Unity中MeshFilter中的Mesh默认情况下使用MeshTopology.Trigangles类型绘制网格，就是通常的绘制三角形网格，实际上Mesh有五种绘制模式，对应MeshTopology的枚举，分别是

        这里以Lines和Quads为例说明Trigangles方式之外的绘制方式。

        效果如下：

        参考代码如下：

using System.Collections.Generic;
using UnityEngine;

public class LineMeshTest : MonoBehaviour
{
	[SerializeField]
	Material material;

	void Start()
	{
		GameObject circle = new GameObject("Circle");
		circle.transform.SetParent(transform);
		circle.transform.localPosition = new Vector3(-5, 0, 0);
		MeshFilter filterCircle = circle.AddComponent<MeshFilter>();
		Mesh meshCircle = GetCircleMesh(2);
		filterCircle.mesh = meshCircle;
		MeshRenderer renderCircle = circle.AddComponent<MeshRenderer>();
		renderCircle.material = material;

		GameObject quad = new GameObject("Quad");
		quad.transform.SetParent(transform);
		quad.transform.localPosition = new Vector3(5, 0, 0);
		MeshFilter filterQuad = quad.AddComponent<MeshFilter>();
		Mesh meshQuad = GetQuadMesh(5);
		filterQuad.mesh = meshQuad;
		MeshRenderer rendeQuad = quad.AddComponent<MeshRenderer>();
		rendeQuad.material = material;
	}

	Mesh GetCircleMesh(float radius)
	{
		List<Vector3> vertexList = new();
		List<int> indexList = new List<int>();
		float radDelta = Mathf.PI / 36;
		for (float i = 0; i < 72f; i++)
		{
			float rad = radDelta * i;
			Vector3 vert = new(radius * Mathf.Cos(rad), radius * Mathf.Sin(rad), 0);
			vertexList.Add(vert);
		}

		indexList.Add(0);
		for (int i = 1; i < 72; i++)
		{
			indexList.Add(i);
			indexList.Add(i);
		}
		indexList.Add(0);

		Mesh mesh = new();
		mesh.SetVertices(vertexList);
		mesh.SetIndices(indexList.ToArray(), MeshTopology.Lines, 0);
		return mesh;
	}

	Mesh GetQuadMesh(float size)
	{
		float s = size * 0.5f;
		Vector3[] vertices = new[] { new Vector3(s, s, 0), new Vector3(s, -s, 0), new Vector3(-s, -s, 0), new Vector3(-s, s, 0) };
		int[] indices = new[] { 0, 1, 2, 3 };

		Mesh mesh = new Mesh();
		mesh.SetVertices(vertices);
		mesh.SetIndices(indices, MeshTopology.Quads, 0);

		return mesh;
	}
}

         这个例子里面使用Mesh绘制了一个圆形线条，注意这两行语句：

mesh.SetIndices(indexList.ToArray(), MeshTopology.Lines, 0);

mesh.SetIndices(indices, MeshTopology.Quads, 0);