When I rotate a mesh with yaw, pitch and roll, the mesh is orbiting around a pivot that is off from the center of the mesh, some imaginary point beyond the extents of the mesh, so it starts rotating in a strange way. How do I reset the pivot to a point where it sits right underneath the lowest point of the mesh itself? so that i can easily rotate it to the right orientation?

thanks
Jack

Easiest way is to move the model to that position in the model editor used to make the model.  If not you'll have to experiment with translating the model in code.  Which is the least efficient way.

18 hours ago, lucky6969b said:

How do I reset the pivot to a point where it sits right underneath the lowest point of the mesh itself? so that i can easily rotate it to the right orientation?

If you don't want to do this using a 3D editor you can rotate around a point.

How you do so changes based on your engine. The math for this is common around the net. https://www.siggraph.org/education/materials/HyperGraph/modeling/mod_tran/3drota.htm