How do you acheive a constant smooth mousewheel page scroll?

How do you acheive a constant smooth mousewheel page scroll?

Hello there,

I was wondering if someone could point me in the right direction.

A lot of sites nowadays use this 'smooth scrolling' effect. When you Google this, to try and find out how to do it, you are left with how to scroll between A and B. Similar to the 'up' arrow that appears to scroll you to the top of the page.

However these sites:-

https://gwbi.org/education/
http://www.buildinamsterdam.com/case/see-buy-fly

Use a constant smooth scroll. There has to be a plugin for such an effect but I have had no luck.

How do they acheive this?

Thanks,
David