Quat.inl

Go to the documentation of this file.

// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
JPH_NAMESPACE_BEGIN
 
Quat Quat::operator * (QuatArg inRHS) const
{
#ifdef JPH_USE_SSE
    __m128 abcd = mValue.mValue;
    __m128 xyzw = inRHS.mValue.mValue;
 
    // Names based on logical order, opposite of shuffle order.
    __m128 abca = _mm_shuffle_ps(abcd, abcd, _MM_SHUFFLE(0, 2, 1, 0));
    __m128 bcab = _mm_shuffle_ps(abcd, abcd, _MM_SHUFFLE(1, 0, 2, 1));
    __m128 cabc = _mm_shuffle_ps(abcd, abcd, _MM_SHUFFLE(2, 1, 0, 2));
    __m128 dddd = _mm_shuffle_ps(abcd, abcd, _MM_SHUFFLE(3, 3, 3, 3));
 
    __m128 wwwx = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(0, 3, 3, 3));
    __m128 zxyy = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(1, 1, 0, 2));
    __m128 yzxz = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(2, 0, 2, 1));
 
    __m128 m2 = _mm_mul_ps(bcab, zxyy);
#ifdef JPH_USE_FMADD
    __m128 m3 = _mm_fmadd_ps(abca, wwwx, m2);
#else
    __m128 m1 = _mm_mul_ps(abca, wwwx);
    __m128 m3 = _mm_add_ps(m1, m2);
#endif
 
    // Negate last (logical) component.
    m3 = _mm_xor_ps(_mm_set_ps(-0.0f, 0.0f, 0.0f, 0.0f), m3);
 
#ifdef JPH_USE_FMADD
    __m128 m5 = _mm_fnmadd_ps(cabc, yzxz, m3);
    __m128 m7 = _mm_fmadd_ps(dddd, xyzw, m5);
#else
    __m128 m4 = _mm_mul_ps(dddd, xyzw);
    __m128 m5 = _mm_mul_ps(cabc, yzxz);
    __m128 m6 = _mm_sub_ps(m4, m5);
    __m128 m7 = _mm_add_ps(m3, m6);
#endif
 
    // [(aw+bz)+(dx-cy),(bw+cx)+(dy-az),(cw+ay)+(dz-bx),-(ax+by)+(dw-cz)]
    return Quat(Vec4(m7));
#else
    float a = mValue.GetX();
    float b = mValue.GetY();
    float c = mValue.GetZ();
    float d = mValue.GetW();
 
    float x = inRHS.mValue.GetX();
    float y = inRHS.mValue.GetY();
    float z = inRHS.mValue.GetZ();
    float w = inRHS.mValue.GetW();
 
    return Quat((a * w + b * z) + (d * x - c * y),
                (b * w + c * x) + (d * y - a * z),
                (c * w + a * y) + (d * z - b * x),
                -(a * x + b * y) + (d * w - c * z));
#endif
}
 
Quat Quat::sMultiplyImaginary(Vec3Arg inLHS, QuatArg inRHS)
{
#ifdef JPH_USE_SSE
    __m128 abc0 = inLHS.mValue;
    __m128 xyzw = inRHS.mValue.mValue;
 
    // Names based on logical order, opposite of shuffle order.
    __m128 abca = _mm_shuffle_ps(abc0, abc0, _MM_SHUFFLE(0, 2, 1, 0));
    __m128 bcab = _mm_shuffle_ps(abc0, abc0, _MM_SHUFFLE(1, 0, 2, 1));
    __m128 cabc = _mm_shuffle_ps(abc0, abc0, _MM_SHUFFLE(2, 1, 0, 2));
 
    __m128 wwwx = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(0, 3, 3, 3));
    __m128 zxyy = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(1, 1, 0, 2));
    __m128 yzxz = _mm_shuffle_ps(xyzw, xyzw, _MM_SHUFFLE(2, 0, 2, 1));
 
    __m128 m2 = _mm_mul_ps(bcab, zxyy);
#ifdef JPH_USE_FMADD
    __m128 m3 = _mm_fmadd_ps(abca, wwwx, m2);
#else
    __m128 m1 = _mm_mul_ps(abca, wwwx);
    __m128 m3 = _mm_add_ps(m1, m2);
#endif
 
    // Negate last (logical) component.
    m3 = _mm_xor_ps(_mm_set_ps(-0.0f, 0.0f, 0.0f, 0.0f), m3);
 
    __m128 m4 = _mm_mul_ps(cabc, yzxz);
 
    // [(aw+bz)-cy,(bw+cx)-az,(cw+ay)-bx,-(ax+by)-cz]
    return Quat(Vec4(_mm_sub_ps(m3, m4)));
#else
    float a = inLHS.GetX();
    float b = inLHS.GetY();
    float c = inLHS.GetZ();
 
    float x = inRHS.mValue.GetX();
    float y = inRHS.mValue.GetY();
    float z = inRHS.mValue.GetZ();
    float w = inRHS.mValue.GetW();
 
    return Quat((a * w + b * z) - c * y,
                (b * w + c * x) - a * z,
                (c * w + a * y) - b * x,
                -(a * x + b * y) - c * z);
#endif
}
 
Quat Quat::sRotation(Vec3Arg inAxis, float inAngle)
{
    // returns [inAxis * sin(0.5f * inAngle), cos(0.5f * inAngle)]
    JPH_ASSERT(inAxis.IsNormalized());
    Vec4 s, c;
    Vec4::sReplicate(0.5f * inAngle).SinCos(s, c);
    return Quat(Vec4::sSelect(Vec4(inAxis) * s, c, UVec4(0, 0, 0, 0xffffffffU)));
}
 
void Quat::GetAxisAngle(Vec3 &outAxis, float &outAngle) const
{
    JPH_ASSERT(IsNormalized());
    Quat w_pos = EnsureWPositive();
    float abs_w = w_pos.GetW();
    if (abs_w >= 1.0f)
    {
        outAxis = Vec3::sZero();
        outAngle = 0.0f;
    }
    else
    {
        outAngle = 2.0f * ACos(abs_w);
        outAxis = w_pos.GetXYZ().NormalizedOr(Vec3::sZero());
    }
}
 
Vec3 Quat::GetAngularVelocity(float inDeltaTime) const
{
    JPH_ASSERT(IsNormalized());
 
    // w = cos(angle / 2), ensure it is positive so that we get an angle in the range [0, PI]
    Quat w_pos = EnsureWPositive();
 
    // The imaginary part of the quaternion is axis * sin(angle / 2),
    // if the length is small use the approximation sin(x) = x to calculate angular velocity
    Vec3 xyz = w_pos.GetXYZ();
    float xyz_len_sq = xyz.LengthSq();
    if (xyz_len_sq < 4.0e-4f) // Max error introduced is sin(0.02) - 0.02 = 7e-5 (when w is near 1 the angle becomes more inaccurate in the code below, so don't make this number too small)
        return (2.0f / inDeltaTime) * xyz;
 
    // Otherwise calculate the angle from w = cos(angle / 2) and determine the axis by normalizing the imaginary part
    // Note that it is also possible to calculate the angle through angle = 2 * atan2(|xyz|, w). This is more accurate but also 2x as expensive.
    float angle = 2.0f * ACos(w_pos.GetW());
    return (xyz / (sqrt(xyz_len_sq) * inDeltaTime)) * angle;
}
 
Quat Quat::sFromTo(Vec3Arg inFrom, Vec3Arg inTo)
{
    /*
        Uses (inFrom = v1, inTo = v2):
 
        angle = arcos(v1 . v2 / |v1||v2|)
        axis = normalize(v1 x v2)
 
        Quaternion is then:
 
        s = sin(angle / 2)
        x = axis.x * s
        y = axis.y * s
        z = axis.z * s
        w = cos(angle / 2)
 
        Using identities:
 
        sin(2 * a) = 2 * sin(a) * cos(a)
        cos(2 * a) = cos(a)^2 - sin(a)^2
        sin(a)^2 + cos(a)^2 = 1
 
        This reduces to:
 
        x = (v1 x v2).x
        y = (v1 x v2).y
        z = (v1 x v2).z
        w = |v1||v2| + v1 . v2
 
        which then needs to be normalized because the whole equation was multiplied by 2 cos(angle / 2)
    */
 
    float len_v1_v2 = sqrt(inFrom.LengthSq() * inTo.LengthSq());
    float w = len_v1_v2 + inFrom.Dot(inTo);
 
    if (w == 0.0f)
    {
        if (len_v1_v2 == 0.0f)
        {
            // If either of the vectors has zero length, there is no rotation and we return identity
            return Quat::sIdentity();
        }
        else
        {
            // If vectors are perpendicular, take one of the many 180 degree rotations that exist
            return Quat(Vec4(inFrom.GetNormalizedPerpendicular(), 0));
        }
    }
 
    Vec3 v = inFrom.Cross(inTo);
    return Quat(Vec4(v, w)).Normalized();
}
 
template <class Random>
Quat Quat::sRandom(Random &inRandom)
{
    std::uniform_real_distribution<float> zero_to_one(0.0f, 1.0f);
    float x0 = zero_to_one(inRandom);
    float r1 = sqrt(1.0f - x0), r2 = sqrt(x0);
    std::uniform_real_distribution<float> zero_to_two_pi(0.0f, 2.0f * JPH_PI);
    Vec4 s, c;
    Vec4(zero_to_two_pi(inRandom), zero_to_two_pi(inRandom), 0, 0).SinCos(s, c);
    return Quat(s.GetX() * r1, c.GetX() * r1, s.GetY() * r2, c.GetY() * r2);
}
 
Quat Quat::sEulerAngles(Vec3Arg inAngles)
{
    Vec4 half(0.5f * inAngles);
    Vec4 s, c;
    half.SinCos(s, c);
 
    float cx = c.GetX();
    float sx = s.GetX();
    float cy = c.GetY();
    float sy = s.GetY();
    float cz = c.GetZ();
    float sz = s.GetZ();
 
    return Quat(
        cz * sx * cy - sz * cx * sy,
        cz * cx * sy + sz * sx * cy,
        sz * cx * cy - cz * sx * sy,
        cz * cx * cy + sz * sx * sy);
}
 
Vec3 Quat::GetEulerAngles() const
{
    float y_sq = GetY() * GetY();
 
    // X
    float t0 = 2.0f * (GetW() * GetX() + GetY() * GetZ());
    float t1 = 1.0f - 2.0f * (GetX() * GetX() + y_sq);
 
    // Y
    float t2 = 2.0f * (GetW() * GetY() - GetZ() * GetX());
    t2 = t2 > 1.0f? 1.0f : t2;
    t2 = t2 < -1.0f? -1.0f : t2;
 
    // Z
    float t3 = 2.0f * (GetW() * GetZ() + GetX() * GetY());
    float t4 = 1.0f - 2.0f * (y_sq + GetZ() * GetZ());
 
    return Vec3(ATan2(t0, t1), ASin(t2), ATan2(t3, t4));
}
 
Quat Quat::GetTwist(Vec3Arg inAxis) const
{
    Quat twist(Vec4(GetXYZ().Dot(inAxis) * inAxis, GetW()));
    float twist_len = twist.LengthSq();
    if (twist_len != 0.0f)
        return twist / sqrt(twist_len);
    else
        return Quat::sIdentity();
}
 
void Quat::GetSwingTwist(Quat &outSwing, Quat &outTwist) const
{
    float x = GetX(), y = GetY(), z = GetZ(), w = GetW();
    float s = sqrt(Square(w) + Square(x));
    if (s != 0.0f)
    {
        outTwist = Quat(x / s, 0, 0, w / s);
        outSwing = Quat(0, (w * y - x * z) / s, (w * z + x * y) / s, s);
    }
    else
    {
        // If both x and w are zero, this must be a 180 degree rotation around either y or z
        outTwist = Quat::sIdentity();
        outSwing = *this;
    }
}
 
Quat Quat::LERP(QuatArg inDestination, float inFraction) const
{
    float scale0 = 1.0f - inFraction;
    return Quat(Vec4::sReplicate(scale0) * mValue + Vec4::sReplicate(inFraction) * inDestination.mValue);
}
 
Quat Quat::SLERP(QuatArg inDestination, float inFraction) const
{
    // Difference at which to LERP instead of SLERP
    const float delta = 0.0001f;
 
    // Calc cosine
    float sign_scale1 = 1.0f;
    float cos_omega = Dot(inDestination);
 
    // Adjust signs (if necessary)
    if (cos_omega < 0.0f)
    {
        cos_omega = -cos_omega;
        sign_scale1 = -1.0f;
    }
 
    // Calculate coefficients
    float scale0, scale1;
    if (1.0f - cos_omega > delta)
    {
        // Standard case (slerp)
        float omega = ACos(cos_omega);
        float sin_omega = Sin(omega);
        scale0 = Sin((1.0f - inFraction) * omega) / sin_omega;
        scale1 = sign_scale1 * Sin(inFraction * omega) / sin_omega;
    }
    else
    {
        // Quaternions are very close so we can do a linear interpolation
        scale0 = 1.0f - inFraction;
        scale1 = sign_scale1 * inFraction;
    }
 
    // Interpolate between the two quaternions
    return Quat(Vec4::sReplicate(scale0) * mValue + Vec4::sReplicate(scale1) * inDestination.mValue).Normalized();
}
 
Vec3 Quat::operator * (Vec3Arg inValue) const
{
    // Rotating a vector by a quaternion is done by: p' = q * (p, 0) * q^-1 (q^-1 = conjugated(q) for a unit quaternion)
    // Using Rodrigues formula: https://en.m.wikipedia.org/wiki/Euler%E2%80%93Rodrigues_formula
    // This is equivalent to: p' = p + 2 * (q.w * q.xyz x p + q.xyz x (q.xyz x p))
    //
    // This is:
    //
    // Vec3 xyz = GetXYZ();
    // Vec3 q_cross_p = xyz.Cross(inValue);
    // Vec3 q_cross_q_cross_p = xyz.Cross(q_cross_p);
    // Vec3 v = mValue.SplatW3() * q_cross_p + q_cross_q_cross_p;
    // return inValue + (v + v);
    //
    // But we can write out the cross products in a more efficient way:
    JPH_ASSERT(IsNormalized());
    Vec3 xyz = GetXYZ();
    Vec3 yzx = xyz.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 q_cross_p = (inValue.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>() * xyz - yzx * inValue).Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 q_cross_q_cross_p = (q_cross_p.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>() * xyz - yzx * q_cross_p).Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 v = mValue.SplatW3() * q_cross_p + q_cross_q_cross_p;
    return inValue + (v + v);
}
 
Vec3 Quat::InverseRotate(Vec3Arg inValue) const
{
    JPH_ASSERT(IsNormalized());
    Vec3 xyz = GetXYZ(); // Needs to be negated, but we do this in the equations below
    Vec3 yzx = xyz.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 q_cross_p = (yzx * inValue - inValue.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>() * xyz).Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 q_cross_q_cross_p = (yzx * q_cross_p - q_cross_p.Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>() * xyz).Swizzle<SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_X>();
    Vec3 v = mValue.SplatW3() * q_cross_p + q_cross_q_cross_p;
    return inValue + (v + v);
}
 
Vec3 Quat::RotateAxisX() const
{
    // This is *this * Vec3::sAxisX() written out:
    JPH_ASSERT(IsNormalized());
    Vec4 t = mValue + mValue;
    return Vec3(t.SplatX() * mValue + (t.SplatW() * mValue.Swizzle<SWIZZLE_W, SWIZZLE_Z, SWIZZLE_Y, SWIZZLE_X>()).FlipSign<1, 1, -1, 1>() - Vec4(1, 0, 0, 0));
}
 
Vec3 Quat::RotateAxisY() const
{
    // This is *this * Vec3::sAxisY() written out:
    JPH_ASSERT(IsNormalized());
    Vec4 t = mValue + mValue;
    return Vec3(t.SplatY() * mValue + (t.SplatW() * mValue.Swizzle<SWIZZLE_Z, SWIZZLE_W, SWIZZLE_X, SWIZZLE_Y>()).FlipSign<-1, 1, 1, 1>() - Vec4(0, 1, 0, 0));
}
 
Vec3 Quat::RotateAxisZ() const
{
    // This is *this * Vec3::sAxisZ() written out:
    JPH_ASSERT(IsNormalized());
    Vec4 t = mValue + mValue;
    return Vec3(t.SplatZ() * mValue + (t.SplatW() * mValue.Swizzle<SWIZZLE_Y, SWIZZLE_X, SWIZZLE_W, SWIZZLE_Z>()).FlipSign<1, -1, 1, 1>() - Vec4(0, 0, 1, 0));
}
 
void Quat::StoreFloat3(Float3 *outV) const
{
    JPH_ASSERT(IsNormalized());
    EnsureWPositive().GetXYZ().StoreFloat3(outV);
}
 
void Quat::StoreFloat4(Float4 *outV) const
{
    mValue.StoreFloat4(outV);
}
 
Quat Quat::sLoadFloat3Unsafe(const Float3 &inV)
{
    Vec3 v = Vec3::sLoadFloat3Unsafe(inV);
    float w = sqrt(max(1.0f - v.LengthSq(), 0.0f)); // It is possible that the length of v is a fraction above 1, and we don't want to introduce NaN's in that case so we clamp to 0
    return Quat(Vec4(v, w));
}
 
JPH_NAMESPACE_END