Terrain.basemapDistance

Description

Heightmap patches beyond basemap distance will use a precomputed low res basemap.

This improves performance for far away patches. Close up Unity renders the heightmap using splat maps by blending between any amount of provided terrain textures.

using UnityEngine;

public class Example : MonoBehaviour
{
    void Start()
    {
        Terrain.activeTerrain.basemapDistance = 100;
    }
}