（一）mesh基礎

印度阿三17 2020-02-02

展開全文

概述

本篇為Unity Mesh基礎的第一篇，通過一個最基本的平面四邊形網(wǎng)格來進行闡述。在此之前先對網(wǎng)格（mesh）做一個簡介。網(wǎng)格為最基本的模型表達，通過點構成線，再由線構成三角形，最后由三角形構成面，然后通過材質來進行網(wǎng)格表面的表達，如陰影，貼圖等。Unity除了ui的mesh，其他都需要MeshFilter來確定網(wǎng)格形狀，通過Material以及MeshRenderer來進行網(wǎng)格渲染。

Mesh的組成

Mesh由頂點組成，再有三個頂點構成。所以Mesh必須定義頂點以及頂點如何構成三角形，這是最基本的三個要素，其次還需要定義uv來確定貼圖如何覆蓋在圖形表面，如果需要還需定義頂點的法線或者切向，法線跟光照有關，而切向則會影響紋理凹凸問題，本文以四邊形為例進行闡述。

四邊形頂點

頂點個數(shù)為4，即左下，右下，右上以及左上。size為正方向尺寸。

    protected override Vector3[] Vertices
    {
        get
        {
            Vector3[] vertices = new Vector3[4];
            vertices[0] = Vector3.zero * size;
            vertices[1] = Vector3.right * size;
            vertices[2] = new Vector3(1, 1, 0) * size;
            vertices[3] = Vector3.up * size;

            return vertices;
        }
    }

三角形排列

三角形排列為int類型數(shù)組，保存頂點的索引號，每三個組成一個三角形。下述代碼即為左下，左上，右下組成第一個三角形，剩下組成第二個三角形，排列順序為順時針方向。

    protected override int[] Triangles
    {
        get
        {
            int[] triangles = new int[6]
            {
                0,3,1,1,3,2
            };

            return triangles;
        }
    }

Mesh的uv

如果給網(wǎng)格賦值貼圖，則需要定義uv，如下定義則為圖片左下角對應mesh的左下角，右上角對應右上角。

    protected override Vector2[] Uvs
    {
        get
        {
            Vector2[] uvs = new Vector2[4];
            uvs[0] = new Vector2(0, 0);
            uvs[1] = new Vector2(1, 0);
            uvs[2] = new Vector2(1, 1);
            uvs[3] = new Vector2(0, 1);

            return uvs;
        }
    }

完整代碼

基類

基類主要是通過OnDrawGizmos來繪制頂點，利于更直觀觀察。

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

[RequireComponent(typeof(MeshFilter),typeof(MeshRenderer))]
public class CreateMeshBase : MonoBehaviour
{
    MeshFilter meshFilter;

    protected Mesh mesh;

    protected virtual Vector3[] Vertices { get; }
    protected virtual int[] Triangles { get; }
    protected virtual Vector3[] Normals { get; }
    protected virtual Vector2[] Uvs { get; }
    protected virtual string MeshName { get; }

    protected virtual void Start()
    {
        GetMeshFilter();
    }

    protected virtual void Reset()
    {
        GetMeshFilter();
    }

    protected virtual void OnValidate()
    {
        GetMeshFilter();
    }

    void GetMeshFilter()
    {
        if (meshFilter == null)
        {
            meshFilter = GetComponent<MeshFilter>();
            mesh = new Mesh();            
        }

        mesh.triangles = null;
        mesh.uv = null;
        mesh.vertices = null;

        mesh.name = MeshName;
        mesh.vertices = Vertices;
        mesh.triangles = Triangles;
        mesh.uv = Uvs;

        meshFilter.mesh = mesh;
    }

    private void OnDrawGizmos()
    {
        if (Vertices == null) return;

        Gizmos.color = Color.red;
        Gizmos.DrawSphere(Vector3.zero, 0.5f);

        Gizmos.color = Color.blue;

        for (int i = 0; i < Vertices.Length; i  )
        {
            Gizmos.DrawSphere(Vertices[i], 0.3f);
        }
    }
}

Quad參數(shù)

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

public class CreateQuad : CreateMeshBase
{
    public int size = 5;

    protected override Vector3[] Vertices
    {
        get
        {
            Vector3[] vertices = new Vector3[4];
            vertices[0] = Vector3.zero * size;
            vertices[1] = Vector3.right * size;
            vertices[2] = new Vector3(1, 1, 0) * size;
            vertices[3] = Vector3.up * size;

            return vertices;
        }
    }

    protected override int[] Triangles
    {
        get
        {
            int[] triangles = new int[6]
            {
                0,3,1,1,3,2
            };

            return triangles;
        }
    }

    protected override string MeshName
    {
        get
        {
            return "Simple quad";
        }
    }

    protected override Vector2[] Uvs
    {
        get
        {
            Vector2[] uvs = new Vector2[4];
            uvs[0] = new Vector2(0, 0);
            uvs[1] = new Vector2(1, 0);
            uvs[2] = new Vector2(1, 1);
            uvs[3] = new Vector2(0, 1);

            return uvs;
        }
    }
}