Unity3D研究院编辑器之合并mesh引发的矩阵推导运算（三十四）

using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
#endif
public class CombineMesh : MonoBehaviour 
{
    public int lightmapIndex = -1;

    private void Awake()
    {
        //初始化设置烘焙贴图的index
        if (lightmapIndex >= 0)
        {
            if(TryGetComponent<MeshRenderer>(out var m))
            {
                m.lightmapIndex = lightmapIndex;
            }
        }
    }

#if UNITY_EDITOR
    [MenuItem("Tools/CombineMesh")]
    static void StartCombineMesh()
    {
        if (Selection.activeTransform)
        {
            MeshFilter[] meshFilters = Selection.activeTransform.GetComponentsInChildren<MeshFilter>();
            //计算父节点的中心点
            Vector3 centerPos = GetCenter(meshFilters);
            CombineInstance[] combine = new CombineInstance[meshFilters.Length];
            Material material=null; 
            int lightmap = -1;
            int i = 0;
            while (i < meshFilters.Length)
            {
                var meshRender = meshFilters[i].GetComponent<MeshRenderer>();
                if (meshRender)
                {
                    if (material == null)
                        material = meshRender.sharedMaterial;
                    if (material!= meshRender.sharedMaterial)
                    {
                        Debug.LogError("存在不同材质不予合并");
                        return;
                    }
                    if (lightmap == -1)
                        lightmap = meshRender.lightmapIndex;
                    if (lightmap != meshRender.lightmapIndex)
                    {
                        Debug.LogError("存在不同烘焙贴图不予合并");
                        return;
                    }
                    combine[i].mesh = meshFilters[i].sharedMesh;
                    //记录参与合批的lightmapOffset
                    combine[i].lightmapScaleOffset = meshRender.lightmapScaleOffset;
                    //每个参与合批mesh的矩阵与中心点进行偏移计算
                    Matrix4x4 matrix4X4 = meshFilters[i].transform.localToWorldMatrix;
                    matrix4X4.m03 -= centerPos.x;
                    matrix4X4.m13 -= centerPos.y;
                    matrix4X4.m23 -= centerPos.z;
                    combine[i].transform = matrix4X4;
                    i++;
                }
            }
            var go = new GameObject("combine", typeof(MeshFilter), typeof(MeshRenderer));
            go.transform.position = centerPos;
            go.AddComponent<CombineMesh>().lightmapIndex = lightmap;

            var mesh = new Mesh();
            mesh.CombineMeshes(combine, true, true, true);
            //合拼会自动生成UV3，但是我们并不需要，可以这样删除
            mesh.uv3 = null;
            AssetDatabase.CreateAsset(mesh, "Assets/combine.asset");
            go.GetComponent<MeshFilter>().sharedMesh = mesh;
            go.GetComponent<MeshRenderer>().sharedMaterial = material;
            if (go)
            {
                PrefabUtility.SaveAsPrefabAssetAndConnect(go, Application.dataPath + "/combine.prefab", InteractionMode.AutomatedAction);
            }
        }

        Vector3 GetCenter(Component[] components)
        {
            if (components != null && components.Length > 0)
            {
                Vector3 min = components[0].transform.position;
                Vector3 max = min;
                foreach (var comp in components)
                {
                    min = Vector3.Min(min, comp.transform.position);
                    max = Vector3.Max(max, comp.transform.position);
                }
                return min + ((max - min) / 2);
            }
            return Vector3.zero;
        }

    }
#endif

}

                    //每个参与合批mesh的矩阵与中心点进行偏移计算
                    Matrix4x4 matrix4X4 = meshFilters[i].transform.localToWorldMatrix;
                    matrix4X4.m03 -= centerPos.x;
                    matrix4X4.m13 -= centerPos.y;
                    matrix4X4.m23 -= centerPos.z;
                    combine[i].transform = matrix4X4;

using UnityEngine;

public class NewBehaviourScript : MonoBehaviour
{
    void Start()
    {

        float rotax = transform.rotation.eulerAngles.x * Mathf.Deg2Rad;
        float rotay = transform.rotation.eulerAngles.y * Mathf.Deg2Rad;
        float rotaz = transform.rotation.eulerAngles.z * Mathf.Deg2Rad;

        //由于Mathf.Sin 和 Mathf.Cos需要的是弧度，所以欧拉角需要乘以Mathf.Deg2Rad
        float sinx = Mathf.Sin(rotax);
        float cosx = Mathf.Cos(rotax);
        float siny = Mathf.Sin(rotay);
        float cosy = Mathf.Cos(rotay);
        float sinz = Mathf.Sin(rotaz);
        float cosz = Mathf.Cos(rotaz);

        //X轴旋转矩阵
        Matrix4x4 rx = Matrix4x4.identity;
        rx.m11 = cosx;  rx.m12 = -sinx;
        rx.m21 = sinx; rx.m22 = cosx;
        //Y轴旋转矩阵
        Matrix4x4 ry = Matrix4x4.identity;
        ry.m00 = cosy; ry.m02 = siny;
        ry.m20 = -siny; ry.m22 = cosy;
        //Z轴旋转矩阵
        Matrix4x4 rz = Matrix4x4.identity;
        rz.m00 = cosz; rz.m01 = -sinz;
        rz.m10 = sinz; rz.m11 = cosz;

        //注意旋转矩阵相乘的顺序，必须满足 Y * X * Z
        Matrix4x4 rall = ry * rx * rz;

        //缩放矩阵
        Matrix4x4 s = Matrix4x4.identity;
        s.m00 = transform.localScale.x;
        s.m11 = transform.localScale.y;
        s.m22 = transform.localScale.z;

        //位置矩阵
        Matrix4x4 p = Matrix4x4.identity;
        p.m03 = transform.position.x;
        p.m13 = transform.position.y;
        p.m23 = transform.position.z;


        //注意矩阵相乘的顺序，必须满足 位置矩阵 * 旋转矩阵 * 缩放矩阵
        Debug.Log(p*rall*s);

        //两个输出结果是完全相等的
        Debug.Log(transform.localToWorldMatrix);

    }

}