def add_vertex(self, x, y, z):
        """
        Add a ``VEC3`` of ``floats`` to the ``vert_data`` buffer
        """
        self.vert_data.write(
            struct.pack('<f', x) +
            struct.pack('<f', y) +
            struct.pack('<f', z)
        )

        # retain min/max values
        self.vert_min = _list3_min(self.vert_min, (x, y, z))
        self.vert_max = _list3_max(self.vert_max, (x, y, z))
Add a ``VEC3`` of ``floats`` to the ``vert_data`` buffer