當(dāng)看完這一課之后,我開始感覺我對OpenlGL有了一定基礎(chǔ)了.我不知道為什么.我能夠很好理解它.
lesson_9當(dāng)中并沒有多大新的知識.全是我們之前所學(xué)的.卻需要完整的組織起來.希望它產(chǎn)生一個(gè)漂亮的圖形.

初看小星星的德數(shù)據(jù)結(jié)構(gòu),我并為能夠得出全部的東西.
typedef struct {
 GLint r,g,b;
 GLfloat dist;
 GLfloat angle;
}stars; 最初看到這個(gè)數(shù)據(jù)結(jié)構(gòu)的時(shí)候我以為星星應(yīng)當(dāng)是個(gè)點(diǎn).結(jié)果我錯(cuò)了.因?yàn)槲铱赐曛笪液鋈幻靼琢瞬还芪覀兘M織任何的圖元,我們都可以將它看成"點(diǎn)".而最后在于我們?nèi)绾蝸肀硎具@個(gè)點(diǎn)罷了.矩陣變換也是基于點(diǎn).
就像是像素一樣.我們始終會(huì)認(rèn)為它僅僅只是個(gè)像素點(diǎn).然其實(shí)應(yīng)該是個(gè)具有面積的小方格.
所以星星的表示.這一課我們也需要使用小方格.這不僅用在這里.也將用于許多許多.如粒子.等.
而這一課也給了我一個(gè)空間感很強(qiáng)的變換操作,這讓我更傾向于使用局部坐標(biāo)系來考慮整個(gè)變化的過程.因?yàn)檫@讓我更能明白 我最后所繪制的圖形的位置.

對于每個(gè)星星我們需要一個(gè)小正方形來表示.結(jié)果在此貼上星星的紋理,在配合混色操作就能達(dá)到非常完美的效果.我們看代碼:我希望我的注釋能夠非常易懂的明白:

        /**//** 以下變換的目的在于,我可以使得星星距離中心dist的一圈,因平移x位移時(shí)候,x軸已經(jīng)被旋轉(zhuǎn)至一定方向了*/
        glTranslatef(0.0,0.0,zoom); /**//** 深入屏幕里面*/
        glRotatef(tilt,1.0,0.0,0.0);/**//** 傾斜角度..x軸 */

        glRotatef(star[loop].angle,0.0,1.0,0.0); /**//**當(dāng)前星星所在的角度*/
        glTranslatef(star[loop].dist,0.0,0.0);/**//** x軸平移 */

        glRotatef(-star[loop].angle,0.0f,1.0f,0.0f); // 取消當(dāng)前星星的角度
        glRotatef(-tilt,1.0f,0.0f,0.0f); // 取消屏幕傾斜

lesson_9


#include "openglglut.h"
#include "BmpLoader.h"

bool twinkle=false;
bool tp=false;
const int num = 50;
typedef struct {
    GLint r,g,b;//顏色
    GLfloat dist;//距中心點(diǎn)距離
    GLfloat angle;//繞y軸角度
}stars;
stars star[num];
GLfloat zoom = -15.f;
GLfloat tilt=90.0f;
GLfloat spin;

GLuint loop;
GLuint texture[1];

bool LoadBmpTexture(const char* filename,GLuint& texid)
{
    BmpLoader bmp;
    if(!bmp.loadBitmap((char*)filename))
    {
        printf("loadBitmap error\n");
        return false;
    }

    glPixelStorei(GL_UNPACK_ALIGNMENT,4);   /**//** ? */

    glGenTextures(1,&texid);     /**//** 創(chuàng)建一個(gè)紋理*/
    glBindTexture(GL_TEXTURE_2D,texid);   /**//** 為它指定一個(gè)紋理*/

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); /**//** 線性濾波 */
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); /**//** 線性濾波 */
    

    glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,bmp.bitInfo->biWidth,bmp.bitInfo->biHeight
            ,0,GL_RGB,GL_UNSIGNED_BYTE,bmp.image);                /**//** 生成紋理*/
    
    //bmp.Free();

    return true;
}
void InitStar()
{
    for(loop=0;loop<num;loop++)
    {
        star[loop].angle=0.0;
        star[loop].dist=(loop/num)*5.0f;
        star[loop].r=rand()%256;
        star[loop].g=rand()%256;
        star[loop].b=rand()%256;
    }
}
int main(int argc,char** argv)
{
    createWindow("opengl lesson_6",&argc,argv); /**//** 初始化并創(chuàng)建窗口*/

    glutDisplayFunc(glutDisplay);               /**//** 注冊重繪函數(shù)*/
    glutIdleFunc(glutIdle);                     /**//** 注冊空閑回調(diào)函數(shù)*/
    glutReshapeFunc(glutResize);                /**//** 注冊窗口調(diào)整函數(shù)*/
    glutSpecialFunc(glutSpecial);               /**//** 注冊特殊按鍵窗口*/
    glutKeyboardFunc(glutKeyboard);             /**//** 注冊鍵盤處理函數(shù)*/

    InitStar();                                 /**//** 初始化本例中星星數(shù)據(jù)*/

    InitTexture();                              /**//** 初始化啟用紋理映射并加載紋理*/
    InitBlend();                                /**//** 初始化混色*/
    InitOpenGL();                               /**//** 初始化opengl 這節(jié)課有必要注釋掉這個(gè)函數(shù)中的深度測試的兩句代碼*/
    
    glutMainLoop();                             /**//** 仿真循環(huán)*/
}
void InitBlend()
{
    glBlendFunc(GL_SRC_ALPHA,GL_ONE);
    glEnable(GL_BLEND);
}
void InitTexture(void)
{
    /**//** 讀入工程目錄下data文件中的bmp文件*/
    if(!LoadBmpTexture("..\\Data\\Star.bmp",texture[0]))
    {
        printf("load texture error!\n");
        exit(0);
    }
    /**//** 若載入紋理成功 則啟用紋理映射*/
    glEnable(GL_TEXTURE_2D);
}
void glutDisplay()
{
    glClear(GL_COLOR_BUFFER_BIT |GL_DEPTH_BUFFER_BIT);
    glBindTexture(GL_TEXTURE_2D,texture[0]);
    for(loop=0;loop<num;loop++)
    {
        glLoadIdentity();
        /**//** 以下變換的目的在于,我可以使得星星距離中心dist的一圈,因平移x位移時(shí)候,x軸已經(jīng)被旋轉(zhuǎn)至一定方向了*/
        glTranslatef(0.0,0.0,zoom); /**//** 深入屏幕里面*/
        glRotatef(tilt,1.0,0.0,0.0);/**//** 傾斜角度..x軸 */

        glRotatef(star[loop].angle,0.0,1.0,0.0); /**//**當(dāng)前星星所在的角度*/
        glTranslatef(star[loop].dist,0.0,0.0);/**//** x軸平移 */

        glRotatef(-star[loop].angle,0.0f,1.0f,0.0f); // 取消當(dāng)前星星的角度
        glRotatef(-tilt,1.0f,0.0f,0.0f); // 取消屏幕傾斜
        

        if (twinkle) // 啟用閃爍效果
        {
            // 使用byte型數(shù)值指定一個(gè)顏色
            glColor4ub(star[(num-loop)-1].r,star[(num-loop)-1].g,star[(num-loop)-1].b,255);
            glBegin(GL_QUADS); // 開始繪制紋理映射過的四邊形
            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 0.0f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f);
            glEnd(); // 四邊形繪制結(jié)束
        }

        glRotatef(spin,0.0f,0.0f,1.0f); // 繞z軸旋轉(zhuǎn)星星
        // 使用byte型數(shù)值指定一個(gè)顏色
        glColor4ub(star[loop].r,star[loop].g,star[loop].b,255);
        glBegin(GL_QUADS); // 開始繪制紋理映射過的四邊形
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 0.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f);
        glEnd(); // 四邊形繪制結(jié)束

        spin+=0.01f; // 星星的公轉(zhuǎn)
        star[loop].angle+=float(loop)/num; // 改變星星的自轉(zhuǎn)角度
        star[loop].dist-=0.01f; // 改變星星離中心的距離
        spin+=0.01;

        if (star[loop].dist<0.0f) // 星星到達(dá)中心了么
        {
            star[loop].dist+=5.0f; // 往外移5個(gè)單位
            star[loop].r=rand()%256; // 賦一個(gè)新紅色分量
            star[loop].g=rand()%256; // 賦一個(gè)新綠色分量
            star[loop].b=rand()%256; // 賦一個(gè)新藍(lán)色分量
        }

    }
    glutSwapBuffers();
}
void glutIdle()
{
    glutPostRedisplay();
}

void glutKeyboard(unsigned char key,int x,int y)
{
    switch(key)
    {
        case 27:                                /**//** Esc按鍵按下后退出程序 */
            exit(0);
            break;
        case 't':
        case 'T':
            twinkle=!twinkle;
        default:
            break;
    }
}
void glutSpecial(int value, int x, int y)
{
    switch (value)
    {
         case GLUT_KEY_F1:        // 按F1鍵時(shí)切換窗口/全屏模式
            if(isFullScreen)
            {
                glutReshapeWindow(GL_WIN_WIDTH, GL_WIN_HEIGHT);
                glutPositionWindow(GL_WIN_INITIAL_X, GL_WIN_INITIAL_Y);
                isFullScreen = false;
            }
            else
            {
                glutFullScreen();
                isFullScreen = true;
            }
            return;
         default:
             return;
    }
}