用OpenGL快速给图形添加纹理含圆柱圆锥

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这里讨论的是二维纹理

1.图取图像数据

void readimage(char* filename, BYTE* imagedata)//所读图片均为24位bmp,且宽度补齐至四字节边界{BITMAPFILEHEADER bf;  //文件头BITMAPINFOHEADER bi;  //信息头int     m_ImageWidth;   //图象宽度int     m_ImageHeight;  //图象高度FILE  *fp1; //文件指针，fp1为源文件//打开文件，到文件指针if ((fp1 = fopen(filename, "rb")) == NULL){MessageBox(NULL, "文件打开错误", "warning", MB_OK);}fread((LPSTR)&bf, sizeof(BITMAPFILEHEADER), 1, fp1);  //读取文件头，读取以后文件指针在文件头末尾（即信息头）fread((LPSTR)&bi, sizeof(BITMAPINFOHEADER), 1, fp1);  //读取信息头m_ImageWidth = bi.biWidth;             //给图象宽度赋值m_ImageHeight = bi.biHeight;           //给图象高度赋值fread(imagedata, m_ImageHeight*m_ImageWidth * 3, 1, fp1);  //读取图象数据fclose(fp1);}

注意：读进来的图像为BGR,要调整为RGB

void adjustimage(BYTE* imagedata, int w, int h){BYTE temp;for (int i = 0; i<w*h; i++){<pre name="code" class="cpp">glEnable(GL_TEXTURE_2D);

temp = imagedata[i * 3];imagedata[i * 3] = imagedata[i * 3 + 2];imagedata[i * 3 + 2] = temp;}}

2.设置纹理（因为一般要用到的纹理比较多，先将所有图片读入，要用到那张时候就使用glBindTexture函数来指定当前所使用的纹理对象）

注意：图像的像素要与数组对应，下面的是256*256

//------------------------设置纹理----------------------------------void loadtexture(){           glGenTextures(2, &texName);//2表示有两个纹理glBindTexture(GL_TEXTURE_2D, texName);{BYTE imagemoon[256][256][3];//墙壁2的纹理readimage("D:\\wall2.bmp", &imagemoon[0][0][0]);adjustimage(&imagemoon[0][0][0], 256, 256);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, imagemoon);}{BYTE imagesky[256][256][3];readimage("D:\\wall1.bmp", &imagesky[0][0][0]);//墙壁1的纹理adjustimage(&imagesky[0][0][0], 256, 256);glBindTexture(GL_TEXTURE_2D, texName + 1);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, imagesky);}}

3.启用纹理

glEnable(GL_TEXTURE_2D);

4.纹理坐标

例子：坐标要对应，纹理用单位表示，（0.0，0.0）表示左下角（1.0,1.0）表示右上角

void display(void){glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);//printf("At:%.2f %.2f %.2f\n",r*cos(c*du),h,r*sin(c*du)); //这就是视点的坐标glLoadIdentity();gluLookAt(r*cos(c*du), h, r*sin(c*du), 0, 0, 0, 0, 1, 0); //从视点看远点,y轴方向(0,1,0)是上方向glColor3f(1.0f, 0.0f, 0.0f);glEnable(GL_TEXTURE_2D);glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);//地面glPushMatrix();glBindTexture(GL_TEXTURE_2D, texName + 2);glColor3f(0.0, 1.0, 1.0);glBegin(GL_QUADS);glTexCoord2f(0.0, 0.0); glVertex3f(5.0f,-2.0f,3.0f);glTexCoord2f(1.0, 0.0); glVertex3f(-5.0f, -2.0f, 3.0f);glTexCoord2f(1.0, 1.0); glVertex3f(-5.0f, -2.0f, -3.0f);glTexCoord2f(0.0, 1.0); glVertex3f(5.0f, -2.0f, -3.0f);glEnd();//左墙glPushMatrix();glBindTexture(GL_TEXTURE_2D, texName + 1);glBegin(GL_POLYGON);glTexCoord2f(0.0, 0.0); glVertex3f(-2.0, 0.0, 1.5);glTexCoord2f(0.0, 0.66); glVertex3f(-2.0, 2.0, 1.5);glTexCoord2f(0.5, 1.0); glVertex3f(-2.0, 3.0, 0.0);glTexCoord2f(1.0, 0.66); glVertex3f(-2.0, 2.0, -1.5);glTexCoord2f(1.0, 0.0); glVertex3f(-2.0, 0.0, -1.5);glEnd();glPopMatrix();glFlush();glutSwapBuffers();glDisable(GL_TEXTURE_2D);}

5.对于圆柱和圆锥

将圆柱和圆锥看做是由很多线组成的，使用三角函数和一个循环就可以画出

        //圆柱glTranslatef(-3.0, -2.0, 2.0);glPushMatrix();glBindTexture(GL_TEXTURE_2D, texName );    glBegin( GL_QUAD_STRIP);    double t = 0.0;double dt = 2*PI/nslice;    for (int j = 0; j <= nslice; ++j) {       glTexCoord2f( t/(2*PI), 1.0); glVertex3f( cos( t), 2.0, -sin( t));       glTexCoord2f( t/(2*PI), 0.0); glVertex3f( cos( t), 0.0, -sin( t));       t = t + dt;     }    glEnd();glPopMatrix();//圆锥glPushMatrix();glBindTexture(GL_TEXTURE_2D, texName + 4 );glBegin( GL_QUAD_STRIP);    double tt = 0.0;double dtt = 2*PI/nslice;    for (int j = 0; j <= nslice; ++j) {       glTexCoord2f( tt/(2*PI), 1.0); glVertex3f( 0.0, 2.0, 0.0);       glTexCoord2f( tt/(2*PI), 0.0); glVertex3f( cos( tt), 0.0, -sin( tt));       tt = tt + dtt;     }    glEnd();glPopMatrix();

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