naga/front/
interpolator.rs

1/*!
2Interpolation defaults.
3*/
4
5impl crate::Binding {
6    /// Apply the usual default interpolation for `ty` to `binding`.
7    ///
8    /// This function is a utility front ends may use to satisfy the Naga IR's
9    /// requirement, meant to ensure that input languages' policies have been
10    /// applied appropriately, that all I/O `Binding`s from the vertex shader to the
11    /// fragment shader must have non-`None` `interpolation` values.
12    ///
13    /// All the shader languages Naga supports have similar rules:
14    /// perspective-correct, center-sampled interpolation is the default for any
15    /// binding that can vary, and everything else either defaults to flat, or
16    /// requires an explicit flat qualifier/attribute/what-have-you.
17    ///
18    /// If `binding` is not a [`Location`] binding, or if its [`interpolation`] is
19    /// already set, then make no changes. Otherwise, set `binding`'s interpolation
20    /// and sampling to reasonable defaults depending on `ty`, the type of the value
21    /// being interpolated:
22    ///
23    /// - If `ty` is a floating-point scalar, vector, or matrix type, then
24    ///   default to [`Perspective`] interpolation and [`Center`] sampling.
25    ///
26    /// - If `ty` is an integral scalar or vector, then default to [`Flat`]
27    ///   interpolation, which has no associated sampling.
28    ///
29    /// - For any other types, make no change. Such types are not permitted as
30    ///   user-defined IO values, and will probably be flagged by the verifier
31    ///
32    /// When structs appear in input or output types, each member ought to have its
33    /// own [`Binding`], so structs are simply covered by the third case.
34    ///
35    /// [`Binding`]: crate::Binding
36    /// [`Location`]: crate::Binding::Location
37    /// [`interpolation`]: crate::Binding::Location::interpolation
38    /// [`Perspective`]: crate::Interpolation::Perspective
39    /// [`Flat`]: crate::Interpolation::Flat
40    /// [`Center`]: crate::Sampling::Center
41    pub fn apply_default_interpolation(&mut self, ty: &crate::TypeInner) {
42        if let crate::Binding::Location {
43            location: _,
44            interpolation: ref mut interpolation @ None,
45            ref mut sampling,
46            second_blend_source: _,
47        } = *self
48        {
49            match ty.scalar_kind() {
50                Some(crate::ScalarKind::Float) => {
51                    *interpolation = Some(crate::Interpolation::Perspective);
52                    *sampling = Some(crate::Sampling::Center);
53                }
54                Some(crate::ScalarKind::Sint | crate::ScalarKind::Uint) => {
55                    *interpolation = Some(crate::Interpolation::Flat);
56                    *sampling = None;
57                }
58                Some(_) | None => {}
59            }
60        }
61    }
62}
naga/front/interpolator.rs

naga/front/
interpolator.rs
