Support rotating Direction3d by Quat
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# Objective It's often necessary to rotate directions, but it currently has to be done like this: ```rust Direction3d::new_unchecked(quat * *direction) ``` It'd be nice if you could rotate `Direction3d` directly: ```rust quat * direction ``` ## Solution Implement `Mul<Direction3d>` for `Quat` ~~and the other way around.~~ (Glam doesn't impl `Mul<Quat>` or `MulAssign<Quat>` for `Vec3`) The quaternion must be a unit quaternion to keep the direction normalized, so there is a `debug_assert!` to be sure. Almost all `Quat` constructors produce unit quaternions, so there should only be issues if doing something like `quat + quat` instead of `quat * quat`, using `Quat::from_xyzw` directly, or when you have significant enough drift caused by e.g. physics simulation that doesn't normalize rotation. In general, these would probably cause unexpected results anyway. I also moved tests around slightly to make `dim2` and `dim3` more consistent (`dim3` had *two* separate `test` modules for some reason). In the future, we'll probably want a `Rotation2d` type that would support the same for `Direction2d`. I considered implementing `Mul<Mat2>` for `Direction2d`, but that would probably be more questionable since `Mat2` isn't as clearly associated with rotations as `Quat` is.
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Objective
It's often necessary to rotate directions, but it currently has to be done like this:
It'd be nice if you could rotate
Direction3ddirectly:quat * directionSolution
Implement
Mul<Direction3d>forQuatand the other way around.(Glam doesn't implMul<Quat>orMulAssign<Quat>forVec3)The quaternion must be a unit quaternion to keep the direction normalized, so there is a
debug_assert!to be sure. Almost allQuatconstructors produce unit quaternions, so there should only be issues if doing something likequat + quatinstead ofquat * quat, usingQuat::from_xyzwdirectly, or when you have significant enough drift caused by e.g. physics simulation that doesn't normalize rotation. In general, these would probably cause unexpected results anyway.I also moved tests around slightly to make
dim2anddim3more consistent (dim3had two separatetestmodules for some reason).In the future, we'll probably want a
Rotation2dtype that would support the same forDirection2d. I considered implementingMul<Mat2>forDirection2d, but that would probably be more questionable sinceMat2isn't as clearly associated with rotations asQuatis.