OpenGL 编程轻松入门之特殊效果操作2006-05-19 11:00作者：黄燕出处：天极开发责任编辑：方舟每个物体在不同的环境在会有不同的视觉效果。为了使效果更加真实需要增加特殊效果。例8：绘制三个互相重叠的矩形，这三个矩形从左到右分别为绿、红、蓝。其中红色、蓝色矩形的透明度分别为50%的透明度，即 alpha 值为0.5，如图九所示。#include #include void myInit(void)glClearColor(0.2,0.8,0.8,0.0);/将背景设置为湖蓝色glEnable(GL_BLEND);/激活 GL_BLENDglBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);/指定像素的数学算法glEnable(GL_FLAT);void myDisplay(void)glClear(GL_COLOR_BUFFER_BIT);/*绘制一个绿色的矩形 alpha = 1.0*/glColor4f(0.0,1.0,0.0,1.0);glBegin(GL_POLYGON);glVertex3f(-0.75,0.5,0.0);glVertex3f(-0.75,-0.75,0.0);glVertex3f(0.5,-0.75,0.0);glVertex3f(0.5,0.5,0.0);glEnd();/*绘制一个红色的矩形 alpha = 0.5*/glColor4f(1.0,0.0,0.0,0.5);glBegin(GL_POLYGON);glVertex3f(-0.25,1.0,0.0);glVertex3f(-0.25,-0.25,0.0);glVertex3f(1.0,-0.25,0.0);glVertex3f(1.0,1.0,0.0);glEnd();/*绘制一个蓝色的矩形 alpha = 0.5*/glColor4f(0.0,0.0,1.0,0.5);glBegin(GL_POLYGON);glVertex3f(0.25,1.5,0.0);glVertex3f(0.25,0.25,0.0);glVertex3f(1.5,0.25,0.0);glVertex3f(1.5,1.5,0.0);glEnd();glFlush();void myReshape(int w,int h)glViewport(0,0,w,h);glMatrixMode(GL_PROJECTION);glLoadIdentity();if(w#include GLfloat light_ambient = 0.1,0.1,0.1,0.0;GLfloat light_diffuse = 1.0,1.0,1.0,0.0;GLfloat light_specular = 1.0,1.0,1.0,0.0;GLfloat light_position = -10.0,0.0,5.0,0.0;GLfloat material_ambient = 0.1745,0.01175,0.01175;GLfloat material_diffuse = 0.61424,0.04136,0.04136;GLfloat material_specular = 0.727811,0.626959,0.62659;GLfloat fogColorWhite = 1.0,1.0,1.0,1.0;GLfloat fogColorGreen = 0.0,1.0,0.0,1.0;float fogDensity = 0.02;void myInit(void)/*设置背景色*/glClearColor(0.5,0.5,0.5,1.0);/*设置光照*/glLightfv(GL_LIGHT0,GL_AMBIENT,light_ambient);glLightfv(GL_LIGHT0,GL_DIFFUSE,light_diffuse);glLightfv(GL_LIGHT0,GL_SPECULAR,light_specular);glLightfv(GL_LIGHT0,GL_POSITION,light_position);/*设置材质*/glMaterialfv(GL_FRONT,GL_AMBIENT,material_ambient);glMaterialfv(GL_FRONT,GL_DIFFUSE,material_diffuse);glMaterialfv(GL_FRONT,GL_SPECULAR,material_specular);glMaterialf(GL_FRONT,GL_SHININESS,0.6*128);glShadeModel(GL_SMOOTH);glEnable(GL_DEPTH_TEST);glDepthFunc(GL_LESS);glEnable(GL_LIGHTING);glEnable(GL_LIGHT0);glEnable(GL_AUTO_NORMAL);glEnable(GL_NORMALIZE);glFrontFace(GL_CW);/*设置雾化*/glEnable(GL_FOG);glFogi(GL_FOG_MODE,GL_LINEAR);glFogfv(GL_FOG_COLOR,fogColorWhite);glFogf(GL_FOG_DENSITY,fogDensity);glFogf(GL_FOG_START,0.0);glFogf(GL_FOG_END,15.0);glHint(GL_FOG_HINT,GL_DONT_CARE);/*根据不同的键值设置不同的雾化效果*/static void myKey(unsigned char key,int x,int y)switch(key)case 33: /shift+1fogDensity *= 1.10;glFogi(GL_FOG_MODE,GL_EXP);glFogf(GL_FOG_DENSITY,fogDensity);glutPostRedisplay();break;case 64: /shift+2fogDensity /= 1.10;glFogi(GL_FOG_MODE,GL_EXP);glFogf(GL_FOG_DENSITY,fogDensity);glutPostRedisplay();break;case 35: /shift+3glFogi(GL_FOG_START,0.0);glFogi(GL_FOG_END,8.0);glutPostRedisplay();break;case 36: /shift+4glFogi(GL_FOG_MODE,GL_EXP2);glutPostRedisplay();break;case 37: /shift+5glFogi(GL_FOG_MODE,GL_LINEAR);glutPostRedisplay();break;case 94: /shift+6glFogfv(GL_FOG_COLOR,fogColorGreen);glutPostRedisplay();break;case 27: /Escexit(0);default:break;/*绘制圆锥体*/void myDisplay(void)glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);glPushMatrix();glTranslatef(-4.0,4.0,0.0);glRotatef(30.0,1.0,1.0,0.0);glutSolidCone(1.0,50.0,20.0,20.0);glPopMatrix();glutSwapBuffers();void myReshape(int w,int h)glViewport(0,0,(GLsizei)w,(GLsizei)h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(100.0,1.0,1.0,20.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();glTranslatef(0.0,0.0,-15.5);int main(int argc,char * argv)/*初始化*/glutInit(&argc,argv);glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);glutInitWindowSize(300,300);glutInitWindowPosition(100,100);/*创建窗口*/glutCreateWindow( FOG );/*绘制与显示*/myInit();glutKeyboardFunc(myKey);glutReshapeFunc(myReshape);glutDisplayFunc(myDisplay);/*进入 GLUT 事件处理循环*/glutMainLoop();return 0;图十：被雾化的圆锥体glFog 指定雾化参数。后面不同的字母表明参数的数据类型。f 表示 float，i 表示integer，v 表示 vector，也就是表明一个指针。GL_FOG_MODE 是一个单值整数或浮点数，该数值指定了用来计算雾化融合因子 f的方程。GL_DENSITY 是一个单值整数或浮点数，该值指定雾化浓度。GL_FOG_START 是一个单值整数或浮点数，该值指定雾化的起始值。GL_FOG_END 是一个单值整数或浮点数，该值指定雾化的终止值。GL_FOG_INDEX 是一个单值整数或浮点数，该值指定雾化索引值 if，缺省的雾化索引值为0.0。GL_FOG_COLOR 包含4个整数值或浮点数值，这些数值指定的是雾化颜色 Cf，整数值进行线性映射。glHint 指定实现的线索。本例中 GL_FOG_HINT 指定雾化计算精度。GL_DONT_CARE 指对选项不做考虑。图十一：雾化为绿色的圆锥体本例中还涉及到键盘操作，glutKeyboardFun。此函数注册当前窗口的键盘回调函数。因为这不是本节的主要内容，我们只简单提一下。此函数的原形为 void glutKeyboardFunc （void（*func） （unsigned char key，int x，int y） ）所以我们自己写的回调函数必须按照原形上规定的写。