public void Timestep(Simulation simulation, float dt, IThreadDispatcher threadDispatcher = null)
{
simulation.Sleep(threadDispatcher);
Slept?.Invoke(dt, threadDispatcher);
simulation.IntegrateVelocitiesBoundsAndInertias(dt, threadDispatcher);
BeforeCollisionDetection?.Invoke(dt, threadDispatcher);
simulation.CollisionDetection(dt, threadDispatcher);
CollisionsDetected?.Invoke(dt, threadDispatcher);
simulation.Solve(dt, threadDispatcher);
ConstraintsSolved?.Invoke(dt, threadDispatcher);
simulation.IntegratePoses(dt, threadDispatcher);
PosesIntegrated?.Invoke(dt, threadDispatcher);
simulation.IncrementallyOptimizeDataStructures(threadDispatcher);
}
public void Timestep(Simulation simulation, float dt, IThreadDispatcher threadDispatcher = null)
{
//Note that there is a reason to put the sleep *after* velocity integration. That sounds a little weird, but there's a good reason:
//When the narrow phase activates a bunch of objects in a pile, their accumulated impulses will represent all forces acting on them at the time of sleep.
//That includes gravity. If we sleep objects *before* gravity is applied in a given frame, then when those bodies are awakened, the accumulated impulses
//will be less accurate because they assume that gravity has already been applied. This can cause a small bump.
//So, velocity integration (and deactivation candidacy management) could come before sleep.
//Sleep at the start, on the other hand, stops some forms of unintuitive behavior when using direct awakenings. Just a matter of preference.
simulation.Sleep(threadDispatcher);
Slept?.Invoke(dt, threadDispatcher);
//Note that pose integrator comes before collision detection and solving. This is a shift from v1, where collision detection went first.
//This is a tradeoff:
//1) Any externally set velocities will be integrated without input from the solver. The v1-style external velocity control won't work as well-
//the user would instead have to change velocities after the pose integrator runs. This isn't perfect either, since the pose integrator is also responsible
//for updating the bounding boxes used for collision detection.
//2) By bundling bounding box calculation with pose integration, you avoid redundant pose and velocity memory accesses.
//3) Generated contact positions are in sync with the integrated poses.
//That's often helpful for gameplay purposes- you don't have to reinterpret contact data when creating graphical effects or positioning sound sources.
//#1 is a difficult problem, though. There is no fully 'correct' place to change velocities. We might just have to bite the bullet and create a
//inertia tensor/bounding box update separate from pose integration. If the cache gets evicted in between (virtually guaranteed unless no stages run),
//this basically means an extra 100-200 microseconds per frame on a processor with ~20GBps bandwidth simulating 32768 bodies.
//Note that the reason why the pose integrator comes first instead of, say, the solver, is that the solver relies on world space inertias calculated by the pose integration.
//If the pose integrator doesn't run first, we either need
//1) complicated on demand updates of world inertia when objects are added or local inertias are changed or
//2) local->world inertia calculation before the solver.
simulation.IntegrateBodiesAndUpdateBoundingBoxes(dt, threadDispatcher);
BeforeCollisionDetection?.Invoke(dt, threadDispatcher);
simulation.CollisionDetection(dt, threadDispatcher);
CollisionsDetected?.Invoke(dt, threadDispatcher);
simulation.Solve(dt, threadDispatcher);
ConstraintsSolved?.Invoke(dt, threadDispatcher);
simulation.IncrementallyOptimizeDataStructures(threadDispatcher);
}
public void Timestep(Simulation simulation, float dt, IThreadDispatcher threadDispatcher = null)
{
simulation.Sleep(threadDispatcher);
Slept?.Invoke(dt, threadDispatcher);
simulation.PredictBoundingBoxes(dt, threadDispatcher);
BeforeCollisionDetection?.Invoke(dt, threadDispatcher);
simulation.CollisionDetection(dt, threadDispatcher);
CollisionsDetected?.Invoke(dt, threadDispatcher);
Debug.Assert(SubstepCount >= 0, "Substep count should be positive.");
var substepDt = dt / SubstepCount;
for (int substepIndex = 0; substepIndex < SubstepCount; ++substepIndex)
{
SubstepStarted?.Invoke(substepIndex, dt, threadDispatcher);
if (substepIndex > 0)
{
//This takes the place of collision detection for the substeps. It uses the current velocity to update penetration depths.
//It's definitely an approximation, but it's important for avoiding some obviously weird behavior.
//Note that we do not run this on the first iteration- the actual collision detection above takes care of it.
simulation.IncrementallyUpdateContactConstraints(substepDt, threadDispatcher);
ContactConstraintsUpdatedForSubstep?.Invoke(substepIndex, dt, threadDispatcher);
}
simulation.IntegrateVelocitiesAndUpdateInertias(substepDt, threadDispatcher);
VelocitiesIntegrated?.Invoke(substepIndex, dt, threadDispatcher);
simulation.Solve(substepDt, threadDispatcher);
ConstraintsSolved?.Invoke(substepIndex, dt, threadDispatcher);
simulation.IntegratePoses(substepDt, threadDispatcher);
PosesIntegrated?.Invoke(substepIndex, dt, threadDispatcher);
SubstepEnded?.Invoke(substepIndex, dt, threadDispatcher);
}
SubstepsComplete?.Invoke(dt, threadDispatcher);
simulation.IncrementallyOptimizeDataStructures(threadDispatcher);
}