euv_engine/lighting/
enum.rs

1use super::*;
2
3/// Describes the kind of light source being represented.
4///
5/// ## Direction convention
6///
7/// Every direction a [`Light`] carries is measured **toward the light
8/// source**, with one deliberate exception:
9///
10/// - [`LightType::Directional`]: `direction` points from the surface
11///   toward the light (sourceward), so a surface is lit when
12///   `dot(normal, direction) > 0`.
13/// - [`LightType::Point`]: the direction is derived from
14///   `position - surface_point` at shading time and is also sourceward;
15///   the light stores no direction of its own.
16/// - [`LightType::Spot`]: `direction` points **outward along the cone
17///   axis**, away from the lamp, i.e. the way the light travels. The
18///   surface→light vector used for shading is its negation. This is the
19///   opposite sense from the other two kinds, so a spot light's cone axis
20///   and a spot light's shading direction are *not* the same vector.
21#[derive(Clone, Copy, Debug, Default, PartialEq)]
22pub enum LightType {
23    /// An infinitely distant directional light (e.g. sunlight).
24    ///
25    /// The `direction` field carries the unit vector pointing from the
26    /// shaded surface toward the light source, matching the convention of
27    /// [`LightType::Point`].
28    #[default]
29    Directional,
30    /// A positional point light with inverse-square falloff.
31    ///
32    /// The light radiates in every direction; the surface→light vector is
33    /// computed from `position` at shading time.
34    Point,
35    /// A positional spotlight with a cone defined by a unit direction and a
36    /// half-angle whose cosine is stored in the light's `spot_cos` field.
37    ///
38    /// The `direction` field is the cone **axis pointing outward** from the
39    /// lamp, in the direction the beam travels — the opposite sense to the
40    /// shading direction derived from `position`.
41    Spot,
42}
43
44/// Describes the shading model applied to a [`Material`] during lighting and
45/// ray-tracing evaluation.
46#[derive(Clone, Copy, Debug, Default, PartialEq)]
47pub enum MaterialKind {
48    /// Pure Lambertian diffuse, no specular highlight.
49    ///
50    /// [`LightingUniforms::shade`] evaluates the diffuse term only.
51    #[default]
52    Lambert,
53    /// Lambertian diffuse plus a Phong specular highlight.
54    ///
55    /// [`LightingUniforms::shade`] evaluates the diffuse term plus a specular
56    /// lobe driven by the material's `specular` and `shininess` fields.
57    Phong,
58    /// Diffuse with a Schlick fresnel rim, and no separate specular lobe.
59    ///
60    /// ## This is not a full PBR model
61    ///
62    /// A physically based renderer would evaluate a microfacet BRDF with
63    /// roughness-driven geometry, a metallic / dielectric split, multiple
64    /// scattering, and per-channel Fresnel. None of that is implemented here.
65    /// What this variant actually does is scale the Lambertian diffuse term
66    /// by [`apply_schlick_fresnel`], which brightens grazing angles and adds
67    /// a rim. That is a *deliberate, documented approximation* rather than
68    /// the physically based model the variant name suggests.
69    ///
70    /// The variant is kept rather than removed so callers can branch on
71    /// material model without a breaking change when a real BRDF lands. Note
72    /// that `specular` and `shininess` are ignored on this path: the diffuse
73    /// fresnel blend replaces them entirely.
74    Pbr,
75}
euv_engine/lighting/enum.rs

euv_engine/lighting/
enum.rs
