Rotation methods for Vec3

[rmheuer]

Methods to rotate a Vec3 around an axis.

pub fn rotate_x(self, angle: f32) -> Self; // = rotate_axis(vec3(1.0, 0.0, 0.0), angle)
pub fn rotate_y(self, angle: f32) -> Self; // = rotate_axis(vec3(0.0, 1.0, 0.0), angle)
pub fn rotate_z(self, angle: f32) -> Self; // = rotate_axis(vec3(0.0, 0.0, 1.0), angle)

// Rotates around the axis defined by `axis`, through the origin
pub fn rotate_axis(self, axis: Self, angle) -> Self;

Example usage:

let pitch = /*...*/;
let yaw = /*...*/;
let forward = Vec3::NEG_Z.rotate_x(pitch).rotate_y(yaw);

Similar methods for Vec2 may be useful as well:

fn rotate(self, angle: f32) -> Self; // = rotate_around(vec2(0.0, 0.0), angle)

// Rotates around the point `pivot`
fn rotate_around(self, pivot: Self, angle: f32) -> Self;

I'm not sure on the naming for the Vec2 methods, as there is already a method called rotate that does something different. I'm also not sure how/if handedness should be considered for the Vec3 rotations.

[bitshifter]

Sure, I guess these would be convenient.

I think handedness wouldn't matter in the 3d case as long as the result of doing v.rotate_x(a) is the same as doing the equivalent of Quat::from_rotation_x(a).mul_vec3(v)` handedness shouldn't matter.

In 2D the rotate method is used with from_angle which returns the a vector that contains (a.sin(), a.cos()) which can be used to rotate a vec2 without any further trig operations.

I am not sure what the 2D equivalent of this API would be.

[cpowell]

Just chiming in with a "me too"... a convenient ability to rotate an existing Vec2 by an arbitrary angle would be quite useful and helpful.