PlayTrajectory

Interpolate through coordinate states in a trajectory.

View source Guide and examplesInherits Animation

from proteinmotion import PlayTrajectory

Constructor

PlayTrajectory(
    protein,
    trajectory=None,
    *,
    start=0,
    end=None,
    rate_func=linear,
    state_easing=linear,
    easing=None,
)

Parameters

Parameter	Default	Description
`protein`	Required	Protein object to read or animate.
`trajectory`	`None`	Trajectory with the same atom identities and order; None uses the protein’s trajectory.
`start`keyword only	`0`	Starting frame index; may be fractional.
`end`keyword only	`None`	Ending frame index; None uses the last frame.
`rate_func`keyword only	`linear`	Callable that maps progress in [0, 1] to a finite value in [0, 1].
`state_easing`keyword only	`linear`	Callable controlling interpolation within each adjacent pair of trajectory frames.
`easing`keyword only	`None`	Named easing (smooth, linear, ease_in_out_sine, there_and_back) or callable mapping [0, 1] to [0, 1]. Per-item easing preserves stagger timing.

Notes

Trajectory topology must match the protein. rate_func controls progress through the clip; state_easing controls interpolation between each pair of frames. Deposited NMR model order represents structural variation rather than measured time.

Example and output

This excerpt runs inside a scene’s construct() method. The full example file includes imports, structure loading, and camera setup. Run it from a repository checkout.

Code Scene excerpt

loaded = Protein.from_file(DATA / "2k39.cif", chains="A")
core = loaded.select(residues=(1, 70), atoms="CA")
aligned = loaded.trajectory.aligned(indices=core.atom_indices)
p = Protein.from_trajectory(aligned).cartoon().center()
frame(self, p)
self.play(
    PlayTrajectory(p, start=0, end=2, state_easing=smooth),
    run_time=6,
)
self.wait(0.5)

Output Preview · 6.5 s · 60 fps

NMR state playback

PDB 2K39 models 1–3. Interpolation shows structural variation.

Full source: NMRStates Download MP4

Methods and properties

Name	Description
apply()method	Evaluate the animation at eased progress alpha. Called by the timeline.
during()method · inherited from Animation	Set this animation duration and start delay in seconds.
bind()method · inherited from Animation	Capture starting values when the scene schedules the animation.
targetsproperty · inherited from Animation	Objects whose state this animation changes.

apply()

View source

PlayTrajectory.apply(alpha)

Evaluate the animation at eased progress alpha. Called by the timeline.

Parameter	Default	Description
`alpha`	Required	Eased animation progress in [0, 1].

Returns: None

during()

View source

Inherited from animation.Animation.

PlayTrajectory.during(seconds, *, delay=0)

Set this animation duration and start delay in seconds.

Parameter	Default	Description
`seconds`	Required	Positive animation duration in seconds.
`delay`keyword only	`0`	Nonnegative animation start delay in seconds.

bind()

View source

Inherited from animation.Animation.

PlayTrajectory.bind()

Capture starting values when the scene schedules the animation.

Returns: None

Called by ProteinScene.play(). An animation instance can be bound once.

targets

View source

Inherited from animation.Animation.

PlayTrajectory.targets

Objects whose state this animation changes.