Regarding Playground Example re-set rotationQuaternion

Questions
1

Hi am new to the world of 3D graphics as well as to Babylon.js.

I read in:
https://doc.babylonjs.com/resources/rotation_conventions

the following:

You cannot use both a rotation and a rotationQuaternion on a mesh. When a rotationQuaternion is applied to a mesh this overwrites the current and subsequent use of rotation producing the wrong orientation. Should you want to use rotation after a rotationQuaternion has been applied, for example on an imported mesh, then the rotationQuaternion has to be set to null.
To see this effect comment out line 48 in the following playground

Playground Example re-set rotationQuaternion (https://www.babylonjs-playground.com/#1ST43U#77)

In my understanding by commenting out line 48 (which set the rotationQuaternion to null) it is expected that the two boxes will not be aligned anymore. But the example doesn’t seem to do that.

Something seems amiss with my understanding / the example ?

2

Actually something is missing in the doc.
For convenience and because we faced a lot of questions regarding that problem we allo you to still change the value of rotation even if rotationQuaternion is set.

In this case the system will ADD that rotation to the rotationQuaternion and then set it back to zero (the mesh.rotation will be (0, 0, 0))

Pinging @JohnK FYI

3

Unfortunately I do not think this is correct.

In https://www.babylonjs-playground.com/#1ST43U#185 I am not seeing this description of events in the console

rotationQuaterion is set  { x: 0.10503269547928776, y: 0.001336730075941206, z: 0.7669894582804743, w: 0.6330035678569939 }
and so rotation is   { x: 0, y: 0, z: 0 }

Following this the rotation is set  { x: 0.1312985505528809, y: 0.16497104582455158, z: 1.7724948616328908 }
and rotationQuaternion is  null

So I think the pattern is
set rotationQuaternion to Q and rotationQuaternion is Q and rotation is zero

Even when rotationQuaternion has been set then setting rotation to R rotation is R and rotationQuaternion is null.

4

OMG! I feel so stupid!

What I described was BEFORE 4.0. Now to make things simpler, we just turn off automatically rotationQuaternion to null if you set the rotation property

Thanks @JohnK! I stand corrected :smiley:

1 Like
5

Hello,

I am having the same problem. I am rotating objects with rotation gizmo but when i try to get rotation values of the meshes, it returns “0”. I tried to apply your solutions, set rotationquaternion to null, still couldnot manage. Could you help me understand the problem?

https://playground.babylonjs.com/#SEIT79#27

6

The rotation gizmo will reset the rotation quaternion as it works on quaternion only so you need to use mesh.rotationQuaternion.toEulerAngles() to get the rotation