Path: blob/main/crates/bevy_pbr/src/render/pbr_lighting.wgsl
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#define_import_path bevy_pbr::lighting
#import bevy_pbr::{
mesh_view_types::POINT_LIGHT_FLAGS_SPOT_LIGHT_Y_NEGATIVE,
mesh_view_bindings as view_bindings,
atmosphere::functions::{calculate_visible_sun_ratio, clamp_to_surface},
atmosphere::bruneton_functions::transmittance_lut_r_mu_to_uv,
}
#import bevy_render::maths::PI
const LAYER_BASE: u32 = 0;
const LAYER_CLEARCOAT: u32 = 1;
// From the Filament design doc
// https://google.github.io/filament/Filament.html#table_symbols
// Symbol Definition
// v View unit vector
// l Incident light unit vector
// n Surface normal unit vector
// h Half unit vector between l and v
// f BRDF
// f_d Diffuse component of a BRDF
// f_r Specular component of a BRDF
// α Roughness, remapped from using input perceptualRoughness
// σ Diffuse reflectance
// Ω Spherical domain
// f0 Reflectance at normal incidence
// f90 Reflectance at grazing angle
// χ+(a) Heaviside function (1 if a>0 and 0 otherwise)
// nior Index of refraction (IOR) of an interface
// ⟨n⋅l⟩ Dot product clamped to [0..1]
// ⟨a⟩ Saturated value (clamped to [0..1])
// The Bidirectional Reflectance Distribution Function (BRDF) describes the surface response of a standard material
// and consists of two components, the diffuse component (f_d) and the specular component (f_r):
// f(v,l) = f_d(v,l) + f_r(v,l)
//
// The form of the microfacet model is the same for diffuse and specular
// f_r(v,l) = f_d(v,l) = 1 / { |n⋅v||n⋅l| } ∫_Ω D(m,α) G(v,l,m) f_m(v,l,m) (v⋅m) (l⋅m) dm
//
// In which:
// D, also called the Normal Distribution Function (NDF) models the distribution of the microfacets
// G models the visibility (or occlusion or shadow-masking) of the microfacets
// f_m is the microfacet BRDF and differs between specular and diffuse components
//
// The above integration needs to be approximated.
// Input to a lighting function for a single layer (either the base layer or the
// clearcoat layer).
struct LayerLightingInput {
// The normal vector.
N: vec3<f32>,
// The reflected vector.
R: vec3<f32>,
// The normal vector ⋅ the view vector.
NdotV: f32,
// The perceptual roughness of the layer.
perceptual_roughness: f32,
// The roughness of the layer.
roughness: f32,
}
// Input to a lighting function (`point_light`, `spot_light`,
// `directional_light`).
struct LightingInput {
#ifdef STANDARD_MATERIAL_CLEARCOAT
layers: array<LayerLightingInput, 2>,
#else // STANDARD_MATERIAL_CLEARCOAT
layers: array<LayerLightingInput, 1>,
#endif // STANDARD_MATERIAL_CLEARCOAT
// The world-space position.
P: vec3<f32>,
// The vector to the view.
V: vec3<f32>,
// The diffuse color of the material.
diffuse_color: vec3<f32>,
// Specular reflectance at the normal incidence angle.
//
// This should be read F₀, but due to Naga limitations we can't name it that.
F0_: vec3<f32>,
// Constants for the BRDF approximation.
//
// See `EnvBRDFApprox` in
// <https://www.unrealengine.com/en-US/blog/physically-based-shading-on-mobile>.
// What we call `F_ab` they call `AB`.
F_ab: vec2<f32>,
#ifdef STANDARD_MATERIAL_CLEARCOAT
// The strength of the clearcoat layer.
clearcoat_strength: f32,
#endif // STANDARD_MATERIAL_CLEARCOAT
#ifdef STANDARD_MATERIAL_ANISOTROPY
// The anisotropy strength, reflecting the amount of increased roughness in
// the tangent direction.
anisotropy: f32,
// The tangent direction for anisotropy: i.e. the direction in which
// roughness increases.
Ta: vec3<f32>,
// The bitangent direction, which is the cross product of the normal with
// the tangent direction.
Ba: vec3<f32>,
#endif // STANDARD_MATERIAL_ANISOTROPY
}
// Values derived from the `LightingInput` for both diffuse and specular lights.
struct DerivedLightingInput {
// The half-vector between L, the incident light vector, and V, the view
// vector.
H: vec3<f32>,
// The normal vector ⋅ the incident light vector.
NdotL: f32,
// The normal vector ⋅ the half-vector.
NdotH: f32,
// The incident light vector ⋅ the half-vector.
LdotH: f32,
}
// distanceAttenuation is simply the square falloff of light intensity
// combined with a smooth attenuation at the edge of the light radius
//
// light radius is a non-physical construct for efficiency purposes,
// because otherwise every light affects every fragment in the scene
fn getDistanceAttenuation(distanceSquare: f32, inverseRangeSquared: f32) -> f32 {
let factor = distanceSquare * inverseRangeSquared;
let smoothFactor = saturate(1.0 - factor * factor);
let attenuation = smoothFactor * smoothFactor;
return attenuation * 1.0 / max(distanceSquare, 0.0001);
}
// Normal distribution function (specular D)
// Based on https://google.github.io/filament/Filament.html#citation-walter07
// D_GGX(h,α) = α^2 / { π ((n⋅h)^2 (α2−1) + 1)^2 }
// Simple implementation, has precision problems when using fp16 instead of fp32
// see https://google.github.io/filament/Filament.html#listing_speculardfp16
fn D_GGX(roughness: f32, NdotH: f32) -> f32 {
let oneMinusNdotHSquared = 1.0 - NdotH * NdotH;
let a = NdotH * roughness;
let k = roughness / (oneMinusNdotHSquared + a * a);
let d = k * k * (1.0 / PI);
return d;
}
// An approximation of the anisotropic GGX distribution function.
//
// 1
// D(𝐡) = ───────────────────────────────────────────────────
// παₜα_b((𝐡 ⋅ 𝐭)² / αₜ²) + (𝐡 ⋅ 𝐛)² / α_b² + (𝐡 ⋅ 𝐧)²)²
//
// * `T` = 𝐭 = the tangent direction = the direction of increased roughness.
//
// * `B` = 𝐛 = the bitangent direction = the direction of decreased roughness.
//
// * `at` = αₜ = the alpha-roughness in the tangent direction.
//
// * `ab` = α_b = the alpha-roughness in the bitangent direction.
//
// This is from the `KHR_materials_anisotropy` spec:
// <https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_anisotropy/README.md#individual-lights>
fn D_GGX_anisotropic(at: f32, ab: f32, NdotH: f32, TdotH: f32, BdotH: f32) -> f32 {
let a2 = at * ab;
let f = vec3(ab * TdotH, at * BdotH, a2 * NdotH);
let w2 = a2 / dot(f, f);
let d = a2 * w2 * w2 * (1.0 / PI);
return d;
}
// Visibility function (Specular G)
// V(v,l,a) = G(v,l,α) / { 4 (n⋅v) (n⋅l) }
// such that f_r becomes
// f_r(v,l) = D(h,α) V(v,l,α) F(v,h,f0)
// where
// V(v,l,α) = 0.5 / { n⋅l sqrt((n⋅v)^2 (1−α2) + α2) + n⋅v sqrt((n⋅l)^2 (1−α2) + α2) }
// Note the two sqrt's, that may be slow on mobile, see https://google.github.io/filament/Filament.html#listing_approximatedspecularv
fn V_SmithGGXCorrelated(roughness: f32, NdotV: f32, NdotL: f32) -> f32 {
let a2 = roughness * roughness;
let lambdaV = NdotL * sqrt((NdotV - a2 * NdotV) * NdotV + a2);
let lambdaL = NdotV * sqrt((NdotL - a2 * NdotL) * NdotL + a2);
let v = 0.5 / (lambdaV + lambdaL);
return v;
}
// The visibility function, anisotropic variant.
fn V_GGX_anisotropic(
at: f32,
ab: f32,
NdotL: f32,
NdotV: f32,
BdotV: f32,
TdotV: f32,
TdotL: f32,
BdotL: f32,
) -> f32 {
let GGX_V = NdotL * length(vec3(at * TdotV, ab * BdotV, NdotV));
let GGX_L = NdotV * length(vec3(at * TdotL, ab * BdotL, NdotL));
let v = 0.5 / (GGX_V + GGX_L);
return saturate(v);
}
// Probability-density function that matches the bounded VNDF sampler
// https://gpuopen.com/download/Bounded_VNDF_Sampling_for_Smith-GGX_Reflections.pdf (Listing 2)
fn ggx_vndf_pdf(i: vec3<f32>, NdotH: f32, roughness: f32) -> f32 {
let ndf = D_GGX(roughness, NdotH);
// Common terms
let ai = roughness * i.xy;
let len2 = dot(ai, ai);
let t = sqrt(len2 + i.z * i.z);
if i.z >= 0.0 {
let a = roughness;
let s = 1.0 + length(i.xy);
let a2 = a * a;
let s2 = s * s;
let k = (1.0 - a2) * s2 / (s2 + a2 * i.z * i.z);
return ndf / (2.0 * (k * i.z + t));
}
// Backfacing case
return ndf * (t - i.z) / (2.0 * len2);
}
// https://gpuopen.com/download/Bounded_VNDF_Sampling_for_Smith-GGX_Reflections.pdf (Listing 1)
fn sample_visible_ggx(
xi: vec2<f32>,
roughness: f32,
normal: vec3<f32>,
view: vec3<f32>,
) -> vec3<f32> {
let n = normal;
let alpha = roughness;
// Decompose view into components parallel/perpendicular to the normal
let wi_n = dot(view, n);
let wi_z = -n * wi_n;
let wi_xy = view + wi_z;
// Warp view vector to the unit-roughness configuration
let wi_std = -normalize(alpha * wi_xy + wi_z);
// Compute wi_std.z once for reuse
let wi_std_z = dot(wi_std, n);
// Bounded VNDF sampling
// Compute the bound parameter k (Eq. 5) and the scaled z–limit b (Eq. 6)
let s = 1.0 + length(wi_xy);
let a = clamp(alpha, 0.0, 1.0);
let a2 = a * a;
let s2 = s * s;
let k = (1.0 - a2) * s2 / (s2 + a2 * wi_n * wi_n);
let b = select(wi_std_z, k * wi_std_z, wi_n > 0.0);
// Sample a spherical cap in (-b, 1]
let z = 1.0 - xi.y * (1.0 + b);
let sin_theta = sqrt(max(0.0, 1.0 - z * z));
let phi = 2.0 * PI * xi.x - PI;
let x = sin_theta * cos(phi);
let y = sin_theta * sin(phi);
let c_std = vec3f(x, y, z);
// Reflect the sample so that the normal aligns with +Z
let up = vec3f(0.0, 0.0, 1.0);
let wr = n + up;
let c = dot(wr, c_std) * wr / wr.z - c_std;
// Half-vector in the standard frame
let wm_std = c + wi_std;
let wm_std_z = n * dot(n, wm_std);
let wm_std_xy = wm_std_z - wm_std;
// Unwarp back to original roughness and compute microfacet normal
let H = normalize(alpha * wm_std_xy + wm_std_z);
// Reflect view to obtain the outgoing (light) direction
return reflect(-view, H);
}
// Smith geometric shadowing function
fn G_Smith(NdotV: f32, NdotL: f32, roughness: f32) -> f32 {
let k = roughness / 2.0;
let GGXL = NdotL / (NdotL * (1.0 - k) + k);
let GGXV = NdotV / (NdotV * (1.0 - k) + k);
return GGXL * GGXV;
}
// A simpler, but nonphysical, alternative to Smith-GGX. We use this for
// clearcoat, per the Filament spec.
//
// https://google.github.io/filament/Filament.html#materialsystem/clearcoatmodel#toc4.9.1
fn V_Kelemen(LdotH: f32) -> f32 {
return 0.25 / (LdotH * LdotH);
}
// Fresnel function
// see https://google.github.io/filament/Filament.html#citation-schlick94
// F_Schlick(v,h,f_0,f_90) = f_0 + (f_90 − f_0) (1 − v⋅h)^5
fn F_Schlick_vec(f0: vec3<f32>, f90: f32, VdotH: f32) -> vec3<f32> {
// not using mix to keep the vec3 and float versions identical
return f0 + (f90 - f0) * pow(1.0 - VdotH, 5.0);
}
fn F_Schlick(f0: f32, f90: f32, VdotH: f32) -> f32 {
// not using mix to keep the vec3 and float versions identical
return f0 + (f90 - f0) * pow(1.0 - VdotH, 5.0);
}
fn fresnel(f0: vec3<f32>, LdotH: f32) -> vec3<f32> {
// f_90 suitable for ambient occlusion
// see https://google.github.io/filament/Filament.html#lighting/occlusion
let f90 = saturate(dot(f0, vec3<f32>(50.0 * 0.33)));
return F_Schlick_vec(f0, f90, LdotH);
}
// Given distribution, visibility, and Fresnel term, calculates the final
// specular light.
//
// Multiscattering approximation:
// <https://google.github.io/filament/Filament.html#listing_energycompensationimpl>
fn specular_multiscatter(
D: f32,
V: f32,
F: vec3<f32>,
F0: vec3<f32>,
F_ab: vec2<f32>,
specular_intensity: f32,
) -> vec3<f32> {
var Fr = (specular_intensity * D * V) * F;
Fr *= 1.0 + F0 * (1.0 / F_ab.x - 1.0);
return Fr;
}
// Specular BRDF
// https://google.github.io/filament/Filament.html#materialsystem/specularbrdf
// N, V, and L must all be normalized.
fn derive_lighting_input(N: vec3<f32>, V: vec3<f32>, L: vec3<f32>) -> DerivedLightingInput {
var input: DerivedLightingInput;
var H: vec3<f32> = normalize(L + V);
input.H = H;
input.NdotL = saturate(dot(N, L));
input.NdotH = saturate(dot(N, H));
input.LdotH = saturate(dot(L, H));
return input;
}
// Returns L in the `xyz` components and the modified roughness in the `w` component.
fn compute_specular_layer_values_for_point_light(
input: ptr<function, LightingInput>,
layer: u32,
V: vec3<f32>,
light_to_frag: vec3<f32>,
light_radius: f32,
distance: f32,
) -> vec4<f32> {
// Unpack.
let R = (*input).layers[layer].R;
let a = (*input).layers[layer].roughness;
// Representative Point Area Lights.
// see http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf p14-16
var LtFdotR = dot(light_to_frag, R);
// HACK: the following line is an amendment to fix a discontinuity when a surface
// intersects the light sphere. See https://github.com/bevyengine/bevy/issues/13318
//
// This sentence in the reference is crux of the problem: "We approximate finding the point with the
// smallest angle to the reflection ray by finding the point with the smallest distance to the ray."
// This approximation turns out to be completely wrong for points inside or near the sphere.
// Clamping this dot product to be positive ensures `centerToRay` lies on ray and not behind it.
// Any non-zero epsilon works here, it just has to be positive to avoid a singularity at zero.
// However, this is still far from physically accurate. Deriving an exact solution would help,
// but really we should adopt a superior solution to area lighting, such as:
// Polygonal-Light Shading with Linearly Transformed Cosines by Eric Heitz et al.
LtFdotR = max(0.0001, LtFdotR);
let centerToRay = LtFdotR * R - light_to_frag;
let closestPoint = light_to_frag + centerToRay * saturate(
light_radius * inverseSqrt(dot(centerToRay, centerToRay)));
let LspecLengthInverse = inverseSqrt(dot(closestPoint, closestPoint));
// Karis 2013, page 14. The constant 2 (or 3) is hand tuned to fit reference.
// https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf
let a_prime = saturate(a + light_radius / (2.0 * distance));
let L: vec3<f32> = closestPoint * LspecLengthInverse; // normalize() equivalent?
return vec4(L, a_prime);
}
// Cook-Torrance approximation of the microfacet model integration using Fresnel law F to model f_m
// f_r(v,l) = { D(h,α) G(v,l,α) F(v,h,f0) } / { 4 (n⋅v) (n⋅l) }
fn specular(
input: ptr<function, LightingInput>,
derived_input: ptr<function, DerivedLightingInput>,
roughness: f32,
specular_intensity: f32,
) -> vec3<f32> {
// Unpack.
let NdotV = (*input).layers[LAYER_BASE].NdotV;
let F0 = (*input).F0_;
let NdotL = (*derived_input).NdotL;
let NdotH = (*derived_input).NdotH;
let LdotH = (*derived_input).LdotH;
// Calculate distribution.
let D = D_GGX(roughness, NdotH);
// Calculate visibility.
let V = V_SmithGGXCorrelated(roughness, NdotV, NdotL);
// Calculate the Fresnel term.
let F = fresnel(F0, LdotH);
// Calculate the specular light.
let Fr = specular_multiscatter(D, V, F, F0, (*input).F_ab, specular_intensity);
return Fr;
}
// Calculates the specular light for the clearcoat layer. Returns Fc, the
// Fresnel term, in the first channel, and Frc, the specular clearcoat light, in
// the second channel.
//
// <https://google.github.io/filament/Filament.html#listing_clearcoatbrdf>
fn specular_clearcoat(
input: ptr<function, LightingInput>,
derived_input: ptr<function, DerivedLightingInput>,
clearcoat_strength: f32,
roughness: f32,
specular_intensity: f32,
) -> vec2<f32> {
// Unpack.
let NdotH = (*derived_input).NdotH;
let LdotH = (*derived_input).LdotH;
// Calculate distribution.
let Dc = D_GGX(roughness, NdotH);
// Calculate visibility.
let Vc = V_Kelemen(LdotH);
// Calculate the Fresnel term.
let Fc = F_Schlick(0.04, 1.0, LdotH) * clearcoat_strength;
// Calculate the specular light.
let Frc = (specular_intensity * Dc * Vc) * Fc;
return vec2(Fc, Frc);
}
#ifdef STANDARD_MATERIAL_ANISOTROPY
fn specular_anisotropy(
input: ptr<function, LightingInput>,
derived_input: ptr<function, DerivedLightingInput>,
L: vec3<f32>,
roughness: f32,
specular_intensity: f32,
) -> vec3<f32> {
// Unpack.
let NdotV = (*input).layers[LAYER_BASE].NdotV;
let V = (*input).V;
let F0 = (*input).F0_;
let anisotropy = (*input).anisotropy;
let Ta = (*input).Ta;
let Ba = (*input).Ba;
let H = (*derived_input).H;
let NdotL = (*derived_input).NdotL;
let NdotH = (*derived_input).NdotH;
let LdotH = (*derived_input).LdotH;
let TdotL = dot(Ta, L);
let BdotL = dot(Ba, L);
let TdotH = dot(Ta, H);
let BdotH = dot(Ba, H);
let TdotV = dot(Ta, V);
let BdotV = dot(Ba, V);
let ab = roughness * roughness;
let at = mix(ab, 1.0, anisotropy * anisotropy);
let Da = D_GGX_anisotropic(at, ab, NdotH, TdotH, BdotH);
let Va = V_GGX_anisotropic(at, ab, NdotL, NdotV, BdotV, TdotV, TdotL, BdotL);
let Fa = fresnel(F0, LdotH);
// Calculate the specular light.
let Fr = specular_multiscatter(Da, Va, Fa, F0, (*input).F_ab, specular_intensity);
return Fr;
}
#endif // STANDARD_MATERIAL_ANISOTROPY
// Diffuse BRDF
// https://google.github.io/filament/Filament.html#materialsystem/diffusebrdf
// fd(v,l) = σ/π * 1 / { |n⋅v||n⋅l| } ∫Ω D(m,α) G(v,l,m) (v⋅m) (l⋅m) dm
//
// simplest approximation
// float Fd_Lambert() {
// return 1.0 / PI;
// }
//
// vec3 Fd = diffuseColor * Fd_Lambert();
//
// Disney approximation
// See https://google.github.io/filament/Filament.html#citation-burley12
// minimal quality difference
fn Fd_Burley(
input: ptr<function, LightingInput>,
derived_input: ptr<function, DerivedLightingInput>,
) -> f32 {
// Unpack.
let roughness = (*input).layers[LAYER_BASE].roughness;
let NdotV = (*input).layers[LAYER_BASE].NdotV;
let NdotL = (*derived_input).NdotL;
let LdotH = (*derived_input).LdotH;
let f90 = 0.5 + 2.0 * roughness * LdotH * LdotH;
let lightScatter = F_Schlick(1.0, f90, NdotL);
let viewScatter = F_Schlick(1.0, f90, NdotV);
return lightScatter * viewScatter * (1.0 / PI);
}
// Scale/bias approximation
// https://www.unrealengine.com/en-US/blog/physically-based-shading-on-mobile
// TODO: Use a LUT (more accurate)
fn F_AB(perceptual_roughness: f32, NdotV: f32) -> vec2<f32> {
let c0 = vec4<f32>(-1.0, -0.0275, -0.572, 0.022);
let c1 = vec4<f32>(1.0, 0.0425, 1.04, -0.04);
let r = perceptual_roughness * c0 + c1;
let a004 = min(r.x * r.x, exp2(-9.28 * NdotV)) * r.x + r.y;
return vec2<f32>(-1.04, 1.04) * a004 + r.zw;
}
fn EnvBRDFApprox(F0: vec3<f32>, F_ab: vec2<f32>) -> vec3<f32> {
return F0 * F_ab.x + F_ab.y;
}
fn perceptualRoughnessToRoughness(perceptualRoughness: f32) -> f32 {
// clamp perceptual roughness to prevent precision problems
// According to Filament design 0.089 is recommended for mobile
// Filament uses 0.045 for non-mobile
let clampedPerceptualRoughness = clamp(perceptualRoughness, 0.089, 1.0);
return clampedPerceptualRoughness * clampedPerceptualRoughness;
}
// this must align with CubemapLayout in decal/clustered.rs
const CUBEMAP_TYPE_CROSS_VERTICAL: u32 = 0;
const CUBEMAP_TYPE_CROSS_HORIZONTAL: u32 = 1;
const CUBEMAP_TYPE_SEQUENCE_VERTICAL: u32 = 2;
const CUBEMAP_TYPE_SEQUENCE_HORIZONTAL: u32 = 3;
const X_PLUS: u32 = 0;
const X_MINUS: u32 = 1;
const Y_PLUS: u32 = 2;
const Y_MINUS: u32 = 3;
const Z_MINUS: u32 = 4;
const Z_PLUS: u32 = 5;
fn cubemap_uv(direction: vec3<f32>, cubemap_type: u32) -> vec2<f32> {
let abs_direction = abs(direction);
let max_axis = max(abs_direction.x, max(abs_direction.y, abs_direction.z));
let face_index = select(
select(X_PLUS, X_MINUS, direction.x < 0.0),
select(
select(Y_PLUS, Y_MINUS, direction.y < 0.0),
select(Z_PLUS, Z_MINUS, direction.z < 0.0),
max_axis != abs_direction.y
),
max_axis != abs_direction.x
);
var face_uv: vec2<f32>;
var divisor: f32;
var corner_uv: vec2<u32> = vec2(0, 0);
var face_size: vec2<f32>;
switch face_index {
case X_PLUS: { face_uv = vec2<f32>(direction.z, -direction.y); divisor = direction.x; }
case X_MINUS: { face_uv = vec2<f32>(-direction.z, -direction.y); divisor = -direction.x; }
case Y_PLUS: { face_uv = vec2<f32>(direction.x, -direction.z); divisor = direction.y; }
case Y_MINUS: { face_uv = vec2<f32>(direction.x, direction.z); divisor = -direction.y; }
case Z_PLUS: { face_uv = vec2<f32>(direction.x, direction.y); divisor = direction.z; }
case Z_MINUS: { face_uv = vec2<f32>(direction.x, -direction.y); divisor = -direction.z; }
default: {}
}
face_uv = (face_uv / divisor) * 0.5 + 0.5;
switch cubemap_type {
case CUBEMAP_TYPE_CROSS_VERTICAL: {
face_size = vec2(1.0/3.0, 1.0/4.0);
corner_uv = vec2<u32>((0x111102u >> (4 * face_index)) & 0xFu, (0x132011u >> (4 * face_index)) & 0xFu);
}
case CUBEMAP_TYPE_CROSS_HORIZONTAL: {
face_size = vec2(1.0/4.0, 1.0/3.0);
corner_uv = vec2<u32>((0x131102u >> (4 * face_index)) & 0xFu, (0x112011u >> (4 * face_index)) & 0xFu);
}
case CUBEMAP_TYPE_SEQUENCE_HORIZONTAL: {
face_size = vec2(1.0/6.0, 1.0);
corner_uv.x = face_index;
}
case CUBEMAP_TYPE_SEQUENCE_VERTICAL: {
face_size = vec2(1.0, 1.0/6.0);
corner_uv.y = face_index;
}
default: {}
}
return (vec2<f32>(corner_uv) + face_uv) * face_size;
}
// This is a modification to Karis 2013 for area lights to fix an issue where the specular
// reflection on smooth materials looks too rough and dim. We lerp between the base roughness
// and Karis2013 roughness with a lerp factor tuned by looking at reference renders. The goal
// is to preserve sharp specular highlights on smooth materials, without blowing out specular
// highlights on rough materials.
//
// The ideal solution is to switch to Linearly Transformed Cosines, which is more accurate in
// all cases, and a popular choice for realtime.
fn specular_fix_remap(a: f32) -> f32 {
let inv_a_sq = (1.0 - a) * (1.0 - a);
return 1.0 - inv_a_sq * inv_a_sq;
}
fn point_light(
light_id: u32,
input: ptr<function, LightingInput>,
enable_diffuse: bool,
enable_texture: bool,
) -> vec3<f32> {
// Unpack.
let diffuse_color = (*input).diffuse_color;
let P = (*input).P;
let N = (*input).layers[LAYER_BASE].N;
let V = (*input).V;
let light = &view_bindings::clustered_lights.data[light_id];
let light_to_frag = (*light).position_radius.xyz - P;
let L = normalize(light_to_frag);
let distance_square = dot(light_to_frag, light_to_frag);
let distance = sqrt(distance_square);
let rangeAttenuation = getDistanceAttenuation(distance_square, (*light).color_inverse_square_range.w);
// Base layer
let a = (*input).layers[LAYER_BASE].roughness;
let specular_L_a_prime = compute_specular_layer_values_for_point_light(
input,
LAYER_BASE,
V,
light_to_frag,
(*light).position_radius.w,
distance,
);
let L_spec = specular_L_a_prime.xyz;
let a_prime = specular_L_a_prime.w;
var specular_derived_input = derive_lighting_input(N, V, L_spec);
let normalizationFactor = a / a_prime;
let specular_intensity = normalizationFactor * normalizationFactor;
let brdf_roughness = mix(a, a_prime, specular_fix_remap(a));
#ifdef STANDARD_MATERIAL_ANISOTROPY
var specular_light = specular_anisotropy(input, &specular_derived_input, L, brdf_roughness, specular_intensity);
#else // STANDARD_MATERIAL_ANISOTROPY
var specular_light = specular(input, &specular_derived_input, brdf_roughness, specular_intensity);
#endif // STANDARD_MATERIAL_ANISOTROPY
// Sphere area light visibility (solid-angle attenuation)
let light_radius = (*light).position_radius.w;
if light_radius > 0.0 {
let solid_angle = light_radius * light_radius / (distance * distance);
specular_light *= saturate(specular_derived_input.NdotL / max(specular_derived_input.NdotL + solid_angle, 1e-4));
}
// Clearcoat
#ifdef STANDARD_MATERIAL_CLEARCOAT
// Unpack.
let clearcoat_N = (*input).layers[LAYER_CLEARCOAT].N;
let clearcoat_strength = (*input).clearcoat_strength;
let clearcoat_a = (*input).layers[LAYER_CLEARCOAT].roughness;
// Perform specular input calculations again for the clearcoat layer. We
// can't reuse the above because the clearcoat normal might be different
// from the main layer normal.
let clearcoat_specular_L_a_prime = compute_specular_layer_values_for_point_light(
input,
LAYER_CLEARCOAT,
V,
light_to_frag,
(*light).position_radius.w,
distance,
);
let L_clearcoat_spec = clearcoat_specular_L_a_prime.xyz;
let clearcoat_a_prime = clearcoat_specular_L_a_prime.w;
var clearcoat_specular_derived_input =
derive_lighting_input(clearcoat_N, V, L_clearcoat_spec);
// Calculate the specular light.
let clearcoat_normalizationFactor = clearcoat_a / clearcoat_a_prime;
let clearcoat_specular_intensity = clearcoat_normalizationFactor * clearcoat_normalizationFactor;
let clearcoat_brdf_roughness = mix(clearcoat_a, clearcoat_a_prime, specular_fix_remap(clearcoat_a));
let Fc_Frc = specular_clearcoat(
input,
&clearcoat_specular_derived_input,
clearcoat_strength,
clearcoat_brdf_roughness,
clearcoat_specular_intensity
);
let inv_Fc = 1.0 - Fc_Frc.r; // Inverse Fresnel term.
var Frc = Fc_Frc.g; // Clearcoat light.
// Sphere area light visibility (solid-angle attenuation) for clearcoat
if light_radius > 0.0 {
let solid_angle = light_radius * light_radius / (distance * distance);
Frc *= saturate(clearcoat_specular_derived_input.NdotL / max(clearcoat_specular_derived_input.NdotL + solid_angle, 1e-4));
}
#endif // STANDARD_MATERIAL_CLEARCOAT
// Diffuse.
// Comes after specular since its N⋅L is used in the lighting equation.
var derived_input = derive_lighting_input(N, V, L);
var diffuse = vec3(0.0);
if (enable_diffuse) {
diffuse = diffuse_color * Fd_Burley(input, &derived_input);
}
// See https://google.github.io/filament/Filament.html#mjx-eqn-pointLightLuminanceEquation
// Lout = f(v,l) Φ / { 4 π d^2 }⟨n⋅l⟩
// where
// f(v,l) = (f_d(v,l) + f_r(v,l)) * light_color
// Φ is luminous power in lumens
// our rangeAttenuation = 1 / d^2 multiplied with an attenuation factor for smoothing at the edge of the non-physical maximum light radius
// For a point light, luminous intensity, I, in lumens per steradian is given by:
// I = Φ / 4 π
// The derivation of this can be seen here: https://google.github.io/filament/Filament.html#mjx-eqn-pointLightLuminousPower
// NOTE: (*light).color.rgb is premultiplied with (*light).intensity / 4 π (which would be the luminous intensity) on the CPU
var color_times_NdotL: vec3<f32>;
#ifdef STANDARD_MATERIAL_CLEARCOAT
// Account for the Fresnel term from the clearcoat darkening the main layer.
//
// <https://google.github.io/filament/Filament.html#materialsystem/clearcoatmodel/integrationinthesurfaceresponse>
color_times_NdotL = (diffuse * derived_input.NdotL + specular_light * specular_derived_input.NdotL * inv_Fc) * inv_Fc + Frc * clearcoat_specular_derived_input.NdotL;
#else // STANDARD_MATERIAL_CLEARCOAT
color_times_NdotL = diffuse * derived_input.NdotL + specular_light * specular_derived_input.NdotL;
#endif // STANDARD_MATERIAL_CLEARCOAT
var texture_sample = 1f;
#ifdef LIGHT_TEXTURES
if enable_texture && (*light).decal_index != 0xFFFFFFFFu {
let relative_position = (view_bindings::clustered_decals.decals[(*light).decal_index].local_from_world * vec4(P, 1.0)).xyz;
let cubemap_type = view_bindings::clustered_decals.decals[(*light).decal_index].tag;
let decal_uv = cubemap_uv(relative_position, cubemap_type);
let image_index = view_bindings::clustered_decals.decals[(*light).decal_index].base_color_texture_index;
texture_sample = textureSampleLevel(
view_bindings::clustered_decal_textures[image_index],
view_bindings::clustered_decal_sampler,
decal_uv,
0.0
).r;
}
#endif
return color_times_NdotL * (*light).color_inverse_square_range.rgb *
rangeAttenuation * texture_sample;
}
fn spot_light(
light_id: u32,
input: ptr<function, LightingInput>,
enable_diffuse: bool
) -> vec3<f32> {
// reuse the point light calculations
let point_light = point_light(light_id, input, enable_diffuse, false);
let light = &view_bindings::clustered_lights.data[light_id];
// reconstruct spot dir from x/z and y-direction flag
var spot_dir = vec3<f32>((*light).light_custom_data.x, 0.0, (*light).light_custom_data.y);
spot_dir.y = sqrt(max(0.0, 1.0 - spot_dir.x * spot_dir.x - spot_dir.z * spot_dir.z));
if ((*light).flags & POINT_LIGHT_FLAGS_SPOT_LIGHT_Y_NEGATIVE) != 0u {
spot_dir.y = -spot_dir.y;
}
let light_to_frag = (*light).position_radius.xyz - (*input).P.xyz;
// calculate attenuation based on filament formula https://google.github.io/filament/Filament.html#listing_glslpunctuallight
// spot_scale and spot_offset have been precomputed
// note we normalize here to get "l" from the filament listing. spot_dir is already normalized
let cd = dot(-spot_dir, normalize(light_to_frag));
let attenuation = saturate(cd * (*light).light_custom_data.z + (*light).light_custom_data.w);
let spot_attenuation = attenuation * attenuation;
var texture_sample = 1f;
#ifdef LIGHT_TEXTURES
if (*light).decal_index != 0xFFFFFFFFu {
let local_position = (view_bindings::clustered_decals.decals[(*light).decal_index].local_from_world *
vec4((*input).P, 1.0)).xyz;
if local_position.z < 0.0 {
let decal_uv = (local_position.xy / (local_position.z * (*light).spot_light_tan_angle)) * vec2(-0.5, 0.5) + 0.5;
let image_index = view_bindings::clustered_decals.decals[(*light).decal_index].base_color_texture_index;
texture_sample = textureSampleLevel(
view_bindings::clustered_decal_textures[image_index],
view_bindings::clustered_decal_sampler,
decal_uv,
0.0
).r;
}
}
#endif
return point_light * spot_attenuation * texture_sample;
}
fn directional_light(
light_id: u32,
input: ptr<function, LightingInput>,
enable_diffuse: bool
) -> vec3<f32> {
// Unpack.
let diffuse_color = (*input).diffuse_color;
let NdotV = (*input).layers[LAYER_BASE].NdotV;
let N = (*input).layers[LAYER_BASE].N;
let V = (*input).V;
let roughness = (*input).layers[LAYER_BASE].roughness;
let light = &view_bindings::lights.directional_lights[light_id];
let L = (*light).direction_to_light.xyz;
var derived_input = derive_lighting_input(N, V, L);
var diffuse = vec3(0.0);
if (enable_diffuse) {
diffuse = diffuse_color * Fd_Burley(input, &derived_input);
}
#ifdef STANDARD_MATERIAL_ANISOTROPY
let specular_light = specular_anisotropy(input, &derived_input, L, roughness, 1.0);
#else // STANDARD_MATERIAL_ANISOTROPY
let specular_light = specular(input, &derived_input, roughness, 1.0);
#endif // STANDARD_MATERIAL_ANISOTROPY
#ifdef STANDARD_MATERIAL_CLEARCOAT
let clearcoat_N = (*input).layers[LAYER_CLEARCOAT].N;
let clearcoat_strength = (*input).clearcoat_strength;
let clearcoat_roughness = (*input).layers[LAYER_CLEARCOAT].roughness;
// Perform specular input calculations again for the clearcoat layer. We
// can't reuse the above because the clearcoat normal might be different
// from the main layer normal.
var derived_clearcoat_input = derive_lighting_input(clearcoat_N, V, L);
let Fc_Frc =
specular_clearcoat(input, &derived_clearcoat_input, clearcoat_strength, clearcoat_roughness, 1.0);
let inv_Fc = 1.0 - Fc_Frc.r;
let Frc = Fc_Frc.g;
#endif // STANDARD_MATERIAL_CLEARCOAT
var color: vec3<f32>;
#ifdef STANDARD_MATERIAL_CLEARCOAT
// Account for the Fresnel term from the clearcoat darkening the main layer.
//
// <https://google.github.io/filament/Filament.html#materialsystem/clearcoatmodel/integrationinthesurfaceresponse>
color = (diffuse + specular_light * inv_Fc) * inv_Fc * derived_input.NdotL +
Frc * derived_clearcoat_input.NdotL;
#else // STANDARD_MATERIAL_CLEARCOAT
color = (diffuse + specular_light) * derived_input.NdotL;
#endif // STANDARD_MATERIAL_CLEARCOAT
var texture_sample = 1f;
#ifdef LIGHT_TEXTURES
if (*light).decal_index != 0xFFFFFFFFu {
let local_position = (view_bindings::clustered_decals.decals[(*light).decal_index].local_from_world *
vec4((*input).P, 1.0)).xyz;
let decal_uv = local_position.xy * vec2(-0.5, 0.5) + 0.5;
// if tiled or within tile
if (view_bindings::clustered_decals.decals[(*light).decal_index].tag != 0u)
|| all(clamp(decal_uv, vec2(0.0), vec2(1.0)) == decal_uv)
{
let image_index = view_bindings::clustered_decals.decals[(*light).decal_index].base_color_texture_index;
texture_sample = textureSampleLevel(
view_bindings::clustered_decal_textures[image_index],
view_bindings::clustered_decal_sampler,
decal_uv - floor(decal_uv),
0.0
).r;
} else {
texture_sample = 0f;
}
}
#endif
color *= (*light).color.rgb * texture_sample;
#ifdef ATMOSPHERE
let P = (*input).P;
let atmosphere = view_bindings::atmosphere_data.atmosphere;
let O = vec3(0.0, atmosphere.bottom_radius, 0.0);
let P_scaled = P * vec3(view_bindings::atmosphere_data.settings.scene_units_to_m);
let P_as = P_scaled + O;
let P_clamped = clamp_to_surface(atmosphere, P_as);
let r = length(P_clamped);
let local_up = normalize(P_clamped);
let mu_light = dot(L, local_up);
// Sample atmosphere
let transmittance = sample_transmittance_lut(r, mu_light);
let sun_visibility = calculate_visible_sun_ratio(atmosphere, r, mu_light, (*light).sun_disk_angular_size);
// Apply atmospheric effects
color *= transmittance * sun_visibility;
#endif
return color;
}
#ifdef ATMOSPHERE
fn sample_transmittance_lut(r: f32, mu: f32) -> vec3<f32> {
let uv = transmittance_lut_r_mu_to_uv(view_bindings::atmosphere_data.atmosphere, r, mu);
return textureSampleLevel(
view_bindings::atmosphere_transmittance_texture,
view_bindings::atmosphere_transmittance_sampler, uv, 0.0).rgb;
}
#endif // ATMOSPHERE