alpha3D.c

/*
 * Copyright (c) 1993-2003, 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
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 * 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.
 *
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 * 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,
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 * 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
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 * 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  Unpublished - rights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.
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 *
 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 */

/*
 *  alpha3D.c
 *  This program demonstrates how to intermix opaque and
 *  alpha blended polygons in the same scene, by using 
 *  glDepthMask.  Press the 'a' key to animate moving the 
 *  transparent object through the opaque object.  Press 
 *  the 'r' key to reset the scene.
 */
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

#define MAXZ 8.0
#define MINZ -8.0
#define ZINC 0.4

static float solidZ = MAXZ;
static float transparentZ = MINZ;
static GLuint sphereList, cubeList;

static void init(void)
{
   GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 0.15 };
   GLfloat mat_shininess[] = { 100.0 };
   GLfloat position[] = { 0.5, 0.5, 1.0, 0.0 };

   glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
   glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
   glLightfv(GL_LIGHT0, GL_POSITION, position);

   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
   glEnable(GL_DEPTH_TEST);

   sphereList = glGenLists(1);
   glNewList(sphereList, GL_COMPILE);
      glutSolidSphere (0.4, 16, 16);
   glEndList();

   cubeList = glGenLists(1);
   glNewList(cubeList, GL_COMPILE);
      glutSolidCube (0.6);
   glEndList();
}

void display(void)
{
   GLfloat mat_solid[] = { 0.75, 0.75, 0.0, 1.0 };
   GLfloat mat_zero[] = { 0.0, 0.0, 0.0, 1.0 };
   GLfloat mat_transparent[] = { 0.0, 0.8, 0.8, 0.6 };
   GLfloat mat_emission[] = { 0.0, 0.3, 0.3, 0.6 };

   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   glPushMatrix ();
      glTranslatef (-0.15, -0.15, solidZ);
      glMaterialfv(GL_FRONT, GL_EMISSION, mat_zero);
      glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_solid);
      glCallList (sphereList);
   glPopMatrix ();

   glPushMatrix ();
      glTranslatef (0.15, 0.15, transparentZ);
      glRotatef (15.0, 1.0, 1.0, 0.0);
      glRotatef (30.0, 0.0, 1.0, 0.0);
      glMaterialfv(GL_FRONT, GL_EMISSION, mat_emission);
      glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_transparent);
      glEnable (GL_BLEND);
      glDepthMask (GL_FALSE);
      glBlendFunc (GL_SRC_ALPHA, GL_ONE);
      glCallList (cubeList);
      glDepthMask (GL_TRUE);
      glDisable (GL_BLEND);
   glPopMatrix ();

   glutSwapBuffers();
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLint) w, (GLint) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if (w <= h)
      glOrtho (-1.5, 1.5, -1.5*(GLfloat)h/(GLfloat)w,
               1.5*(GLfloat)h/(GLfloat)w, -10.0, 10.0);
   else
      glOrtho (-1.5*(GLfloat)w/(GLfloat)h,
               1.5*(GLfloat)w/(GLfloat)h, -1.5, 1.5, -10.0, 10.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void animate(void)
{
   if (solidZ <= MINZ || transparentZ >= MAXZ)
      glutIdleFunc(NULL);
   else {
      solidZ -= ZINC;
      transparentZ += ZINC;
      glutPostRedisplay();
   }
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 'a':
      case 'A':
         solidZ = MAXZ;
         transparentZ = MINZ;
         glutIdleFunc(animate);
         break;
      case 'r':
      case 'R':
         solidZ = MAXZ;
         transparentZ = MINZ;
         glutPostRedisplay();
         break;
      case 27:
        exit(0);
    }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize(500, 500);
   glutCreateWindow(argv[0]);
   init();
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}