• opengl中的抗锯齿


    opengl的抗锯齿

    1.对直线和点主要用函数GL_Enable(GL_LINE_SMOOTH)或GL_Enable(GL_POINT_SMOOTH)

    2.对RGBA模式需要启动混合功能,最常用的混合模式为GL_SRC_ALPHA和GL_ONE_MINUS_SRC_ALPHA(用GL_Blend开启混合模式)

    以下摘自OPENGL编程指南的aargb.c代码

    /*
     *  aargb.c
     *  This program draws shows how to draw anti-aliased lines. It draws
     *  two diagonal lines to form an X; when 'r' is typed in the window,
     *  the lines are rotated in opposite directions.
     */


    #include <GL/glut.h>
    #include <stdlib.h>
    #include <stdio.h>

    static float rotAngle = 0.;

    /*  Initialize antialiasing for RGBA mode, including alpha
     *  blending, hint, and line width.  Print out implementation
     *  specific info on line width granularity and width.
     */
    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);
    }

    /* Draw 2 diagonal lines to form an X
     */
    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, w, 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:  /*  Escape Key  */
             exit(0);
             break;
          default:
             break;
        }
    }

    /*  Main Loop
     *  Open window with initial window size, title bar,
     *  RGBA display mode, and handle input events.
     */
    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;
    }
    

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  • 原文地址:https://www.cnblogs.com/djcsch2001/p/2010372.html
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