Mesh.subMeshCount

Description

The number of sub-meshes inside the Mesh object.

Each sub-mesh corresponds to a Material in a Renderer, such as MeshRenderer or SkinnedMeshRenderer. A sub-mesh consists of a list of triangles, which refer to a set of vertices. Vertices can be shared between multiple sub-meshes. See Also: GetTriangles, SetTriangles.

using UnityEngine;
using System.Collections;

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