Standardise segment lengths (camera-distance correction)

In 2D video, apparent bone lengths shrink and grow as the subject moves toward or away from the camera, biasing kinematics. This rescales each limb segment so its length matches a stable reference (the recording's median or mean of that segment), repositioning the distal keypoint along the bone direction and chaining proximal to distal. Generalised form of the length correction in PoseFixeR (Sugiyama, Uno & Matsui 2023).

Usage

poseLengthCorrect(pe, chains = NULL, reference = c("median", "mean"))

Arguments

pe

A pose PhysioExperiment (assays keypoint_x, keypoint_y; colData$label), e.g. from readOpenPose() or after poseFix().

chains

Optional list of kinematic chains, each a proximal-to-distal vector of keypoint names (default: both legs and both arms, restricted to the present keypoints).

reference

"median" (default, robust) or "mean" reference length.

Value

A PhysioExperiment with length-standardised keypoint_x/y; metadata()$poseLengthCorrect holds the reference length per segment.

References

Sugiyama S, Uno K, Matsui Y (2023). PLOS Comput Biol 19:e1009989. doi:10.1371/journal.pcbi.1009989

See also

poseFix()