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--- visual3d:documentation:modeling:marker_sets:cluster_size [2024/07/16 16:57] – removed sgranger
+++ visual3d:documentation:modeling:marker_sets:cluster_size [2024/07/17 15:45] (current) – created sgranger
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+====== Cluster Size ======
+To track a segment, a minimum of three noncolinear targets are required.
+As long as the three targets are not in a straight line, the segment can be tracked. However, the distance between the targets will affect your tracking.
+For example, assume you have a segment as shown below:\\
+{{:ClusterSize_Segment.png}}\\
+There are two options, you can either:
+  * put the targets spread out over the entire segment
+  * place the targets close together
+=== Spread Out Tracking Targets ===
+If the targets are spread out over the segment:\\
+{{:ClusterSize_Large_Segment.png}}\\
+It takes a large amount of target movement to produce a large change in the position and orientation of the segment:\\
+{{:ClusterSize_Large_Segment_Rotation.png}}\\
+=== Close Together Tracking Targets ===
+If the targets are spread close together:\\
+{{:ClusterSize_Small_Segment.png}}\\
+It takes a small amount of target movement to produce a large change in the position and orientation of the segment:\\
+{{:ClusterSize_Small_Segment_Rotation.png}}\\
+=== Application ===
+The closer the targets are together, the more susceptible the tracking will be to noise. So try to use best judgement when placing markers/defining clusters.
+This is true for tracking any segment, but it tends to be most relevant when tracking the pelvis (using a small cluster on the lower back vs using the ASIS and PSIS) or tracking the foot (using a heel cluster vs heel and met targets).