Transform::from_translation + Transform::looking_at matrix is different from Mat4::look_at_lh/rh

[alnyan]

Hi everyone, I'm not sure if that's an issue, but I get different results with methods in question when trying to setup my camera orientation.

I'm currently trying to make my own proof-of-concept vulkan renderer plugin for bevy, which uses Transform::compute_matrix for model matrices when rendering objects and setting up view matrix. When I try to use Transform::from_translation followed by Transform::looking_at to build my camera's transform, it produces an invalid matrix. I tried using Transform::from_matrix with Mat4::look_at_rh instead, that works fine for view matrix (objects are displayed correctly from camera point of view), but transform.translation becomes broken and contains nonsensical values.

Here I setup three matrices and compare their values, third one being significantly different from expected:

let camera_position = Vec3::new(
    10.0
    10.0,
    10.0,
);
let m0 = Mat4::look_at_rh(camera_position, Vec3::ZERO, Vec3::Y);
let m1 = Mat4::look_at_lh(camera_position, Vec3::ZERO, Vec3::Y);
let m2 = Transform::from_translation(camera_position)
    .looking_at(Vec3::ZERO, Vec3::Y)
    .compute_matrix();

Can anyone please suggest if I'm doing anything wrong with transform setup?

[superdump]

I’ve noted previously that Mat4::look_at_rh and Transform::look_at seem to be inverses of each other but I don’t remember figuring out why to be able to fix it.

[superdump]

Oh, you should use the inverse of m2 for transforming from the world to the view. If you look at something in front of you and turn your head to the left, the object appears to move to the right.

[alnyan]

Thanks for suggestion, that indeed resolves my issue!