README: relation to MotionPersonaX

README.md

@@ -225,6 +225,26 @@ Blender, MotionBuilder or Maya.
 - **Coverage.** Not every participant has every context–locomotion combination (see the figure in Section 2).
   Participant `b15` contributes 17 clips.
 
+## 6. Related dataset: MotionPersonaX
+
+<p align="center">
+  <img src="assets/grid_fill.gif" width="90%" alt="Persona by body grid: captured data occupy only the diagonal, MotionPersonaX fills all 44 x 128 cells">
+</p>
+<p align="center"><em>MotionPersona captures each participant in exactly one body, their own: the diagonal of the
+persona × body grid. MotionPersonaX fills all 44 × 128 cells.</em></p>
+
+In MotionPersona, who performs a motion and the body that carries it are inseparable, since each participant is
+recorded only in their own body. [MotionPersonaX](https://huggingface.co/datasets/myshi/MotionPersonaX) removes this
+coupling: it retargets the 2,570 clips of the 44 annotated participants onto 128 SMPL-X bodies (the 48 bodies of this
+dataset and 80 synthetic bodies spanning 1.05–1.95 m in height and eight girth levels), giving 328,960 clips (about
+4,200 h) in which persona and body vary independently. The retargeting is an explicit optimisation that preserves the
+timing of the source and adapts posture, contacts, balance and trunk lean to the target body.
+
+The two datasets share identifiers and clip names: `<body>/p02_angry_fw.npz` in MotionPersonaX is clip `p02_angry_fw`
+of this dataset on body `<body>`, and the clip on the participant's own body is the source motion itself.
+MotionPersonaX clips are sampled at half the frame rate of the SMPL-X fits (frame *k* corresponds to frame 2*k* − 1
+here), use the same SMPL-X conventions, and carry the same static hand pose per clip (Section 3.3).
+
 ## License & Commercial Use
 
 This dataset is released under the CC-BY-NC 4.0 License for non-commercial and research purposes only.