If you’re using Elegant Theme’s Divi, and you have a full width slider at the top of your page you wish to extend down to the bottom of the view port, at first add a css class name to< that particular slider module, say: my_slider.
After that add the following css code into custom css of your theme’s Divi theme options
.my_slider.et_pb_slider .et_pb_slide {
height: calc(100vh - 80px) ;
}
The above CSS takes into account a header height (which contains the logo and navigation) of 80px.