基于xbim在unity中生成模型

所需数据结构

根据上一篇文章，我们得知在解析wexbim时，我们主要获取了region,color,product,shapeInstance,faceTriangulation故我们要先构建他们相应的数据结构，这里我分别用了五个structure来储存他们。

//储存读取的region数据
public struct MyBimRegion
{
    public int population;
    public Vector3 position;
    public Vector3 scale;
    public XbimRegion bimRegion;
    public MyBimRegion(int population, float px, float py, float pz, float sx, float sy, float sz)
    {
        this.population = population;
        position = new Vector3(px, py, pz);
        scale = new Vector3(sx, sy, sz);
        bimRegion = new XbimRegion()
        {
            Population = population,
            Centre = new XbimPoint3D(px, py, pz),
            Size = new XbimVector3D(sx, sy, sz)
        };
    }
}

//储存读取的color数据
public struct MyBimColor
{
    public int styleLabel;
    public float r, g, b, a;
    public Color color;
    public XbimColour xbimColour;
    public MyBimColor(int label, float r, float g, float b, float a = 1)
    {
        styleLabel = label;
        this.r = r; this.g = g;
        this.b = b; this.a = a;
        color = new Color(r, g, b, a);
        xbimColour = new XbimColour(r, g, b, a);
    }
}

//储存读取的product数据
public struct MyBimProduct
{
    public int entityLabel;
    public short typeId;
    public Vector3 position;
    public Vector3 scale;
    public List<MyBimShape> shapes;

    public MyBimProduct(int label, short id, Vector3 pos, Vector3 scale)
    {
        entityLabel = label; 
        typeId = id;
        position = pos;
        this.scale = scale;
        shapes = new List<MyBimShape>();
    }

    public void AddShape(MyBimShape shape)
    {
        shapes.Add(shape);
    }
}

//储存读取的shapeInstance数据
public struct MyBimShape 
{
    public XbimShapeInstance shape;
    public int ifcProductLabel;
    public short ifcTypeId;
    public int instanceLabel;
    public int styleLabel;
    public List<MyBimTriangulation> triangulations;
    public XbimMatrix3D transform;
    public MyBimShape(int productLabel, short typeId, int instanceLabel,int styleLabel,XbimMatrix3D matrix)
    {
        this.ifcProductLabel = productLabel;
        this.ifcTypeId = typeId;
        this.instanceLabel = instanceLabel;
        this.styleLabel = styleLabel;
        this.triangulations = new List<MyBimTriangulation>();
        shape = new XbimShapeInstance(instanceLabel)
        {
            IfcProductLabel = productLabel,
            IfcTypeId = typeId,
            StyleLabel = styleLabel,
            Transformation = matrix
        };
        transform = matrix;
    }

    public void AddTriangulation(MyBimTriangulation ta)
    {
        triangulations.Add(ta);
    }
}

//储存读取的shapeTriangulation数据
public struct MyBimTriangulation
{
    public XbimShapeTriangulation bimTriangulation;
    public List<Vector3> vertices;

    public List<int> triangles;
    public List<Vector3> normals;
    public MyBimTriangulation(XbimShapeTriangulation triangulation, float scale, Vector3 offsite, XbimMatrix3D matrix = new XbimMatrix3D(), bool bMatrix = false)
    {
    	//判断是否需要对三角形进行几何操作
        if (bMatrix)
        {
            bimTriangulation = triangulation.Transform(matrix);
        }
        else
            bimTriangulation = triangulation;

        vertices = new List<Vector3>();
        triangles = new List<int>();
        normals = new List<Vector3>();
        foreach (var v in bimTriangulation.Vertices)
        {
            vertices.Add(new Vector3((float)v.X, (float)v.Y, (float)v.Z) / scale - offsite);
        }
        foreach(var f in bimTriangulation.Faces)
        {
            triangles.AddRange(f.Indices);
            foreach (var n in f.Normals)
            {
                normals.Add(new Vector3((float)n.Normal.X, (float)n.Normal.Y, (float)n.Normal.Z));
            }
        }
    }
}

存储读取的数据

而后在解析wexbim文件时用List把相应的数据储存起来。
tips1：在存储坐标数据时，记得除以最开始读取的meter值，meter代表了游戏中的一个坐标单位和真实世界中1米的对应比例，如果不除的话，模型可能过大
tips2：region的center坐标是整体模型的偏移量，如果想要每次模型的中心都在原点处记得对所有的坐标都减去region的center坐标

    List<MyBimColor> colors = new List<MyBimColor>();
    List<MyBimShape> shapeInstances = new List<MyBimShape>();
    List<MyBimTriangulation> triangulations = new List<MyBimTriangulation>();
    List<MyBimRegion> regions = new List<MyBimRegion>();
    List<MyBimProduct> products = new List<MyBimProduct>();

在for循环解析wexbim文件时，将对应的数据存储其中方便之后的模型重建。
这里主要讲一下shapeInstance的存储。

if (shapeRepetition > 1)
{
	List<MyBimShape> myshapes = new List<MyBimShape>();
	for (int j = 0; j < shapeRepetition; j++)
	{
	//读取数据
	var ifcProductLabel = br.ReadInt32();
	var ifcTypeId = br.ReadInt16();
    var instanceLabel = br.ReadInt32();
    var styleLabel = br.ReadInt32();
    var transform = XbimMatrix3D.FromArray(br.ReadBytes(sizeof(double) * 16));
    
	//将读取的shapeInstance添加到list中，并根据label获得他的product
	myShape = new MyBimShape(ifcProductLabel, ifcTypeId, instanceLabel, styleLabel, transform);
	shapeInstances.Add(myShape);
    myshapes.Add(myShape);
    var p = products.Find(product => product.entityLabel == ifcProductLabel);
    p.AddShape(myShape);
	}
    var triangulation = br.ReadShapeTriangulation();
    //给这些重复的shapeInstance分别添加对应的三角形，并在三角形初始化时进行几何操作
	foreach (var ms in myshapes)
	{
		var tri = new MyBimTriangulation(triangulation, scale, offsite, ms.transform, true);
		ms.AddTriangulation(tri);
		triangulations.Add(tri);
	}
}

由于shapeInstance中含有较多的label和id故需要以它为中心把其它数据给连接起来。
因为shapeInstance相当于是product的一个部分，故在shapeInstance初始化时就把它添加给对应的prooduct。
同时shapeInstance要包含相应的mesh信息，故在读取triangulation时，也将对应的shapeInstance添加对应的triangulation。

模型的生成

模型的生成主要依靠的是unity的mesh类。方法如下：

遍历products，生成相应的空的gameObject（物体名字可为product.EntityLabel方便后面查找使用）
再遍历product.shapes，生成相应的带有mesh的gameObject。并将这些新生成的gameObject的父对象设置为对应的product的gameObject
再将所有的product放置在一个空物体下，旋转(-90,0,0)的欧拉角。这是因为ifc文件是z轴向上，而unity则是y轴向上。

代码如下：

    List<GameObject> productGO = new List<GameObject>();
    GameObject mainGO;
    public void GenerateProduct(MyBimProduct product)
    {
        var go = new GameObject
        {
            name = product.entityLabel.ToString()
        };
        go.transform.position = product.position;
        go.transform.localScale = product.scale;
        productGO.Add(go);
        foreach (var s in product.shapes)
            GenerateShape(s);
        go.transform.parent = mainGO.transform;
    }

    private void GenerateShape(MyBimShape shape)
    {
        GameObject shapeGO = new GameObject(shape.instanceLabel.ToString());
        var go = productGO.Find(p => p.name == shape.ifcProductLabel.ToString());
        shapeGO.transform.parent = go.transform;

		//添加mesh
        var mf = shapeGO.AddComponent<MeshFilter>();
        var mesh = mf.mesh;
        foreach(var tri in shape.triangulations)
        {
            mesh.vertices = tri.vertices.ToArray();
            mesh.triangles = tri.triangles.ToArray();
            mesh.Optimize();
            mesh.RecalculateNormals();
        }
        
        //添加texture
        var mr = shapeGO.AddComponent<MeshRenderer>();
        var mat = new Material(Shader.Find("Standard"));     
        var c = colors.Find(cl => cl.styleLabel == shape.styleLabel);
        mat.color = c.color;
        mr.material = mat;  
    }

在添加mesh的时候我只是读取了triangulation的vertices和triangles这两个值，并未读取当时存储的normals。

这是因为：wex在存储法线时是按照一个面一个面的存储法线，这就导致了如果这个点是被多个面共享的话，那么这个点的法线就被多次存储，即tri.vertices.Count<=tri.normals.Count但unity中mesh.vertices.Count==mesh.normals.Count，如不相等会报错。故在这里使用了unity的mesh.RecalculateNormals()方法，发现效果还不错就先暂时这样解决，如果以后有时间会进一步修改。

最后整体在start方法中的调用如下：

    void Start()
    {
        mainGO = new GameObject();
        ReadWexbimFile(fileName);
        foreach (var product in products)
            GenerateProduct(product);
        mainGO.transform.rotation = Quaternion.Euler(-90, 0, 0);
    }