Analysis Preferences
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Theia Axiom - v2025
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The Analysis preferences pane contains advanced options and parameters for adjusting how the movement is analyzed, including subject identification and person tracking, model parameters, and 3D reconstruction parameters.
First and last frame to analyze (inclusive). Modified frame range values are included when preferences are saved. (Default: full trial length)
Image exclusion border size. Image matte area is displayed as a grey border around the camera views when active. The greyed-out portions of the videos will not be used when running the analysis, allowing poorly calibrated image borders to be ignored. Image matte area is not applied during lens calibration.
Maximum number of people to track. (Default: No max)
Select the method for determining person tracking priority. Run Analysis (without 2D) must be performed in order to update person tracking.
Most Visible: Person identification and tracking performed by prioritizing people who are visible in >75% of the total frames from all cameras throughout the entire trial, and ordering them by their distance to the global coordinate system origin.
Closest to Origin: Person identification and tracking performed by ordering all people by their minimum distance to the global coordinate system origin throughout the entire trial. For example, if a person walks directly over the origin, they will likely be identified as person 0.
Order of Appearance: Person identification and tracking performed by numbering people in order of appearance within the capture volume.
Remove any person IDs that are missing for 100 consecutive frames or more. This allows a person who is tracked repeatedly within a single trial (e.g. during several passes into and out of the volume) to be tracked and therefore exported separately, for instance as multiple separate c3d files.
Improve tracking of rotating and non-upright people at the expense of speed. (Default: Off)
If not selected, the generic model will be scaled during Solve Skeleton. If selected, a previously saved model can be used by the inverse kinematics algorithm. Use the Use Saved Model button on the next line to select the model to be used. Note that this option is only available when Max People is 1. (Default: Off)
Uses a larger grid for lens distortion correction. Only use if there is a lot of distortion and loading is slow. (Default: Off)
If selected, the model used by the inverse kinematics algorithm will have three degrees of freedom at the knee (flexion/extension, ab/adduction, and internal/external rotation). If not selected, the model will have two degrees of freedom at the knee (flexion/extension and ab/adduction). (Default: Off)
The cutoff frequency of the lowpass filter used to smooth the pose from the inverse kinematics. The default GCVSPL cutoff frequency is 20 Hz, cutoff frequency provides some smoothing and noise reduction while generally being sufficiently high to avoid ‘over-smoothing’ most movements.
General Recommendations:
For slow movements (e.g. sway, slow walking), a lower cutoff frequency around 6–12 Hz can be used.
For faster movements (e.g. running or jumping), a higher cutoff frequency around 10–20 Hz may be required.
Movements with very high segment velocities or accelerations such as baseball pitching or very dynamic changes of direction, cutoff frequencies above 20 Hz may be required.
If the smoothing frequency is set too low when processing very fast movements such as pitching, tracking dropouts may occur as the fastest moving segments are detected as outliers. If you encounter this situation, try increasing the smoothing frequency and using Solve Skeleton to implement the new setting, which may restore segment tracking.
When applying the filter using the selected smoothing frequency, Theia3D checks whether the applied smoothing frequency is appropriate for the movement and warns the user if they should consider adjusting the frequency. This test can occasionally produce false positive warnings, so these warnings can be disabled if desired.
Enables the 3D Analysis Bounding Box for use, which restricts person tracking to within a specified 3D volume. This allows people who are visible but not of interested to be ignored, such as the experimenter or other observers. Run Analysis (without 2D) must be performed in order to update person tracking and skeleton visibility.
The 3D camera locations will be used to establish the edges of the analysis bounding box, rather than the x, y, and z origin positions and length, width, and height dimension definitions.
Origin X: Position of the center of the bounding box along the global coordinate system X-axis.
Origin Y: Position of the center of the bounding box along the global coordinate system Y-axis.
Origin Z: Position of the center of the bounding box along the global coordinate system Z-axis. Minimum value is half the bounding box height.
Length: Bounding box dimension along the global coordinate system X-axis.
Width: Bounding box dimension along the global coordinate system Y-axis.
Height: Bounding box dimension along the global coordinate system Z-axis.
Uses separated IK chains for the lower body (pelvis and legs) and upper body (torso, arms, and head). No abdomen or neck segments. Shoulder joints and head segment are allowed 6 degrees of freedom. See for a detailed description of this model.
Uses a single, whole-body IK chain including pelvis, abdomen, and thorax segments. See for a detailed description of this model. Must be used if saving skeleton poses using FBX format.
Uses separated IK chains for the lower body (pelvis and legs), torso, arms, and head segments. No abdomen or neck segments. Shoulder joints and head segment are allowed 6 degrees of freedom. See for a detailed description of this model.
The smoothing frequency used is based on the which provides results equivalent to applying a double-pass Butterworth filter. Theia3D automatically fills gaps and smooths the 3D pose data for all individuals tracked in processed movement trials.
