Using USD Python API compute velocities attribute (poor man's example)

usd_compute_velocities.py

from pxr import Usd, UsdGeom, Sdf, Vt, Gf

# Create a new stage in memory
stage =Usd.Stage.Open(r"path/to/file.usd")
fps = stage.GetFramesPerSecond() or 24.0  # default when not authored is 24

for prim in stage.Traverse():
    if not prim.IsA(UsdGeom.PointBased):
        continue

    geo = UsdGeom.PointBased(prim)
    points_attr = geo.GetPointsAttr()
    velocities_attr = geo.GetVelocitiesAttr()
    
    # Write velocities only if points data has more than one timesample
    write_velocities = points_attr.GetNumTimeSamples() > 1
    if not write_velocities:
        continue
       
    time_samples = points_attr.GetTimeSamples()
    velocities_attr = geo.CreateVelocitiesAttr()
    for i, t in enumerate(time_samples):
        try:
            t_next = time_samples[i+1]
        except IndexError:
            # This will compute zero velocity essentially
            t_next = t
            
        points = points_attr.Get(t)
        points_next = points_attr.Get(t_next)
        
        t_delta = t_next - t
        
        velocities = [b - a for a, b in zip(points, points_next)]
        
        # Multiply velocity with the FPS
        if t_delta != 0:
            velocities = [(v / t_delta) * fps for v in velocities]
        velocities_attr.Set(velocities, t)


# Print the stage to USD format to verify the result
print(stage.GetRootLayer().ExportToString())