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comment cleanup and final tuning

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This commit is contained in:
Andrew Meadows 2019-08-28 09:48:15 -07:00
parent 6be3750b38
commit 1beafbdd35
1 changed files with 19 additions and 11 deletions
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30
libraries/physics/src/CharacterController.cpp
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@ -572,6 +572,7 @@ void CharacterController::setPhysicsEngine(const PhysicsEnginePointer& engine) {
float CharacterController::getCollisionBrakeAttenuationFactor() const {
// _collisionBrake ranges from 0.0 (no brake) to 1.0 (max brake)
// which we use to compute a corresponding attenutation factor from 1.0 to 0.5
return 1.0f - 0.5f * _collisionBrake;
}
@ -792,19 +793,21 @@ void CharacterController::computeNewVelocity(btScalar dt, btVector3& velocity) {
const float SAFE_COLLISION_SPEED = glm::abs(STUCK_PENETRATION) * (float)NUM_SUBSTEPS_PER_SECOND;
const float SAFE_COLLISION_SPEED_SQUARED = SAFE_COLLISION_SPEED * SAFE_COLLISION_SPEED;
// NOTE: the thresholds are negative because that indicates the vectors oppose each other
// NOTE: the thresholds are negative which indicates the vectors oppose each other
// and which means comparison operators against them may look wrong at first glance.
// The magnitudes of the thresholds have been tuned manually.
const float STRONG_OPPOSING_IMPACT_THRESHOLD = -1000.0f;
const float VERY_STRONG_OPPOSING_IMPACT_THRESHOLD = -2000.0f;
float velocityDotImpulse = velocity.dot(_netCollisionImpulse);
const float COLLISION_BRAKE_DECAY_TIMESCALE = 0.20f; // seconds
const float COLLISION_BRAKE_TIMESCALE = 0.20f; // must be > PHYSICS_ENGINE_FIXED_SUBSTEP for stability
const float MIN_COLLISION_BRAKE = 0.05f;
if ((velocityDotImpulse > VERY_STRONG_OPPOSING_IMPACT_THRESHOLD && _stuckTransitionCount == 0) || _isStuck) {
// we are either definitely NOT stuck (in which case nothing to do)
// or definitely are (in which case we'll be temporarily disabling collisions with the offending object
// and we don't mind tunnelling as an escape route out of stuck)
if (_collisionBrake > MIN_COLLISION_BRAKE) {
_collisionBrake *= (1.0f - dt / COLLISION_BRAKE_DECAY_TIMESCALE);
_collisionBrake *= (1.0f - dt / COLLISION_BRAKE_TIMESCALE);
if (_collisionBrake < MIN_COLLISION_BRAKE) {
_collisionBrake = 0.0f;
}
@ -815,30 +818,35 @@ void CharacterController::computeNewVelocity(btScalar dt, btVector3& velocity) {
if (velocityDotImpulse < VERY_STRONG_OPPOSING_IMPACT_THRESHOLD ||
(velocityDotImpulse < STRONG_OPPOSING_IMPACT_THRESHOLD && velocity.length2() > SAFE_COLLISION_SPEED_SQUARED)) {
if (_collisionBrake < 1.0f) {
_collisionBrake += (1.0f - _collisionBrake) * (dt / COLLISION_BRAKE_DECAY_TIMESCALE);
_collisionBrake += (1.0f - _collisionBrake) * (dt / COLLISION_BRAKE_TIMESCALE);
const float MAX_COLLISION_BRAKE = 1.0f - MIN_COLLISION_BRAKE;
if (_collisionBrake > MAX_COLLISION_BRAKE) {
_collisionBrake = 1.0f;
}
}
const float REFLECTION_COEFFICIENT = 1.0f;
// NOTE about REFLECTION_COEFFICIENT: a value of 2.0 provides full reflection
// (zero attenuation) whereas a value of 1.0 zeros it (full attenuation).
const float REFLECTION_COEFFICIENT = 1.1f;
if (velocity.dot(currentVelocity) > 0.0f) {
// our new velocity points in the same direction as our currentVelocity
// but strongImpact means new velocity points against netImpulse
// but negative "impact" means new velocity points against netCollisionImpulse
if (currentVelocity.dot(_netCollisionImpulse) > 0.0f) {
// currentVelocity points positively with netImpulse
// so we will assume collisions will save us and use it for our new velocity
// currentVelocity points positively with netCollisionImpulse --> trust physics to save us
velocity = currentVelocity;
} else {
// can't trust physical simulation --> reflect velocity against netImpulse
// can't trust physics --> use new velocity but reflect it
btVector3 impulseDirection = _netCollisionImpulse.normalized();
velocity -= (REFLECTION_COEFFICIENT * velocity.dot(impulseDirection)) * impulseDirection;
}
} else {
// currentVelocity points against new velocity, which means it is probably better but...
// this doesn't mean it points in a good direction yet, so we must check
// when the physical simulation starts to fail (e.g. in deep penetration in mesh geometry)
// the currentVelocity can point in unhelpful directions, so we check it and reflect any component
// opposing netCollisionImpulse in hopes netCollisionImpulse points toward good exit
if (currentVelocity.dot(_netCollisionImpulse) < 0.0f) {
// currentVelocity points against netImpulse, so we reflect it
// currentVelocity points against netCollisionImpulse --> reflect
btVector3 impulseDirection = _netCollisionImpulse.normalized();
currentVelocity -= (REFLECTION_COEFFICIENT * currentVelocity.dot(impulseDirection)) * impulseDirection;
}