sometimes you want to do a knife project on a object
for that you have to select the object you want to do
knife on and then the second object and go to flat view and use knife project


what if i want to do the same thing but on a curved surface ?

let me show you this with a photo so you understand better




as you can see if i use project from view i get a cut based one the view and if i zoom out i get a diffrwnt result


so what we do to get the best result


we join both objects
go to edit mode

select the secend object with L KEY



choose intersect (kinfe) from face




done