Rotation different between box and triangle

[bert.struik]

Why do boxes and triangles rotated about the X axis act differently?

When a box is shaped as a board with 1" width, 6" height and 48" depth, it's depth is along the Y axis. It will rotate about the X axis as expected. The dimensions make a board that would be flat against a vertical wall that is along the Y axis.

When a triangle is shaped as a board with 6" width, 6" height and 1" depth, it's width is in the Y axis. It will rotate about the Y axis when a value is inserted in the X axis of the modify furniture menu. The dimensions make a triangle that would be flat against a vertical wall that is along the Y axis.

[bert.struik]

It is probably that the coordinate system of the object is different than the coordinate system of the drawing. Sorry I did not figure that out before posting.

[Puybaret]

As you noticed, the axes of the horizontal rotation of the objects depends on how you already rotated around its vertical axis: their X rotation axis is parallel to the thick line drawn in front of the object in the plan, and their Y rotation axis is perpendicular to this thick line.
The little arrow used to handle the rotation around a horizontal axis is also supposed to help you guess this axis.

Object rotated around its X rotation axis:


Object rotated around its Y rotation axis: