Add pivot sphere

[Kurtil]

Add a pivot sphere that resizes according to the distance between the camera and the pivot position. It is possible to enabled or disabled it (default) and change its size and material.

[Amoki]

Don't merge it now.

The sphere geometry breaks with xkt v6 models.

Is there a way to create the sphere in performance mode to allow big coordinates?

[Amoki]

I read the section plane plugin's code and I didn't see anything special. Do you have an idea about why the sphere created like that doesn't render properly with xktv6? @xeolabs

[xeolabs]

@Amoki to position the sphere using double-precision World-space coordinates, you need to split the coordinates into an 32-bit RTC center and a 32-bit offset - see how the SectionPlanePlugin edition control does this the link below.

The idea is that, given a dynamically-changing double-precision 3D world position, we can use worldtoRTCPos to split that into an RTC center and an offset from that center. The Mesh#rtcCenter is dynamically set to the center, and Mesh#position is dynamically set to the offset.

https://github.com/xeokit/xeokit-sdk/blob/master/src/plugins/SectionPlanesPlugin/Control.js#L96

[Amoki]

Should be good now!

[xeolabs]

I might be misreading, but will this be destroying/creating the sphere mesh as the pivot pos updates?

https://github.com/xeokit/xeokit-sdk/blob/24cf44535f2bd59587a69a594ab6b79bf64f7bbd/src/viewer/scene/CameraControl/lib/controllers/PivotController.js#L128

I think you could just dynamically update Mesh#rtcCenter and Mesh#position here, reusing the same Mesh instance.

[Amoki]

The size of the sphere depends on the distance of the pivot point so we can't keep the geometry. I just fixed a bug where the geometry was constantly recreated even if the pivot point was not.

[Amoki]

We don't need a very precise sphere, but we can't reduce the resolution: https://github.com/xeokit/xeokit-sdk/blob/b01f6ddef6e33171dc247a7cced3f001570d2c75/src/viewer/scene/geometry/builders/buildSphereGeometry.js#L72

Is there a reason for these limits?

[ghost]

👇 Click on the image for a new way to code review

Legend

[Amoki]

We've been using it for 3 years, it's stable.

https://github.com/xeokit/xeokit-sdk/assets/1349751/e08463ec-c2bd-417e-a801-c65905645028

If you don't want this feature, you can close this PR