Refactor particle age logic
Move to a model that only needs floats, and puts the age in the
SkParticleState struct. Add a better test case for spawn affector
animation, to verify that things are still working.
Bug: skia:
Change-Id: I97d99de5f5d4cb302b76116e67ecc93368fb1677
Reviewed-on: https://skia-review.googlesource.com/c/193580
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/modules/particles/src/SkParticleEffect.cpp b/modules/particles/src/SkParticleEffect.cpp
index 4dfb7c2..d158836 100644
--- a/modules/particles/src/SkParticleEffect.cpp
+++ b/modules/particles/src/SkParticleEffect.cpp
@@ -54,22 +54,26 @@
return;
}
+ double now = timer.secs();
+ float deltaTime = static_cast<float>(now - fLastTime);
+ if (deltaTime < 0.0f) {
+ return;
+ }
+ fLastTime = now;
+
// Handle user edits to fMaxCount
if (fParams->fMaxCount != fCapacity) {
this->setCapacity(fParams->fMaxCount);
}
- double now = timer.secs();
- float deltaTime = static_cast<float>(now - fLastTime);
- fLastTime = now;
-
SkParticleUpdateParams updateParams;
updateParams.fDeltaTime = deltaTime;
updateParams.fRandom = &fRandom;
- // Remove particles that have reached their end of life
+ // Advance age for existing particles, and remove any that have reached their end of life
for (int i = 0; i < fCount; ++i) {
- if (now > fParticles[i].fTimeOfDeath) {
+ fParticles[i].fAge += fParticles[i].fInvLifetime * deltaTime;
+ if (fParticles[i].fAge > 1.0f) {
// NOTE: This is fast, but doesn't preserve drawing order. Could be a problem...
fParticles[i] = fParticles[fCount - 1];
fStableRandoms[i] = fStableRandoms[fCount - 1];
@@ -85,16 +89,17 @@
numToSpawn = SkTPin(numToSpawn, 0, fParams->fMaxCount - fCount);
if (fParams->fEmitter) {
// This isn't "particle" t, it's effect t.
- double t = (now - fSpawnTime) / fParams->fEffectDuration;
- updateParams.fParticleT = static_cast<float>(fLooping ? fmod(t, 1.0) : SkTPin(t, 0.0, 1.0));
+ float t = static_cast<float>((now - fSpawnTime) / fParams->fEffectDuration);
+ t = fLooping ? fmodf(t, 1.0f) : SkTPin(t, 0.0f, 1.0f);
for (int i = 0; i < numToSpawn; ++i) {
// Mutate our SkRandom so each particle definitely gets a different stable generator
fRandom.nextU();
- fParticles[fCount].fTimeOfBirth = now;
- fParticles[fCount].fTimeOfDeath = now + fParams->fLifetime.eval(updateParams.fParticleT,
- fRandom);
+ // Temporarily set our age to the *effect* age, so spawn affectors are driven by that
+ fParticles[fCount].fAge = t;
+ fParticles[fCount].fInvLifetime =
+ sk_ieee_float_divide(1.0f, fParams->fLifetime.eval(t, fRandom));
fParticles[fCount].fPose = fParams->fEmitter->emit(fRandom);
fParticles[fCount].fVelocity.fLinear = { 0.0f, 0.0f };
fParticles[fCount].fVelocity.fAngular = 0.0f;
@@ -105,13 +110,14 @@
fCount++;
}
- // Apply spawn affectors
+ // Apply spawn affectors, then reset our age to 0 (the *particle* age)
for (int i = fCount - numToSpawn; i < fCount; ++i) {
for (auto affector : fParams->fSpawnAffectors) {
if (affector) {
affector->apply(updateParams, fParticles[i]);
}
}
+ fParticles[i].fAge = 0.0f;
}
}
@@ -122,11 +128,6 @@
// Apply update rules
for (int i = 0; i < fCount; ++i) {
- // Compute fraction of lifetime that's elapsed
- updateParams.fParticleT =
- static_cast<float>((now - fParticles[i].fTimeOfBirth) /
- (fParticles[i].fTimeOfDeath - fParticles[i].fTimeOfBirth));
-
for (auto affector : fParams->fUpdateAffectors) {
if (affector) {
affector->apply(updateParams, fParticles[i]);