1#import bevy_hanabi::vfx_common::{
2    ChildInfo, ChildInfoBuffer, EventBuffer, DispatchIndirectArgs, IndirectBuffer,
3    EffectMetadata, RenderGroupIndirect, SimParams, Spawner, DrawIndexedIndirectArgs,
4    seed, tau, pcg_hash, to_float01, frand, frand2, frand3, frand4,
5    rand_uniform_f, rand_uniform_vec2, rand_uniform_vec3, rand_uniform_vec4,
6    rand_normal_f, rand_normal_vec2, rand_normal_vec3, rand_normal_vec4, proj
7}
8
9struct Particle {
10{{ATTRIBUTES}}
11}
12
13struct ParticleBuffer {
14    particles: array<Particle>,
15}
16
17#ifdef READ_PARENT_PARTICLE
18
19struct ParentParticle {
20    {{PARENT_ATTRIBUTES}}
21}
22
23struct ParentParticleBuffer {
24    particles: array<ParentParticle>,
25}
26
27#endif
28
29{{PROPERTIES}}
30
31@group(0) @binding(0) var<uniform> sim_params : SimParams;
32@group(0) @binding(1) var<storage, read_write> draw_indirect_buffer : array<DrawIndexedIndirectArgs>;
33
34// "particle" group @1
35@group(1) @binding(0) var<storage, read_write> particle_buffer : ParticleBuffer;
36@group(1) @binding(1) var<storage, read_write> indirect_buffer : IndirectBuffer;
37#ifdef READ_PARENT_PARTICLE
38@group(1) @binding(2) var<storage, read> parent_particle_buffer : ParentParticleBuffer;
39#endif
40
41// "spawner" group @2
42@group(2) @binding(0) var<storage, read> spawner : Spawner;
43{{PROPERTIES_BINDING}}
44
45// "metadata" group @3
46@group(3) @binding(0) var<storage, read_write> effect_metadata : EffectMetadata;
47#ifdef EMITS_GPU_SPAWN_EVENTS
48{{EMIT_EVENT_BUFFER_BINDINGS}}
49#endif
50
51{{UPDATE_EXTRA}}
52
53#ifdef EMITS_GPU_SPAWN_EVENTS
54{{EMIT_EVENT_BUFFER_APPEND_FUNCS}}
55#endif
56
57@compute @workgroup_size(64)
58fn main(@builtin(global_invocation_id) global_invocation_id: vec3<u32>) {
59    let thread_index = global_invocation_id.x;
60
61    // Cap at maximum number of alive particles.
62    if (thread_index >= effect_metadata.max_update) {
63        return;
64    }
65
66    let write_index = effect_metadata.indirect_write_index;
67    let read_index = 1u - write_index;
68
69    let particle_index = indirect_buffer
70        .rows[thread_index]
71        .particle_index[read_index];
72
73    // Initialize the PRNG seed
74    seed = pcg_hash(particle_index ^ spawner.seed);
75
76    var particle: Particle = particle_buffer.particles[particle_index];
77    {{AGE_CODE}}
78    {{REAP_CODE}}
79    {{UPDATE_CODE}}
80
81    {{WRITEBACK_CODE}}
82
83    // Check if alive
84    if (!is_alive) {
85        // Save dead index
86        let alive_index = atomicSub(&effect_metadata.alive_count, 1u);
87        let dead_index = effect_metadata.capacity - alive_index;
88        indirect_buffer.rows[dead_index].dead_index = particle_index;
89
90        // Also increment copy of dead count, which was updated in dispatch indirect
91        // pass just before, and need to remain correct after this pass. We wouldn't have
92        // to do that here if we had a per-effect pass between update and the next init.
93        atomicAdd(&effect_metadata.max_spawn, 1u);
94    } else {
95        // Increment visible particle count (in the absence of any GPU culling), and write
96        // the indirection index for later rendering.
97        let indirect_index = atomicAdd(&draw_indirect_buffer[effect_metadata.indirect_render_index].instance_count, 1u);
98        indirect_buffer.rows[indirect_index].particle_index[write_index] = particle_index;
99    }
100}