bevy_pbr/render/
morph.rs

1use core::{iter, mem};
2
3use bevy_camera::visibility::ViewVisibility;
4use bevy_ecs::prelude::*;
5use bevy_mesh::morph::{MeshMorphWeights, MAX_MORPH_WEIGHTS};
6use bevy_render::sync_world::MainEntityHashMap;
7use bevy_render::{
8    batching::NoAutomaticBatching,
9    render_resource::{BufferUsages, RawBufferVec},
10    renderer::{RenderDevice, RenderQueue},
11    Extract,
12};
13use bytemuck::NoUninit;
14
15#[derive(Component)]
16pub struct MorphIndex {
17    pub index: u32,
18}
19
20/// Maps each mesh affected by morph targets to the applicable offset within the
21/// [`MorphUniforms`] buffer.
22///
23/// We store both the current frame's mapping and the previous frame's mapping
24/// for the purposes of motion vector calculation.
25#[derive(Default, Resource)]
26pub struct MorphIndices {
27    /// Maps each entity with a morphed mesh to the appropriate offset within
28    /// [`MorphUniforms::current_buffer`].
29    pub current: MainEntityHashMap<MorphIndex>,
30
31    /// Maps each entity with a morphed mesh to the appropriate offset within
32    /// [`MorphUniforms::prev_buffer`].
33    pub prev: MainEntityHashMap<MorphIndex>,
34}
35
36/// The GPU buffers containing morph weights for all meshes with morph targets.
37///
38/// This is double-buffered: we store the weights of the previous frame in
39/// addition to those of the current frame. This is for motion vector
40/// calculation. Every frame, we swap buffers and reuse the morph target weight
41/// buffer from two frames ago for the current frame.
42#[derive(Resource)]
43pub struct MorphUniforms {
44    /// The morph weights for the current frame.
45    pub current_buffer: RawBufferVec<f32>,
46    /// The morph weights for the previous frame.
47    pub prev_buffer: RawBufferVec<f32>,
48}
49
50impl Default for MorphUniforms {
51    fn default() -> Self {
52        Self {
53            current_buffer: RawBufferVec::new(BufferUsages::UNIFORM),
54            prev_buffer: RawBufferVec::new(BufferUsages::UNIFORM),
55        }
56    }
57}
58
59pub fn prepare_morphs(
60    render_device: Res<RenderDevice>,
61    render_queue: Res<RenderQueue>,
62    mut uniform: ResMut<MorphUniforms>,
63) {
64    if uniform.current_buffer.is_empty() {
65        return;
66    }
67    let len = uniform.current_buffer.len();
68    uniform.current_buffer.reserve(len, &render_device);
69    uniform
70        .current_buffer
71        .write_buffer(&render_device, &render_queue);
72
73    // We don't need to write `uniform.prev_buffer` because we already wrote it
74    // last frame, and the data should still be on the GPU.
75}
76
77const fn can_align(step: usize, target: usize) -> bool {
78    step.is_multiple_of(target) || target.is_multiple_of(step)
79}
80
81const WGPU_MIN_ALIGN: usize = 256;
82
83/// Align a [`RawBufferVec`] to `N` bytes by padding the end with `T::default()` values.
84fn add_to_alignment<T: NoUninit + Default>(buffer: &mut RawBufferVec<T>) {
85    let n = WGPU_MIN_ALIGN;
86    let t_size = size_of::<T>();
87    if !can_align(n, t_size) {
88        // This panic is stripped at compile time, due to n, t_size and can_align being const
89        panic!(
90            "RawBufferVec should contain only types with a size multiple or divisible by {n}, \
91            {} has a size of {t_size}, which is neither multiple or divisible by {n}",
92            core::any::type_name::<T>()
93        );
94    }
95
96    let buffer_size = buffer.len();
97    let byte_size = t_size * buffer_size;
98    let bytes_over_n = byte_size % n;
99    if bytes_over_n == 0 {
100        return;
101    }
102    let bytes_to_add = n - bytes_over_n;
103    let ts_to_add = bytes_to_add / t_size;
104    buffer.extend(iter::repeat_with(T::default).take(ts_to_add));
105}
106
107// Notes on implementation: see comment on top of the extract_skins system in skin module.
108// This works similarly, but for `f32` instead of `Mat4`
109pub fn extract_morphs(
110    morph_indices: ResMut<MorphIndices>,
111    uniform: ResMut<MorphUniforms>,
112    query: Extract<Query<(Entity, &ViewVisibility, &MeshMorphWeights)>>,
113) {
114    // Borrow check workaround.
115    let (morph_indices, uniform) = (morph_indices.into_inner(), uniform.into_inner());
116
117    // Swap buffers. We need to keep the previous frame's buffer around for the
118    // purposes of motion vector computation.
119    mem::swap(&mut morph_indices.current, &mut morph_indices.prev);
120    mem::swap(&mut uniform.current_buffer, &mut uniform.prev_buffer);
121    morph_indices.current.clear();
122    uniform.current_buffer.clear();
123
124    for (entity, view_visibility, morph_weights) in &query {
125        if !view_visibility.get() {
126            continue;
127        }
128        let start = uniform.current_buffer.len();
129        let weights = morph_weights.weights();
130        let legal_weights = weights.iter().take(MAX_MORPH_WEIGHTS).copied();
131        uniform.current_buffer.extend(legal_weights);
132        add_to_alignment::<f32>(&mut uniform.current_buffer);
133
134        let index = (start * size_of::<f32>()) as u32;
135        morph_indices
136            .current
137            .insert(entity.into(), MorphIndex { index });
138    }
139}
140
141// NOTE: Because morph targets require per-morph target texture bindings, they cannot
142// currently be batched.
143pub fn no_automatic_morph_batching(
144    mut commands: Commands,
145    query: Query<Entity, (With<MeshMorphWeights>, Without<NoAutomaticBatching>)>,
146) {
147    for entity in &query {
148        commands.entity(entity).try_insert(NoAutomaticBatching);
149    }
150}
bevy_pbr/render/morph.rs

bevy_pbr/render/
morph.rs
