subdiv_kernels/
interpolate.rs

1//! Interpolation trait for subdivision-compatible data.
2
3use core::ops::AddAssign;
4
5/// Trait for data that can be interpolated by subdivision rules.
6///
7/// Implement this for any type you want to subdivide: positions, UVs,
8/// colors, normals, scalar weights, custom attributes.
9///
10/// Follows the OpenSubdiv `Clear()` / `AddWithWeight()` pattern.
11/// Using a local trait avoids orphan-rule problems that arise with
12/// `Mul<f32>` on foreign array types.
13///
14/// # Example
15///
16/// ```
17/// use subdiv_kernels::Interpolatable;
18///
19/// #[derive(Default, Clone)]
20/// struct Color { r: f32, g: f32, b: f32, a: f32 }
21///
22/// impl Interpolatable for Color {
23///     fn add_with_weight(&mut self, src: &Self, weight: f32) {
24///         self.r += src.r * weight;
25///         self.g += src.g * weight;
26///         self.b += src.b * weight;
27///         self.a += src.a * weight;
28///     }
29/// }
30/// ```
31pub trait Interpolatable: Default + Clone {
32    /// Accumulate `src` scaled by `weight` into `self`.
33    fn add_with_weight(&mut self, src: &Self, weight: f32);
34}
35
36// ── Blanket impls for scalars ──────────────────────────────────────────
37
38impl Interpolatable for f32 {
39    #[inline]
40    fn add_with_weight(&mut self, src: &Self, weight: f32) {
41        *self += src * weight;
42    }
43}
44
45impl Interpolatable for f64 {
46    #[inline]
47    fn add_with_weight(&mut self, src: &Self, weight: f32) {
48        *self += *src * weight as f64;
49    }
50}
51
52// ── Blanket impls for fixed-size float arrays ──────────────────────────
53//
54// Const-generic over the length, so any `[f32; N]` / `[f64; N]` works
55// (`[1.0; 3]` positions, `[_; 2]` UVs, `[_; 4]` colors, `[_; 8]` skin weights,
56// …). The `where [_; N]: Default` bound is required because the standard
57// library only implements `Default` for arrays up to length 32.
58
59impl<const N: usize> Interpolatable for [f32; N]
60where
61    [f32; N]: Default,
62{
63    #[inline]
64    fn add_with_weight(&mut self, src: &Self, weight: f32) {
65        self.iter_mut()
66            .zip(src.iter())
67            .for_each(|(dst, s)| dst.add_assign(s * weight));
68    }
69}
70
71impl<const N: usize> Interpolatable for [f64; N]
72where
73    [f64; N]: Default,
74{
75    #[inline]
76    fn add_with_weight(&mut self, src: &Self, weight: f32) {
77        let w = weight as f64;
78        self.iter_mut()
79            .zip(src.iter())
80            .for_each(|(dst, s)| dst.add_assign(s * w));
81    }
82}
subdiv_kernels/interpolate.rs

subdiv_kernels/
interpolate.rs
