When rotating the door on front side of the car choose to rotate then move the dot in the middle to the exact point where you want the door to pivot, then you rotate and it will look better already. a easy way i found also to solve most of the shading and perspective issues is to take a door from another m3 and use it rather than the 1 from this car. Because the shading is already diferent you hardly have to do any more editing afterwards. As for the door on oppisite side try to find a m3 or any car even where the door is open so you can see the inside of the door and the cut that door off and pit it on that side, you will now see the iside of the door which is how it would have been in real life. If you cant find 1 let me know as i must have 1 saved somewhere, then i'll send it to you.
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