# [solved]how to ratate a node around a custom pivot

Hi,
I can’t find a way to rotate a node around a custom pivot, the Quaternion has no such method, and the Node doesn’t too.
Would you please tell me how to do this?

Edit:
The new API of class Node that RotateAround is good for using, thank you all!

Either position your model’s space around the pivot, or use a redundant scene node parented to the main node, which is some distance away from that node. Then, when you rotate the parent node, the whole thing will rotate.

Thank you GIMB4L.
Is there a way to set the pivot? I mean how to position the model’ space around the pivot, my pivot is a local point.
eg. the origin point is (0, 0, 0), and now I want to set it (0, 0, 5) ahead of the model. Do you mean that position the pivot in 3d model builder like as blender or 3dx max?

You can kind of get a glimpse into how to do it from the editor orbiting bits EditorView.as[ln:1166]

``` if (input.mouseButtonDown[MOUSEB_MIDDLE] && (selectedNodes.length > 0 || selectedComponents.length > 0)) { Vector3 centerPoint = SelectedNodesCenterPoint(); Vector3 d = cameraNode.worldPosition - centerPoint; cameraNode.worldPosition = centerPoint - q * Vector3(0.0, 0.0, d.length); orbiting = true; }```

Essentially you need to add or subtract a fix length vector from another point (d) and optionally rotate the d by multiplying a quaternion.

Bonus: Math sucks

Thank you, friesencr.
I tried this way, and it is ok for orbiting, but it can’t solve my problem.
What I want is an anchor point, like as the figure shows:

The point is pivot, is there a way to achieve this purpose?
I think if the class Node provide an API that SetRotatePivot or RotateAround is better for using.

This code (example is in AngelScript) should do what you’re after, pivoting around a local space point (Vector3 localPivot). Because the coordinate space choice isn’t obvious and there are many kinds of orbits you might want, I believe it’s better to do with existing API functions and not expand the Node class to contain extra state for a pivot point, so that it stays as lean and simple as possible.

``````    Quaternion delta(0, 10 * timeStep, 0); // This could be any rotation
Vector3 rotatedPivot = delta * -localPivot + localPivot;
Vector3 newPos = node.transform * rotatedPivot;
Quaternion newRot = delta * node.rotation;
node.SetTransform(newPos, newRot);``````

EDIT: now that the transform space refactoring is in, you should also be able to do this simply with

``node.RotateAround(localPivot, delta, TS_LOCAL);``

Note that the localPivot will be affected by the node’s local scale.