Trying to solve the issues I have with rotation matrices and quaternions

[anonymous_user_4ec4b74b]

@Antidamage

It’s easier than you’d think. Quaternions are basically a vector with a magnitude. The vector is your rotational axis in 3D space, and your magnitude is how much to rotate around it in radians. The polarity of the vector determines the direction of rotation around the axis, giving rise to the term “right-handed system”. (Using your right hand: thumb up, fingers curl in direction of rotation.)

Store your initial orientation as a quaternion created from the normal actor rotation. From then on add your rotational offsets by making a new quaternion from the rotation you want and combine the two. To use your rotation either expose SetActorRotation(Quaternion) to blueprints or get the rotator back out each frame and use it as-is.

Don’t bother trying to make quaternions from their components. They’re not too hard to understand, but getting the result you want is exceedingly difficult in game dev because of how we approach it. You’d end up lerping your current axial vector to a new axial vector and that won’t give linear rotation. God knows how you’d get the magnitude around the axis. Just use the built-in methods.

Avoiding doing any FRotator transformational operations or avoiding splitting the axes to do operations is enough to avoid gimbal lock.

Thanks for your reply!

I was looking for something like you said on forums, could you give me an example? How to add an rotation offset aka (x,y,z) translation to a quaternion, without coverting to a homogenous 4x4 matrix, to have a rotation around a point instead rotating the actor around its own center?

Maybe something like this snippet?

FQuat OrbitingActorOrientation = TempArr[Index]->GetOwner()->GetActorRotation().Quaternion;
FQuat OrientationQuat = FVector(
                                                          OrbitDataArr[Index].MajorOrbitRadius,
                                                          OrbitDataArr[Index].MajorOrbitRadius *
                                                          MajorEllipticOrbitFraction,
                                                          0.f
                                                     ).ToOrientationQuat() +
     FQuat(
                    FVector::UpVector,
                    FMath::DegreesToRadians(OrbitDataArr[Index].XYAngle)
     );
OrbitingActorOrientation *= OrientationQuat;
TempArr[Index]->GetOwner()->SetActorRotation(OrbitingActorOrientation);

EDIT: Doesn’t work this way, doesn’t rotate TempArr[Index]->GetOwner() around the BlackHoleLocation elliptically.