3Drotate

is the direction of rotation completely random?

No, it is not.

To determine the direction of rotation you must orient yourself at a positive point on the axis,

facing towards the origin (0).

As if you were in Plan looking down at your screen and doing a regular Rotate command on the Z access.

For those who choose to use the define axis by 2 points method, this can become confusing,

as the direction of rotation will be determined by the relative position,

positive or negative, from the first point picked.

I prefer using this in an isometric view, to be sure that everything is as you would want it to be.

An old trick often used, is to position your right hand as if you were hitch hiking, and point your thumb in the positive direction

along any given axis. Your fingers will curl in the positive direction of rotation for that axis.

The way I remember it

imagine holding the axis that you are going to use with your right hand, with your thumb pointing towards the head of the arrow, positive rotation is the way your fingers folding

Hoss maybe correct image is thumb up 1st finger full extend 2nd finger 1/2 extend so you get a XYZ axis physics about 40 years ago "Right hand rule"

Mikekmx I only do real basic 3d but most times use the axis option even do twice, rotate3d X 90, I usually view in a 3d view so can see object as I rotate often undo and -90, use simple vpoint 1,1,1 to see.

Using UCS OB can have un predictable results if object has 3d points of a XYZ plane.

hand/thumb thing seems to work, thanks.

In general most AutoCAD commands follow the Right Hand Rule (RHR). Point the thumb of your right hand in the direction the axis points and the curl of your right hand fingers define the positive rotation direction. 3DROTATE violates this convention for rotations about the y-axis! 3DROTATE uses RHR for the X and Z axis but a left hand convention for the y-axis. Go figure!

I prefer ROTATE3D for keyboard specified rotations which always follows the RHR convention.

In general most AutoCAD commands follow the Right Hand Rule (RHR). Point the thumb of your right hand in the direction the axis points and the curl of your right hand fingers define the positive rotation direction. 3DROTATE violates this convention for rotations about the y-axis! 3DROTATE uses RHR for the X and Z axis but a left hand convention for the y-axis. Go figure!

 

I prefer ROTATE3D for keyboard specified rotations which always follows the RHR convention.

That seems really strange.

I have no use for the 3D Gizmo, so had never noticed that.

I just checked, and you are correct, damn that is a bug if ever I saw one!

In general most AutoCAD commands follow the Right Hand Rule (RHR). Point the thumb of your right hand in the direction the axis points and the curl of your right hand fingers define the positive rotation direction. 3DROTATE violates this convention for rotations about the y-axis! 3DROTATE uses RHR for the X and Z axis but a left hand convention for the y-axis. Go figure!

That is very curious. I tried my Rotate3D, and it followed the RHR in X, Y and Z axes.

Am I doing something wrong

Rotate3d works fine. It's 3drotate that uses a left hand convention for rotations about the y axis.

Rotate3d works fine. It's 3drotate that uses a left hand convention for rotations about the y axis.

A bug is a bug, nothing more nor less.

I have a hard time imagining what sort of explanation there might possibly be,

if Autodesk were to claim it was intentional, and or, logical.