How to rotate a mesh having a rotation matrix?

[Gibser]

Hello everyone. This is my second post here, I have recently been using the Qt framework and it's my first time working with 3D graphics.
How can I rotate a mesh having a 3x3 rotation matrix?
I am using Qt for Python and C ++, I haven't used QML yet.

Thanks in advance!

[gde23]

You just need to multiply each point of the mesh with the matrix.
Let R be your rotation matrix and P your point, then P_rot = R * P will be the point in the rotated coordinate system.