Best practice for texture resolution on bird's eye view in relation to the render output resolution

#1

I need your help in how to calculate texture size.

Imagine an arch-viz scene from a bird’s eye perspective. I am not looking down to the ground perpendicular and hence cannot calculate the texture size (planar projection on the ground) to match the render size.

Some areas are near the camera while others are further away on the horizon. How should I calculate the required texture size if eg the render output is 1024x1024? I am willing to split the terrain into different regions with different texture size - the important area with proper texture size, and the areas further away with less resolution.
I’d like to hear your opinion on the calculation principle.

#2

is this for realtime rendering? or offline rendering?

#3

I think I defined this question for offline-render at first, but maybe realtime as well. When you ask realtime, are you counting on the possibility of a movable camera, ie the rendered area differs from time to time?

#4

Im referring to realtime rendering (unreal engine/unity) or offline rendering (vray/corona/arnold within 3dsmax/maya or another DCC).

for offline rendering:
texture size isnt such a big deal, if the details look good @ 1024 px then thats enough. With PC specs these days 2048 res is a good base point for nearly all newly created objects, you can go up or down if you require, there is also plugins that can do this on the fly by creating proxy textures based on distance if you really need to optimize.

real-time rendering:
Depending on your workflow, if you have no defined constraints then texel density is a good base point. If everything you model has the same texel density then when you bring it into unreal/unity you can move textures around on things and the scale will be the same. For example if you had 3 different floors with the same texel density you can swap the floor tiles to timber boards, and you know that when you made your textures to start with they were made to scale then no matter which floor you put this on the scale of the timber/tiles will be constant.