82 lines
2.9 KiB
C++
82 lines
2.9 KiB
C++
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
|
|
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
|
|
// SPDX-License-Identifier: MIT
|
|
|
|
#include <Jolt/Jolt.h>
|
|
|
|
#include <Jolt/Physics/Vehicle/VehicleDifferential.h>
|
|
#include <Jolt/ObjectStream/TypeDeclarations.h>
|
|
|
|
JPH_NAMESPACE_BEGIN
|
|
|
|
JPH_IMPLEMENT_SERIALIZABLE_NON_VIRTUAL(VehicleDifferentialSettings)
|
|
{
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mLeftWheel)
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mRightWheel)
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mDifferentialRatio)
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mLeftRightSplit)
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mLimitedSlipRatio)
|
|
JPH_ADD_ATTRIBUTE(VehicleDifferentialSettings, mEngineTorqueRatio)
|
|
}
|
|
|
|
void VehicleDifferentialSettings::SaveBinaryState(StreamOut &inStream) const
|
|
{
|
|
inStream.Write(mLeftWheel);
|
|
inStream.Write(mRightWheel);
|
|
inStream.Write(mDifferentialRatio);
|
|
inStream.Write(mLeftRightSplit);
|
|
inStream.Write(mLimitedSlipRatio);
|
|
inStream.Write(mEngineTorqueRatio);
|
|
}
|
|
|
|
void VehicleDifferentialSettings::RestoreBinaryState(StreamIn &inStream)
|
|
{
|
|
inStream.Read(mLeftWheel);
|
|
inStream.Read(mRightWheel);
|
|
inStream.Read(mDifferentialRatio);
|
|
inStream.Read(mLeftRightSplit);
|
|
inStream.Read(mLimitedSlipRatio);
|
|
inStream.Read(mEngineTorqueRatio);
|
|
}
|
|
|
|
void VehicleDifferentialSettings::CalculateTorqueRatio(float inLeftAngularVelocity, float inRightAngularVelocity, float &outLeftTorqueFraction, float &outRightTorqueFraction) const
|
|
{
|
|
// Start with the default torque ratio
|
|
outLeftTorqueFraction = 1.0f - mLeftRightSplit;
|
|
outRightTorqueFraction = mLeftRightSplit;
|
|
|
|
if (mLimitedSlipRatio < FLT_MAX)
|
|
{
|
|
JPH_ASSERT(mLimitedSlipRatio > 1.0f);
|
|
|
|
// This is a limited slip differential, adjust torque ratios according to wheel speeds
|
|
float omega_l = max(1.0e-3f, abs(inLeftAngularVelocity)); // prevent div by zero by setting a minimum velocity and ignoring that the wheels may be rotating in different directions
|
|
float omega_r = max(1.0e-3f, abs(inRightAngularVelocity));
|
|
float omega_min = min(omega_l, omega_r);
|
|
float omega_max = max(omega_l, omega_r);
|
|
|
|
// Map into a value that is 0 when the wheels are turning at an equal rate and 1 when the wheels are turning at mLimitedSlipRotationRatio
|
|
float alpha = min((omega_max / omega_min - 1.0f) / (mLimitedSlipRatio - 1.0f), 1.0f);
|
|
JPH_ASSERT(alpha >= 0.0f);
|
|
float one_min_alpha = 1.0f - alpha;
|
|
|
|
if (omega_l < omega_r)
|
|
{
|
|
// Redirect more power to the left wheel
|
|
outLeftTorqueFraction = outLeftTorqueFraction * one_min_alpha + alpha;
|
|
outRightTorqueFraction = outRightTorqueFraction * one_min_alpha;
|
|
}
|
|
else
|
|
{
|
|
// Redirect more power to the right wheel
|
|
outLeftTorqueFraction = outLeftTorqueFraction * one_min_alpha;
|
|
outRightTorqueFraction = outRightTorqueFraction * one_min_alpha + alpha;
|
|
}
|
|
}
|
|
|
|
// Assert the values add up to 1
|
|
JPH_ASSERT(abs(outLeftTorqueFraction + outRightTorqueFraction - 1.0f) < 1.0e-6f);
|
|
}
|
|
|
|
JPH_NAMESPACE_END
|