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=);
}; 

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=);
};  

#include "Skybox.h"  

CSkybox::CSkybox(IDirect3DDevice9 *pd3dDevice)
{
    m_pd3dDevice     = pd3dDevice;
    m_pTexture       = NULL;
    m_pIndexBuf      = NULL;
    m_pVertexBuf     = NULL;
    m_nNumVertices   = ;
    m_nNumLatitudes  = ;
    m_nNumLongitudes = ;
    m_nVertsPerLongi = ;
    m_nVertsPerLati  = ;
    m_fSkyboxRadius  = ;
}  

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  =  / nAlpha;            // 维度线的条数
    m_nNumLongitudes =   / nBeta;             // 经度线的条数
    m_nVertsPerLongi = m_nNumLatitudes + ;     // 每条经度线上的顶点数
    m_nVertsPerLati  = m_nNumLongitudes + ;    // 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, )))
        return FALSE;  

    SKYBOXVERTEX *pVertices = NULL;
    m_pVertexBuf->Lock(, , (void**)&pVertices, );  

    int nIndex = ;
    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 = ; row < m_nNumLongitudes+; row++)
    {
        for (int col = ; col < m_nNumLatitudes+; 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 *  *sizeof(WORD),
        D3DUSAGE_WRITEONLY, D3DFMT_INDEX16, D3DPOOL_MANAGED, &m_pIndexBuf, )))
        return FALSE;  

    WORD* pIndices = NULL;
    m_pIndexBuf->Lock(, , (void**)&pIndices, );  

    nIndex = ;
    for (int row = ; row < m_nNumLongitudes; row++)
    {
        for (int col = ; col < m_nNumLatitudes; col++)
        {
            pIndices[nIndex+] =   row   * m_nVertsPerLongi + col;
            pIndices[nIndex+] = (row+) * m_nVertsPerLongi + col;
            pIndices[nIndex+] = (row+) * m_nVertsPerLongi + col + ;  

            pIndices[nIndex+] =   row   * m_nVertsPerLongi + col;
            pIndices[nIndex+] = (row+) * m_nVertsPerLongi + col + ;
            pIndices[nIndex+] =   row   * m_nVertsPerLongi + col + ;
            nIndex += ;
        }
    }
    m_pIndexBuf->Unlock();  

    return TRUE;
}  

BOOL CSkybox::DrawSkybox(D3DXMATRIX *pMatWorld, bool bDrawFrame)
{
    //纹理模式渲染
    m_pd3dDevice->SetStreamSource(, m_pVertexBuf, , sizeof(SKYBOXVERTEX));
    m_pd3dDevice->SetFVF(SKYBOXVERTEX::FVF);
    m_pd3dDevice->SetIndices(m_pIndexBuf);
    m_pd3dDevice->SetTexture(, 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, , ,
        m_nNumVertices, , m_nNumVertices * );  

    m_pd3dDevice->SetTexture(, );
    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, , ,
            m_nNumVertices, , m_nNumVertices * );
        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 = ;
        //int MaxLatitude = 180;
        int MinLatitude = ;

        int MaxLongitude = ;
        int MinLongitude = ;

        int LaInterval = ;
        int LongInterval =;

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

        int TotalVertexes=;

        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 + ) * (this.Columns + );//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 = ;
            this.LongInterval = ;
            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 ) * , pDevice, Usage.WriteOnly, Pool.Default);
            this.indices = new int[(this.Columns ) * (this.Rows ) * ];//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 = , j=, index=;
            for (int a = ; a <= this.MaxLongitude; a += this.LongInterval)//经度
            {
                i = a / this.LongInterval;//用来遍历列
                for (int b = ; 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 -  && j <= this.Rows - )//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 *  + ] = i * this.Rows + j;
                        this.indices[index *  + ] = (i + ) * this.Rows + j;
                        this.indices[index *  + ] = i * this.Rows + (j + );

                        this.indices[index *  + ] = i * this.Rows + (j + );
                        this.indices[index *  + ] = (i + ) * this.Rows + j;
                        this.indices[index *  + ] = (i + ) * this.Rows + (j + );
                    }
                }
            }
            #endregion
            m_pVB.SetData(verts, , 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, , LockFlags.None);
        }

        public void Render(Microsoft.DirectX.Direct3D.Device pDevice)
        {
            pDevice.VertexFormat = CustomVertex.PositionTextured.Format;
            pDevice.SetStreamSource(, m_pVB, );
            pDevice.Indices = m_pIB;
            pDevice.SetTexture(, 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(, TextureStageStates.AlphaOperation, TextureOperation.SelectArg1.GetHashCode());
            pDevice.SetTextureStageState(, 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, , , (this.Rows + ) * (this.Columns + ), , indices.Length / );
            //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 = ; i < ; i++)
            {
                if (m_pTex!= null)
                {
                    m_pTex.Dispose();
                }
            }
        }
    }
}