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創(chuàng)建3D圖形引擎（4）

本篇是創(chuàng)建3D圖形引擎（3）的續(xù)篇，3D圖形引擎的代碼以創(chuàng)建游戲內(nèi)核中編寫的代碼為基礎(chǔ)進(jìn)行開發(fā)。

將三維物體添加到世界中

盲目地繪制成千的物體而沒有執(zhí)行任何的剪切，是導(dǎo)致在圖形-渲染通道中時(shí)間延遲的一個(gè)主要原因。需要再次使用視錐以快速確定哪些物體位于視野中，為了確定哪些物體是可見的，可將每個(gè)三維物體包圍到一個(gè)可見的球體中，稱之為框界球體（bounding sphere）。

下圖演示了框界球體和視錐的運(yùn)用，它展示了一個(gè)場(chǎng)景，其中有三個(gè)物體和一個(gè)視錐，每個(gè)網(wǎng)格模型都有一個(gè)可見的框界球體圍繞著它。當(dāng)一個(gè)球體位于構(gòu)成視錐的6個(gè)平面前時(shí)，它就被認(rèn)為是可見的。可以看出僅兩個(gè)位于視錐中的物體是可見的，而另一個(gè)物體完全位于視錐外，繪制時(shí)能完全跳過那個(gè)位于視錐之外的物體。為了實(shí)現(xiàn)這一點(diǎn)，必須計(jì)算每個(gè)物體的框界球體，然后檢測(cè)球體是否位于視錐之內(nèi)。

網(wǎng)格模型的碰撞

為了檢測(cè)一個(gè)多邊形是否堵塞了節(jié)點(diǎn)之間的路徑，可以在兩個(gè)節(jié)點(diǎn)發(fā)射一條想象中的射線，以檢測(cè)它們是否與一個(gè)平面相交。如下圖所示：

有一個(gè)功能函數(shù)負(fù)責(zé)執(zhí)行交集的測(cè)試，以確保射線與平面的相交點(diǎn)位于多邊形內(nèi)，并給出那個(gè)相交點(diǎn)的確切坐標(biāo)，同時(shí)顯示從射線的開始點(diǎn)到相交點(diǎn)的距離長(zhǎng)度，它是一個(gè)非常有用的功能函數(shù)。

Determines if a ray intersects with a mesh.

HRESULT D3DXIntersect(
  LPD3DXBASEMESH pMesh,
  CONST D3DXVECTOR3 * pRayPos,
  CONST D3DXVECTOR3 * pRayDir,
  BOOL * pHit,
  DWORD * pFaceIndex,
  FLOAT * pU,
  FLOAT * pV,
  FLOAT * pDist,
  LPD3DXBUFFER * ppAllHits,
  DWORD * pCountOfHits
);

Parameters

pMesh: [in] Pointer to an ID3DXBaseMesh interface, representing the mesh to be tested.
pRayPos: [in] Pointer to a D3DXVECTOR3 structure, specifying the point where the ray begins.
pRayDir: [in] Pointer to a D3DXVECTOR3 structure, specifying the direction of the ray.
pHit: [out] Pointer to a BOOL. If the ray intersects a triangular face on the mesh, this value will be set to TRUE. Otherwise, this value is set to FALSE.
pFaceIndex: [out] Pointer to an index value of the face closest to the ray origin, if pHit is TRUE.
pU: [out] Pointer to a barycentric hit coordinate, U.
pV: [out] Pointer to a barycentric hit coordinate, V.
pDist: [out] Pointer to a ray intersection parameter distance.
ppAllHits: [out] Pointer to an ID3DXBuffer object, containing an array of D3DXINTERSECTINFO structures.
pCountOfHits: [out] Pointer to a DWORD that contains the number of entries in the ppAllHits array.

Return Values

If the function succeeds, the return value is D3D_OK. If the function fails, the return value can be: E_OUTOFMEMORY.

Remarks

The D3DXIntersect function provides a way to understand points in and around a triangle, independent of where the triangle is actually located. This function returns the resulting point by using the following equation: V1 + U(V2 - V1) + V(V3 - V1).

Any point in the plane V1V2V3 can be represented by the barycentric coordinate (U,V). The parameter U controls how much V2 gets weighted into the result, and the parameter V controls how much V3 gets weighted into the result. Lastly, the value of [1 - (U + V)] controls how much V1 gets weighted into the result.

Barycentric coordinates are a form of general coordinates. In this context, using barycentric coordinates represents a change in coordinate systems. What holds true for Cartesian coordinates holds true for barycentric coordinates.

Barycentric coordinates define a point inside a triangle in terms of the triangle's vertices. For a more in-depth description of barycentric coordinates, see Mathworld's Barycentric Coordinates Description.

我們編寫一個(gè)函數(shù)來檢測(cè)一條線段是否與一個(gè)網(wǎng)格中的三角形面相交。

//------------------------------------------------------------------------------
// Check if a polygon blocks path from start to end.
//------------------------------------------------------------------------------
BOOL is_ray_intersect_mesh(LPD3DXBASEMESH mesh,
                           float x_start, float y_start, float z_start,
                           float x_end, float y_end, float z_end,
                           float* distance)
{
    float x_diff, y_diff, z_diff;

    x_diff = x_end - x_start;
    y_diff = y_end - y_start;
    z_diff = z_end - z_start;

    D3DXVECTOR3 ray_pos(x_start, y_start, z_start);

    D3DXVECTOR3 ray_dir;
    D3DXVec3Normalize(&ray_dir, &D3DXVECTOR3(x_diff, y_diff, z_diff));

    BOOL is_hit;
    float u, v, dist;
    DWORD face_index;

    // determins if a ray intersects with a mesh
    D3DXIntersect(mesh, &ray_pos, &ray_dir, &is_hit, &face_index, &u, &v, &dist, NULL, NULL);

    if(is_hit)
    {
        float ray_length = (float) sqrt(x_diff * x_diff + y_diff * y_diff + z_diff * z_diff);

        if(dist > ray_length)
            return FALSE;
        else
        {
            if(distance != NULL)
                *distance = dist;
        }
    }

    return TRUE;
}

在一個(gè)多邊形層次中運(yùn)用碰撞檢測(cè)的另一個(gè)好處就是可以使物體隨著其下多邊形變化的高度而變化。換句話說，可以使物體永遠(yuǎn)在多邊形上移動(dòng)，這樣就能在一個(gè)三維建模軟件里繪制層次，而不用定義哪些區(qū)域是物體可以“行走”的，因?yàn)槎噙呅尉褪悄切﹨^(qū)域，這使得四叉樹和八叉樹網(wǎng)格模型的處理更加容易。

可通過下面這三個(gè)函數(shù)來執(zhí)行物體與多邊形的相交測(cè)試：

//------------------------------------------------------------------------------
// Get closest height above or below point.
//------------------------------------------------------------------------------
float get_closest_height(LPD3DXBASEMESH mesh, float x_pos, float y_pos, float z_pos)
{
    float y_above, y_below;

    y_above = get_closest_height_above(mesh, x_pos, y_pos, z_pos);
    y_below = get_closest_height_below(mesh, x_pos, y_pos, z_pos);

    if(fabs(y_above - y_pos) < fabs(y_below - y_pos))
        return y_above;

    return y_below;
}

//------------------------------------------------------------------------------
// Get closet height below point.
//------------------------------------------------------------------------------
float get_closest_height_below(LPD3DXBASEMESH mesh, float x_pos, float y_pos, float z_pos)
{
    BOOL is_hit;
    float u, v, dist;
    DWORD face_index;

    D3DXVECTOR3 ray_pos(x_pos, y_pos, z_pos);
    D3DXVECTOR3 ray_dir(0.0f, -1.0f, 0.0f);

    D3DXIntersect(mesh, &ray_pos, &ray_dir, &is_hit, &face_index, &u, &v, &dist, NULL, NULL);

    if(is_hit)
        return y_pos - dist;

    return y_pos;
}

//------------------------------------------------------------------------------
// Get closet height above point.
//------------------------------------------------------------------------------
float get_closest_height_above(LPD3DXBASEMESH mesh, float x_pos, float y_pos, float z_pos)
{
    BOOL is_hit;
    float u, v, dist;
    DWORD face_index;

    D3DXVECTOR3 ray_pos(x_pos, y_pos, z_pos);
    D3DXVECTOR3 ray_dir(0.0f, 1.0f, 0.0f);

    D3DXIntersect(mesh, &ray_pos, &ray_dir, &is_hit, &face_index, &u, &v, &dist, NULL, NULL);

    if(is_hit)
        return y_pos + dist;

    return y_pos;
}

為了方便，在NODE_TREE_MESH類中繼續(xù)封裝這些函數(shù)：

//------------------------------------------------------------------------------
// Get closest height above or below point.
//------------------------------------------------------------------------------
float NODE_TREE_MESH::get_closest_height(float x_pos, float y_pos, float z_pos)
{
    return ::get_closest_height(m_root_mesh->m_mesh, x_pos, y_pos, z_pos);
}

//------------------------------------------------------------------------------
// Get closest height below point.
//------------------------------------------------------------------------------
float NODE_TREE_MESH::get_closest_height_below(float x_pos, float y_pos, float z_pos)
{
    return ::get_closest_height_below(m_root_mesh->m_mesh, x_pos, y_pos, z_pos);
}

//------------------------------------------------------------------------------
// Get closest height above point.
//------------------------------------------------------------------------------
float NODE_TREE_MESH::get_closest_height_above(float x_pos, float y_pos, float z_pos)
{
    return ::get_closest_height_above(m_root_mesh->m_mesh, x_pos, y_pos, z_pos);
}

//------------------------------------------------------------------------------
// Check if a polygon blocks path from start to end.
//------------------------------------------------------------------------------
BOOL NODE_TREE_MESH::is_ray_intersect_mesh(float x_start, float y_start, float z_start,
                                     float x_end, float y_end, float z_end,
                                     float* distance)
{
    return ::is_ray_intersect_mesh(m_root_mesh->m_mesh,
                             x_start, y_start, z_start,
                             x_end, y_end, z_end,
                             distance);
}

當(dāng)網(wǎng)格模型發(fā)生碰撞時(shí)

除了檢測(cè)物體網(wǎng)格模型與構(gòu)造世界的網(wǎng)格模型之間的碰撞，還需要知道較小網(wǎng)格模型碰撞的情況。舉個(gè)例子，如果不希望角色穿透其他的角色，就需要結(jié)合物體和物體之間（object-to-object）的碰撞檢測(cè)。進(jìn)行操作前需要了解一些事情，包括框界球體使用的知識(shí)。如下圖所示，其顯示了兩個(gè)怪物，它們都有長(zhǎng)長(zhǎng)的尾巴，那些尾巴影響了網(wǎng)格模型的框界球體的整體尺寸，為了包圍住整個(gè)網(wǎng)格模型（包括尾巴），球體將會(huì)很大。如果將這兩個(gè)怪物移動(dòng)到下圖所示的位置，會(huì)看到這兩個(gè)框界球體相交，但怪物并沒有那么靠近。

盡管有許多辦法解決大型框界球體問題，但有一種快速執(zhí)行的方法。取代使用網(wǎng)格模型的框界球體，而是為每個(gè)網(wǎng)格模型計(jì)算自己的框界球體半徑，通過計(jì)算框界球體的半徑，可以快速調(diào)節(jié)它以覆蓋網(wǎng)格模型確實(shí)需要的空間。

我們編寫一個(gè)函數(shù)來檢測(cè)兩個(gè)框界球體是否相交：

//------------------------------------------------------------------------------
// Check if two spheres intersect.
//------------------------------------------------------------------------------
BOOL is_tow_sphere_intersect(float x_center_1, float y_center_1, float z_center_1,
                             float radius1,
                             float x_center_2, float y_center_2, float z_center_2,
                             float radius2)
{
    float x_diff, y_diff, z_diff, dist;

    // calculate distance between two sphere center]

    x_diff = fabs(x_center_2 - x_center_1);
    y_diff = fabs(y_center_2 - y_center_1);
    z_diff = fabs(z_center_2 - z_center_1);

    dist = (float) sqrt(x_diff * x_diff + y_diff * y_diff + z_diff * z_diff);

    // if two spheres intersect, retuen TRUE.
    if(dist <= radius1 + radius2)
        return TRUE;

    return FALSE;
}

天框的使用

天框（sky box）是一種圍繞觀察者進(jìn)行紋理映射的三維立方體的圖形技術(shù)，渲染一個(gè)天框時(shí)，觀察點(diǎn)總是定于中心位置，以便用戶始終能夠看到方框內(nèi)部紋理映射的表面，這種技術(shù)能夠制造出一種世界圍繞用戶的效果，如下圖所示：

天框是非常容易是實(shí)現(xiàn)，只需一個(gè)立方體網(wǎng)格模型（其表面朝向里面）即可，通過一個(gè)頂點(diǎn)緩沖區(qū)存儲(chǔ)立方體網(wǎng)格模型會(huì)非常不錯(cuò)。至于紋理，可以使用多達(dá)6個(gè)的紋理，每個(gè)表面一個(gè)紋理。網(wǎng)格模型并不需要很大，僅20.0單元大小的立方體就行了。紋理大小應(yīng)該為256 x 256或者更高，較小的紋理將出現(xiàn)拉伸而且不生動(dòng)。

創(chuàng)建一個(gè)天框類

SKY_BOX負(fù)責(zé)控制天框的每個(gè)方面，從創(chuàng)建渲染盒子所使用的頂點(diǎn)緩沖區(qū)，到渲染時(shí)所使用的紋理。

定義：

enum SKY_BOX_SIDES  { TOP = 0, BOTTOM, LEFT, RIGHT, FRONT, BACK };

//=====================================================================================
// This calss encapsulate how to make sky box.
//=====================================================================================
typedef class SKY_BOX
{
private:
    typedef struct SKY_BOX_VERTEX
    {
        float x, y, z;
        float u, v;
    } *SKY_BOX_VERTEX_PTR;

    #define SKY_BOX_FVF (D3DFVF_XYZ | D3DFVF_TEX1)

private:
    GRAPHICS_PTR    m_graphics;         // parent GRAPHICS object
    TEXTURE         m_textures[6];      // face texture (0 - 5)
    VERTEX_BUFFER   m_vertex_buffer;    // mesh vertex buffer
    WORLD_POSITION  m_pos;              // sky box position

public:
    SKY_BOX();
    ~SKY_BOX();

    BOOL create(GRAPHICS_PTR graphics);
    void free();

    BOOL load_texture(short side, pcstr filename, D3DCOLOR transparent = 0, D3DFORMAT format = D3DFMT_UNKNOWN);

    void rotate(float x_rot, float y_rot, float z_rot);
    void rotate_rel(float x_rot, float y_rot, float z_rot);

    BOOL render(CAMERA_PTR camera, BOOL alpha_blend = FALSE);
} *SKY_BOX_PTR;

實(shí)現(xiàn):

//----------------------------------------------------------------------------------
// Constructor, initialize member data.
//----------------------------------------------------------------------------------
SKY_BOX::SKY_BOX()
{
    m_graphics = NULL;
}

//----------------------------------------------------------------------------------
// Destructor, release allocated resource.
//----------------------------------------------------------------------------------
SKY_BOX::~SKY_BOX()
{
    free();
}

//----------------------------------------------------------------------------------
// Release allocated resource.
//----------------------------------------------------------------------------------
void SKY_BOX::free()
{
    m_graphics = NULL;

    for(short i = 0; i < 6; i++)
        m_textures[i].free();

    m_vertex_buffer.free();
}

//----------------------------------------------------------------------------------
// Create a sky box class object.
//----------------------------------------------------------------------------------
BOOL SKY_BOX::create(GRAPHICS_PTR graphics)
{
    SKY_BOX_VERTEX verts[24] = {
        { -10.0f,  10.0f, -10.0f, 0.0f, 0.0f },  // Top
        {  10.0f,  10.0f, -10.0f, 1.0f, 0.0f },
        { -10.0f,  10.0f,  10.0f, 0.0f, 1.0f },
        {  10.0f,  10.0f,  10.0f, 1.0f, 1.0f },

        { -10.0f, -10.0f,  10.0f, 0.0f, 0.0f },  // Bottom
        {  10.0f, -10.0f,  10.0f, 1.0f, 0.0f },
        { -10.0f, -10.0f, -10.0f, 0.0f, 1.0f },
        {  10.0f, -10.0f, -10.0f, 1.0f, 1.0f },

        { -10.0f,  10.0f, -10.0f, 0.0f, 0.0f },  // Left
        { -10.0f,  10.0f,  10.0f, 1.0f, 0.0f },
        { -10.0f, -10.0f, -10.0f, 0.0f, 1.0f },
        { -10.0f, -10.0f,  10.0f, 1.0f, 1.0f },

        {  10.0f,  10.0f,  10.0f, 0.0f, 0.0f },  // Right
        {  10.0f,  10.0f, -10.0f, 1.0f, 0.0f },
        {  10.0f, -10.0f,  10.0f, 0.0f, 1.0f },
        {  10.0f, -10.0f, -10.0f, 1.0f, 1.0f },

        { -10.0f,  10.0f,  10.0f, 0.0f, 0.0f },  // Front
        {  10.0f,  10.0f,  10.0f, 1.0f, 0.0f },
        { -10.0f, -10.0f,  10.0f, 0.0f, 1.0f },
        {  10.0f, -10.0f,  10.0f, 1.0f, 1.0f },

        {  10.0f,  10.0f, -10.0f, 0.0f, 0.0f },  // Back
        { -10.0f,  10.0f, -10.0f, 1.0f, 0.0f },
        {  10.0f, -10.0f, -10.0f, 0.0f, 1.0f },
        { -10.0f, -10.0f, -10.0f, 1.0f, 1.0f },
    };

    free();     // free a prior sky box

    // error checking
    if((m_graphics = graphics) == NULL)
        return FALSE;

    // create the vertex buffer (and copy over sky box vertices)
    if(m_vertex_buffer.create(m_graphics, 24, sizeof(SKY_BOX_VERTEX), SKY_BOX_FVF))
        m_vertex_buffer.set(0, 24, (void*)verts);

    // rotate the sky box into default orientation
    rotate(0.0f, 0.0f, 0.0f);

    return TRUE;
}

//----------------------------------------------------------------------------------
// Set a specific side's texture map, allow for transparent and storage format changes.
//----------------------------------------------------------------------------------
BOOL SKY_BOX::load_texture(short side, pcstr filename, D3DCOLOR transparent, D3DFORMAT format)
{
    // error checking
    if(m_graphics == NULL || side < 0 || side > 5)
        return FALSE;

    m_textures[side].free();    // free prior texture

    return m_textures[side].load(m_graphics, filename, transparent, format);
}

//----------------------------------------------------------------------------------
// Rotate box to an absolute rotation.
//----------------------------------------------------------------------------------
void SKY_BOX::rotate(float x_rot, float y_rot, float z_rot)
{
    m_pos.rotate(x_rot, y_rot, z_rot);
}

//----------------------------------------------------------------------------------
// Rotate box to an relative rotation.
//----------------------------------------------------------------------------------
void SKY_BOX::rotate_rel(float x_rot, float y_rot, float z_rot)
{
    m_pos.rotate_rel(x_rot, y_rot, z_rot);
}

//----------------------------------------------------------------------------------
// Render the sky box (using optional alpha-blending) and using current view
// transformation from Camera.
//----------------------------------------------------------------------------------
BOOL SKY_BOX::render(CAMERA_PTR camera, BOOL alpha_blend)
{
    // error checking
    if(m_graphics == NULL || camera == NULL)
        return FALSE;

    // position sky box around viewer
    m_pos.move(camera->get_x_pos(), camera->get_y_pos(), camera->get_z_pos());
    m_graphics->set_world_position(&m_pos);

    // enable alpha testing and alpha blending

    m_graphics->enable_alpha_blending(TRUE);

    if(alpha_blend)
        m_graphics->enable_alpha_blending(TRUE, D3DBLEND_SRCCOLOR, D3DBLEND_DESTCOLOR);

    // draw each layer
    for(short i = 0; i < 6; i++)
    {
        if(m_textures[i].is_loaded())
        {
            m_graphics->set_texture(0, &m_textures[i]);
            m_vertex_buffer.render(i * 4, 2, D3DPT_TRIANGLESTRIP);
        }
    }

    // disable alpha testing and alpha blending

    m_graphics->enable_alpha_blending(FALSE);

    if(alpha_blend)
        m_graphics->enable_alpha_blending(FALSE);

    return TRUE;
}

測(cè)試代碼：

/************************************************************************************
PURPOSE:
     node tree mesh test.
************************************************************************************/

#include "core_global.h"
#include "frustum.h"
#include "node_tree.h"
#include "sky_box.h"

class APP : public APPLICATION
{
public:
    APP()
    {
        _width  = 640;
        _height = 480;

        APPLICATION::_x_pos = (get_screen_width()  - _width) / 2;
        APPLICATION::_y_pos = (get_screen_height() - _height) / 4;

        _style = WS_BORDER | WS_CAPTION | WS_MINIMIZEBOX | WS_SYSMENU;

        strcpy(_class_name, "node tree class");
        strcpy(_caption, "node tree demo");
    }

    BOOL init()
    {
        // initialize graphics and set display mode
        _graphics.init();
        _graphics.set_mode(get_hwnd(), TRUE, TRUE);
        _graphics.set_perspective(D3DX_PI / 4, 1.3333f, 1.0f, 10000.0f);

        show_mouse(TRUE);

        // enable lighting and setup light

        _graphics.enable_lighting(TRUE);
        _graphics.set_ambient_light(24, 24, 24);
        _graphics.enable_light(0, TRUE);

        _light.set_attenuation_0(0.4f);
        _light.set_range(1000.0f);

        // initialize input and input device
        _input.init(get_hwnd(), get_inst());
        _keyboard.create(&_input, KEYBOARD);
        _mouse.create(&_input, MOUSE, TRUE);

        // load the mesh and create a nodetree mesh from it

        if(! _mesh.load(&_graphics, "..\\Data\\Level.x", "..\\Data\\"))
            return FALSE;

        _node_tree_mesh.create(&_graphics, &_mesh, QUADTREE);

        // position view at origin
        _x_pos = _y_pos = _z_pos = 0.0f;

        // setup sky box
        _sky_box.create(&_graphics);

        for(short i = 0; i < 6; i++)
            _sky_box.load_texture(i, "..\\data\\stars.bmp");

        // initialize the sound system to play with
        _sound.init(get_hwnd());
        _sound_data.load_wav("..\\data\\cricket.wav");

        for(short i = 0; i < 3; i++)
            _sound_channel[i].create(&_sound, &_sound_data);

        return TRUE;
    }

    BOOL frame()
    {
        static DWORD time_now = timeGetTime();

        // play a random cricket sound
        for(short i = 0; i< 3; i++)
        {
            if(!_sound_channel[i].is_playing() && rand()%256 < 16)
                _sound_channel[i].play(&_sound_data, 10);
        }

        // calculate elapsed time (plus speed boost)
        ulong time_elapsed = timeGetTime() - time_now;
        time_now = timeGetTime();

        // read keyboard and mouse data
        _keyboard.read();
        _mouse.read();

        // process input and update everything, ESC quits program.

        if(_keyboard.get_key_state(KEY_ESC))
            return FALSE;

        float x_move, z_move;

        // process movement
        x_move = z_move = 0.0f;

        if(_keyboard.get_key_state(KEY_UP) || _keyboard.get_key_state(KEY_W))
        {
            x_move = (float) sin(_camera.get_y_rotation()) * time_elapsed;
            z_move = (float) cos(_camera.get_y_rotation()) * time_elapsed;
        }

        if(_keyboard.get_key_state(KEY_DOWN) || _keyboard.get_key_state(KEY_S))
        {
            x_move = (float) -sin(_camera.get_y_rotation()) * time_elapsed;
            z_move = (float) -cos(_camera.get_y_rotation()) * time_elapsed;
        }

        if(_keyboard.get_key_state(KEY_LEFT) || _keyboard.get_key_state(KEY_A))
        {
            x_move = (float) sin(_camera.get_y_rotation() - 1.57f) * time_elapsed;
            z_move = (float) cos(_camera.get_y_rotation() - 1.57f) * time_elapsed;
        }

        if(_keyboard.get_key_state(KEY_RIGHT) || _keyboard.get_key_state(KEY_D))
        {
            x_move = (float) sin(_camera.get_y_rotation() + 1.57f) * time_elapsed;
            z_move = (float) cos(_camera.get_y_rotation() + 1.57f) * time_elapsed;
        }

        // check for height changes (can step up to 64 units)
        float height = _node_tree_mesh.get_closest_height_below(_x_pos, _y_pos + _above_floor, _z_pos);

        if(_y_pos > height)
        {
            // dropping
            if((_y_pos -= (float)time_elapsed) < height)
                _y_pos = height;
            else
                x_move = z_move = 0.0f;
        }
        else
        {
            // climbing
            _y_pos = height;
        }

        float dist;

        // check for movement collision - can not walk past anything blocking path.
        if(_node_tree_mesh.is_ray_intersect_mesh(_x_pos, _y_pos + _above_floor, _z_pos,
                                                 _x_pos + x_move, _y_pos + _above_floor, _z_pos + z_move,
                                                 &dist))
        {
            // adjust coordinates to be exactly 2.5 units away from target

            float diff = dist - 2.5f;

            D3DXVECTOR2 dir;
            D3DXVec2Normalize(&dir, &D3DXVECTOR2(x_move, z_move));

            dir *= diff;

            x_move = dir.x;
            z_move = dir.y;
        }

        // update view coordinats
        _x_pos += x_move;
        _z_pos += z_move;

        // position camera and rotate based on mouse position

        _camera.move(_x_pos, _y_pos + 50.0f, _z_pos);

        // _mouse.get_y_delta():
        //      get mouse's relative x movement coordinate.
        //
        // _mouse.get_x_delta():
        //      get mouse's relative y movement coordinate.
        _camera.rotate_rel((float) _mouse.get_y_delta() / 200.0f, (float) _mouse.get_x_delta() / 200.0f, 0.0f);

        // position
        _light.move(_x_pos, _y_pos + 60.0f, _z_pos);
        _graphics.set_light(0, &_light);

        FRUSTUM frustum;

        // set camera and calculate frustum
        _graphics.set_camera(&_camera);
        frustum.construct(&_graphics);

        // render everything
        _graphics.clear_zbuffer(1.0f);

        // begin render now
        if(_graphics.begin_scene())
        {
            _graphics.enable_zbuffer(FALSE);
            _graphics.enable_lighting(FALSE);
            _sky_box.render(&_camera);

            _graphics.enable_zbuffer(TRUE);
            _graphics.enable_lighting(TRUE);
            _node_tree_mesh.render(&frustum);

            _graphics.end_scene();
        }

        _graphics.display();

        return TRUE;
    }

    BOOL shutdown()
    {
        return TRUE;
    }

private:
    GRAPHICS        _graphics;
    CAMERA          _camera;
    LIGHT           _light;

    SOUND           _sound;
    SOUND_DATA      _sound_data;
    SOUND_CHANNEL   _sound_channel[3];

    SKY_BOX         _sky_box;

    INPUT           _input;
    INPUT_DEVICE    _keyboard;
    INPUT_DEVICE    _mouse;

    MESH            _mesh;
    NODE_TREE_MESH  _node_tree_mesh;

    float           _x_pos, _y_pos, _z_pos;

    static const float _above_floor;
};

const float APP::_above_floor = 64.0f;

int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR cmd_line, int cmd_show)
{
    APP app;

    return app.run();
}

截圖：

posted on 2007-10-24 18:57 lovedday 閱讀(1516) 評(píng)論(1) 編輯收藏引用

評(píng)論

# re: 創(chuàng)建3D圖形引擎（4）[未登錄] 2009-04-16 22:41 cloud

你寫的文章都挺不錯(cuò)的，至少我收獲不少，期待下一編。。。回復(fù) 更多評(píng)論

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# re: 創(chuàng)建3D圖形引擎（4）[未登錄] 2009-04-16 22:41 cloud

天行健君子當(dāng)自強(qiáng)而不息