Struct bevy::prelude::CubicBezier

pub struct CubicBezier<P>
where
    P: VectorSpace,
{ /* private fields */ }

A spline composed of a single cubic Bezier curve.

Useful for user-drawn curves with local control, or animation easing. See CubicSegment::new_bezier for use in easing.

Interpolation

The curve only passes through the first and last control point in each set of four points. The curve is divided into “segments” by every fourth control point.

Tangency

Tangents are manually defined by the two intermediate control points within each set of four points. You can think of the control points the curve passes through as “anchors”, and as the intermediate control points as the anchors displaced along their tangent vectors

Continuity

A Bezier curve is at minimum C0 continuous, meaning it has no holes or jumps. Each curve segment is C2, meaning the tangent vector changes smoothly between each set of four control points, but this doesn’t hold at the control points between segments. Making the whole curve C1 or C2 requires moving the intermediate control points to align the tangent vectors between segments, and can result in a loss of local control.

Usage

let points = [[
    vec2(-1.0, -20.0),
    vec2(3.0, 2.0),
    vec2(5.0, 3.0),
    vec2(9.0, 8.0),
]];
let bezier = CubicBezier::new(points).to_curve();
let positions: Vec<_> = bezier.iter_positions(100).collect();

Implementations

impl<P> CubicBezier<P>

where P: VectorSpace,

pub fn new(control_points: impl Into<Vec<[P; 4]>>) -> CubicBezier<P>

Create a new cubic Bezier curve from sets of control points.

Examples found in repository

examples/animation/color_animation.rs (line 81)

fn spawn_curve_sprite<T: CurveColor>(commands: &mut Commands, y: f32, points: [T; 4]) {
    commands.spawn((
        SpriteBundle {
            transform: Transform::from_xyz(0., y, 0.),
            sprite: Sprite {
                custom_size: Some(Vec2::new(75., 75.)),
                ..Default::default()
            },
            ..Default::default()
        },
        Curve(CubicBezier::new([points]).to_curve()),
    ));
}

examples/animation/cubic_curve.rs (line 37)

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    // Define your control points
    // These points will define the curve
    // You can learn more about bezier curves here
    // https://en.wikipedia.org/wiki/B%C3%A9zier_curve
    let points = [[
        vec3(-6., 2., 0.),
        vec3(12., 8., 0.),
        vec3(-12., 8., 0.),
        vec3(6., 2., 0.),
    ]];

    // Make a CubicCurve
    let bezier = CubicBezier::new(points).to_curve();

    // Spawning a cube to experiment on
    commands.spawn((
        PbrBundle {
            mesh: meshes.add(Cuboid::default()),
            material: materials.add(Color::from(ORANGE)),
            transform: Transform::from_translation(points[0][0]),
            ..default()
        },
        Curve(bezier),
    ));

    // Some light to see something
    commands.spawn(PointLightBundle {
        point_light: PointLight {
            shadows_enabled: true,
            intensity: 10_000_000.,
            range: 100.0,
            ..default()
        },
        transform: Transform::from_xyz(8., 16., 8.),
        ..default()
    });

    // ground plane
    commands.spawn(PbrBundle {
        mesh: meshes.add(Plane3d::default().mesh().size(50., 50.)),
        material: materials.add(Color::from(SILVER)),
        ..default()
    });

    // The camera
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(0., 6., 12.).looking_at(Vec3::new(0., 3., 0.), Vec3::Y),
        ..default()
    });
}

Trait Implementations

impl<P> CubicGenerator<P> for CubicBezier<P>

where P: VectorSpace,

fn to_curve(&self) -> CubicCurve<P>

Build a CubicCurve by computing the interpolation coefficients for each curve segment.