Unity将模型的世界坐标下的中心点归到模型中心

效果对比：
调整前：

调整后：

需求：由于建模时的疏忽或者网上找的一些测试模型不规范，会出现导入unity中，模型的世界坐标下的中心点与模型实际的位置差出很多。

方法一：改变模型原文件的网格位置，通过添加空父物体调整

#region 重置模型父物体和父父物体的中心点
            Bounds bounds = new Bounds(Vector3.zero, Vector3.zero);
            //获取所有MeshRenderer 包括子物体
            var mrs = transform.GetComponentsInChildren<MeshRenderer>(true);
            Vector3 center = Vector3.zero;
            for (int i = 0; i < mrs.Length; i++)
            {
    
    
                center += mrs[i].bounds.center;
                //Encapsulate函数重新计算bounds
                bounds.Encapsulate(mrs[i].bounds);
            }
            center /= mrs.Length;

            //设置父物体中心点
            GameObject obj = transform.parent.gameObject;
            transform.SetParent(obj.transform.parent);
            obj.transform.position = center;
            obj.transform.rotation = Quaternion.identity;
            transform.SetParent(obj.transform);

            //设置物体中心点
            List<Transform> list = new List<Transform>();
            for (int i = 0; i < transform.childCount; i++)
            {
    
    
                list.Add(transform.GetChild(i).transform);
                transform.GetChild(i).SetParent(obj.transform);
            }
            transform.localPosition = Vector3.zero;
            transform.localRotation = Quaternion.identity;
            for (int i = 0; i < list.Count; i++)
            {
    
    
                list[i].SetParent(transform);
            }
            #endregion

注意：物体中心点和父物体中心点的设置代码隐忍而异，看模型结构需求

方法二：通过改变模型原文件的网格位置来达到目的

 #region 重置模型的中心点 
            Vector3 position = transform.position;
            Quaternion quaternion = transform.rotation;
            Vector3 scale = transform.localScale;
            transform.position = Vector3.zero;
            transform.rotation = Quaternion.Euler(Vector3.zero);
            transform.localScale = Vector3.one;

            MeshFilter[] meshFilters = transform.GetComponentsInChildren<MeshFilter>();
            for (int i = 0; i < meshFilters.Length; i++)
            {
    
    
                MeshFilter meshFilter = meshFilters[i];
                Vector3 meshCenterPos = meshFilter.sharedMesh.bounds.center;
                Vector3 worldPos = meshFilter.transform.position;
                //模型中心和世界坐标的差值向量
                Vector3 offSet = worldPos - meshCenterPos;
                Vector3[] vectices = meshFilter.sharedMesh.vertices;
                for (int j = 0; j < vectices.Length; j++)
                {
    
    
                    vectices[j] += offSet;
                }
                meshFilter.sharedMesh.vertices = vectices;

                //重新构建mesh 
                meshFilter.sharedMesh.RecalculateBounds();
                meshFilter.sharedMesh.RecalculateNormals();
                meshFilter.sharedMesh.RecalculateTangents();
                //若最终坐标位置不对，可能由于原模型有旋转等造成，可根据实际调整坐标赋值。
                //meshFilter.transform.position = new Vector3(meshCenterPos.x, meshCenterPos.z, -meshCenterPos.y);
                meshFilter.transform.position = meshCenterPos;
            }

            transform.position = position;
            transform.rotation = quaternion;
            transform.localScale = scale;
            #endregion

注意：这里模型的位置必须Reset，这样才能保证计算准确。计算完以后，再把原位置赋值回去即可。

总结：因为需求，我们的模型都是代码生成的，所以最后我们采用了二者结合的方式。

/// <summary>
        /// 设置模型的中心点
        /// </summary>
        /// <param name="transform"></param>
        private void SetModelCenter(Transform transform)
        {
    
    
            #region 重置模型的中心点 
            Vector3 position = transform.position;
            Quaternion quaternion = transform.rotation;
            Vector3 scale = transform.localScale;
            transform.position = Vector3.zero;
            transform.rotation = Quaternion.Euler(Vector3.zero);
            transform.localScale = Vector3.one;

            MeshFilter[] meshFilters = transform.GetComponentsInChildren<MeshFilter>();
            for (int i = 0; i < meshFilters.Length; i++)
            {
    
    
                MeshFilter meshFilter = meshFilters[i];
                Vector3 meshCenterPos = meshFilter.sharedMesh.bounds.center;
                Vector3 worldPos = meshFilter.transform.position;
                //模型中心和世界坐标的差值向量
                Vector3 offSet = worldPos - meshCenterPos;
                Vector3[] vectices = meshFilter.sharedMesh.vertices;
                for (int j = 0; j < vectices.Length; j++)
                {
    
    
                    vectices[j] += offSet;
                }
                meshFilter.sharedMesh.vertices = vectices;

                //重新构建mesh 
                meshFilter.sharedMesh.RecalculateBounds();
                meshFilter.sharedMesh.RecalculateNormals();
                meshFilter.sharedMesh.RecalculateTangents();
                //若最终坐标位置不对，可能由于原模型有旋转等造成，可根据实际调整坐标赋值。
                //meshFilter.transform.position = new Vector3(meshCenterPos.x, meshCenterPos.z, -meshCenterPos.y);
                meshFilter.transform.position = meshCenterPos;
            }

            transform.position = position;
            transform.rotation = quaternion;
            transform.localScale = scale;
            #endregion

            #region 重置模型父物体和父父物体的中心点
            Bounds bounds = new Bounds(Vector3.zero, Vector3.zero);
            //获取所有MeshRenderer 包括子物体
            var mrs = transform.GetComponentsInChildren<MeshRenderer>(true);
            Vector3 center = Vector3.zero;
            for (int i = 0; i < mrs.Length; i++)
            {
    
    
                center += mrs[i].bounds.center;
                //Encapsulate函数重新计算bounds
                bounds.Encapsulate(mrs[i].bounds);
            }
            center /= mrs.Length;

            //设置父物体中心点
            GameObject obj = transform.parent.gameObject;
            transform.SetParent(obj.transform.parent);
            obj.transform.position = center;
            obj.transform.rotation = Quaternion.identity;
            transform.SetParent(obj.transform);

            //设置物体中心点
            List<Transform> list = new List<Transform>();
            for (int i = 0; i < transform.childCount; i++)
            {
    
    
                list.Add(transform.GetChild(i).transform);
                transform.GetChild(i).SetParent(obj.transform);
            }
            transform.localPosition = Vector3.zero;
            transform.localRotation = Quaternion.identity;
            for (int i = 0; i < list.Count; i++)
            {
    
    
                list[i].SetParent(transform);
            }
            #endregion
        }

参考博文：

https://blog.csdn.net/weixin_39562801/article/details/107842345