solved How to rotate a sphere around a tilted axis?

[d13]

Hi Everyone!

I'm trying to figure out how to do the following:

1. Tilt a sphere about 20 degrees on it's z axis.

2. Then spin the sphere around its tilted axis.

The code I've been using up till looks something like this:

When I create the mesh, I set up its z rotation like this:

mesh.rotation.z = tiltValue * 180 / Math.PI;

This does give me the axis that I need.

Then I've been trying to spin the sphere around that tilted axis in the game loop, like this:

mesh.rotation.y -= rotationValue

But, this causes the mesh to wobble around the y and z a axis instead of spinning on the tilted y axis.

That seems to make sense, but I don't know how to get the effect I need.

 

Can anyone help?

I've tried some of the code from this older thread

 

 

Specifically this bit:

mesh.rotate(BABYLON.Axis.z, 1, BABYLON.Space.LOCAL)

... but this throws an error: TypeError:

t is undefined babylon.js:7:6425

 

I don't know if I'm on the right track or not, but any help will be much appreciated!

 

[Wingnut]

Hi d13.  I used about the same method as you... but it worked.

https://www.babylonjs-playground.com/#012I9K#2

*shrug*    My "local" isn't all-caps, just the first letter.  Not sure if that is the issue.

Update:  Oh, when I change my .Z to .z, I get the same error as you.

https://www.babylonjs-playground.com/#012I9K#3

I bet your "z" should be capitalized.  weird.

[BitOfGold]

If you use Quaternions, you can multiply rotations.

Feel free to copy from my code:
http://www.bitofgold.com/solarsystem/

Like this:

Setup:
mesh.baseRotationQuaternion = BABYLON.Quaternion.RotationYawPitchRoll(0.0, 0.0, 20.0 * Math.PI / 180, 0.0));
mesh.rotationQuaternion = new BABYLON.Quaternion();


...
at every frame:

mesh.rotationQuaternion.copyFrom(mesh.baseRotationQuaternion);
mesh.rotationQuaternion.multiplyInPlace(BABYLON.Quaternion.RotationYawPitchRoll(alpha, 0.0, 0.0));

 

[d13]

Awesomeness!
Thank you Mr Wingnut, Sir, it works beautifully