how to convince my dad that i don't have any interest in engineering?

tell him women ain't suitable for engineering field.

He is worried about your career. He is not bad at his end. As you want to choose animation as career, you must have done some research about it's scope and career opportunities. Discuss with him in detail about your plans and also tell him that many of the engineers don't have promising career opportunities. And if you are good at animation, you can work for movies, projects, advertisements etc. Your income could be multiple times that of an Engineer.

..........

He will consider your opinion 10 times betterthan 3 idiots movie or advice of your relatives.

Just be honest. However make sure your plans to be an animator have a promising future. I reccomend always having a backup plan to your career.

Tell him you want to choose your own career and that engineering isn't 'your thing'

First tell them that your interest is in animation and it also has scope in future and that you know that you wont be able to handle engg. Then show them 3 idiots.

Call him for a meeting and inform him about the decision. Show your prowess in the field of animation, if you have done something about it, or talk to him about animation in detail.

tell him clearly, about ur lack of interest in engineering and about ur interest in animation. tell him that since you don't like engineering and if u don't do well and if ur career is ruined, he will be the one to blame !!

Take broken appliances and turn them into art.