diff --git a/crates/effects/src/sim.rs b/crates/effects/src/sim.rs index 2c7b97d14..8bb3c2ea7 100644 --- a/crates/effects/src/sim.rs +++ b/crates/effects/src/sim.rs @@ -784,6 +784,14 @@ pub(crate) struct PState { pub parts: Vec, pub carry: f64, pub next_id: u32, + /// The birth rates of the steps so far (see [`rates_hash`]): a checkpoint is only resumed + /// from with the same history. + pub hist: u64, +} + +/// `hist` after one more step at `rate` particles per second. +fn rates_hash(hist: u64, rate: f64) -> u64 { + (hist ^ rate.to_bits()).wrapping_mul(0x0100_0000_01b3).rotate_left(5) } /// Physics configuration (world units; y down). @@ -862,6 +870,12 @@ impl Phys { } pub(crate) fn step(&self, st: &mut PState, step: u64) { + self.step_at_rate(st, step, self.rate); + } + + /// One step with `rate` particles per second born during it (rather than [`Phys::rate`]): + /// the rate only decides the births, particles already alive move and age as ever. + pub(crate) fn step_at_rate(&self, st: &mut PState, step: u64, rate: f64) { let dt = (1.0 / SPS) as f32; let t = step as f32 * dt; let mut drag = self.resistance; @@ -919,7 +933,8 @@ impl Phys { q.age += dt; }); st.parts.retain(|q| q.age < q.life); - st.carry += self.rate / SPS; + st.hist = rates_hash(st.hist, rate); + st.carry += rate / SPS; let n = st.carry.floor() as u32; st.carry -= n as f64; for _ in 0..n { @@ -966,31 +981,73 @@ impl Phys { } /// The state at layer time `ctx.time` from the host's particle backend (GPU particles), or -/// `None` (simulate on the CPU). -fn accelerated(ctx: &EffectCtx, key: u64, phys: &Phys) -> Option> { +/// `None` (simulate on the CPU). `rates`: the birth rate of each step, when it changes over time +/// (else [`Phys::rate`]). +fn accelerated(ctx: &EffectCtx, key: u64, phys: &Phys, rates: Option<&[f64]>) -> Option> { let backend = ctx.env.host?.particles()?; let steps = steps_at(ctx.time); - let births = crate::psim::births(phys.rate, steps, phys.max)?; + let births = match rates { + Some(r) => crate::psim::births_at(steps, phys.max, |i| r.get(i as usize).copied().unwrap_or(0.0))?, + None => crate::psim::births(phys.rate, steps, phys.max)?, + }; let req = crate::psim::SimRequest { key, steps, births: &births, system: crate::psim::ParticleSystem::Engine(phys.desc()) }; let parts = backend.simulate(&req)?; Some(std::sync::Arc::new(PState { parts: parts.into_iter().map(|q| Particle { p: q.p, v: q.v, age: q.age, life: q.life, rnd: q.rnd, id: q.id }).collect(), carry: 0.0, next_id: births.len() as u32, + hist: 0, })) } +/// The birth rate (particles per second) of each step up to layer time `ctx.time`: parameter +/// `id` × `k`, sampled where the step starts (a keyframed or expression-driven Birth Rate only +/// decides the births of its own time, #1373). Without a host that evaluates the effect at +/// other times, the current value for every step. +fn rate_history(ctx: &EffectCtx, id: &str, k: f64) -> Vec { + let now = ctx.params.f(id); + let host = ctx.env.host; + (0..steps_at(ctx.time)) + .map(|i| { + let v = host.and_then(|h| h.param_at(ctx.env.effect_index, id, i as f64 / SPS)).map_or(now, |v| v.as_f64()); + if v.is_finite() { v.max(0.0) * k } else { 0.0 } + }) + .collect() +} + +/// Run a particle system through `rates` (one birth rate per step, see [`rate_history`]) with +/// `cache`, resuming only from checkpoints reached with the same rates. +fn simulate_rates(cache: &SimCache, key: u64, phys: &Phys, rates: &[f64]) -> std::sync::Arc { + // `hist` of the state after each number of steps. + let mut prefix = Vec::with_capacity(rates.len() + 1); + prefix.push(0u64); + for r in rates { + prefix.push(rates_hash(prefix.last().copied().unwrap_or(0), *r)); + } + let rate = |i: u64| rates.get(i as usize).copied().unwrap_or(0.0); + cache.run_where(key, rates.len() as u64, PState::default, |st, i| phys.step_at_rate(st, i, rate(i)), |s, st| prefix.get(s as usize) == Some(&st.hist)) +} + +/// CC Particle World's particles at `ctx.time`, born at the Birth Rate of their own time. +fn pw_state(ctx: &EffectCtx, phys: &Phys) -> std::sync::Arc { + let rates = rate_history(ctx, "birthRate", PW_RATE); + // Every parameter but Birth Rate (its history is checked through `PState::hist`). + let key = params_key_except(ctx, &Buf { img: Image::new(0, 0), offset: [0.0; 2], scale: 1.0 }, 1, &[PW_EFFECT_CAMERA, "birthRate"]); + accelerated(ctx, key, phys, Some(&rates)).unwrap_or_else(|| simulate_rates(&PW_CACHE, key, phys, &rates)) +} + /// The live particles of a stepped particle effect (`ec.sim.ccparticleworld`, /// `ec.sim.ccparticlesystems2`) at `ctx.time`: from the host's particle backend when it has /// one (GPU particles), else from the CPU simulation. For comparing the two. pub fn particle_state(id: &str, ctx: &EffectCtx) -> Option> { - let (phys, cache, salt) = match id { - "ec.sim.ccparticleworld" => (pw_phys(ctx), &PW_CACHE, 1), - "ec.sim.ccparticlesystems2" => (ps2_phys(ctx), &PS2_CACHE, 2), + let st = match id { + "ec.sim.ccparticleworld" => pw_state(ctx, &pw_phys(ctx)), + "ec.sim.ccparticlesystems2" => { + let (phys, key) = (ps2_phys(ctx), sim_key(ctx, 2)); + accelerated(ctx, key, &phys, None).unwrap_or_else(|| simulate(&PS2_CACHE, key, ctx.time, &phys)) + } _ => return None, }; - let key = sim_key(ctx, salt); - let st = accelerated(ctx, key, &phys).unwrap_or_else(|| simulate(cache, key, ctx.time, &phys)); Some(st.parts.iter().map(|q| crate::psim::SimParticle { p: q.p, v: q.v, age: q.age, life: q.life, rnd: q.rnd, id: q.id }).collect()) } @@ -1042,11 +1099,14 @@ fn type_sprite(kind: u32, x: f32, y: f32, r: f32, c: [f32; 4], vx: f32, vy: f32, static PW_CACHE: SimCache = SimCache::new(6); +/// Particles per second per unit of CC Particle World's Birth Rate. +const PW_RATE: f64 = 120.0; + /// CC Particle World's physics. fn pw_phys(ctx: &EffectCtx) -> Phys { let pr = ctx.params; Phys { - rate: pr.f("birthRate").max(0.0) * 120.0, + rate: pr.f("birthRate").max(0.0) * PW_RATE, life: pr.f("longevity").max(0.0) as f32, producer: [pr.f("producer/producerX") as f32, pr.f("producer/producerY") as f32, pr.f("producer/producerZ") as f32], radius: [pr.f("producer/radiusX").max(0.0) as f32, pr.f("producer/radiusY").max(0.0) as f32, pr.f("producer/radiusZ").max(0.0) as f32], @@ -1167,8 +1227,7 @@ fn particle_world_plan(ctx: &EffectCtx, b: &Buf) -> Option { if phys.rate <= 0.0 && ctx.time <= 0.0 { return None; } - let key = sim_key(ctx, 1); - let st = accelerated(ctx, key, &phys).unwrap_or_else(|| simulate(&PW_CACHE, key, ctx.time, &phys)); + let st = pw_state(ctx, &phys); let kind = pr.e("particle/particleType"); let birth = pr.color("particle/birthColor"); let death = pr.color("particle/deathColor"); @@ -1242,7 +1301,7 @@ fn particle_systems2_plan(ctx: &EffectCtx, b: &Buf) -> SpritePlan { let unit = lh.max(1.0); let phys = ps2_phys(ctx); let key = sim_key(ctx, 2); - let st = accelerated(ctx, key, &phys).unwrap_or_else(|| simulate(&PS2_CACHE, key, ctx.time, &phys)); + let st = accelerated(ctx, key, &phys, None).unwrap_or_else(|| simulate(&PS2_CACHE, key, ctx.time, &phys)); let kind = pr.e("particle/particleType"); let birth = pr.color("particle/birthColor"); let death = pr.color("particle/deathColor"); @@ -1969,4 +2028,5 @@ mod tests { let sum = |i: &Image| i.data.iter().map(|p| p[0]).sum::() / i.data.len() as f32; assert!((sum(&full.img) - sum(&half.img)).abs() < 0.05, "{} {}", sum(&full.img), sum(&half.img)); } + } diff --git a/crates/gpu/src/particles.rs b/crates/gpu/src/particles.rs index 7934dee0c..837746547 100644 --- a/crates/gpu/src/particles.rs +++ b/crates/gpu/src/particles.rs @@ -23,10 +23,25 @@ struct Checkpoint { key: u64, steps: u64, n: u32, + /// The birth steps of its particles (see [`born`]). + born: u64, buf: wgpu::Buffer, used: u64, } +/// The particles born in the first `steps` steps of `births` (ascending birth steps) and a hash +/// of their birth steps: a checkpoint is only resumed from when the request's births before it +/// are the same (a keyframed Birth Rate isn't part of the system key, #1373). +fn born(births: &[u32], steps: u64) -> (u32, u64) { + let mut h = 0xcbf2_9ce4_8422_2325u64; + let mut n = 0u32; + for &b in births.iter().take_while(|&&b| u64::from(b) < steps) { + h = (h ^ u64::from(b)).wrapping_mul(0x0100_0000_01b3); + n += 1; + } + (n, h) +} + #[derive(Default)] pub(crate) struct Checkpoints { list: Vec, @@ -141,7 +156,7 @@ pub(crate) fn simulate(g: &GpuContext, req: &SimRequest) -> Option { k.used = now; (k.steps, Some(k.buf.clone()), k.n) @@ -232,7 +247,8 @@ fn keep_checkpoint(g: &GpuContext, req: &SimRequest, n: u32, next: wgpu::Buffer) if let Ok(mut c) = g.particle_states.lock() { let now = c.clock; c.list.retain(|k| !(k.key == req.key && k.steps == req.steps)); - c.list.push(Checkpoint { key: req.key, steps: req.steps, n, buf: next, used: now }); + let (_, h) = born(req.births, req.steps); + c.list.push(Checkpoint { key: req.key, steps: req.steps, n, born: h, buf: next, used: now }); while c.list.len() > CHECKPOINTS { let Some(i) = c.list.iter().enumerate().min_by_key(|(_, k)| k.used).map(|(i, _)| i) else { break }; c.list.remove(i);