学步园

     可能读者有注意到了，在有些OpenGL图像中，直线（尤其是接近于水平或垂直的直线）会呈现出锯齿状边缘，这种“锯齿”现象是由于理想的直线是由一系列的像素模拟的，而这些像素又必须位于它们各自的像素网格中，下面我有一个呈现来说明减少这种“锯齿”效果的抗锯齿技巧。

  效果图如下：

程序如下：

#include "GLUT.H"<br /> #include <stdio.h></p> <p>static float rotAngle = 0.;<br /> //初始化函数<br /> void init(void)<br /> {<br /> GLfloat values[2];<br /> glGetFloatv(GL_LINE_WIDTH_GRANULARITY, values);<br /> printf("GL_LINE_WIDTH_GRANULARITY value is %3.1f/n",values[0]);<br /> glGetFloatv(GL_LINE_WIDTH_RANGE, values);<br /> printf("GL_LINE_WIDTH_RANGLE values are %3.1f %3.1f/n", values[0], values[1]);</p> <p> glEnable(GL_LINE_SMOOTH); //启用抗锯齿<br /> glEnable(GL_BLEND); //启用混合<br /> glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);<br /> glHint(GL_LINE_SMOOTH_HINT, GL_DONT_CARE); //设置抗锯齿的参数<br /> glLineWidth(1.5); //设置直线宽度</p> <p> glClearColor(0.0, 0.0, 0.0, 0.0); //设置背景颜色<br /> }<br /> //显示函数<br /> void display(void)<br /> {<br /> glClear(GL_COLOR_BUFFER_BIT);</p> <p> glColor3f(0.0, 1.0, 0.0);<br /> glPushMatrix();<br /> glRotatef(-rotAngle, 0.0, 0.0, 0.1);<br /> glBegin(GL_LINES);<br /> glVertex2f(-0.5, 0.5);<br /> glVertex2f(0.5, -0.5);</p> <p> glEnd();<br /> glPopMatrix();</p> <p> glColor3f(0.0, 0.0, 1.0);<br /> glPushMatrix();<br /> glRotatef(rotAngle, 0.0, 0.0, 0.1);<br /> glBegin(GL_LINES);<br /> glVertex2f(0.5, 0.5);<br /> glVertex2f(-0.5, -0.5);<br /> glEnd();<br /> glPopMatrix();</p> <p> glFlush();<br /> }<br /> //窗口调整函数<br /> void reshape(int w, int h)<br /> {<br /> glViewport(0, 0, (GLint)w, (GLint)h); //设置视口<br /> glMatrixMode(GL_PROJECTION); //设置投影<br /> glLoadIdentity();<br /> if(w <= h)<br /> gluOrtho2D(-1.0, 1.0, -1.0*(GLfloat)h/(GLfloat)w, 1.0*(GLfloat)h/(GLfloat)w);<br /> else<br /> gluOrtho2D(-1.0*(GLfloat)w/(GLfloat)h, 1.0*(GLfloat)w/(GLfloat)h, -1.0, 1.0);<br /> glMatrixMode(GL_MODELVIEW);<br /> glLoadIdentity();<br /> }<br /> //键盘回调函数<br /> void keyboard(unsigned char key, int x, int y)<br /> {<br /> switch(key)<br /> {<br /> case 'r':<br /> case 'R':<br /> rotAngle += 5;<br /> if(rotAngle >= 360)<br /> rotAngle = 0.;<br /> glutPostRedisplay();<br /> break;;<br /> case 27:<br /> exit(0);<br /> break;<br /> default:<br /> break;<br /> }<br /> }<br /> //主函数<br /> int main(int argc, char** argv)<br /> {<br /> glutInit(&argc, argv);<br /> glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);<br /> glutInitWindowSize(200, 200);<br /> glutCreateWindow(argv[0]);<br /> init();<br /> glutReshapeFunc(reshape); //窗口大小回调函数<br /> glutKeyboardFunc(keyboard); //键盘回调函数<br /> glutDisplayFunc(display); //显示回调函数<br /> glutMainLoop();<br /> return 0;<br /> }