1#define_import_path bevy_pbr::pbr_functions
2
3#import bevy_pbr::{
4    pbr_types,
5    pbr_bindings,
6    mesh_view_bindings as view_bindings,
7    mesh_view_types,
8    lighting,
9    lighting::{LAYER_BASE, LAYER_CLEARCOAT},
10    transmission,
11    clustered_forward as clustering,
12    shadows,
13    ambient,
14    irradiance_volume,
15    mesh_types::{MESH_FLAGS_SHADOW_RECEIVER_BIT, MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT},
16}
17#import bevy_render::maths::{E, powsafe}
18
19#ifdef MESHLET_MESH_MATERIAL_PASS
20#import bevy_pbr::meshlet_visibility_buffer_resolve::VertexOutput
21#else ifdef PREPASS_PIPELINE
22#import bevy_pbr::prepass_io::VertexOutput
23#else   // PREPASS_PIPELINE
24#import bevy_pbr::forward_io::VertexOutput
25#endif  // PREPASS_PIPELINE
26
27#ifdef ENVIRONMENT_MAP
28#import bevy_pbr::environment_map
29#endif
30
31#ifdef TONEMAP_IN_SHADER
32#import bevy_core_pipeline::tonemapping::{tone_mapping, screen_space_dither}
33#endif
34
35
36// Biasing info needed to sample from a texture when calling `sample_texture`.
37// How this is done depends on whether we're rendering meshlets or regular
38// meshes.
39struct SampleBias {
40#ifdef MESHLET_MESH_MATERIAL_PASS
41    ddx_uv: vec2<f32>,
42    ddy_uv: vec2<f32>,
43#else   // MESHLET_MESH_MATERIAL_PASS
44    mip_bias: f32,
45#endif  // MESHLET_MESH_MATERIAL_PASS
46}
47
48// This is the standard 4x4 ordered dithering pattern from [1].
49//
50// We can't use `array<vec4<u32>, 4>` because they can't be indexed dynamically
51// due to Naga limitations. So instead we pack into a single `vec4` and extract
52// individual bytes.
53//
54// [1]: https://en.wikipedia.org/wiki/Ordered_dithering#Threshold_map
55const DITHER_THRESHOLD_MAP: vec4<u32> = vec4(
56    0x0a020800,
57    0x060e040c,
58    0x09010b03,
59    0x050d070f
60);
61
62// Processes a visibility range dither value and discards the fragment if
63// needed.
64//
65// Visibility ranges, also known as HLODs, are crossfades between different
66// levels of detail.
67//
68// The `dither` value ranges from [-16, 16]. When zooming out, positive values
69// are used for meshes that are in the process of disappearing, while negative
70// values are used for meshes that are in the process of appearing. In other
71// words, when the camera is moving backwards, the `dither` value counts up from
72// -16 to 0 when the object is fading in, stays at 0 while the object is
73// visible, and then counts up to 16 while the object is fading out.
74// Distinguishing between negative and positive values allows the dither
75// patterns for different LOD levels of a single mesh to mesh together properly.
76#ifdef VISIBILITY_RANGE_DITHER
77fn visibility_range_dither(frag_coord: vec4<f32>, dither: i32) {
78    // If `dither` is 0, the object is visible.
79    if (dither == 0) {
80        return;
81    }
82
83    // If `dither` is less than -15 or greater than 15, the object is culled.
84    if (dither <= -16 || dither >= 16) {
85        discard;
86    }
87
88    // Otherwise, check the dither pattern.
89    let coords = vec2<u32>(floor(frag_coord.xy)) % 4u;
90    let threshold = i32((DITHER_THRESHOLD_MAP[coords.y] >> (coords.x * 8)) & 0xff);
91    if ((dither >= 0 && dither + threshold >= 16) || (dither < 0 && 1 + dither + threshold <= 0)) {
92        discard;
93    }
94}
95#endif
96
97fn alpha_discard(material: pbr_types::StandardMaterial, output_color: vec4<f32>) -> vec4<f32> {
98    var color = output_color;
99    let alpha_mode = material.flags & pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
100    if alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_OPAQUE {
101        // NOTE: If rendering as opaque, alpha should be ignored so set to 1.0
102        color.a = 1.0;
103    }
104
105#ifdef MAY_DISCARD
106    // NOTE: `MAY_DISCARD` is only defined in the alpha to coverage case if MSAA
107    // was off. This special situation causes alpha to coverage to fall back to
108    // alpha mask.
109    else if alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_MASK ||
110            alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ALPHA_TO_COVERAGE {
111        if color.a >= material.alpha_cutoff {
112            // NOTE: If rendering as masked alpha and >= the cutoff, render as fully opaque
113            color.a = 1.0;
114        } else {
115            // NOTE: output_color.a < in.material.alpha_cutoff should not be rendered
116            discard;
117        }
118    }
119#endif
120
121    return color;
122}
123
124// Samples a texture using the appropriate biasing metric for the type of mesh
125// in use (mesh vs. meshlet).
126fn sample_texture(
127    texture: texture_2d<f32>,
128    samp: sampler,
129    uv: vec2<f32>,
130    bias: SampleBias,
131) -> vec4<f32> {
132#ifdef MESHLET_MESH_MATERIAL_PASS
133    return textureSampleGrad(texture, samp, uv, bias.ddx_uv, bias.ddy_uv);
134#else
135    return textureSampleBias(texture, samp, uv, bias.mip_bias);
136#endif
137}
138
139fn prepare_world_normal(
140    world_normal: vec3<f32>,
141    double_sided: bool,
142    is_front: bool,
143) -> vec3<f32> {
144    var output: vec3<f32> = world_normal;
145#ifndef VERTEX_TANGENTS
146#ifndef STANDARD_MATERIAL_NORMAL_MAP
147    // NOTE: When NOT using normal-mapping, if looking at the back face of a double-sided
148    // material, the normal needs to be inverted. This is a branchless version of that.
149    output = (f32(!double_sided || is_front) * 2.0 - 1.0) * output;
150#endif
151#endif
152    return output;
153}
154
155// Calculates the three TBN vectors according to [mikktspace]. Returns a matrix
156// with T, B, N columns in that order.
157//
158// [mikktspace]: http://www.mikktspace.com/
159fn calculate_tbn_mikktspace(world_normal: vec3<f32>, world_tangent: vec4<f32>) -> mat3x3<f32> {
160    // NOTE: The mikktspace method of normal mapping explicitly requires that the world normal NOT
161    // be re-normalized in the fragment shader. This is primarily to match the way mikktspace
162    // bakes vertex tangents and normal maps so that this is the exact inverse. Blender, Unity,
163    // Unreal Engine, Godot, and more all use the mikktspace method. Do not change this code
164    // unless you really know what you are doing.
165    // http://www.mikktspace.com/
166    var N: vec3<f32> = world_normal;
167
168    // NOTE: The mikktspace method of normal mapping explicitly requires that these NOT be
169    // normalized nor any Gram-Schmidt applied to ensure the vertex normal is orthogonal to the
170    // vertex tangent! Do not change this code unless you really know what you are doing.
171    // http://www.mikktspace.com/
172    var T: vec3<f32> = world_tangent.xyz;
173    var B: vec3<f32> = world_tangent.w * cross(N, T);
174
175#ifdef MESHLET_MESH_MATERIAL_PASS
176    // https://www.jeremyong.com/graphics/2023/12/16/surface-gradient-bump-mapping/#a-note-on-mikktspace-usage
177    let inverse_length_n = 1.0 / length(N);
178    T *= inverse_length_n;
179    B *= inverse_length_n;
180    N *= inverse_length_n;
181#endif
182
183    return mat3x3(T, B, N);
184}
185
186fn apply_normal_mapping(
187    standard_material_flags: u32,
188    TBN: mat3x3<f32>,
189    double_sided: bool,
190    is_front: bool,
191    in_Nt: vec3<f32>,
192) -> vec3<f32> {
193    // Unpack the TBN vectors.
194    var T = TBN[0];
195    var B = TBN[1];
196    var N = TBN[2];
197
198    // Nt is the tangent-space normal.
199    var Nt = in_Nt;
200    if (standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_TWO_COMPONENT_NORMAL_MAP) != 0u {
201        // Only use the xy components and derive z for 2-component normal maps.
202        Nt = vec3<f32>(Nt.rg * 2.0 - 1.0, 0.0);
203        Nt.z = sqrt(1.0 - Nt.x * Nt.x - Nt.y * Nt.y);
204    } else {
205        Nt = Nt * 2.0 - 1.0;
206    }
207    // Normal maps authored for DirectX require flipping the y component
208    if (standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_FLIP_NORMAL_MAP_Y) != 0u {
209        Nt.y = -Nt.y;
210    }
211
212    if double_sided && !is_front {
213        Nt = -Nt;
214    }
215
216    // NOTE: The mikktspace method of normal mapping applies maps the tangent-space normal from
217    // the normal map texture in this way to be an EXACT inverse of how the normal map baker
218    // calculates the normal maps so there is no error introduced. Do not change this code
219    // unless you really know what you are doing.
220    // http://www.mikktspace.com/
221    N = Nt.x * T + Nt.y * B + Nt.z * N;
222
223    return normalize(N);
224}
225
226#ifdef STANDARD_MATERIAL_ANISOTROPY
227
228// Modifies the normal to achieve a better approximate direction from the
229// environment map when using anisotropy.
230//
231// This follows the suggested implementation in the `KHR_materials_anisotropy` specification:
232// https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_anisotropy/README.md#image-based-lighting
233fn bend_normal_for_anisotropy(lighting_input: ptr<function, lighting::LightingInput>) {
234    // Unpack.
235    let N = (*lighting_input).layers[LAYER_BASE].N;
236    let roughness = (*lighting_input).layers[LAYER_BASE].roughness;
237    let V = (*lighting_input).V;
238    let anisotropy = (*lighting_input).anisotropy;
239    let Ba = (*lighting_input).Ba;
240
241    var bent_normal = normalize(cross(cross(Ba, V), Ba));
242
243    // The `KHR_materials_anisotropy` spec states:
244    //
245    // > This heuristic can probably be improved upon
246    let a = pow(2.0, pow(2.0, 1.0 - anisotropy * (1.0 - roughness)));
247    bent_normal = normalize(mix(bent_normal, N, a));
248
249    // The `KHR_materials_anisotropy` spec states:
250    //
251    // > Mixing the reflection with the normal is more accurate both with and
252    // > without anisotropy and keeps rough objects from gathering light from
253    // > behind their tangent plane.
254    let R = normalize(mix(reflect(-V, bent_normal), bent_normal, roughness * roughness));
255
256    (*lighting_input).layers[LAYER_BASE].N = bent_normal;
257    (*lighting_input).layers[LAYER_BASE].R = R;
258}
259
260#endif  // STANDARD_MATERIAL_ANISTROPY
261
262// NOTE: Correctly calculates the view vector depending on whether
263// the projection is orthographic or perspective.
264fn calculate_view(
265    world_position: vec4<f32>,
266    is_orthographic: bool,
267) -> vec3<f32> {
268    var V: vec3<f32>;
269    if is_orthographic {
270        // Orthographic view vector
271        V = normalize(vec3<f32>(view_bindings::view.clip_from_world[0].z, view_bindings::view.clip_from_world[1].z, view_bindings::view.clip_from_world[2].z));
272    } else {
273        // Only valid for a perspective projection
274        V = normalize(view_bindings::view.world_position.xyz - world_position.xyz);
275    }
276    return V;
277}
278
279// Diffuse strength is inversely related to metallicity, specular and diffuse transmission
280fn calculate_diffuse_color(
281    base_color: vec3<f32>,
282    metallic: f32,
283    specular_transmission: f32,
284    diffuse_transmission: f32
285) -> vec3<f32> {
286    return base_color * (1.0 - metallic) * (1.0 - specular_transmission) *
287        (1.0 - diffuse_transmission);
288}
289
290// Remapping [0,1] reflectance to F0
291// See https://google.github.io/filament/Filament.html#materialsystem/parameterization/remapping
292fn calculate_F0(base_color: vec3<f32>, metallic: f32, reflectance: f32) -> vec3<f32> {
293    return 0.16 * reflectance * reflectance * (1.0 - metallic) + base_color * metallic;
294}
295
296#ifndef PREPASS_FRAGMENT
297fn apply_pbr_lighting(
298    in: pbr_types::PbrInput,
299) -> vec4<f32> {
300    var output_color: vec4<f32> = in.material.base_color;
301
302    let emissive = in.material.emissive;
303
304    // calculate non-linear roughness from linear perceptualRoughness
305    let metallic = in.material.metallic;
306    let perceptual_roughness = in.material.perceptual_roughness;
307    let roughness = lighting::perceptualRoughnessToRoughness(perceptual_roughness);
308    let ior = in.material.ior;
309    let thickness = in.material.thickness;
310    let reflectance = in.material.reflectance;
311    let diffuse_transmission = in.material.diffuse_transmission;
312    let specular_transmission = in.material.specular_transmission;
313
314    let specular_transmissive_color = specular_transmission * in.material.base_color.rgb;
315
316    let diffuse_occlusion = in.diffuse_occlusion;
317    let specular_occlusion = in.specular_occlusion;
318
319    // Neubelt and Pettineo 2013, "Crafting a Next-gen Material Pipeline for The Order: 1886"
320    let NdotV = max(dot(in.N, in.V), 0.0001);
321    let R = reflect(-in.V, in.N);
322
323#ifdef STANDARD_MATERIAL_CLEARCOAT
324    // Do the above calculations again for the clearcoat layer. Remember that
325    // the clearcoat can have its own roughness and its own normal.
326    let clearcoat = in.material.clearcoat;
327    let clearcoat_perceptual_roughness = in.material.clearcoat_perceptual_roughness;
328    let clearcoat_roughness = lighting::perceptualRoughnessToRoughness(clearcoat_perceptual_roughness);
329    let clearcoat_N = in.clearcoat_N;
330    let clearcoat_NdotV = max(dot(clearcoat_N, in.V), 0.0001);
331    let clearcoat_R = reflect(-in.V, clearcoat_N);
332#endif  // STANDARD_MATERIAL_CLEARCOAT
333
334    let diffuse_color = calculate_diffuse_color(
335        output_color.rgb,
336        metallic,
337        specular_transmission,
338        diffuse_transmission
339    );
340
341    // Diffuse transmissive strength is inversely related to metallicity and specular transmission, but directly related to diffuse transmission
342    let diffuse_transmissive_color = output_color.rgb * (1.0 - metallic) * (1.0 - specular_transmission) * diffuse_transmission;
343
344    // Calculate the world position of the second Lambertian lobe used for diffuse transmission, by subtracting material thickness
345    let diffuse_transmissive_lobe_world_position = in.world_position - vec4<f32>(in.world_normal, 0.0) * thickness;
346
347    let F0 = calculate_F0(output_color.rgb, metallic, reflectance);
348    let F_ab = lighting::F_AB(perceptual_roughness, NdotV);
349
350    var direct_light: vec3<f32> = vec3<f32>(0.0);
351
352    // Transmitted Light (Specular and Diffuse)
353    var transmitted_light: vec3<f32> = vec3<f32>(0.0);
354
355    // Pack all the values into a structure.
356    var lighting_input: lighting::LightingInput;
357    lighting_input.layers[LAYER_BASE].NdotV = NdotV;
358    lighting_input.layers[LAYER_BASE].N = in.N;
359    lighting_input.layers[LAYER_BASE].R = R;
360    lighting_input.layers[LAYER_BASE].perceptual_roughness = perceptual_roughness;
361    lighting_input.layers[LAYER_BASE].roughness = roughness;
362    lighting_input.P = in.world_position.xyz;
363    lighting_input.V = in.V;
364    lighting_input.diffuse_color = diffuse_color;
365    lighting_input.F0_ = F0;
366    lighting_input.F_ab = F_ab;
367#ifdef STANDARD_MATERIAL_CLEARCOAT
368    lighting_input.layers[LAYER_CLEARCOAT].NdotV = clearcoat_NdotV;
369    lighting_input.layers[LAYER_CLEARCOAT].N = clearcoat_N;
370    lighting_input.layers[LAYER_CLEARCOAT].R = clearcoat_R;
371    lighting_input.layers[LAYER_CLEARCOAT].perceptual_roughness = clearcoat_perceptual_roughness;
372    lighting_input.layers[LAYER_CLEARCOAT].roughness = clearcoat_roughness;
373    lighting_input.clearcoat_strength = clearcoat;
374#endif  // STANDARD_MATERIAL_CLEARCOAT
375#ifdef STANDARD_MATERIAL_ANISOTROPY
376    lighting_input.anisotropy = in.anisotropy_strength;
377    lighting_input.Ta = in.anisotropy_T;
378    lighting_input.Ba = in.anisotropy_B;
379#endif  // STANDARD_MATERIAL_ANISOTROPY
380
381    // And do the same for transmissive if we need to.
382#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
383    var transmissive_lighting_input: lighting::LightingInput;
384    transmissive_lighting_input.layers[LAYER_BASE].NdotV = 1.0;
385    transmissive_lighting_input.layers[LAYER_BASE].N = -in.N;
386    transmissive_lighting_input.layers[LAYER_BASE].R = vec3(0.0);
387    transmissive_lighting_input.layers[LAYER_BASE].perceptual_roughness = 1.0;
388    transmissive_lighting_input.layers[LAYER_BASE].roughness = 1.0;
389    transmissive_lighting_input.P = diffuse_transmissive_lobe_world_position.xyz;
390    transmissive_lighting_input.V = -in.V;
391    transmissive_lighting_input.diffuse_color = diffuse_transmissive_color;
392    transmissive_lighting_input.F0_ = vec3(0.0);
393    transmissive_lighting_input.F_ab = vec2(0.1);
394#ifdef STANDARD_MATERIAL_CLEARCOAT
395    transmissive_lighting_input.layers[LAYER_CLEARCOAT].NdotV = 0.0;
396    transmissive_lighting_input.layers[LAYER_CLEARCOAT].N = vec3(0.0);
397    transmissive_lighting_input.layers[LAYER_CLEARCOAT].R = vec3(0.0);
398    transmissive_lighting_input.layers[LAYER_CLEARCOAT].perceptual_roughness = 0.0;
399    transmissive_lighting_input.layers[LAYER_CLEARCOAT].roughness = 0.0;
400    transmissive_lighting_input.clearcoat_strength = 0.0;
401#endif  // STANDARD_MATERIAL_CLEARCOAT
402#ifdef STANDARD_MATERIAL_ANISOTROPY
403    lighting_input.anisotropy = in.anisotropy_strength;
404    lighting_input.Ta = in.anisotropy_T;
405    lighting_input.Ba = in.anisotropy_B;
406#endif  // STANDARD_MATERIAL_ANISOTROPY
407#endif  // STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
408
409    let view_z = dot(vec4<f32>(
410        view_bindings::view.view_from_world[0].z,
411        view_bindings::view.view_from_world[1].z,
412        view_bindings::view.view_from_world[2].z,
413        view_bindings::view.view_from_world[3].z
414    ), in.world_position);
415    let cluster_index = clustering::fragment_cluster_index(in.frag_coord.xy, view_z, in.is_orthographic);
416    let offset_and_counts = clustering::unpack_offset_and_counts(cluster_index);
417
418    // Point lights (direct)
419    for (var i: u32 = offset_and_counts[0]; i < offset_and_counts[0] + offset_and_counts[1]; i = i + 1u) {
420        let light_id = clustering::get_clusterable_object_id(i);
421        var shadow: f32 = 1.0;
422        if ((in.flags & MESH_FLAGS_SHADOW_RECEIVER_BIT) != 0u
423                && (view_bindings::clusterable_objects.data[light_id].flags & mesh_view_types::POINT_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
424            shadow = shadows::fetch_point_shadow(light_id, in.world_position, in.world_normal);
425        }
426
427        let light_contrib = lighting::point_light(light_id, &lighting_input);
428        direct_light += light_contrib * shadow;
429
430#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
431        // NOTE: We use the diffuse transmissive color, the second Lambertian lobe's calculated
432        // world position, inverted normal and view vectors, and the following simplified
433        // values for a fully diffuse transmitted light contribution approximation:
434        //
435        // roughness = 1.0;
436        // NdotV = 1.0;
437        // R = vec3<f32>(0.0) // doesn't really matter
438        // F_ab = vec2<f32>(0.1)
439        // F0 = vec3<f32>(0.0)
440        var transmitted_shadow: f32 = 1.0;
441        if ((in.flags & (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)) == (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)
442                && (view_bindings::clusterable_objects.data[light_id].flags & mesh_view_types::POINT_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
443            transmitted_shadow = shadows::fetch_point_shadow(light_id, diffuse_transmissive_lobe_world_position, -in.world_normal);
444        }
445
446        let transmitted_light_contrib =
447            lighting::point_light(light_id, &transmissive_lighting_input);
448        transmitted_light += transmitted_light_contrib * transmitted_shadow;
449#endif
450    }
451
452    // Spot lights (direct)
453    for (var i: u32 = offset_and_counts[0] + offset_and_counts[1]; i < offset_and_counts[0] + offset_and_counts[1] + offset_and_counts[2]; i = i + 1u) {
454        let light_id = clustering::get_clusterable_object_id(i);
455
456        var shadow: f32 = 1.0;
457        if ((in.flags & MESH_FLAGS_SHADOW_RECEIVER_BIT) != 0u
458                && (view_bindings::clusterable_objects.data[light_id].flags &
459                    mesh_view_types::POINT_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
460            shadow = shadows::fetch_spot_shadow(
461                light_id,
462                in.world_position,
463                in.world_normal,
464                view_bindings::clusterable_objects.data[light_id].shadow_map_near_z,
465            );
466        }
467
468        let light_contrib = lighting::spot_light(light_id, &lighting_input);
469        direct_light += light_contrib * shadow;
470
471#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
472        // NOTE: We use the diffuse transmissive color, the second Lambertian lobe's calculated
473        // world position, inverted normal and view vectors, and the following simplified
474        // values for a fully diffuse transmitted light contribution approximation:
475        //
476        // roughness = 1.0;
477        // NdotV = 1.0;
478        // R = vec3<f32>(0.0) // doesn't really matter
479        // F_ab = vec2<f32>(0.1)
480        // F0 = vec3<f32>(0.0)
481        var transmitted_shadow: f32 = 1.0;
482        if ((in.flags & (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)) == (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)
483                && (view_bindings::clusterable_objects.data[light_id].flags & mesh_view_types::POINT_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
484            transmitted_shadow = shadows::fetch_spot_shadow(
485                light_id,
486                diffuse_transmissive_lobe_world_position,
487                -in.world_normal,
488                view_bindings::clusterable_objects.data[light_id].shadow_map_near_z,
489            );
490        }
491
492        let transmitted_light_contrib =
493            lighting::spot_light(light_id, &transmissive_lighting_input);
494        transmitted_light += transmitted_light_contrib * transmitted_shadow;
495#endif
496    }
497
498    // directional lights (direct)
499    let n_directional_lights = view_bindings::lights.n_directional_lights;
500    for (var i: u32 = 0u; i < n_directional_lights; i = i + 1u) {
501        // check if this light should be skipped, which occurs if this light does not intersect with the view
502        // note point and spot lights aren't skippable, as the relevant lights are filtered in `assign_lights_to_clusters`
503        let light = &view_bindings::lights.directional_lights[i];
504        if (*light).skip != 0u {
505            continue;
506        }
507
508        var shadow: f32 = 1.0;
509        if ((in.flags & MESH_FLAGS_SHADOW_RECEIVER_BIT) != 0u
510                && (view_bindings::lights.directional_lights[i].flags & mesh_view_types::DIRECTIONAL_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
511            shadow = shadows::fetch_directional_shadow(i, in.world_position, in.world_normal, view_z);
512        }
513
514        var light_contrib = lighting::directional_light(i, &lighting_input);
515
516#ifdef DIRECTIONAL_LIGHT_SHADOW_MAP_DEBUG_CASCADES
517        light_contrib = shadows::cascade_debug_visualization(light_contrib, i, view_z);
518#endif
519        direct_light += light_contrib * shadow;
520
521#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
522        // NOTE: We use the diffuse transmissive color, the second Lambertian lobe's calculated
523        // world position, inverted normal and view vectors, and the following simplified
524        // values for a fully diffuse transmitted light contribution approximation:
525        //
526        // roughness = 1.0;
527        // NdotV = 1.0;
528        // R = vec3<f32>(0.0) // doesn't really matter
529        // F_ab = vec2<f32>(0.1)
530        // F0 = vec3<f32>(0.0)
531        var transmitted_shadow: f32 = 1.0;
532        if ((in.flags & (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)) == (MESH_FLAGS_SHADOW_RECEIVER_BIT | MESH_FLAGS_TRANSMITTED_SHADOW_RECEIVER_BIT)
533                && (view_bindings::lights.directional_lights[i].flags & mesh_view_types::DIRECTIONAL_LIGHT_FLAGS_SHADOWS_ENABLED_BIT) != 0u) {
534            transmitted_shadow = shadows::fetch_directional_shadow(i, diffuse_transmissive_lobe_world_position, -in.world_normal, view_z);
535        }
536
537        let transmitted_light_contrib =
538            lighting::directional_light(i, &transmissive_lighting_input);
539        transmitted_light += transmitted_light_contrib * transmitted_shadow;
540#endif
541    }
542
543#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
544    // NOTE: We use the diffuse transmissive color, the second Lambertian lobe's calculated
545    // world position, inverted normal and view vectors, and the following simplified
546    // values for a fully diffuse transmitted light contribution approximation:
547    //
548    // perceptual_roughness = 1.0;
549    // NdotV = 1.0;
550    // F0 = vec3<f32>(0.0)
551    // diffuse_occlusion = vec3<f32>(1.0)
552    transmitted_light += ambient::ambient_light(diffuse_transmissive_lobe_world_position, -in.N, -in.V, 1.0, diffuse_transmissive_color, vec3<f32>(0.0), 1.0, vec3<f32>(1.0));
553#endif
554
555    // Diffuse indirect lighting can come from a variety of sources. The
556    // priority goes like this:
557    //
558    // 1. Lightmap (highest)
559    // 2. Irradiance volume
560    // 3. Environment map (lowest)
561    //
562    // When we find a source of diffuse indirect lighting, we stop accumulating
563    // any more diffuse indirect light. This avoids double-counting if, for
564    // example, both lightmaps and irradiance volumes are present.
565
566    var indirect_light = vec3(0.0f);
567    var found_diffuse_indirect = false;
568
569#ifdef LIGHTMAP
570    indirect_light += in.lightmap_light * diffuse_color;
571    found_diffuse_indirect = true;
572#endif
573
574#ifdef IRRADIANCE_VOLUME
575    // Irradiance volume light (indirect)
576    if (!found_diffuse_indirect) {
577        let irradiance_volume_light = irradiance_volume::irradiance_volume_light(
578            in.world_position.xyz, in.N);
579        indirect_light += irradiance_volume_light * diffuse_color * diffuse_occlusion;
580        found_diffuse_indirect = true;
581    }
582#endif
583
584    // Environment map light (indirect)
585#ifdef ENVIRONMENT_MAP
586
587#ifdef STANDARD_MATERIAL_ANISOTROPY
588    var bent_normal_lighting_input = lighting_input;
589    bend_normal_for_anisotropy(&bent_normal_lighting_input);
590    let environment_map_lighting_input = &bent_normal_lighting_input;
591#else   // STANDARD_MATERIAL_ANISOTROPY
592    let environment_map_lighting_input = &lighting_input;
593#endif  // STANDARD_MATERIAL_ANISOTROPY
594
595    let environment_light = environment_map::environment_map_light(
596        environment_map_lighting_input,
597        found_diffuse_indirect
598    );
599
600    // If screen space reflections are going to be used for this material, don't
601    // accumulate environment map light yet. The SSR shader will do it.
602#ifdef SCREEN_SPACE_REFLECTIONS
603    let use_ssr = perceptual_roughness <=
604        view_bindings::ssr_settings.perceptual_roughness_threshold;
605#else   // SCREEN_SPACE_REFLECTIONS
606    let use_ssr = false;
607#endif  // SCREEN_SPACE_REFLECTIONS
608
609    if (!use_ssr) {
610        let environment_light = environment_map::environment_map_light(
611            &lighting_input,
612            found_diffuse_indirect
613        );
614
615        indirect_light += environment_light.diffuse * diffuse_occlusion +
616            environment_light.specular * specular_occlusion;
617    }
618
619#endif  // ENVIRONMENT_MAP
620
621    // Ambient light (indirect)
622    indirect_light += ambient::ambient_light(in.world_position, in.N, in.V, NdotV, diffuse_color, F0, perceptual_roughness, diffuse_occlusion);
623
624    // we'll use the specular component of the transmitted environment
625    // light in the call to `specular_transmissive_light()` below
626    var specular_transmitted_environment_light = vec3<f32>(0.0);
627
628#ifdef ENVIRONMENT_MAP
629
630#ifdef STANDARD_MATERIAL_DIFFUSE_OR_SPECULAR_TRANSMISSION
631    // NOTE: We use the diffuse transmissive color, inverted normal and view vectors,
632    // and the following simplified values for the transmitted environment light contribution
633    // approximation:
634    //
635    // diffuse_color = vec3<f32>(1.0) // later we use `diffuse_transmissive_color` and `specular_transmissive_color`
636    // NdotV = 1.0;
637    // R = T // see definition below
638    // F0 = vec3<f32>(1.0)
639    // diffuse_occlusion = 1.0
640    //
641    // (This one is slightly different from the other light types above, because the environment
642    // map light returns both diffuse and specular components separately, and we want to use both)
643
644    let T = -normalize(
645        in.V + // start with view vector at entry point
646        refract(in.V, -in.N, 1.0 / ior) * thickness // add refracted vector scaled by thickness, towards exit point
647    ); // normalize to find exit point view vector
648
649    var transmissive_environment_light_input: lighting::LightingInput;
650    transmissive_environment_light_input.diffuse_color = vec3(1.0);
651    transmissive_environment_light_input.layers[LAYER_BASE].NdotV = 1.0;
652    transmissive_environment_light_input.P = in.world_position.xyz;
653    transmissive_environment_light_input.layers[LAYER_BASE].N = -in.N;
654    transmissive_environment_light_input.V = in.V;
655    transmissive_environment_light_input.layers[LAYER_BASE].R = T;
656    transmissive_environment_light_input.layers[LAYER_BASE].perceptual_roughness = perceptual_roughness;
657    transmissive_environment_light_input.layers[LAYER_BASE].roughness = roughness;
658    transmissive_environment_light_input.F0_ = vec3<f32>(1.0);
659    transmissive_environment_light_input.F_ab = vec2(0.1);
660#ifdef STANDARD_MATERIAL_CLEARCOAT
661    // No clearcoat.
662    transmissive_environment_light_input.clearcoat_strength = 0.0;
663    transmissive_environment_light_input.layers[LAYER_CLEARCOAT].NdotV = 0.0;
664    transmissive_environment_light_input.layers[LAYER_CLEARCOAT].N = in.N;
665    transmissive_environment_light_input.layers[LAYER_CLEARCOAT].R = vec3(0.0);
666    transmissive_environment_light_input.layers[LAYER_CLEARCOAT].perceptual_roughness = 0.0;
667    transmissive_environment_light_input.layers[LAYER_CLEARCOAT].roughness = 0.0;
668#endif  // STANDARD_MATERIAL_CLEARCOAT
669
670    let transmitted_environment_light =
671        environment_map::environment_map_light(&transmissive_environment_light_input, false);
672
673#ifdef STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
674    transmitted_light += transmitted_environment_light.diffuse * diffuse_transmissive_color;
675#endif  // STANDARD_MATERIAL_DIFFUSE_TRANSMISSION
676#ifdef STANDARD_MATERIAL_SPECULAR_TRANSMISSION
677    specular_transmitted_environment_light = transmitted_environment_light.specular * specular_transmissive_color;
678#endif  // STANDARD_MATERIAL_SPECULAR_TRANSMISSION
679
680#endif  // STANDARD_MATERIAL_SPECULAR_OR_DIFFUSE_TRANSMISSION
681
682#endif  // ENVIRONMENT_MAP
683
684    var emissive_light = emissive.rgb * output_color.a;
685
686    // "The clearcoat layer is on top of emission in the layering stack.
687    // Consequently, the emission is darkened by the Fresnel term."
688    //
689    // <https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_clearcoat/README.md#emission>
690#ifdef STANDARD_MATERIAL_CLEARCOAT
691    emissive_light = emissive_light * (0.04 + (1.0 - 0.04) * pow(1.0 - clearcoat_NdotV, 5.0));
692#endif
693
694    emissive_light = emissive_light * mix(1.0, view_bindings::view.exposure, emissive.a);
695
696#ifdef STANDARD_MATERIAL_SPECULAR_TRANSMISSION
697    transmitted_light += transmission::specular_transmissive_light(in.world_position, in.frag_coord.xyz, view_z, in.N, in.V, F0, ior, thickness, perceptual_roughness, specular_transmissive_color, specular_transmitted_environment_light).rgb;
698
699    if (in.material.flags & pbr_types::STANDARD_MATERIAL_FLAGS_ATTENUATION_ENABLED_BIT) != 0u {
700        // We reuse the `atmospheric_fog()` function here, as it's fundamentally
701        // equivalent to the attenuation that takes place inside the material volume,
702        // and will allow us to eventually hook up subsurface scattering more easily
703        var attenuation_fog: mesh_view_types::Fog;
704        attenuation_fog.base_color.a = 1.0;
705        attenuation_fog.be = pow(1.0 - in.material.attenuation_color.rgb, vec3<f32>(E)) / in.material.attenuation_distance;
706        // TODO: Add the subsurface scattering factor below
707        // attenuation_fog.bi = /* ... */
708        transmitted_light = bevy_pbr::fog::atmospheric_fog(
709            attenuation_fog, vec4<f32>(transmitted_light, 1.0), thickness,
710            vec3<f32>(0.0) // TODO: Pass in (pre-attenuated) scattered light contribution here
711        ).rgb;
712    }
713#endif
714
715    // Total light
716    output_color = vec4<f32>(
717        (view_bindings::view.exposure * (transmitted_light + direct_light + indirect_light)) + emissive_light,
718        output_color.a
719    );
720
721    output_color = clustering::cluster_debug_visualization(
722        output_color,
723        view_z,
724        in.is_orthographic,
725        offset_and_counts,
726        cluster_index,
727    );
728
729    return output_color;
730}
731#endif // PREPASS_FRAGMENT
732
733fn apply_fog(fog_params: mesh_view_types::Fog, input_color: vec4<f32>, fragment_world_position: vec3<f32>, view_world_position: vec3<f32>) -> vec4<f32> {
734    let view_to_world = fragment_world_position.xyz - view_world_position.xyz;
735
736    // `length()` is used here instead of just `view_to_world.z` since that produces more
737    // high quality results, especially for denser/smaller fogs. we get a "curved"
738    // fog shape that remains consistent with camera rotation, instead of a "linear"
739    // fog shape that looks a bit fake
740    let distance = length(view_to_world);
741
742    var scattering = vec3<f32>(0.0);
743    if fog_params.directional_light_color.a > 0.0 {
744        let view_to_world_normalized = view_to_world / distance;
745        let n_directional_lights = view_bindings::lights.n_directional_lights;
746        for (var i: u32 = 0u; i < n_directional_lights; i = i + 1u) {
747            let light = view_bindings::lights.directional_lights[i];
748            scattering += pow(
749                max(
750                    dot(view_to_world_normalized, light.direction_to_light),
751                    0.0
752                ),
753                fog_params.directional_light_exponent
754            ) * light.color.rgb * view_bindings::view.exposure;
755        }
756    }
757
758    if fog_params.mode == mesh_view_types::FOG_MODE_LINEAR {
759        return bevy_pbr::fog::linear_fog(fog_params, input_color, distance, scattering);
760    } else if fog_params.mode == mesh_view_types::FOG_MODE_EXPONENTIAL {
761        return bevy_pbr::fog::exponential_fog(fog_params, input_color, distance, scattering);
762    } else if fog_params.mode == mesh_view_types::FOG_MODE_EXPONENTIAL_SQUARED {
763        return bevy_pbr::fog::exponential_squared_fog(fog_params, input_color, distance, scattering);
764    } else if fog_params.mode == mesh_view_types::FOG_MODE_ATMOSPHERIC {
765        return bevy_pbr::fog::atmospheric_fog(fog_params, input_color, distance, scattering);
766    } else {
767        return input_color;
768    }
769}
770
771#ifdef PREMULTIPLY_ALPHA
772fn premultiply_alpha(standard_material_flags: u32, color: vec4<f32>) -> vec4<f32> {
773// `Blend`, `Premultiplied` and `Alpha` all share the same `BlendState`. Depending
774// on the alpha mode, we premultiply the color channels by the alpha channel value,
775// (and also optionally replace the alpha value with 0.0) so that the result produces
776// the desired blend mode when sent to the blending operation.
777#ifdef BLEND_PREMULTIPLIED_ALPHA
778    // For `BlendState::PREMULTIPLIED_ALPHA_BLENDING` the blend function is:
779    //
780    //     result = 1 * src_color + (1 - src_alpha) * dst_color
781    let alpha_mode = standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
782    if alpha_mode == pbr_types::STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ADD {
783        // Here, we premultiply `src_color` by `src_alpha`, and replace `src_alpha` with 0.0:
784        //
785        //     src_color *= src_alpha
786        //     src_alpha = 0.0
787        //
788        // We end up with:
789        //
790        //     result = 1 * (src_alpha * src_color) + (1 - 0) * dst_color
791        //     result = src_alpha * src_color + 1 * dst_color
792        //
793        // Which is the blend operation for additive blending
794        return vec4<f32>(color.rgb * color.a, 0.0);
795    } else {
796        // Here, we don't do anything, so that we get premultiplied alpha blending. (As expected)
797        return color.rgba;
798    }
799#endif
800// `Multiply` uses its own `BlendState`, but we still need to premultiply here in the
801// shader so that we get correct results as we tweak the alpha channel
802#ifdef BLEND_MULTIPLY
803    // The blend function is:
804    //
805    //     result = dst_color * src_color + (1 - src_alpha) * dst_color
806    //
807    // We premultiply `src_color` by `src_alpha`:
808    //
809    //     src_color *= src_alpha
810    //
811    // We end up with:
812    //
813    //     result = dst_color * (src_color * src_alpha) + (1 - src_alpha) * dst_color
814    //     result = src_alpha * (src_color * dst_color) + (1 - src_alpha) * dst_color
815    //
816    // Which is the blend operation for multiplicative blending with arbitrary mixing
817    // controlled by the source alpha channel
818    return vec4<f32>(color.rgb * color.a, color.a);
819#endif
820}
821#endif
822
823// fog, alpha premultiply
824// for non-hdr cameras, tonemapping and debanding
825fn main_pass_post_lighting_processing(
826    pbr_input: pbr_types::PbrInput,
827    input_color: vec4<f32>,
828) -> vec4<f32> {
829    var output_color = input_color;
830
831    // fog
832    if (view_bindings::fog.mode != mesh_view_types::FOG_MODE_OFF && (pbr_input.material.flags & pbr_types::STANDARD_MATERIAL_FLAGS_FOG_ENABLED_BIT) != 0u) {
833        output_color = apply_fog(view_bindings::fog, output_color, pbr_input.world_position.xyz, view_bindings::view.world_position.xyz);
834    }
835
836#ifdef TONEMAP_IN_SHADER
837    output_color = tone_mapping(output_color, view_bindings::view.color_grading);
838#ifdef DEBAND_DITHER
839    var output_rgb = output_color.rgb;
840    output_rgb = powsafe(output_rgb, 1.0 / 2.2);
841    output_rgb += screen_space_dither(pbr_input.frag_coord.xy);
842    // This conversion back to linear space is required because our output texture format is
843    // SRGB; the GPU will assume our output is linear and will apply an SRGB conversion.
844    output_rgb = powsafe(output_rgb, 2.2);
845    output_color = vec4(output_rgb, output_color.a);
846#endif
847#endif
848#ifdef PREMULTIPLY_ALPHA
849    output_color = premultiply_alpha(pbr_input.material.flags, output_color);
850#endif
851    return output_color;
852}