MotionProperties.inl

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
JPH_NAMESPACE_BEGIN
 
void MotionProperties::SetMassProperties(const MassProperties &inMassProperties)
{
    // Set inverse mass
    JPH_ASSERT(inMassProperties.mMass > 0.0f);
    mInvMass = 1.0f / inMassProperties.mMass;
 
    // Set inverse inertia
    Mat44 rotation;
    Vec3 diagonal;
    if (inMassProperties.DecomposePrincipalMomentsOfInertia(rotation, diagonal) 
        && !diagonal.IsNearZero())
    {   
        mInvInertiaDiagonal = diagonal.Reciprocal();
        mInertiaRotation = rotation.GetQuaternion();
    }
    else
    {
        // Failed! Fall back to inertia tensor of sphere with radius 1.
        mInvInertiaDiagonal = Vec3::sReplicate(2.5f * mInvMass);
        mInertiaRotation = Quat::sIdentity();
    }
}
 
void MotionProperties::MoveKinematic(Vec3Arg inDeltaPosition, QuatArg inDeltaRotation, float inDeltaTime)
{
    JPH_ASSERT(BodyAccess::sCheckRights(BodyAccess::sVelocityAccess, BodyAccess::EAccess::ReadWrite)); 
    JPH_ASSERT(BodyAccess::sCheckRights(BodyAccess::sPositionAccess, BodyAccess::EAccess::Read)); 
    JPH_ASSERT(mCachedMotionType != EMotionType::Static);
 
    // Calculate required linear velocity
    mLinearVelocity = inDeltaPosition / inDeltaTime;
 
    // Calculate required angular velocity
    Vec3 axis;
    float angle;
    inDeltaRotation.GetAxisAngle(axis, angle);
    mAngularVelocity = axis * (angle / inDeltaTime);
}
 
void MotionProperties::ClampLinearVelocity()
{ 
    JPH_ASSERT(BodyAccess::sCheckRights(BodyAccess::sVelocityAccess, BodyAccess::EAccess::ReadWrite)); 
 
    float len_sq = mLinearVelocity.LengthSq(); 
    JPH_ASSERT(isfinite(len_sq)); 
    if (len_sq > Square(mMaxLinearVelocity)) 
        mLinearVelocity *= mMaxLinearVelocity / sqrt(len_sq); 
}
 
void MotionProperties::ClampAngularVelocity()
{ 
    JPH_ASSERT(BodyAccess::sCheckRights(BodyAccess::sVelocityAccess, BodyAccess::EAccess::ReadWrite)); 
 
    float len_sq = mAngularVelocity.LengthSq(); 
    JPH_ASSERT(isfinite(len_sq)); 
    if (len_sq > Square(mMaxAngularVelocity)) 
        mAngularVelocity *= mMaxAngularVelocity / sqrt(len_sq); 
}
 
inline Mat44 MotionProperties::GetLocalSpaceInverseInertiaUnchecked() const
{ 
    Mat44 rotation = Mat44::sRotation(mInertiaRotation);
    Mat44 rotation_mul_scale_transposed(mInvInertiaDiagonal.SplatX() * rotation.GetColumn4(0), mInvInertiaDiagonal.SplatY() * rotation.GetColumn4(1), mInvInertiaDiagonal.SplatZ() * rotation.GetColumn4(2), Vec4(0, 0, 0, 1));
    return rotation.Multiply3x3RightTransposed(rotation_mul_scale_transposed);
}
 
inline Mat44 MotionProperties::GetLocalSpaceInverseInertia() const
{
    JPH_ASSERT(mCachedMotionType == EMotionType::Dynamic);
    return GetLocalSpaceInverseInertiaUnchecked();
}
 
Mat44 MotionProperties::GetInverseInertiaForRotation(Mat44Arg inRotation) const
{ 
    JPH_ASSERT(mCachedMotionType == EMotionType::Dynamic);
 
    Mat44 rotation = inRotation * Mat44::sRotation(mInertiaRotation); 
    Mat44 rotation_mul_scale_transposed(mInvInertiaDiagonal.SplatX() * rotation.GetColumn4(0), mInvInertiaDiagonal.SplatY() * rotation.GetColumn4(1), mInvInertiaDiagonal.SplatZ() * rotation.GetColumn4(2), Vec4(0, 0, 0, 1));
    return rotation.Multiply3x3RightTransposed(rotation_mul_scale_transposed);
}
 
Vec3 MotionProperties::MultiplyWorldSpaceInverseInertiaByVector(QuatArg inBodyRotation, Vec3Arg inV) const
{ 
    JPH_ASSERT(mCachedMotionType == EMotionType::Dynamic);
 
    Mat44 rotation = Mat44::sRotation(inBodyRotation * mInertiaRotation); 
    return rotation.Multiply3x3(mInvInertiaDiagonal * rotation.Multiply3x3Transposed(inV)); 
}
 
void MotionProperties::ApplyForceTorqueAndDragInternal(QuatArg inBodyRotation, Vec3Arg inGravity, float inDeltaTime)
{
    JPH_ASSERT(BodyAccess::sCheckRights(BodyAccess::sVelocityAccess, BodyAccess::EAccess::ReadWrite)); 
    JPH_ASSERT(mCachedMotionType == EMotionType::Dynamic);
 
    // Update linear velocity
    mLinearVelocity += inDeltaTime * (mGravityFactor * inGravity + mInvMass * Vec3::sLoadFloat3Unsafe(mForce));
 
    // Update angular velocity
    mAngularVelocity += inDeltaTime * MultiplyWorldSpaceInverseInertiaByVector(inBodyRotation, Vec3::sLoadFloat3Unsafe(mTorque));
 
    // Linear damping: dv/dt = -c * v
    // Solution: v(t) = v(0) * e^(-c * t) or v2 = v1 * e^(-c * dt)
    // Taylor expansion of e^(-c * dt) = 1 - c * dt + ...
    // Since dt is usually in the order of 1/60 and c is a low number too this approximation is good enough
    mLinearVelocity *= max(0.0f, 1.0f - mLinearDamping * inDeltaTime);
    mAngularVelocity *= max(0.0f, 1.0f - mAngularDamping * inDeltaTime);
 
    // Clamp velocities
    ClampLinearVelocity();
    ClampAngularVelocity();
}
 
void MotionProperties::ResetSleepTestSpheres(const RVec3 *inPoints)
{
#ifdef JPH_DOUBLE_PRECISION
    // Make spheres relative to the first point and initialize them to zero radius
    DVec3 offset = inPoints[0];
    offset.StoreDouble3(&mSleepTestOffset);
    mSleepTestSpheres[0] = Sphere(Vec3::sZero(), 0.0f);
    for (int i = 1; i < 3; ++i)
        mSleepTestSpheres[i] = Sphere(Vec3(inPoints[i] - offset), 0.0f);
#else
    // Initialize the spheres to zero radius around the supplied points
    for (int i = 0; i < 3; ++i)
        mSleepTestSpheres[i] = Sphere(inPoints[i], 0.0f);
#endif
 
    mSleepTestTimer = 0.0f;
}
 
JPH_NAMESPACE_END