Add animation/fade to modal/dialogue box (without using the bootstrap)
What do you need the modal to do? I often use animated modals for my Drupal projects - http://joaopereirawd.github.io/animatedModal.js/

It seems to work pretty well for menus and forms in my experience.

It uses animate.css ( https://daneden.github.io/animate.css/ ) which you can use also to create some nice transitional effects.