How to Get a Complete Segmentation Mask

I want a complete segmentation mask, such as a whole car. While SAM gives me several masks that about the car such as the windows, wheels, and other parts using auto_generator_sam. I try to adjust the threshold and the point numbers, but the outcome is still not satisfactory. I wonder whether there is a post-processing method to combine some of the masks to get a whole object. Or maybe there is a suitable setting for me to get a image with less and fit masks.