Change rotation axis

I have an orthogonal drawing that's basically a tall cube. I want to spin it along its central Z axis. Using the rotate option, I selected the bottom/center point, but that makes it rotate down -- such as a domino tipping over -- how do I tell LibreCAD that I'd like to "spin" the drawing instead?

do you mean you want to rotate by -90 degrees instead of 90?

Evan K wrote

I have an orthogonal drawing that's basically a tall cube. I want to spin it along its central Z axis. Using the rotate option, I selected the bottom/center point, but that makes it rotate down -- such as a domino tipping over -- how do I tell LibreCAD that I'd like to "spin" the drawing instead?

Hello,

No, I want to rotate along a different axis.

I am making a 3D drawing -- or at least a 3D perspective in the 2D software -- by using an orthogonal grid.

Is it impossible to rotate along the virtuao Z axis?

I mis-spoke. I am using the isometric grid. Keep getting the names confused, sorry!

in general, 3D rotation can not be based only on the projected, because 3D rotation needs 3D information, while the projected contains only 2D.

consider 3D as a linear mapping of 3D space V=(x, y, z), while the only available information is projected V'=(x', y', 0)

V' = P V
R(V') = P R(V)

with R(V) denotes the linear mapping of rotation.

Only if the rotation is in the range space of projection P, P R(V) = R(P V), the rotation can be done using only projected coordinates, i.e. the rotation is around the null space of projection.

in a simple case of isometric projection, the null space is the 3D line, x=y=z, rotation is around this axis is the same as rotation in the projected space.

Evan K wrote

I mis-spoke. I am using the isometric grid. Keep getting the names confused, sorry!