var oRoot = Application.ActiveProject.ActiveScene.Root;
var oCube = oRoot.AddGeometry("Cube","MeshSurface", "CubeParent");
var oTrans = oCube.Kinematics.Local.Transform;
var oRot = XSIMath.CreateRotation();
oRot.SetFromXYZAnglesValues( 0, XSIMath.DegreesToRadians( 45 ), XSIMath.DegreesToRadians( 45 ) );
oTrans.SetRotation( oRot );             
oCube.Kinematics.Local.Transform = oTrans;