OpenGLUT 0.6.3 development - OpenGLUT: polyoff.c File Reference
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# polyoff.c File Reference

## Detailed Description

This program demonstrates polygon offset to draw a shaded polygon and its wireframe counterpart without ugly visual artifacts ("stitching").

    /*
     * 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     * Unpublished-- rights reserved under the copyright laws of the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 <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    #ifdef GL_VERSION_1_1
    GLuint list;
    GLint fill = 1;
    GLfloat spinx = 0;
    GLfloat spiny = 0;
    GLfloat tdist = 0.0;
    GLfloat polyfactor = 1.0;
    GLfloat polyunits = 1.0;
    GLboolean doubleBuffer;

    /*  display() draws two spheres, one with a gray, diffuse material,
     *  the other sphere with a magenta material with a specular highlight.
     */
    void display (void)
    {
        GLfloat gray[] = { 0.8, 0.8, 0.8, 1.0 };
        GLfloat black[] = { 0.0, 0.0, 0.0, 1.0 };

        glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glPushMatrix ();
        glTranslatef (0.0, 0.0, tdist);
        glRotatef ((GLfloat) spinx, 1.0, 0.0, 0.0);
        glRotatef ((GLfloat) spiny, 0.0, 1.0, 0.0);

        glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, gray);
        glMaterialfv(GL_FRONT, GL_SPECULAR, black);
        glMaterialf(GL_FRONT, GL_SHININESS, 0.0);
        if (fill) {
           glEnable(GL_LIGHTING);
           glEnable(GL_LIGHT0);
           glEnable(GL_POLYGON_OFFSET_FILL);
           glPolygonOffset(polyfactor, polyunits);
           glCallList (list);
           glDisable(GL_POLYGON_OFFSET_FILL);
        }

        glDisable(GL_LIGHTING);
        glDisable(GL_LIGHT0);
        glColor3f (1.0, 1.0, 1.0);
        glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
        glPolygonOffset(-polyfactor, -polyunits);
        if (!fill) glEnable(GL_POLYGON_OFFSET_LINE);
        glCallList (list);
        glDisable(GL_POLYGON_OFFSET_LINE);
        glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

        if (!fill) {
           glEnable(GL_LIGHTING);
           glEnable(GL_LIGHT0);
           glCallList (list);
        }

        glPopMatrix ();
        glFlush ();
        if (doubleBuffer) glutSwapBuffers();
    }

    /*  specify initial properties
     *  create display list with sphere
     *  initialize lighting and depth buffer
     */
    void gfxinit (void)
    {
        GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 };
        GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
        GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 };
        GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };

        GLfloat global_ambient[] = { 0.2, 0.2, 0.2, 1.0 };

        glClearColor (0.0, 0.0, 0.0, 1.0);

        list = glGenLists(1);
        glNewList (list, GL_COMPILE);
           glutSolidSphere(1.0, 20, 12);
        glEndList ();

        glEnable(GL_DEPTH_TEST);

        glLightfv (GL_LIGHT0, GL_AMBIENT, light_ambient);
        glLightfv (GL_LIGHT0, GL_DIFFUSE, light_diffuse);
        glLightfv (GL_LIGHT0, GL_SPECULAR, light_specular);
        glLightfv (GL_LIGHT0, GL_POSITION, light_position);
        glLightModelfv (GL_LIGHT_MODEL_AMBIENT, global_ambient);
    }

    /*  call when window is resized  */
    void reshape(int width, int height)
    {
        glViewport (0, 0, width, height);
        glMatrixMode (GL_PROJECTION);
        glLoadIdentity ();
        gluPerspective(45.0, (GLdouble)width/(GLdouble)height,
            1.0, 10.0);
        glMatrixMode (GL_MODELVIEW);
        glLoadIdentity ();
        gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    }

    static void Benchmark( float xdiff, float ydiff )
    {
       int startTime, endTime;
       int draws;
       double seconds, fps;

       printf("Benchmarking...\n");

       draws = 0;
       startTime = glutGet(GLUT_ELAPSED_TIME);
       spinx = spiny = 0.0;
       do {
          spinx += xdiff;
          spiny += ydiff;
          display();
          draws++;
          endTime = glutGet(GLUT_ELAPSED_TIME);
       } while (endTime - startTime < 5000);   /* 5 seconds */

       /* Results */
       seconds = (double) (endTime - startTime) / 1000.0;
       fps = draws / seconds;
       printf("Result:  fps: %g\n", fps);
    }

    /*  call when mouse button is pressed  */
    /* ARGSUSED2 */
    void mouse(int button, int state, int x, int y) {
        switch (button) {
        case GLUT_LEFT_BUTTON:
            switch (state) {
            case GLUT_DOWN:
                spinx += 5;
                        glutPostRedisplay();
                break;
            default:
                break;
                }
                break;
        case GLUT_MIDDLE_BUTTON:
            switch (state) {
            case GLUT_DOWN:
                spiny += 5;
                        glutPostRedisplay();
                break;
            default:
                break;
                }
                break;
        case GLUT_RIGHT_BUTTON:
            switch (state) {
            case GLUT_UP:
                exit(0);
                break;
            default:
                break;
                }
                break;
            default:
                break;
        }
    }

    /* ARGSUSED1 */
    void keyboard (unsigned char key, int x, int y)
    {
       switch (key) {
          case 't':
             if (tdist < 4.0) {
                tdist = (tdist + 0.5);
                glutPostRedisplay();
             }
             break;
          case 'T':
             if (tdist > -5.0) {
                tdist = (tdist - 0.5);
                glutPostRedisplay();
             }
             break;
          case 'F':
             polyfactor = polyfactor + 0.1;
         printf ("polyfactor is %f\n", polyfactor);
             glutPostRedisplay();
             break;
          case 'f':
             polyfactor = polyfactor - 0.1;
         printf ("polyfactor is %f\n", polyfactor);
             glutPostRedisplay();
             break;
          case 'U':
             polyunits = polyunits + 1.0;
         printf ("polyunits is %f\n", polyunits);
             glutPostRedisplay();
             break;
          case 'u':
             polyunits = polyunits - 1.0;
         printf ("polyunits is %f\n", polyunits);
             glutPostRedisplay();
             break;
          case 'b':
         Benchmark(5.0, 0);
         break;
          case 'B':
         Benchmark(0, 5.0);
         break;
          case ' ':
         fill = !fill;
         printf ("fill/line: %d\n", fill);
             glutPostRedisplay();
             break;
          case 27:  /* Escape */
             exit(0);
             break;
          default:
             break;
       }
    }

    static void
    key(unsigned char k, int x, int y)
    {
      switch (k) {
      case 27:  /* Escape */
        exit(0);
        break;
      default:
        return;
      }
      glutPostRedisplay();
    }

    GLenum Args(int argc, char **argv)
    {
        GLint i;

        doubleBuffer = GL_FALSE;

        for (i = 1; i < argc; i++) {
            if (strcmp(argv[i], "-sb") == 0) {
            doubleBuffer = GL_FALSE;
        } else if (strcmp(argv[i], "-db") == 0) {
            doubleBuffer = GL_TRUE;
        } else {
            printf("%s (Bad option).\n", argv[i]);
            return GL_FALSE;
        }
        }
        return GL_TRUE;
    }

    /*  Main Loop
     *  Open window with initial window size, title bar,
     *  RGBA display mode, and handle input events.
     */
    int main(int argc, char** argv)
    {
        GLuint type;
        glutInit(&argc, argv);

        Args(argc, argv);

        type = GLUT_DEPTH | GLUT_RGB;
         type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;

        glutInitDisplayMode(type);
        glutCreateWindow("polyoff");
        glutReshapeFunc(reshape);
        glutDisplayFunc(display);
        glutMouseFunc(mouse);
        glutKeyboardFunc(keyboard);
        gfxinit();
        glutMainLoop();
        return 0;
    }
    #else
    int main(int argc, char** argv)
    {
        fprintf (stderr, "This program demonstrates a feature which is not in OpenGL Version 1.0.\n");
        fprintf (stderr, "If your implementation of OpenGL Version 1.0 has the right extensions,\n");
        fprintf (stderr, "you may be able to modify this program to make it run.\n");
        return 0;
    }
    #endif

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