D3D中的地形绘制基础（5）

13.6例子程序: Terrain

该例子是用一个包含高度信息的 RAW 文件创建一个地形，纹理和光源。用方向键在地形上行走。

fps.h:

fps.cpp:

    /*********************************************************************************
    PURPOISE:
        Wraps the code to compute and display the frames rendered per second.
    *********************************************************************************/

    #include <cstdio>
    #include "d3dUtility.h"
    #include "fps.h"

    #pragma warning(disable : 4996)

    cFpsCounter::cFpsCounter(IDirect3DDevice9* device)
    {
        m_device = device;

        D3DXFONT_DESC font_desc;
        ZeroMemory(&font_desc, sizeof (font_desc));

        font_desc.Height            = 25;         // in logical units
            font_desc.Width                = 12;         // in logical units
            font_desc.Weight            = 500;         // boldness, range 0(light) - 1000(bold)
            font_desc.Italic            = FALSE;
        font_desc.CharSet            = DEFAULT_CHARSET;
        font_desc.OutputPrecision    = 0;
        font_desc.Quality            = 0;
        font_desc.PitchAndFamily    = 0;

        strcpy(font_desc.FaceName, "Times New Roman");

        D3DXCreateFontIndirect(device, &font_desc, &m_font);

        m_frame_count   = 0;
        m_time_elapsed  = 0.0f;
        m_fps            = 0.0f;
        m_fps_string[0] = '\0';
    }

    cFpsCounter::~cFpsCounter()
    {
        safe_release<ID3DXFont*>(m_font);
    }

    void cFpsCounter::render(D3DCOLOR color, float time_delta,
                              int window_width, int window_height)
    {
         if (m_font == NULL)
             return ;

        m_frame_count++;
        m_time_elapsed += time_delta;

         if (m_time_elapsed >= 1.0f)
        {
            m_fps = m_frame_count / m_time_elapsed;

            sprintf(m_fps_string, "%f", m_fps);
            m_fps_string[8] = '\0';         // mark end of string

            m_time_elapsed = 0.0f;
            m_frame_count  = 0;
        }

        RECT rect = {0, 0, window_width, window_height};
        m_font->DrawText(NULL, m_fps_string, -1, &rect, DT_TOP | DT_LEFT, color);
    }

TerrainApp.cpp:

     /**************************************************************************************
      Renders a terrain and allows you to walk around it.
    **************************************************************************************/

    #include "d3dUtility.h"
    #include "camera.h"
    #include "terrain.h"
    #include "fps.h"

    #pragma warning(disable : 4100)

    const int WIDTH  = 640;
    const int HEIGHT = 480;

    IDirect3DDevice9*    g_device;
    cTerrain*            g_terrain;
    cCamera                g_camera(LAND_OBJECT);
    cFpsCounter*        g_fps_counter;
    bool                 g_draw_triangle;

    /////////////////////////////////////////////////////////////////////////////////////////////////// /

    bool setup()
    {
         // create the terrain

        D3DXVECTOR3 dir_to_light(0.0f, 1.0f, 0.0f);
        g_terrain = new cTerrain(g_device, "coastMountain64.raw", 64, 64, 10, 0.5f);
        g_terrain->generate_texture(&dir_to_light);

        g_fps_counter = new cFpsCounter(g_device);

         // set texture filters
            g_device->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
        g_device->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
        g_device->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);

         // set the projection matrix
        D3DXMATRIX proj;
        D3DXMatrixPerspectiveFovLH(&proj, D3DX_PI/2.0f, ( float )WIDTH/HEIGHT, 1.0f, 1000.0f);
        g_device->SetTransform(D3DTS_PROJECTION, &proj);

         return true ;
    }

    ////////////////////////////////////////////////////////////////////////////////////////////////////// /

    void cleanup()
    {
        delete g_terrain;
        delete g_fps_counter;
    }

    ////////////////////////////////////////////////////////////////////////////////////////////////////// /

    bool display( float time_delta)
    {
         // update the camera

         if (GetAsyncKeyState(VK_UP) & 0x80000f)
            g_camera.walk(100.0f * time_delta);

         if ( GetAsyncKeyState(VK_DOWN) & 0x8000f )
            g_camera.walk(-100.0f * time_delta);

         if ( GetAsyncKeyState(VK_LEFT) & 0x8000f )
            g_camera.yaw(-1.0f * time_delta);

         if ( GetAsyncKeyState(VK_RIGHT) & 0x8000f )
            g_camera.yaw(1.0f * time_delta);

         if ( GetAsyncKeyState('N') & 0x8000f )
            g_camera.strafe(-100.0f * time_delta);

         if ( GetAsyncKeyState('M') & 0x8000f )
            g_camera.strafe(100.0f * time_delta);

         if (GetAsyncKeyState('W') & 0x8000f)
            g_camera.pitch(1.0f * time_delta);

         if (GetAsyncKeyState('S') & 0x8000f)
            g_camera.pitch(-1.0f * time_delta);

         // set camera height
         float height = g_terrain->get_height(g_camera.m_pos.x, g_camera.m_pos.z);
        g_camera.m_pos.y = height + 5.0f;     // add height because we're standing up

        // update the view matrix representing the camera's new position/orientation
        D3DXMATRIX view_matrix;
        g_camera.get_view_matrix(&view_matrix);
        g_device->SetTransform(D3DTS_VIEW, &view_matrix);

         // render now

        g_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0x00000000, 1.0f, 0);

        g_device->BeginScene();

        D3DXMATRIX identity_matrix;
        D3DXMatrixIdentity(&identity_matrix);

        g_terrain->draw(&identity_matrix, g_draw_triangle);
        g_fps_counter->render(0xffffffff, time_delta, WIDTH, HEIGHT);

        g_device->EndScene();

        g_device->Present(NULL, NULL, NULL, NULL);

         return true ;
    }

    ////////////////////////////////////////////////////////////////////////////////////////////////////// /

    LRESULT CALLBACK wnd_proc(HWND hwnd, UINT msg, WPARAM word_param, LPARAM long_param)
    {
         switch (msg)
        {
         case WM_DESTROY:
            PostQuitMessage(0);
             break ;

         case WM_KEYDOWN:
             if (word_param == VK_ESCAPE)
                DestroyWindow(hwnd);

             if (word_param == VK_SPACE)
                g_draw_triangle = !g_draw_triangle;

             break ;
        }

         return DefWindowProc(hwnd, msg, word_param, long_param);
    }

    ////////////////////////////////////////////////////////////////////////////////////////////////////// /

    int WINAPI WinMain(HINSTANCE inst, HINSTANCE, PSTR cmd_line, int cmd_show)
    {
         if (! init_d3d(inst, WIDTH, HEIGHT, true , D3DDEVTYPE_HAL, &g_device))
        {
            MessageBox(NULL, "init_d3d() - failed.", 0, MB_OK);
             return 0;
        }

         if (! setup())
        {
            MessageBox(NULL, "Steup() - failed.", 0, MB_OK);
             return 0;
        }

        enter_msg_loop(display);

        cleanup();
        g_device->Release();

         return 0;
    }

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13.7 一些改进

Terrain读取顶点数据到一个很大的缓存，在多重的顶点缓存中划分地形结构，在速度和可测量性方面都十分有利。为我们提出一个问题：顶点缓存最大支持多大？回答是，这依赖于你的硬件。所以你必须先检测。

将地图划分为许多小的顶点缓存是重要的练习，然后将类似矩阵的数据结构编入索引，并且管理数据，这不需要引入新的概念。我们不必详细讨论它。简单的说，你基本上站在地形中一个我们叫做“blocks”的矩阵上,每个block是地形的一个矩形区域。另外，每个block区域（在它自己的顶点索引缓存中）的下方包含地形中的几何信息，为了画它在地形中的位置。

另外，你可以读取地形到一个很大的ID3DXMesh接口。使用D3D函数D3DXSplitMesh划分地形为许多小的Mesh,以下是D3DXSplitMesh函数原型：

void D3DXSplitMesh(

const LPD3DXMESH pMeshIn,

const DWORD *pAdjacencyIn,

const DWORD MaxSize,

const DWORD Options,

DWORD *pMeshesOut,

LPD3DXBUFFER *ppMeshArrayOut,

LPD3DXBUFFER *ppAdjacencyArrayOut,

LPD3DXBUFFER *ppFaceRemapArrayOut,

LPD3DXBUFFER *ppVertRemapArrayOut

);

这个函数将一个源Mesh划分多个小的Mesh,，pMeshIn参数是一个指针，指向想划分的Mesh，pAdjacencyIn指向一个邻接数组，MaxSize参数指定作为结果返回的最大顶点数，为返回的Meshe使用指定的创建标记，pMeshesOut参数返回ppMeshArrayOut数组中的Mesh数量，最后3个参数是可选的（可以指定为null），返回邻接信息的数组。

D3D中的地形绘制基础（5）