ディテールオブジェクトの密度
This number goes from 0.0 to 1.0, with 1.0 being the original density, and lower numbers
resulting in less detail objects being rendered.
Additional resources: detailObjectDistance.
using UnityEngine;
public class Example : MonoBehaviour { void Start() { Terrain.activeTerrain.detailObjectDensity = 0.5f; } }