When it's better to create just one object and from it create for example car and there will be one mesh or better to create it from many pieces(like doors(1 object), front(another object)) and then through ctrl+j make one object, i'm asking as heard that for example mobile games should use one object, but how for example ctrl+j object will work, what better?
Hey SSunn ,
It's a good question, and there is no right or wrong answer. It depends on your modeling preference and what the model is used for.
Have a read of this question and the answers, its basically the same as what you ask.
Don't worry too much about it and just start modeling; you can always change your mind along the way (in Edit Mode: P > Separate, in Object Mode CTRL+J).
(I switch often during modeling). There is one thing to be aware of though; if you Join Objects, you end up with an Object that has the Modifier Stack of the last Selected (Active) Object.
So if you, for instance have a car, with a door that has an X-Mirror Modifier and a wheel that has an X- and Y-Mirror Modifier, and you Join the wheel to the door, you end up with two wheels and two doors. And Joining the door to the wheel gives you four doors and four wheels.
Might be best to Apply the Modifiers that are not the same among all Objects, before joining them.
I concur, doctors. It will depend on the situation, there is no right r wrong per se. What I usually do is take my queue from reality, if I see a door, the hinges and handle will be separate things, or a glass bottle and the cap, whereas a cup will usually have its handle as part of a one cohesive object.
If it's for 3D printing it should be a solid single mesh. Many game engines today can handle multiple mesh pieces in a single object. All game engines can handle multiple objects acting as one. Even ones from the 1980s. Other than those guidelines it's pretty much up to the artist or person the artist is working for.