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modify extrapolation behavior when bullet enabled

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Allows Bullet to specify an object as "at rest"
by setting velocity to zero.
Also, moved velocity damping above position integration
to get the same order of operations as Bullet.
This commit is contained in:
Andrew Meadows 2014-12-31 16:29:55 -08:00
parent bd88e0f38d
commit 0d3e78fdb8
2 changed files with 39 additions and 23 deletions
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1
libraries/entities/CMakeLists.txt
View file

@ -4,6 +4,7 @@ set(TARGET_NAME entities)
setup_hifi_library(Network Script)
include_glm()
include_bullet()
link_hifi_libraries(avatars shared octree gpu model fbx networking animation)

61
libraries/entities/src/EntityItem.cpp
View file

@ -648,7 +648,8 @@ void EntityItem::simulate(const quint64& now) {
glm::vec3 angularVelocity = glm::radians(getAngularVelocity());
float angularSpeed = glm::length(angularVelocity);
if (angularSpeed < EPSILON_VELOCITY_LENGTH) {
const float EPSILON_ANGULAR_VELOCITY_LENGTH = 0.0017453f; // ~0.1 degree/sec
if (angularSpeed < EPSILON_ANGULAR_VELOCITY_LENGTH) {
setAngularVelocity(NO_ANGULAR_VELOCITY);
} else {
float angle = timeElapsed * angularSpeed;
@ -670,9 +671,31 @@ void EntityItem::simulate(const quint64& now) {
}
}
#ifdef USE_BULLET_PHYSICS
// When Bullet is available we assume that "zero velocity" means "at rest"
// because of collision conditions this simulation does not know about
// so we don't fall in for the non-zero gravity case here.
if (hasVelocity()) {
#else // !USE_BULLET_PHYSICS
if (hasVelocity() || hasGravity()) {
glm::vec3 position = getPosition();
#endif // USE_BULLET_PHYSICS
// linear damping
glm::vec3 velocity = getVelocity();
float dampingTimescale = getDamping();
if (dampingTimescale > 0.0f) {
float dampingFactor = glm::clamp(timeElapsed / dampingTimescale, 0.0f, 1.0f);
velocity *= (1.0f - dampingFactor);
if (wantDebug) {
qDebug() << " dampingTimescale:" << dampingTimescale;
qDebug() << " velocity AFTER dampingResistance:" << velocity;
qDebug() << " glm::length(velocity):" << glm::length(velocity);
qDebug() << " EPSILON_VELOCITY_LENGTH:" << EPSILON_VELOCITY_LENGTH;
}
}
// integrate position forward
glm::vec3 position = getPosition();
glm::vec3 newPosition = position + (velocity * timeElapsed);
if (wantDebug) {
@ -701,10 +724,10 @@ void EntityItem::simulate(const quint64& now) {
position.y = getDistanceToBottomOfEntity();
}
// handle gravity....
// apply gravity
if (hasGravity()) {
// handle resting on surface case, this is definitely a bit of a hack, and it only works on the
// "ground" plane of the domain, but for now it what we've got
// "ground" plane of the domain, but for now it's what we've got
if (isRestingOnSurface()) {
velocity.y = 0.0f;
position.y = getDistanceToBottomOfEntity();
@ -712,28 +735,15 @@ void EntityItem::simulate(const quint64& now) {
velocity += getGravity() * timeElapsed;
}
}
// handle damping for velocity
float dampingTimescale = getDamping();
if (dampingTimescale > 0.0f) {
float dampingFactor = glm::clamp(timeElapsed / dampingTimescale, 0.0f, 1.0f);
velocity *= (1.0f - dampingFactor);
if (wantDebug) {
qDebug() << " dampingTimescale:" << dampingTimescale;
qDebug() << " newVelocity:" << velocity;
}
}
if (wantDebug) {
qDebug() << " velocity AFTER dampingResistance:" << velocity;
qDebug() << " glm::length(velocity):" << glm::length(velocity);
qDebug() << " EPSILON_VELOCITY_LENGTH:" << EPSILON_VELOCITY_LENGTH;
}
// round velocity to zero if it's close enough...
#ifdef USE_BULLET_PHYSICS
// When Bullet is available we assume that it will tell us when velocities go to zero...
#else // !USE_BULLET_PHYSICS
// ... otherwise we help things come to rest by clamping small velocities.
if (glm::length(velocity) <= EPSILON_VELOCITY_LENGTH) {
velocity = NO_VELOCITY;
}
#endif // USE_BULLET_PHYSICS
// NOTE: the simulation should NOT set any DirtyFlags on this entity
setPosition(position); // this will automatically recalculate our collision shape
@ -751,7 +761,13 @@ void EntityItem::simulate(const quint64& now) {
}
bool EntityItem::isMoving() const {
#ifdef USE_BULLET_PHYSICS
// When Bullet is available we assume that "zero velocity" means "at rest"
// because of collision conditions this simulation does not know about.
return hasVelocity() || hasAngularVelocity();
#else // !USE_BULLET_PHYSICS
return hasVelocity() || (hasGravity() && !isRestingOnSurface()) || hasAngularVelocity();
#endif //USE_BULLET_PHYSICS
}
bool EntityItem::lifetimeHasExpired() const {
@ -1009,7 +1025,6 @@ const float MIN_GRAVITY_DELTA = 0.001f;
const float MIN_SPIN_DELTA = 0.0003f;
void EntityItem::updatePosition(const glm::vec3& value) {
glm::vec3 debugPosition = value * (float) TREE_SCALE;
if (glm::distance(_position, value) * (float)TREE_SCALE > MIN_POSITION_DELTA) {
_position = value;
recalculateCollisionShape();