aargb.c

OpenGL学习资料

/*
 * Copyright (c) 1993-1999, Silicon Graphics, Inc.
 * ALL RIGHTS RESERVED 
 * Permission to use, copy, modify, and distribute this software for 
 * any purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation, and that 
 * the name of Silicon Graphics, Inc. not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission. 
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
 * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * US Government Users Restricted Rights 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
 * United States.  Contractor/manufacturer is Silicon Graphics,
 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 */

/*
 *  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;
}