1 仅绘制三角形网格

        1）创建游戏对象 

        创建一个空对象，重命名为 Grid，并在其下添加需要绘制网格的对象，如下：

         场景显示如下：

        2）添加脚本组件

        GridController.cs

using System;
using UnityEngine;

public class GridController : MonoBehaviour {

	private void Start () {
		ForAllChildren(transform, RebuildMesh);
	}

	private void RebuildMesh(Transform transform) {
		MeshFilter meshFilter = transform.GetComponent<MeshFilter>();
		if (meshFilter != null && meshFilter.mesh != null) {
			int[] indices = MakeIndices(meshFilter.mesh.triangles);
			meshFilter.mesh.SetIndices(indices, MeshTopology.Lines, 0);
		}
	}

	private int[] MakeIndices(int[] triangles) {
		int[] indices = new int[2 * triangles.Length];
		for( int i = 0; i < triangles.Length; i += 3 ) {
			for (int j = 0; j < 6; j++) {
				// 每个三角形转换为3条线段, 每个顶点使用2次, 对应的顶点序列是: 0, 1, 1, 2, 2, 0, 通式: (j + 1) % 6 / 2, j 的范围: 1 ~ 5
				indices[2 * i + j] = triangles[i + (j + 1) % 6 / 2];
			}
		}
		return indices;
	}

	private void ForAllChildren(Transform transform, Action<Transform> action) {
		action.Invoke(transform);
		for (int i = 0; i < transform.childCount; i++) {
			ForAllChildren(transform.GetChild(i), action);
		}
	}
}

        说明： GridController 脚本组件挂在 Grid 对象上。

        运行效果：

        3）给网格添加新材质

        GridController.cs

using System;
using UnityEngine;

public class GridController : MonoBehaviour {
	public Material material;

	private void Start () {
		ForAllChildren(transform, RebuildMesh);
	}

	private void RebuildMesh(Transform transform) {
		MeshFilter meshFilter = transform.GetComponent<MeshFilter>();
		MeshRenderer meshRenderer = transform.GetComponent<MeshRenderer>();
		if (meshFilter != null && meshFilter.mesh != null && meshRenderer != null) {
			meshRenderer.material = material;
			int[] indices = MakeIndices(meshFilter.mesh.triangles);
			meshFilter.mesh.SetIndices(indices, MeshTopology.Lines, 0);
		}
	}

	private int[] MakeIndices(int[] triangles) {
		int[] indices = new int[2 * triangles.Length];
		for( int i = 0; i < triangles.Length; i += 3 ) {
			for (int j = 0; j < 6; j++) {
				// 每个三角形转换为3条线段, 每个顶点使用2次, 对应的顶点序列是: 0, 1, 1, 2, 2, 0, 通式: (j + 1) % 6 / 2, j 的范围: 1 ~ 5
				indices[2 * i + j] = triangles[i + (j + 1) % 6 / 2];
			}
		}
		return indices;
	}

	private void ForAllChildren(Transform transform, Action<Transform> action) {
		action.Invoke(transform);
		for (int i = 0; i < transform.childCount; i++) {
			ForAllChildren(transform.GetChild(i), action);
		}
	}
}

        运行效果：

2 绘制表面和三角形网格

        场景中所有对象同第 1 节，脚本组件如下：

        GridController.cs

using System;
using UnityEngine;
using UnityEngine.Rendering;

public class GridController : MonoBehaviour {
	public Material material;

	private void Start () {
		ForAllChildren(transform, RebuildMesh);
	}

	private void RebuildMesh(Transform transform) {
		MeshFilter meshFilter = transform.GetComponent<MeshFilter>();
		MeshRenderer meshRenderer = transform.GetComponent<MeshRenderer>();
		if (meshFilter != null && meshFilter.mesh != null && meshRenderer != null) {
			InitMaterials(meshRenderer);
			int[] indices = MakeIndices(meshFilter.mesh.triangles);
			InitSubMesh(meshFilter.mesh, indices, indices.Length / 3);
		}
	}

	private void InitMaterials(MeshRenderer meshRenderer) {
		Material[] materials = new Material[meshRenderer.materials.Length + 1];
		meshRenderer.materials.CopyTo(materials, 0);
		materials[materials.Length - 1] = material;
		meshRenderer.materials = materials;
	}

	private void InitSubMesh(Mesh mesh, int[] indices, int divide) {
		mesh.SetIndexBufferParams(indices.Length, IndexFormat.UInt32);
        mesh.SetIndexBufferData(indices, 0, 0, indices.Length);
        mesh.subMeshCount = 2; // 设置2个子网格
		// 第一部分绘制三角形内部
        SubMeshDescriptor subMeshDescriptor1 = new SubMeshDescriptor(0, divide, MeshTopology.Triangles);
        mesh.SetSubMesh(0, subMeshDescriptor1);
		// 第二部分绘制线段
        SubMeshDescriptor subMeshDescriptor2 = new SubMeshDescriptor(divide, indices.Length - divide, MeshTopology.Lines);
        mesh.SetSubMesh(1, subMeshDescriptor2);
	}

	private int[] MakeIndices(int[] triangles) {
		int[] indices = new int[3 * triangles.Length];
		triangles.CopyTo(indices, 0);
		for( int i = 0; i < triangles.Length; i += 3 ) {
			for (int j = 0; j < 6; j++) {
				// 每个三角形转换为3条线段, 每个顶点使用2次, 对应的顶点序列是: 0, 1, 1, 2, 2, 0, 通式: (j + 1) % 6 / 2, j 的范围: 1 ~ 5
				indices[triangles.Length + 2 * i + j] = triangles[i + (j + 1) % 6 / 2];
			}
		}
		return indices;
	}

	private void ForAllChildren(Transform transform, Action<Transform> action) {
		action.Invoke(transform);
		for (int i = 0; i < transform.childCount; i++) {
			ForAllChildren(transform.GetChild(i), action);
		}
	}
}

        运行效果：