splines/
interpolation.rs

1//! Available interpolation modes.
2
3#[cfg(feature = "serde")]
4use serde::{Deserialize, Serialize};
5
6/// Available kind of interpolations.
7///
8/// Feel free to visit each variant for more documentation.
9#[non_exhaustive]
10#[derive(Copy, Clone, Debug, Eq, PartialEq)]
11#[cfg_attr(
12  feature = "serde",
13  derive(Deserialize, Serialize),
14  serde(rename_all = "snake_case")
15)]
16pub enum Interpolation<T, V> {
17  /// Hold a [`Key`] until the sampling value passes the normalized step threshold, in which
18  /// case the next key is used.
19  ///
20  /// > Note: if you set the threshold to `0.5`, the first key will be used until half the time
21  /// > between the two keys; the second key will be in used afterwards. If you set it to `1.0`, the
22  /// > first key will be kept until the next key. Set it to `0.` and the first key will never be
23  /// > used.
24  ///
25  /// [`Key`]: crate::key::Key
26  Step(T),
27
28  /// Linear interpolation between a key and the next one.
29  Linear,
30
31  /// Cosine interpolation between a key and the next one.
32  Cosine,
33
34  /// Catmull-Rom interpolation, performing a cubic Hermite interpolation using four keys.
35  ///
36  /// # Notes
37  ///
38  /// Given four keys `P0`, `P1`, `P2` and `P3`, interpolated values are only possible between
39  /// `P1` and `P2`. Trying to sample before `P1` and after `P2` will result with no values, as
40  /// four keys (one before the beginning key, the beginning key, the end key and one after the
41  /// end key) are required to perform interpolation.
42  ///
43  /// This requires uniform spacing.
44  CatmullRom,
45
46  /// Bézier interpolation.
47  ///
48  /// A control point that uses such an interpolation is associated with an extra point. The segment
49  /// connecting both is called the _tangent_ at this point. The part of the spline defined between
50  /// this control point and the next one will be interpolated across with Bézier interpolation. Two
51  /// cases are possible:
52  ///
53  /// - The next control point also has a Bézier interpolation mode. In this case, its tangent is
54  ///   used for the interpolation process. This is called _cubic Bézier interpolation_ and it
55  ///   kicks ass.
56  /// - The next control point doesn’t have a Bézier interpolation mode set. In this case, the
57  ///   tangent used for the next control point is defined as the segment connecting that control
58  ///   point and the current control point’s associated point. This is called _quadratic Bézer
59  ///   interpolation_ and it kicks ass too, but a bit less than cubic.
60  Bezier(V),
61
62  /// A special Bézier interpolation using an _input tangent_ and an _output tangent_.
63  ///
64  /// With this kind of interpolation, a control point has an input tangent, which has the same role
65  /// as the one defined by [`Interpolation::Bezier`], and an output tangent, which has the same
66  /// role defined by the next key’s [`Interpolation::Bezier`] if present, normally.
67  ///
68  /// What it means is that instead of setting the output tangent as the next key’s Bézier tangent,
69  /// this interpolation mode allows you to manually set the output tangent. That will yield more
70  /// control on the tangents but might generate discontinuities. Use with care.
71  ///
72  /// Stroke Bézier interpolation is always a cubic Bézier interpolation by default.
73  StrokeBezier(V, V),
74}
75
76impl<T, V> Default for Interpolation<T, V> {
77  /// [`Interpolation::Linear`] is the default.
78  fn default() -> Self {
79    Interpolation::Linear
80  }
81}
splines/interpolation.rs

splines/
interpolation.rs
