The special GL_SRC_ALPHA_SATURATE blending function is used.
Pressing the 't' key turns the antialiasing on and off.
/* * Copyright (c) 1993-1997, 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 * Unpublished-- rights reserved under the copyright laws of the * United States.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. */ #include <GL/openglut.h> #include <stdlib.h> #include <stdio.h> #include <string.h> GLboolean polySmooth = GL_TRUE; static void init(void) { glCullFace (GL_BACK); glEnable (GL_CULL_FACE); glBlendFunc (GL_SRC_ALPHA_SATURATE, GL_ONE); glClearColor (0.0, 0.0, 0.0, 0.0); } #define NFACE 6 #define NVERT 8 void drawCube(GLdouble x0, GLdouble x1, GLdouble y0, GLdouble y1, GLdouble z0, GLdouble z1) { static GLfloat v[8][3]; static GLfloat c[8][4] = { {0.0, 0.0, 0.0, 1.0}, {1.0, 0.0, 0.0, 1.0}, {0.0, 1.0, 0.0, 1.0}, {1.0, 1.0, 0.0, 1.0}, {0.0, 0.0, 1.0, 1.0}, {1.0, 0.0, 1.0, 1.0}, {0.0, 1.0, 1.0, 1.0}, {1.0, 1.0, 1.0, 1.0} }; /* indices of front, top, left, bottom, right, back faces */ static GLubyte indices[NFACE][4] = { {4, 5, 6, 7}, {2, 3, 7, 6}, {0, 4, 7, 3}, {0, 1, 5, 4}, {1, 5, 6, 2}, {0, 3, 2, 1} }; v[0][0] = v[3][0] = v[4][0] = v[7][0] = x0; v[1][0] = v[2][0] = v[5][0] = v[6][0] = x1; v[0][1] = v[1][1] = v[4][1] = v[5][1] = y0; v[2][1] = v[3][1] = v[6][1] = v[7][1] = y1; v[0][2] = v[1][2] = v[2][2] = v[3][2] = z0; v[4][2] = v[5][2] = v[6][2] = v[7][2] = z1; #ifdef GL_VERSION_1_1 glEnableClientState (GL_VERTEX_ARRAY); glEnableClientState (GL_COLOR_ARRAY); glVertexPointer (3, GL_FLOAT, 0, v); glColorPointer (4, GL_FLOAT, 0, c); glDrawElements (GL_QUADS, NFACE*4, GL_UNSIGNED_BYTE, indices); glDisableClientState (GL_VERTEX_ARRAY); glDisableClientState (GL_COLOR_ARRAY); #else printf ("If this is GL Version 1.0, "); printf ("vertex arrays are not supported.\n"); exit(1); #endif } /* Note: polygons must be drawn from front to back * for proper blending. */ void display(void) { if (polySmooth) { glClear (GL_COLOR_BUFFER_BIT); glEnable (GL_BLEND); glEnable (GL_POLYGON_SMOOTH); glDisable (GL_DEPTH_TEST); } else { glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glDisable (GL_BLEND); glDisable (GL_POLYGON_SMOOTH); glEnable (GL_DEPTH_TEST); } glPushMatrix (); glTranslatef (0.0, 0.0, -8.0); glRotatef (30.0, 1.0, 0.0, 0.0); glRotatef (60.0, 0.0, 1.0, 0.0); drawCube(-0.5, 0.5, -0.5, 0.5, -0.5, 0.5); glPopMatrix (); glFlush (); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(30.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } /* ARGSUSED1 */ void keyboard(unsigned char key, int x, int y) { switch (key) { case 't': case 'T': polySmooth = !polySmooth; glutPostRedisplay(); break; case 27: exit(0); /* Escape key */ break; default: break; } } /* Main Loop */ int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_ALPHA | GLUT_DEPTH); glutInitWindowSize(200, 200); glutCreateWindow(argv[0]); init (); glutReshapeFunc (reshape); glutKeyboardFunc (keyboard); glutDisplayFunc (display); glutMainLoop(); return 0; }