How to change transition to fade on Boostrap Carousel module?
you could do that with CSS transitions so it can be done easily without any Javascript.

The CSS:

.carousel .item {-webkit-transition: opacity 3s; -moz-transition: opacity 3s; -ms-transition: opacity 3s; -o-transition: opacity 3s; transition: opacity 3s;}
.carousel .active.left {left:0;opacity:0;z-index:2;}
.carousel .next {left:0;opacity:1;z-index:1;}


I noticed however that the transition end event was firing prematurely with the default interval of 5s and a fade transition of 3s. Bumping the carousel interval to 8s provides a nice effect.

Very smooth.