void grits_viewer_get_rotation(GritsViewer *viewer, gdouble *x, gdouble *y, gdouble *z);
void grits_viewer_rotate (GritsViewer *viewer, gdouble x, gdouble y, gdouble z);
void grits_viewer_get_rotation(GritsViewer *viewer, gdouble *x, gdouble *y, gdouble *z);
void grits_viewer_rotate (GritsViewer *viewer, gdouble x, gdouble y, gdouble z);