deciding the marker configuration to be used it is necessary to be aware of the limitations that can be imposed on the measurement of 3-D coordinates simply as a result of the marker set. Optimally, markers should be placed on a pin inserted into the bone itself. However, this is not always feasible. Consequently, the researcher must decide which of the externally placed marker configurations will be optimal for the task under investigation. Furthermore, the accuracy of measurement from segment to segment and axis to axis is different. It is clear that relatively reliable measures can be made for all segments in terms of flexion/extension movements. However, the secondary axis motions are less reliable, particularly the internal/external rotation about the long axis of the segments. Therefore, in deciding the marker configuration to be used it is necessary to be aware of the limitations that can be imposed on the measurement of 3-D coordinates simply as a result of the marker set. Optimally, markers should be placed on a pin inserted into the bone itself. However, this is not always feasible. Consequently, the researcher must decide which of the externally placed marker configurations will be optimal for the task under investigation. Furthermore, the accuracy of measurement from segment to segment and axis to axis is different. It is clear that relatively reliable measures can be made for all segments in terms of flexion/extension movements. However, the secondary axis motions are less reliable, particularly the internal/external rotation about the long axis of the segments.
  
-===== Basic Rules =====+==== Basic Rules ====
  
 Visual3D does not require the user to adopt a special marker configuration. The skeletal model defined in Visual3D has a precise definition that the user can follow to create any number of segments within a model. Following these basic rules allows Visual3D to calculate the 6 degree of freedom pose (position and orientation) of every segment using optimal techniques. Visual3D does not require the user to adopt a special marker configuration. The skeletal model defined in Visual3D has a precise definition that the user can follow to create any number of segments within a model. Following these basic rules allows Visual3D to calculate the 6 degree of freedom pose (position and orientation) of every segment using optimal techniques.
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-{{scsxperptoyzplane.gif}}\\+{{:scsxperptoyzplane.gif}}\\
  
  
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 Note that the Helen Hayes marker sets typically have two tracking markers per segment and the proximal joint center. Because the proximal joint center has been calculated using information from the proximal segment, the Helen Hayes marker set does not have 6 degrees of freedom. This dependence on the proximal segment causes errors to propogate from segment to segment (e.g. errors in the hip joint center cause errors in determining the pose of the foot). Note that the Helen Hayes marker sets typically have two tracking markers per segment and the proximal joint center. Because the proximal joint center has been calculated using information from the proximal segment, the Helen Hayes marker set does not have 6 degrees of freedom. This dependence on the proximal segment causes errors to propogate from segment to segment (e.g. errors in the hip joint center cause errors in determining the pose of the foot).
  
-===== Marker Placement =====+==== Marker Placement ====
  
 Visual3D interprets all marker sets in a similar fashion. The marker configuration promoted for Visual3D consists of a combination of arrays of markers placed on a rigid surface and markers placed on anatomical landmarks. Visual3D interprets all marker sets in a similar fashion. The marker configuration promoted for Visual3D consists of a combination of arrays of markers placed on a rigid surface and markers placed on anatomical landmarks.
  
-==== Marker Clusters ====+=== Marker Clusters ===
  
-==== Marker Set Guidelines ====+=== Marker Set Guidelines ===
  
  
  
visual3d/documentation/modeling/marker_sets/marker_sets_overview.1718805469.txt.gz · Last modified: 2024/06/19 13:57 by sgranger