visual3d:documentation:modeling:marker_sets:marker_placement
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| visual3d:documentation:modeling:marker_sets:marker_placement [2024/06/17 18:17] – created sgranger | visual3d:documentation:modeling:marker_sets:marker_placement [2024/07/17 15:45] (current) – created sgranger | ||
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| + | ====== Marker Placement ====== | ||
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| 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 landmarks can also be used instead of physical markers but the user should be aware that landmarks used to define one segment that are created with respect to another segment result in the two segments having less than 6 degrees of freedom each. | 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 landmarks can also be used instead of physical markers but the user should be aware that landmarks used to define one segment that are created with respect to another segment result in the two segments having less than 6 degrees of freedom each. | ||
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| Each segment requires at least three calibration markers (TARGETS or LANDMARKS) that are used to locate the proximal and distal ends of the segment and define the frontal plane of the LCS. The significance of this strategy lies in the fact that LANDMARKS can be created in a wide variety of ways, which allows Visual3D to mimic the models created by any marker configuration protocol whether traditional to gait analysis (e.g. Helen Hayes), or custom made in a laboratory. This has proved to be extremely useful for clinics or laboratories that are switching (or have switched) from one hardware vendor to another. | Each segment requires at least three calibration markers (TARGETS or LANDMARKS) that are used to locate the proximal and distal ends of the segment and define the frontal plane of the LCS. The significance of this strategy lies in the fact that LANDMARKS can be created in a wide variety of ways, which allows Visual3D to mimic the models created by any marker configuration protocol whether traditional to gait analysis (e.g. Helen Hayes), or custom made in a laboratory. This has proved to be extremely useful for clinics or laboratories that are switching (or have switched) from one hardware vendor to another. | ||
| - | ===== The minimum number of markers needed for 6 DOF segments. | + | ==== The minimum number of markers needed for 6 DOF segments. ==== |
| At least 3 non colinear markers are required for tracking a segment with 6 degrees of freedom. Visual3D' | At least 3 non colinear markers are required for tracking a segment with 6 degrees of freedom. Visual3D' | ||
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| The user should be aware that if a landmark is defined with respect to one segment coordinate system (e.g. the hip joint center landmark being defined relative to the pelvis segment coordinate system) and then used as a tracking marker for another segment (e.g. the thigh), the thigh segment is still tracked using 6 Degree of Freedom - HOWEVER, errors in tracking the pelvis contribute errors to the tracking of the thigh (so information from the pelvis is used to track the thigh). | The user should be aware that if a landmark is defined with respect to one segment coordinate system (e.g. the hip joint center landmark being defined relative to the pelvis segment coordinate system) and then used as a tracking marker for another segment (e.g. the thigh), the thigh segment is still tracked using 6 Degree of Freedom - HOWEVER, errors in tracking the pelvis contribute errors to the tracking of the thigh (so information from the pelvis is used to track the thigh). | ||
| - | ===== References | + | ==== References ==== |
| **Angeloni, C., Cappozzo, A., Catani, F., Leardini, A. (1993).** Quantification of relative displacement of skin- and plate-mounted markers with respect to bones. Journal of Biomechanics 26:864. | **Angeloni, C., Cappozzo, A., Catani, F., Leardini, A. (1993).** Quantification of relative displacement of skin- and plate-mounted markers with respect to bones. Journal of Biomechanics 26:864. | ||
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| **Reinschmidt, | **Reinschmidt, | ||
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visual3d/documentation/modeling/marker_sets/marker_placement.1718648228.txt.gz · Last modified: 2024/06/17 18:17 by sgranger