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Merge pull request #115327 from jrouwe/115180

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Jolt Physics: Make MoveKinematic more accurate when rotating a body by a very small angle
This commit is contained in:
Thaddeus Crews
2026-01-26 15:01:59 -06:00
parent 131c54270b 67d385e910
commit a4bbad2ba8
3 changed files with 24 additions and 4 deletions
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3
thirdparty/jolt_physics/Jolt/Math/Quat.h vendored
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@@ -111,6 +111,9 @@ public:
/// Get axis and angle that represents this quaternion, outAngle will always be in the range \f$[0, \pi]\f$
JPH_INLINE void GetAxisAngle(Vec3 &outAxis, float &outAngle) const;
/// Calculate angular velocity given that this quaternion represents the rotation that is reached after inDeltaTime when starting from identity rotation
JPH_INLINE Vec3 GetAngularVelocity(float inDeltaTime) const;
/// Create quaternion that rotates a vector from the direction of inFrom to the direction of inTo along the shortest path
/// @see https://www.euclideanspace.com/maths/algebra/vectors/angleBetween/index.htm
JPH_INLINE static Quat sFromTo(Vec3Arg inFrom, Vec3Arg inTo);

20
thirdparty/jolt_physics/Jolt/Math/Quat.inl vendored
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@@ -151,6 +151,26 @@ void Quat::GetAxisAngle(Vec3 &outAxis, float &outAngle) const
}
}
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)
{
/*

5
thirdparty/jolt_physics/Jolt/Physics/Body/MotionProperties.inl vendored
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@@ -17,10 +17,7 @@ void MotionProperties::MoveKinematic(Vec3Arg inDeltaPosition, QuatArg inDeltaRot
mLinearVelocity = LockTranslation(inDeltaPosition / inDeltaTime);
// Calculate required angular velocity
Vec3 axis;
float angle;
inDeltaRotation.GetAxisAngle(axis, angle);
mAngularVelocity = LockAngular(axis * (angle / inDeltaTime));
mAngularVelocity = LockAngular(inDeltaRotation.GetAngularVelocity(inDeltaTime));
}
void MotionProperties::ClampLinearVelocity()