How to roll a billboard in LibGDX?

Question

Java

A sprite is a decal in 3d space. It is always facing the viewer
motoSpr.lookAt( MyGdxGame.cam.position,MyGdxGame.cam.up);
As soon as I specify after this line motoSpr.setRotationZ(angle) (X,Y are responsible for the rotation towards the camera), so the rotation values ​​​​to the camera are reset (X,Y included).
For the sake of experiment, I wrote it down like this motoSpr.setRotationZ(motoSpr.getRotation().z); and what do you think? Anyway, the value was reset, and the sprite does not look towards the camera, but by default.

Answer 1

Here is the source code on the github
setRotationZ does not rotate only around Z, but specifies a new orientation, which is a rotation around the Z axis.

public void setRotationZ (float angle) {
    rotation.set(Vector3.Z, angle);
    updated = false;
}

If you want to modify an existing position, you can try this method:

public void rotateZ (float angle) {
    rotator.set(Vector3.Z, angle);
    rotation.mul(rotator);
    updated = false;
}

It rotates the sprite around the Z axis.