Quat MUST_USE_RESULT Quat::RotateFromTo(const float4 &sourceDirection, const float4 &targetDirection)
{
#if defined(MATH_AUTOMATIC_SSE) && defined(MATH_SSE)
// Best: 12.289 nsecs / 33.144 ticks, Avg: 12.489 nsecs, Worst: 14.210 nsecs
simd4f cosAngle = dot4_ps(sourceDirection.v, targetDirection.v);
cosAngle = negate3_ps(cosAngle); // [+ - - -]
// XYZ channels use the trigonometric formula sin(x/2) = +/-sqrt(0.5-0.5*cosx))
// The W channel uses the trigonometric formula cos(x/2) = +/-sqrt(0.5+0.5*cosx))
simd4f half = set1_ps(0.5f);
simd4f cosSinHalfAngle = sqrt_ps(add_ps(half, mul_ps(half, cosAngle))); // [cos(x/2), sin(x/2), sin(x/2), sin(x/2)]
simd4f axis = cross_ps(sourceDirection.v, targetDirection.v);
simd4f recipLen = rsqrt_ps(dot4_ps(axis, axis));
axis = mul_ps(axis, recipLen); // [0 z y x]
// Set the w component to one.
simd4f one = add_ps(half, half); // [1 1 1 1]
simd4f highPart = _mm_unpackhi_ps(axis, one); // [_ _ 1 z]
axis = _mm_movelh_ps(axis, highPart); // [1 z y x]
Quat q;
q.q = mul_ps(axis, cosSinHalfAngle);
return q;
#else
// Best: 19.970 nsecs / 53.632 ticks, Avg: 20.197 nsecs, Worst: 21.122 nsecs
assume(EqualAbs(sourceDirection.w, 0.f));
assume(EqualAbs(targetDirection.w, 0.f));
return Quat::RotateFromTo(sourceDirection.xyz(), targetDirection.xyz());
#endif
}
Quat MUST_USE_RESULT Quat::Conjugated() const
{
#ifdef MATH_AUTOMATIC_SSE
return negate3_ps(q);
#else
return Quat(-x, -y, -z, w);
#endif
}
void Quat::Conjugate()
{
#ifdef MATH_AUTOMATIC_SSE
q = negate3_ps(q);
#else
x = -x;
y = -y;
z = -z;
#endif
}
