基于DirectX的半球形天空类的C++和C#实现

　　目前，天空绘制主要有三种方法：矩形天空、天空盒和球形天空。
　　(1)矩形天空使用一个与地面垂直或呈一定夹角的矩形表示天空，用接近于天空的颜色或云彩纹理贴于矩形上。这种方法简单易行，但需要不断调整视角或观察点来改变场景可视域，还会对运行效率造成一定影响。
　　(2)天空盒是构建一个包含场景的方盒来表示天空，然后在方盒四周和顶部贴上云彩纹理。但这种方法当视角对准两个面的边界时，能够明显看到交接痕迹。
　　(3)球形天空通常使用半球形网格模型来表示天空，并在半球形网格上贴上一幅云彩纹理，可以使半球形网格模型绕Y轴旋转来模拟动态效果。

半球形天空类的头文件:
#pragma once  #include <d3d9.h> #include <d3dx9.h> #ifndef SAFE_DELETE #define SAFE_DELETE(p) { if(p) { delete (p); (p)=NULL; } } #endif  #ifndef SAFE_RELEASE #define SAFE_RELEASE(p) { if(p) { (p)->Release(); (p)=NULL; } } #endif //-------------------------------------------------------------------------------------- // Name: class CSkybox // Desc: 球形地形 //--------------------------------------------------------------------------------------  class CSkybox { private: LPDIRECT3DDEVICE9 m_pd3dDevice; LPDIRECT3DTEXTURE9 m_pTexture; LPDIRECT3DINDEXBUFFER9 m_pIndexBuf; LPDIRECT3DVERTEXBUFFER9 m_pVertexBuf; INT m_nNumLatitudes; INT m_nNumLongitudes; INT m_nVertsPerLati; INT m_nVertsPerLongi; INT m_nNumVertices; // 顶点数  FLOAT m_fSkyboxRadius; // 半径  struct SKYBOXVERTEX { FLOAT _x, _y, _z; FLOAT _u, _v; SKYBOXVERTEX(FLOAT x, FLOAT y, FLOAT z, FLOAT u, FLOAT v) : _x(x), _y(y), _z(z), _u(u), _v(v) {} static const DWORD FVF = D3DFVF_XYZ | D3DFVF_TEX1; }; public: CSkybox(IDirect3DDevice9 *pd3dDevice); virtual ~CSkybox(void); public: BOOL LoadSkybox(LPCSTR pTextureFile); BOOL InitSkybox(INT nAlpha, INT nBeta, FLOAT nRadius); BOOL DrawSkybox(D3DXMATRIX *pMatWorld, bool bDrawFrame=0); }; 

半球形天空类的实现文件:

#pragma once  

  

#include <d3d9.h>  

#include <d3dx9.h>  

  

#ifndef SAFE_DELETE  

#define SAFE_DELETE(p)  { if(p) { delete (p); (p)=NULL; } }  

#endif   

#ifndef SAFE_RELEASE  

#define SAFE_RELEASE(p) { if(p) { (p)->Release(); (p)=NULL; } }  

#endif  

  

//--------------------------------------------------------------------------------------  

// Name: class CSkybox  

// Desc: 球形地形  

//--------------------------------------------------------------------------------------  

class CSkybox  

{  

private:  

    LPDIRECT3DDEVICE9       m_pd3dDevice;  

    LPDIRECT3DTEXTURE9      m_pTexture;  

    LPDIRECT3DINDEXBUFFER9  m_pIndexBuf;  

    LPDIRECT3DVERTEXBUFFER9 m_pVertexBuf;  

  

    INT     m_nNumLatitudes;  

    INT     m_nNumLongitudes;  

    INT     m_nVertsPerLati;  

    INT     m_nVertsPerLongi;  

    INT     m_nNumVertices;     // 顶点数  

    FLOAT   m_fSkyboxRadius;    // 半径  

  

    struct SKYBOXVERTEX  

    {  

        FLOAT _x, _y, _z;  

        FLOAT _u, _v;  

        SKYBOXVERTEX(FLOAT x, FLOAT y, FLOAT z, FLOAT u, FLOAT v)   

            : _x(x), _y(y), _z(z), _u(u), _v(v) {}  

        static const DWORD FVF = D3DFVF_XYZ | D3DFVF_TEX1;  

    };  

  

public:  

    CSkybox(IDirect3DDevice9 *pd3dDevice);  

    virtual ~CSkybox(void);  

  

public:  

    BOOL LoadSkybox(LPCSTR pTextureFile);  

    BOOL InitSkybox(INT nAlpha, INT nBeta, FLOAT nRadius);  

    BOOL DrawSkybox(D3DXMATRIX *pMatWorld, bool bDrawFrame=0);  

};  

#include "Skybox.h"  

  

CSkybox::CSkybox(IDirect3DDevice9 *pd3dDevice)  

{  

    m_pd3dDevice     = pd3dDevice;  

    m_pTexture       = NULL;  

    m_pIndexBuf      = NULL;  

    m_pVertexBuf     = NULL;  

    m_nNumVertices   = 0;  

    m_nNumLatitudes  = 0;  

    m_nNumLongitudes = 0;  

    m_nVertsPerLongi = 0;  

    m_nVertsPerLati  = 0;  

    m_fSkyboxRadius  = 0;  

}  

  

CSkybox::~CSkybox(void)  

{  

    SAFE_RELEASE(m_pTexture);  

    SAFE_RELEASE(m_pIndexBuf);  

    SAFE_RELEASE(m_pVertexBuf);  

}  

  

BOOL CSkybox::LoadSkybox(LPCSTR pTextureFile)   

{  

    // 加载天空纹理  

    if (FAILED(D3DXCreateTextureFromFile(m_pd3dDevice, pTextureFile, &m_pTexture)))  

        return FALSE;  

    return TRUE;  

}  

  

BOOL CSkybox::InitSkybox(INT nAlpha, INT nBeta, FLOAT fRadius)   

{  

    m_fSkyboxRadius  = fRadius;                 // 半球体的半径  

    m_nNumLatitudes  = 360 / nAlpha;            // 维度线的条数  

    m_nNumLongitudes =  90 / nBeta;             // 经度线的条数  

    m_nVertsPerLongi = m_nNumLatitudes + 1;     // 每条经度线上的顶点数  

    m_nVertsPerLati  = m_nNumLongitudes + 1;    // 每条维度线上的顶点数  

    m_nNumVertices   = m_nVertsPerLati * m_nVertsPerLongi;  

  

    // 计算天空的灵活顶点  

    if (FAILED(m_pd3dDevice->CreateVertexBuffer(m_nNumVertices * sizeof(SKYBOXVERTEX),   

        D3DUSAGE_WRITEONLY, SKYBOXVERTEX::FVF, D3DPOOL_MANAGED, &m_pVertexBuf, 0)))  

        return FALSE;  

  

    SKYBOXVERTEX *pVertices = NULL;  

    m_pVertexBuf->Lock(0, 0, (void**)&pVertices, 0);  

  

    int nIndex = 0;  

    FLOAT fAlpha = 2.0f * D3DX_PI * nAlpha / 360.0f;    // 经度角转换为弧度表示  

    FLOAT fBeta  = 2.0f * D3DX_PI * nBeta  / 360.0f;    // 维度角转换为弧度表示  

    for (int row = 0; row < m_nNumLongitudes+1; row++)   

    {  

        for (int col = 0; col < m_nNumLatitudes+1; col++)   

        {  

            // 计算顶点的坐标  

            pVertices[nIndex]._x = fRadius * cosf(row * fBeta) * cosf(col * fAlpha);   

            pVertices[nIndex]._y = fRadius * sinf(row * fBeta);  

            pVertices[nIndex]._z = fRadius * cosf(row * fBeta) * sinf(col * fAlpha);  

            // 计算顶点的纹理坐标  

            pVertices[nIndex]._u = col * fAlpha / (2.0f * D3DX_PI);  

            pVertices[nIndex]._v = row * fBeta  / (D3DX_PI / 2.0f);  

  

            nIndex++;  

        }  

    }  

    m_pVertexBuf->Unlock();  

  

    // 计算天空的顶点索引  

    if (FAILED(m_pd3dDevice->CreateIndexBuffer(m_nNumVertices * 6 *sizeof(WORD),   

        D3DUSAGE_WRITEONLY, D3DFMT_INDEX16, D3DPOOL_MANAGED, &m_pIndexBuf, 0)))  

        return FALSE;  

  

    WORD* pIndices = NULL;  

    m_pIndexBuf->Lock(0, 0, (void**)&pIndices, 0);  

  

    nIndex = 0;   

    for (int row = 0; row < m_nNumLongitudes; row++)   

    {  

        for (int col = 0; col < m_nNumLatitudes; col++)   

        {  

            pIndices[nIndex+0] =   row   * m_nVertsPerLongi + col;  

            pIndices[nIndex+1] = (row+1) * m_nVertsPerLongi + col;  

            pIndices[nIndex+2] = (row+1) * m_nVertsPerLongi + col + 1;  

  

            pIndices[nIndex+3] =   row   * m_nVertsPerLongi + col;  

            pIndices[nIndex+4] = (row+1) * m_nVertsPerLongi + col + 1;  

            pIndices[nIndex+5] =   row   * m_nVertsPerLongi + col + 1;  

            nIndex += 6;  

        }  

    }  

    m_pIndexBuf->Unlock();  

  

    return TRUE;  

}  

  

BOOL CSkybox::DrawSkybox(D3DXMATRIX *pMatWorld, bool bDrawFrame)   

{  

    //纹理模式渲染  

    m_pd3dDevice->SetStreamSource(0, m_pVertexBuf, 0, sizeof(SKYBOXVERTEX));  

    m_pd3dDevice->SetFVF(SKYBOXVERTEX::FVF);  

    m_pd3dDevice->SetIndices(m_pIndexBuf);  

    m_pd3dDevice->SetTexture(0, m_pTexture);  

  

    m_pd3dDevice->SetTransform(D3DTS_WORLD, pMatWorld);  

  

    m_pd3dDevice->SetRenderState(D3DRS_LIGHTING, FALSE);  

    m_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CW);  

  

    m_pd3dDevice->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0,   

        m_nNumVertices, 0, m_nNumVertices * 2);  

  

    m_pd3dDevice->SetTexture(0, 0);  

    m_pd3dDevice->SetRenderState(D3DRS_LIGHTING, TRUE);  

    m_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW);  

  

    //网格模式渲染  

    if (bDrawFrame)  

    {  

        m_pd3dDevice->SetRenderState(D3DRS_FILLMODE, D3DFILL_WIREFRAME);  

        m_pd3dDevice->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0,   

            m_nNumVertices, 0, m_nNumVertices * 2);  

        m_pd3dDevice->SetRenderState(D3DRS_FILLMODE, D3DFILL_SOLID);  

    }  

  

    return TRUE;  

}  

 

半形天空体的演示C#实现代码如下：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using Microsoft.DirectX;

using Microsoft.DirectX.Direct3D;

using Microsoft.DirectX.DirectInput;



namespace TerrainVIS

{

    class DomeSky

    {

        public IndexBuffer m_pIB;

        private int[] indices; //索引缓冲区的大小为。三角形总数：(Columns)X(Rows)X2，每个三角形需要3个顶点索引值。



        public VertexBuffer m_pVB;

        public Texture m_pTex;

        public float m_Radius=1f;  //定义球形天空的半径



        int MaxLatitude = 90;

        //int MaxLatitude = 180;

        int MinLatitude = 0;



        int MaxLongitude = 360;

        int MinLongitude = 0;



        int LaInterval = 6;

        int LongInterval =6;



        int Rows = 1;//划分的格网行数，代表高度。//真正的顶点的行数和列数比网格的行数和列数均大1。

        int Columns = 1;//划分的格网列数，代表宽度。



        int TotalVertexes=1;



        public int GetTotalVertexes()

        {

            this.Columns = (this.MaxLongitude - this.MinLongitude) / this.LongInterval;//在经度上分割得到格网的列数

            this.Rows = (this.MaxLatitude - this.MinLatitude) / this.LaInterval;//在纬度上分割得到格网的行数

            return (this.Rows + 1) * (this.Columns + 1);//真正的顶点的行数和列数比网格的行数和列数均大1。

        }



        /// <summary>

        /// 构造函数应该完成成员变量初始化和内存空间申请的任务

        /// </summary>

        /// <param name="pDevice"></param>

        /// <param name="L"></param>

        public DomeSky(Microsoft.DirectX.Direct3D.Device pDevice,float L)

        {

            this.m_pTex = null;

            this.m_Radius = L;

            this.LaInterval = 6;

            this.LongInterval = 6;

            this.TotalVertexes=GetTotalVertexes();//为了完成首尾对接需要申请

            this.m_pVB = new VertexBuffer(typeof(CustomVertex.PositionTextured), this.TotalVertexes, pDevice, Usage.Dynamic | Usage.WriteOnly, CustomVertex.PositionTextured.Format, Pool.Default);

            this.m_pIB = new IndexBuffer(typeof(int), (this.Columns ) * (this.Rows ) * 6, pDevice, Usage.WriteOnly, Pool.Default);

            this.indices = new int[(this.Columns ) * (this.Rows ) * 6];//申请指定大小的索引缓冲区

        }



        public void Create(Microsoft.DirectX.Direct3D.Device pDevice)

        {            

            #region 定义顶点数组

            CustomVertex.PositionTextured[] verts = new CustomVertex.PositionTextured[this.TotalVertexes];

            int i = 0, j=0, index=0;

            for (int a = 0; a <= this.MaxLongitude; a += this.LongInterval)//经度

            {

                i = a / this.LongInterval;//用来遍历列

                for (int b = 0; b <= this.MaxLatitude; b += this.LaInterval)//纬度

                {   

                    //把球面坐标转化成空间直角坐标，设置球半径为2，竖直角从天顶到天底为0~90度，水平角0~360度

                    j = b / this.LaInterval;//用来遍历行

                    index = i * this.Rows + j;

                    verts[index] = new CustomVertex.PositionTextured();

                    verts[index].X = Convert.ToSingle(this.m_Radius * Math.Sin((float)b / 180.0 * Math.PI) * Math.Cos((float)a / 180.0 * Math.PI));

                    verts[index].Y = Convert.ToSingle(this.m_Radius * Math.Sin((float)b / 180.0 * Math.PI) * Math.Sin((float)a / 180.0 * Math.PI));

                    verts[index].Z = Convert.ToSingle(this.m_Radius * Math.Cos((float)b / 180.0 * Math.PI));

                    //计算纹理坐标的方法一

                    //verts[index].Tu = (float)(a / this.LongInterval) / this.Columns;

                    //verts[index].Tv = (float)(b / this.LaInterval) / this.Rows;

                    //计算纹理坐标的方法一

                    verts[index].Tu = (float)a / this.MaxLongitude;//单位用度或者弧度做比值结果都一样

                    verts[index].Tv = (float)b / this.MaxLatitude;



                    if (i <= this.Columns - 1 && j <= this.Rows - 1)//从最后一行或者一列格网的前一个顶点即可索引下一个顶点，故次数限定范围。

                    {

                        this.indices[index * 6 + 0] = i * this.Rows + j;

                        this.indices[index * 6 + 1] = (i + 1) * this.Rows + j;

                        this.indices[index * 6 + 2] = i * this.Rows + (j + 1);



                        this.indices[index * 6 + 3] = i * this.Rows + (j + 1);

                        this.indices[index * 6 + 4] = (i + 1) * this.Rows + j;

                        this.indices[index * 6 + 5] = (i + 1) * this.Rows + (j + 1);

                    }

                }

            }        

            #endregion

            m_pVB.SetData(verts, 0, LockFlags.None);//设置顶点缓冲区的顶点数据为上面申请的顶点的数组中包含的数据

            m_pTex = TextureLoader.FromFile(pDevice, "DomeSky.jpg");

            m_pIB.SetData(this.indices, 0, LockFlags.None);

        }



        public void Render(Microsoft.DirectX.Direct3D.Device pDevice)

        {

            pDevice.VertexFormat = CustomVertex.PositionTextured.Format;

            pDevice.SetStreamSource(0, m_pVB, 0);

            pDevice.Indices = m_pIB;

            pDevice.SetTexture(0, m_pTex);



            //绘制半透明状态

            pDevice.SetRenderState(RenderStates.AlphaBlendEnable, true);

            pDevice.SetRenderState(RenderStates.BlendOperation, true);

            pDevice.SetRenderState(RenderStates.SourceBlend, Blend.SourceAlpha.GetHashCode());

            pDevice.SetRenderState(RenderStates.DestinationBlend, Blend.InvSourceAlpha.GetHashCode());

            //下面的代码用于多层纹理映射。在此不起作用。

            //pDevice.SetTextureStageState(0, TextureStageStates.AlphaOperation, TextureOperation.Modulate.GetHashCode());

            //pDevice.SetTextureStageState(0, TextureStageStates.ColorArgument1, TextureArgument.Diffuse.GetHashCode());

            pDevice.SetTextureStageState(0, TextureStageStates.AlphaOperation, TextureOperation.SelectArg1.GetHashCode());

            pDevice.SetTextureStageState(0, TextureStageStates.AlphaArgument1, TextureArgument.TextureColor.GetHashCode());

            pDevice.SetRenderState(RenderStates.MultisampleAntiAlias, true);//启用多重采样，反锯齿。

            //需要调用带索引的图元绘制函数

            pDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, (this.Rows + 1) * (this.Columns + 1), 0, indices.Length / 3);

            //绘制完毕应将及时关闭Alpha混合状态

            //pDevice.SetRenderState(RenderStates.AlphaBlendEnable, false);

        }

        public void Destroy()

        {

            if (m_pVB != null)

            {

                m_pVB.Dispose();

            }



            for (int i = 0; i < 5; i++)

            {

                if (m_pTex!= null)

                {

                    m_pTex.Dispose();

                }

            }

        }

    }

}