simvx.core.nodes_2d.spring_follow

SpringFollow2D – critically-damped spring follow toward a target Vec2.

Module Contents

Classes

SpringFollow2D

Critically-damped spring follow toward a target Vec2.

Data

log

API

simvx.core.nodes_2d.spring_follow.log

‘getLogger(…)’

class simvx.core.nodes_2d.spring_follow.SpringFollow2D(**kwargs)[source]

Bases: simvx.core.nodes_2d.node2d.Node2D

Critically-damped spring follow toward a target Vec2.

The reusable primitive behind “the piece glides into its slot” motion: dealt cards, snapping inventory icons, a reticle easing onto a target, a camera-adjacent marker trailing an actor.

The follower’s position is integrated each frame toward

Attr:

target_position. A critically-damped spring is used: no oscillation, asymptotic approach, all controlled by a single

Attr:

half_life parameter (seconds for the gap to halve).

Two ways to drive the target:

  1. Direct write – assign to :attr:target_position from outside.

  2. Track another node – set :attr:target_path to a node path (e.g. "../HandSlot"); the follower will read that node’s position each frame.

Direct write wins when both are set (so animations can override the tracked node temporarily). Set target_path="" to clear tracking.

Example::

slot = Node2D(name="HandSlot", position=(400, 300))
card = SpringFollow2D(name="Card3H", position=(0, 0), half_life=0.12)
card.target_path = "../HandSlot"

Implementation uses the critically-damped spring formulation::

omega = 1.67835 / half_life     # gap halves every `half_life` seconds
a = (target - position) * omega**2 - velocity * 2 * omega
velocity += a * dt
position += velocity * dt

The constant 1.67835 is the numerical solution of (1 + omega*t) * exp(-omega*t) == 0.5 – the envelope of a critically-damped spring – so half_life is an honest “seconds for the gap to halve” knob. Stable at typical frame rates without sub-stepping.

Initialization

target_position

‘Property(…)’

target_path

‘NodePathProp(…)’

half_life

‘Property(…)’

enabled

‘Property(…)’

property velocity: simvx.core.math.types.Vec2[source]

Current per-second velocity of the follower (read-only).

reset(position=None) → None[source]

Snap to position (or the current target) with zero velocity.

on_update(dt: float) → None[source]
position

‘_SpatialVecProperty(…)’

rotation

‘Property(…)’

scale

‘_SpatialVecProperty(…)’

z_index

‘Property(…)’

z_as_relative

‘Property(…)’

render_layer

‘Property(…)’

set_render_layer(index: int, enabled: bool = True) → None
is_on_render_layer(index: int) → bool
property absolute_z_index: int
property rotation_degrees: float
property world_position: simvx.core.math.types.Vec2
property world_rotation: float
property world_scale: simvx.core.math.types.Vec2
property world_transform: tuple[simvx.core.math.types.Vec2, simvx.core.math.types.Vec2, float]
property forward: simvx.core.math.types.Vec2
property right: simvx.core.math.types.Vec2
translate(offset: tuple[float, float] | numpy.ndarray)
rotate(radians: float)
rotate_deg(degrees: float)
look_at(target: tuple[float, float] | numpy.ndarray)
transform_points(points: list[simvx.core.math.types.Vec2]) → list[simvx.core.math.types.Vec2]
draw_polygon(renderer, points: list[simvx.core.math.types.Vec2], closed=True, colour=None)
wrap_screen(margin: float = 20)
hdr

‘Property(…)’

property transform_render_dirty: bool
strict_errors: ClassVar[bool]

True

dev_checks: ClassVar[bool]

None

script_error_raised

‘Signal(…)’

dynamic: bool

False

visible

‘Property(…)’

update_mode

‘Property(…)’

__properties__: ClassVar[dict[str, simvx.core.descriptors.Property]]

None

classmethod __init_subclass__(**kwargs)
property name: str
property visible_in_tree: bool
reset_error() → None
add_child(node: simvx.core.node.T) → simvx.core.node.T
remove_child(node: simvx.core.node.Node) → None
reparent(new_parent: simvx.core.node.Node)
node_at(path, default=_NO_DEFAULT)
find(target, *, direct: bool = False)
find_all(target, *, direct: bool = False)
expect(target, *, direct: bool = False)
ancestor(target)
walk(*, include_self: bool = True) → collections.abc.Iterator[simvx.core.node.Node]
property path: str
property is_scene_root: bool
add_to_group(group: str)
remove_from_group(group: str)
is_in_group(group: str) → bool
on_ready() → None
on_enter_tree() → None
on_exit_tree() → None
on_fixed_update(dt: float) → None
on_draw(renderer) → None
on_picked(event: simvx.core.events.InputEvent) → None
on_unhandled_input(event: simvx.core.events.TreeInputEvent) → None
start_coroutine(gen: simvx.core.descriptors.Coroutine) → simvx.core.descriptors.CoroutineHandle
stop_coroutine(gen_or_handle)
queue_redraw() → None
property render_dirty: bool
clear_children()
destroy()
property destroying: bool
call_deferred(method: collections.abc.Callable[..., Any], *args: Any) → None
property app
property tree: simvx.core.scene_tree.SceneTree
property physics
property physics_2d
__getitem__(key: str)
classmethod get_properties() → dict[str, simvx.core.descriptors.Property]
__repr__()