Version: 2017.2

Mesh.subMeshCount

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public int subMeshCount ;

Description

The number of sub-Meshes. Every Material has a separate triangle list.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { void Start() { Mesh mesh = GetComponent<MeshFilter>().mesh; Debug.Log("Submeshes: " + mesh.subMeshCount); } }