OpenGL编程轻松入门之特殊效果操作

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1、OpenGL编程轻松入门之特殊效果操作2006-05-1911:00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#includevoidmyInit(void){　glClearColor(0.2,0.8,0.8,0.

2、0);//将背景设置为湖蓝色　glEnable(GL_BLEND);//激活GL_BLEND　glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);//指定像素的数学算法　glEnable(GL_FLAT);}voidmyDisplay(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);　g

3、lVertex3f(-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);　glVerte

4、x3f(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();}v

5、oidmyReshape(intw,inth){　glViewport(0,0,w,h);　glMatrixMode(GL_PROJECTION);　glLoadIdentity();　if(w

6、1.5,1.5,-1.5,1.5);　glMatrixMode(GL_MODELVIEW);　glLoadIdentity();　glTranslatef(-0.4,0.0,0.0);}intmain(intargc,char**argv){　/*初始化*/　glutInit(&argc,argv);　glutInitDisplayMode(GLUT_SINGLE

7、GLUT_RGB);　glutInitWindowSize(300,400);　glutInitWindowPosition(200,

8、200);　/*创建窗口*/　glutCreateWindow("BLENDPOLYGON");　/*绘制与显示*/　myInit();　glutReshapeFunc(myReshape);　glutDisplayFunc(myDisplay);　/*进入GLUT事件处理循环*/　glutMainLoop();　return(0);}图九：三个互相重叠的矩形　　·glBlendFunc（GLenumsfactor，GLenumdfactor）指定像素算法。sfactor指定红，绿，蓝及alpha

9、源混合因素是如何计算的。dfactor指定红，绿，蓝及alpha目标混合因素是如何计算的。　　例9：绘制一个被雾化的圆锥体，如图十所示，为了观察不同的雾化参数，程序中加入了键盘操作。"shift+1"，"shift+2"键分别增加和减弱雾化浓度，"shift+3"设置雾化的起始点和终止点，"shift+4"和"shift+5"键改变雾化方程，"shift+6"将雾化颜色由白改为绿色，如图十一所示。#include#includeGLfloa