Rotate a transformation matrix by an angle around an axis

[nihalkenkre]

Hello.

I would like to rotate an object by an angle around a axis.

in cglm the following can be done
glm_rotate(object_transform_matrix, angle, axis);

How can this be achieved in glam?

Do i need to extract the rotation from the object transformation matrix and then somehow rotate it further by the angle and around the axis and then create another matrix which would be the new object_transform_matrix.

Thank you in advance.
Cheers

Someone with experience with this crate please add a few examples.

[nihalkenkre]

well. could have passed on some information regarding rotating an object after moving this from issues to discussions :/

[bitshifter]

"Examples !?" is not very descriptive. Are you requesting a new feature? Are you asking for documentation improvements? it looks like a question, this one has more detail than your other question. I am not familiar with cglm, what does glm_rotate actually do? Does it only operate on the rotation but not the translation part of the input matrix? Could you provide a link to the docs for the glm_rotate function that you are trying to replicate?

[nihalkenkre]

I realized there is a discussions tab just after i created the "issue". my mistake!

[nihalkenkre]

I am trying to rotate an object around an axis by an angle. how can it be done with glam.

currently what I am doing is
Mat4::from_quat(Quat::from_mat4(object_matrix) + Quat::from_axis_angle(axis, angle))

then adding this Mat4 to the object_matrix.

would this be the way to rotate an object around some axis by and angle

[bitshifter]

To rotate you can multiply your matrix by your rotation matrix that you created with Mat4::from_axis_angle.

[bitshifter]

looking at https://github.com/recp/cglm/blob/master/include/cglm/affine-mat.h#L116 it looks like glm_rotate doesn't rotate the translation part

there's no equivalent method for doing that in glam, it's probably easier to do it using the Affine3A type instead of a Mat4 since it stores the translation separately, assuming

let mut affine = Affine3A::from_mat4(object_transform);
affine = Affine3A::from_mat3_translation(affine.matrix3 * Mat3A::from_axis_angle(axis, angle), affine.translation);

probably something like that would do the same thing

[nihalkenkre]

thank you for the information. closing for now..