How can I have large textures and good performance?

The less textures you use on a mesh, the less draw calls it has to go through. It’s probably better to combine them, however, you do sacrifice quality that way, if its important.

What you can also try doing is lowering the resolution of some of the textures where its not needed as well. Good luck!

It might be a silly question about I still want to know the answer.
I was plan to create a high definition vehicle in UE4, plan to use 4 pieces of 20482048 texture, how about I combine them into one 40964096 textures? Which solution would have better performance?

Not entirely true. Number of draw calls depends on number of mesh sections, number of meshes and number of passes.

Putting multiple textures into one bigger texture is called a texture atlas. It helps to save expensive texture sampling operations in pixel shader(which is important on mobile devices and low spec computers).You can also use this technique for flipbook textures in particle systems.

I guess what it used depends if you are going to use many or only one of these meshes.

Thanks guys, but I am still confused;
In my case, the mesh would be only one:
Solution 1: use one 40964096 texture
Solution 2: Break the mesh into four material ids, and use four 2048
2048 textures
The texture density would be the same, and I prefer solution 2 as it makes thing easy to manage, my question is:
Does UE4 support 4k texture well?
Which solution would get better performance on technical side not art side, I means frame rate for example.

I would probably go with solution two, as the performance impact would probably be negligible. It would also make it easier to manage textures and keep things reasonably high res. Especially if you are using glass.

UE4 can import textures up to 8192*8192

that is clear