抗锯齿说

抗锯齿处理依赖混合处理，借助混合处理功能。

#include <GL/glut.h>
static float rotAngle =0.;
#include <stdio.h>
void init(void){
    GLfloat values[2];
    glGetFloatv(GL_LINE_WIDTH_GRANULARITY,values);
    printf("GL_LINE_WIDTH_GRANULARITY value is %3.1f\n",values[0]);
    glGetFloatv(GL_LINE_WIDTH_RANGE,values);
    printf("GL_LINE_WIDTH_RANGE values are %3.1f   %3.1f\n",values[0],values[1]);

    glEnable(GL_LINE_SMOOTH);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
    glHint(GL_LINE_SMOOTH_HINT,GL_DONT_CARE);
    glLineWidth(1.5);

    glClearColor(0.0,0.0,0.0,0.0);
}

void display(void){
    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(0.0,1.0,0.0);
    glPushMatrix();
        glRotatef(-rotAngle,0.0,0.0,0.1);
        glBegin(GL_LINES);
            glVertex2f(-0.5,-0.5);
            glVertex2f(0.5,0.5);
        glEnd();
    glPopMatrix();

    glColor3f(0.0,0.0,1.0);
    glPushMatrix();
        glRotatef(rotAngle,0.0,0.0,0.1);
        glBegin(GL_LINES);
            glVertex2f(-0.5,0.5);
            glVertex2f(0.5,-0.5);
        glEnd();
    glPopMatrix();

    glFlush();
}

void reshape(int w,int h){
    glViewport(0,0,(GLint)w,(GLint)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if(w<=h){
        gluOrtho2D(-1.0,1.0,-1.0*(GLfloat)h/(GLfloat)w,1.0*(GLfloat)h/(GLfloat)w);
    }else{
        gluOrtho2D(-1.0*(GLfloat)w/(GLfloat)h,1.0*(GLfloat)w/(GLfloat)h,-1.0,1.0);
    }
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void keyboard(unsigned char key,int x,int y)
{
    switch(key){
    case ‘r‘:
    case ‘R‘:
        rotAngle +=20;
        if(rotAngle >=360.)rotAngle=0.;
        glutPostRedisplay();
        break;
    case 27:
        exit(0);
        break;
    default:
        break;
    }
}
int main(int argc,char** argv){
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(200,200);
    glutCreateWindow(argv[0]);
    init();
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyboard);
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}