TriangleMesh.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public static class TriangleMesh {

	public static Mesh Create(float scale){
       Mesh triangle = new Mesh();
       Vector3[] vertexes = new Vector3[3];
       Vector2[] uv = new Vector2[3];
       for(int i=0;i<3;i++){
            uv[i].x = vertexes[i].x = Mathf.Sin( i*2f*Mathf.PI/3f );
            uv[i].y = vertexes[i].y = Mathf.Cos( i*2f*Mathf.PI/3f );

            vertexes[i] *= scale;


       }
       int[] triangles = new int[]{ 0,1,2 };
       triangle.vertices = vertexes;
       triangle.triangles = triangles;
       triangle.uv = uv;

       triangle.RecalculateNormals();
       triangle.UploadMeshData(false);
    }
}