1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
pub mod visibility;
pub mod window;

use bevy_asset::{load_internal_asset, Handle};
pub use visibility::*;
pub use window::*;

use crate::{
    camera::{
        CameraMainTextureUsages, ClearColor, ClearColorConfig, Exposure, ExtractedCamera,
        ManualTextureViews, MipBias, TemporalJitter,
    },
    extract_resource::{ExtractResource, ExtractResourcePlugin},
    prelude::{Image, Shader},
    primitives::Frustum,
    render_asset::RenderAssets,
    render_phase::ViewRangefinder3d,
    render_resource::{DynamicUniformBuffer, ShaderType, Texture, TextureView},
    renderer::{RenderDevice, RenderQueue},
    texture::{BevyDefault, CachedTexture, ColorAttachment, DepthAttachment, TextureCache},
    Render, RenderApp, RenderSet,
};
use bevy_app::{App, Plugin};
use bevy_ecs::prelude::*;
use bevy_math::{Mat4, UVec4, Vec3, Vec4, Vec4Swizzles};
use bevy_reflect::{std_traits::ReflectDefault, Reflect};
use bevy_transform::components::GlobalTransform;
use bevy_utils::HashMap;
use std::sync::{
    atomic::{AtomicUsize, Ordering},
    Arc,
};
use wgpu::{
    Extent3d, RenderPassColorAttachment, RenderPassDepthStencilAttachment, StoreOp,
    TextureDescriptor, TextureDimension, TextureFormat, TextureUsages,
};

pub const VIEW_TYPE_HANDLE: Handle<Shader> = Handle::weak_from_u128(15421373904451797197);

pub struct ViewPlugin;

impl Plugin for ViewPlugin {
    fn build(&self, app: &mut App) {
        load_internal_asset!(app, VIEW_TYPE_HANDLE, "view.wgsl", Shader::from_wgsl);

        app.register_type::<InheritedVisibility>()
            .register_type::<ViewVisibility>()
            .register_type::<Msaa>()
            .register_type::<NoFrustumCulling>()
            .register_type::<RenderLayers>()
            .register_type::<Visibility>()
            .register_type::<VisibleEntities>()
            .register_type::<ColorGrading>()
            .init_resource::<Msaa>()
            // NOTE: windows.is_changed() handles cases where a window was resized
            .add_plugins((ExtractResourcePlugin::<Msaa>::default(), VisibilityPlugin));

        if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
            render_app.init_resource::<ViewUniforms>().add_systems(
                Render,
                (
                    prepare_view_targets
                        .in_set(RenderSet::ManageViews)
                        .after(prepare_windows)
                        .after(crate::render_asset::prepare_assets::<Image>)
                        .ambiguous_with(crate::camera::sort_cameras), // doesn't use `sorted_camera_index_for_target`
                    prepare_view_uniforms.in_set(RenderSet::PrepareResources),
                ),
            );
        }
    }
}

/// Configuration resource for [Multi-Sample Anti-Aliasing](https://en.wikipedia.org/wiki/Multisample_anti-aliasing).
///
/// The number of samples to run for Multi-Sample Anti-Aliasing. Higher numbers result in
/// smoother edges.
/// Defaults to 4 samples.
///
/// Note that web currently only supports 1 or 4 samples.
///
/// # Example
/// ```
/// # use bevy_app::prelude::App;
/// # use bevy_render::prelude::Msaa;
/// App::new()
///     .insert_resource(Msaa::default())
///     .run();
/// ```
#[derive(
    Resource, Default, Clone, Copy, ExtractResource, Reflect, PartialEq, PartialOrd, Debug,
)]
#[reflect(Resource)]
pub enum Msaa {
    Off = 1,
    Sample2 = 2,
    #[default]
    Sample4 = 4,
    Sample8 = 8,
}

impl Msaa {
    #[inline]
    pub fn samples(&self) -> u32 {
        *self as u32
    }
}

#[derive(Component)]
pub struct ExtractedView {
    pub projection: Mat4,
    pub transform: GlobalTransform,
    // The view-projection matrix. When provided it is used instead of deriving it from
    // `projection` and `transform` fields, which can be helpful in cases where numerical
    // stability matters and there is a more direct way to derive the view-projection matrix.
    pub view_projection: Option<Mat4>,
    pub hdr: bool,
    // uvec4(origin.x, origin.y, width, height)
    pub viewport: UVec4,
    pub color_grading: ColorGrading,
}

impl ExtractedView {
    /// Creates a 3D rangefinder for a view
    pub fn rangefinder3d(&self) -> ViewRangefinder3d {
        ViewRangefinder3d::from_view_matrix(&self.transform.compute_matrix())
    }
}

/// Configures basic color grading parameters to adjust the image appearance. Grading is applied just before/after tonemapping for a given [`Camera`](crate::camera::Camera) entity.
#[derive(Component, Reflect, Debug, Copy, Clone, ShaderType)]
#[reflect(Component, Default)]
pub struct ColorGrading {
    /// Exposure value (EV) offset, measured in stops.
    pub exposure: f32,

    /// Non-linear luminance adjustment applied before tonemapping. y = pow(x, gamma)
    pub gamma: f32,

    /// Saturation adjustment applied before tonemapping.
    /// Values below 1.0 desaturate, with a value of 0.0 resulting in a grayscale image
    /// with luminance defined by ITU-R BT.709.
    /// Values above 1.0 increase saturation.
    pub pre_saturation: f32,

    /// Saturation adjustment applied after tonemapping.
    /// Values below 1.0 desaturate, with a value of 0.0 resulting in a grayscale image
    /// with luminance defined by ITU-R BT.709
    /// Values above 1.0 increase saturation.
    pub post_saturation: f32,
}

impl Default for ColorGrading {
    fn default() -> Self {
        Self {
            exposure: 0.0,
            gamma: 1.0,
            pre_saturation: 1.0,
            post_saturation: 1.0,
        }
    }
}

#[derive(Clone, ShaderType)]
pub struct ViewUniform {
    view_proj: Mat4,
    unjittered_view_proj: Mat4,
    inverse_view_proj: Mat4,
    view: Mat4,
    inverse_view: Mat4,
    projection: Mat4,
    inverse_projection: Mat4,
    world_position: Vec3,
    exposure: f32,
    // viewport(x_origin, y_origin, width, height)
    viewport: Vec4,
    frustum: [Vec4; 6],
    color_grading: ColorGrading,
    mip_bias: f32,
    render_layers: u32,
}

#[derive(Resource, Default)]
pub struct ViewUniforms {
    pub uniforms: DynamicUniformBuffer<ViewUniform>,
}

#[derive(Component)]
pub struct ViewUniformOffset {
    pub offset: u32,
}

#[derive(Component)]
pub struct ViewTarget {
    main_textures: MainTargetTextures,
    main_texture_format: TextureFormat,
    /// 0 represents `main_textures.a`, 1 represents `main_textures.b`
    /// This is shared across view targets with the same render target
    main_texture: Arc<AtomicUsize>,
    out_texture: TextureView,
    out_texture_format: TextureFormat,
}

pub struct PostProcessWrite<'a> {
    pub source: &'a TextureView,
    pub destination: &'a TextureView,
}

impl ViewTarget {
    pub const TEXTURE_FORMAT_HDR: TextureFormat = TextureFormat::Rgba16Float;

    /// Retrieve this target's main texture's color attachment.
    pub fn get_color_attachment(&self) -> RenderPassColorAttachment {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            self.main_textures.a.get_attachment()
        } else {
            self.main_textures.b.get_attachment()
        }
    }

    /// Retrieve this target's "unsampled" main texture's color attachment.
    pub fn get_unsampled_color_attachment(&self) -> RenderPassColorAttachment {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            self.main_textures.a.get_unsampled_attachment()
        } else {
            self.main_textures.b.get_unsampled_attachment()
        }
    }

    /// The "main" unsampled texture.
    pub fn main_texture(&self) -> &Texture {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            &self.main_textures.a.texture.texture
        } else {
            &self.main_textures.b.texture.texture
        }
    }

    /// The _other_ "main" unsampled texture.
    /// In most cases you should use [`Self::main_texture`] instead and never this.
    /// The textures will naturally be swapped when [`Self::post_process_write`] is called.
    ///
    /// A use case for this is to be able to prepare a bind group for all main textures
    /// ahead of time.
    pub fn main_texture_other(&self) -> &Texture {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            &self.main_textures.b.texture.texture
        } else {
            &self.main_textures.a.texture.texture
        }
    }

    /// The "main" unsampled texture.
    pub fn main_texture_view(&self) -> &TextureView {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            &self.main_textures.a.texture.default_view
        } else {
            &self.main_textures.b.texture.default_view
        }
    }

    /// The _other_ "main" unsampled texture view.
    /// In most cases you should use [`Self::main_texture_view`] instead and never this.
    /// The textures will naturally be swapped when [`Self::post_process_write`] is called.
    ///
    /// A use case for this is to be able to prepare a bind group for all main textures
    /// ahead of time.
    pub fn main_texture_other_view(&self) -> &TextureView {
        if self.main_texture.load(Ordering::SeqCst) == 0 {
            &self.main_textures.b.texture.default_view
        } else {
            &self.main_textures.a.texture.default_view
        }
    }

    /// The "main" sampled texture.
    pub fn sampled_main_texture(&self) -> Option<&Texture> {
        self.main_textures
            .a
            .resolve_target
            .as_ref()
            .map(|sampled| &sampled.texture)
    }

    /// The "main" sampled texture view.
    pub fn sampled_main_texture_view(&self) -> Option<&TextureView> {
        self.main_textures
            .a
            .resolve_target
            .as_ref()
            .map(|sampled| &sampled.default_view)
    }

    #[inline]
    pub fn main_texture_format(&self) -> TextureFormat {
        self.main_texture_format
    }

    /// Returns `true` if and only if the main texture is [`Self::TEXTURE_FORMAT_HDR`]
    #[inline]
    pub fn is_hdr(&self) -> bool {
        self.main_texture_format == ViewTarget::TEXTURE_FORMAT_HDR
    }

    /// The final texture this view will render to.
    #[inline]
    pub fn out_texture(&self) -> &TextureView {
        &self.out_texture
    }

    /// The format of the final texture this view will render to
    #[inline]
    pub fn out_texture_format(&self) -> TextureFormat {
        self.out_texture_format
    }

    /// This will start a new "post process write", which assumes that the caller
    /// will write the [`PostProcessWrite`]'s `source` to the `destination`.
    ///
    /// `source` is the "current" main texture. This will internally flip this
    /// [`ViewTarget`]'s main texture to the `destination` texture, so the caller
    /// _must_ ensure `source` is copied to `destination`, with or without modifications.
    /// Failing to do so will cause the current main texture information to be lost.
    pub fn post_process_write(&self) -> PostProcessWrite {
        let old_is_a_main_texture = self.main_texture.fetch_xor(1, Ordering::SeqCst);
        // if the old main texture is a, then the post processing must write from a to b
        if old_is_a_main_texture == 0 {
            self.main_textures.b.mark_as_cleared();
            PostProcessWrite {
                source: &self.main_textures.a.texture.default_view,
                destination: &self.main_textures.b.texture.default_view,
            }
        } else {
            self.main_textures.a.mark_as_cleared();
            PostProcessWrite {
                source: &self.main_textures.b.texture.default_view,
                destination: &self.main_textures.a.texture.default_view,
            }
        }
    }
}

#[derive(Component)]
pub struct ViewDepthTexture {
    pub texture: Texture,
    attachment: DepthAttachment,
}

impl ViewDepthTexture {
    pub fn new(texture: CachedTexture, clear_value: Option<f32>) -> Self {
        Self {
            texture: texture.texture,
            attachment: DepthAttachment::new(texture.default_view, clear_value),
        }
    }

    pub fn get_attachment(&self, store: StoreOp) -> RenderPassDepthStencilAttachment {
        self.attachment.get_attachment(store)
    }

    pub fn view(&self) -> &TextureView {
        &self.attachment.view
    }
}

pub fn prepare_view_uniforms(
    mut commands: Commands,
    render_device: Res<RenderDevice>,
    render_queue: Res<RenderQueue>,
    mut view_uniforms: ResMut<ViewUniforms>,
    views: Query<(
        Entity,
        Option<&ExtractedCamera>,
        &ExtractedView,
        Option<&Frustum>,
        Option<&TemporalJitter>,
        Option<&MipBias>,
        Option<&RenderLayers>,
    )>,
) {
    let view_iter = views.iter();
    let view_count = view_iter.len();
    let Some(mut writer) =
        view_uniforms
            .uniforms
            .get_writer(view_count, &render_device, &render_queue)
    else {
        return;
    };
    for (
        entity,
        extracted_camera,
        extracted_view,
        frustum,
        temporal_jitter,
        mip_bias,
        maybe_layers,
    ) in &views
    {
        let viewport = extracted_view.viewport.as_vec4();
        let unjittered_projection = extracted_view.projection;
        let mut projection = unjittered_projection;

        if let Some(temporal_jitter) = temporal_jitter {
            temporal_jitter.jitter_projection(&mut projection, viewport.zw());
        }

        let inverse_projection = projection.inverse();
        let view = extracted_view.transform.compute_matrix();
        let inverse_view = view.inverse();

        let view_proj = if temporal_jitter.is_some() {
            projection * inverse_view
        } else {
            extracted_view
                .view_projection
                .unwrap_or_else(|| projection * inverse_view)
        };

        // Map Frustum type to shader array<vec4<f32>, 6>
        let frustum = frustum
            .map(|frustum| frustum.half_spaces.map(|h| h.normal_d()))
            .unwrap_or([Vec4::ZERO; 6]);

        let view_uniforms = ViewUniformOffset {
            offset: writer.write(&ViewUniform {
                view_proj,
                unjittered_view_proj: unjittered_projection * inverse_view,
                inverse_view_proj: view * inverse_projection,
                view,
                inverse_view,
                projection,
                inverse_projection,
                world_position: extracted_view.transform.translation(),
                exposure: extracted_camera
                    .map(|c| c.exposure)
                    .unwrap_or_else(|| Exposure::default().exposure()),
                viewport,
                frustum,
                color_grading: extracted_view.color_grading,
                mip_bias: mip_bias.unwrap_or(&MipBias(0.0)).0,
                render_layers: maybe_layers.copied().unwrap_or_default().bits(),
            }),
        };

        commands.entity(entity).insert(view_uniforms);
    }
}

#[derive(Clone)]
struct MainTargetTextures {
    a: ColorAttachment,
    b: ColorAttachment,
    /// 0 represents `main_textures.a`, 1 represents `main_textures.b`
    /// This is shared across view targets with the same render target
    main_texture: Arc<AtomicUsize>,
}

#[allow(clippy::too_many_arguments)]
pub fn prepare_view_targets(
    mut commands: Commands,
    windows: Res<ExtractedWindows>,
    images: Res<RenderAssets<Image>>,
    msaa: Res<Msaa>,
    clear_color_global: Res<ClearColor>,
    render_device: Res<RenderDevice>,
    mut texture_cache: ResMut<TextureCache>,
    cameras: Query<(
        Entity,
        &ExtractedCamera,
        &ExtractedView,
        &CameraMainTextureUsages,
    )>,
    manual_texture_views: Res<ManualTextureViews>,
) {
    let mut textures = HashMap::default();
    for (entity, camera, view, texture_usage) in cameras.iter() {
        if let (Some(target_size), Some(target)) = (camera.physical_target_size, &camera.target) {
            if let (Some(out_texture_view), Some(out_texture_format)) = (
                target.get_texture_view(&windows, &images, &manual_texture_views),
                target.get_texture_format(&windows, &images, &manual_texture_views),
            ) {
                let size = Extent3d {
                    width: target_size.x,
                    height: target_size.y,
                    depth_or_array_layers: 1,
                };

                let main_texture_format = if view.hdr {
                    ViewTarget::TEXTURE_FORMAT_HDR
                } else {
                    TextureFormat::bevy_default()
                };

                let clear_color = match camera.clear_color {
                    ClearColorConfig::Custom(color) => Some(color),
                    ClearColorConfig::None => None,
                    _ => Some(clear_color_global.0),
                };

                let (a, b, sampled) = textures
                    .entry((camera.target.clone(), view.hdr))
                    .or_insert_with(|| {
                        let descriptor = TextureDescriptor {
                            label: None,
                            size,
                            mip_level_count: 1,
                            sample_count: 1,
                            dimension: TextureDimension::D2,
                            format: main_texture_format,
                            usage: texture_usage.0,
                            view_formats: match main_texture_format {
                                TextureFormat::Bgra8Unorm => &[TextureFormat::Bgra8UnormSrgb],
                                TextureFormat::Rgba8Unorm => &[TextureFormat::Rgba8UnormSrgb],
                                _ => &[],
                            },
                        };
                        let a = texture_cache.get(
                            &render_device,
                            TextureDescriptor {
                                label: Some("main_texture_a"),
                                ..descriptor
                            },
                        );
                        let b = texture_cache.get(
                            &render_device,
                            TextureDescriptor {
                                label: Some("main_texture_b"),
                                ..descriptor
                            },
                        );
                        let sampled = if msaa.samples() > 1 {
                            let sampled = texture_cache.get(
                                &render_device,
                                TextureDescriptor {
                                    label: Some("main_texture_sampled"),
                                    size,
                                    mip_level_count: 1,
                                    sample_count: msaa.samples(),
                                    dimension: TextureDimension::D2,
                                    format: main_texture_format,
                                    usage: TextureUsages::RENDER_ATTACHMENT,
                                    view_formats: descriptor.view_formats,
                                },
                            );
                            Some(sampled)
                        } else {
                            None
                        };
                        (a, b, sampled)
                    });

                let main_textures = MainTargetTextures {
                    a: ColorAttachment::new(a.clone(), sampled.clone(), clear_color),
                    b: ColorAttachment::new(b.clone(), sampled.clone(), clear_color),
                    main_texture: Arc::new(AtomicUsize::new(0)),
                };

                commands.entity(entity).insert(ViewTarget {
                    main_texture: main_textures.main_texture.clone(),
                    main_textures,
                    main_texture_format,
                    out_texture: out_texture_view.clone(),
                    out_texture_format: out_texture_format.add_srgb_suffix(),
                });
            }
        }
    }
}