progs/trivial/pgon-mode.c

   1 /**
   2  * Test glPolygonMode.
   3  * A tri-strip w/ two tris is drawn so that the first tri is front-facing
   4  * but the second tri is back-facing.
   5  * Set glPolygonMode differently for the front/back faces
   6  *
   7  */
   8
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <math.h>
  13 #include <GL/glut.h>
  14
  15 static int Win;
  16 static GLfloat Zrot = 0;
  17 static GLboolean FrontFillBackUnfilled = GL_TRUE;
  18 static GLboolean Lines = GL_TRUE;
  19
  20
  21 static void
  22 Draw(void)
  23 {
  24    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  25
  26    if (FrontFillBackUnfilled) {
  27       if (Lines) {
  28          printf("FrontMode = FILL, BackMode = LINE\n");
  29          glPolygonMode(GL_BACK, GL_LINE);
  30       }
  31       else {
  32          printf("FrontMode = FILL, BackMode = POINT\n");
  33          glPolygonMode(GL_BACK, GL_POINT);
  34       }
  35       glPolygonMode(GL_FRONT, GL_FILL);
  36    }
  37    else {
  38       if (Lines) {
  39          printf("FrontMode = LINE, BackMode = FILL\n");
  40          glPolygonMode(GL_FRONT, GL_LINE);
  41       }
  42       else {
  43          printf("FrontMode = POINT, BackMode = FILL\n");
  44          glPolygonMode(GL_FRONT, GL_POINT);
  45       }
  46       glPolygonMode(GL_BACK, GL_FILL);
  47    }
  48
  49    glPushMatrix();
  50    glRotatef(Zrot, 0, 0, 1);
  51
  52    glBegin(GL_TRIANGLE_STRIP);
  53    glVertex2f(-1, 0);
  54    glVertex2f( 1, 0);
  55    glVertex2f(0,  1);
  56    glVertex2f(0, -1);
  57    glEnd();
  58
  59    glPopMatrix();
  60
  61    glutSwapBuffers();
  62 }
  63
  64
  65 static void
  66 Reshape(int width, int height)
  67 {
  68    glViewport(0, 0, width, height);
  69    glMatrixMode(GL_PROJECTION);
  70    glLoadIdentity();
  71    glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
  72    glMatrixMode(GL_MODELVIEW);
  73    glLoadIdentity();
  74    glTranslatef(0.0, 0.0, -15.0);
  75 }
  76
  77
  78 static void
  79 Key(unsigned char key, int x, int y)
  80 {
  81    const GLfloat step = 3.0;
  82    (void) x;
  83    (void) y;
  84    switch (key) {
  85    case 'p':
  86       FrontFillBackUnfilled = !FrontFillBackUnfilled;
  87       break;
  88    case 'l':
  89       Lines = !Lines;
  90       break;
  91    case 'z':
  92       Zrot -= step;
  93       break;
  94    case 'Z':
  95       Zrot += step;
  96       break;
  97    case 27:
  98       glutDestroyWindow(Win);
  99       exit(0);
 100       break;
 101    }
 102    glutPostRedisplay();
 103 }
 104
 105
 106 static void
 107 Init(void)
 108 {
 109    printf("GL_RENDERER = %s\n", (char*) glGetString(GL_RENDERER));
 110
 111    glLineWidth(3.0);
 112    glPointSize(3.0);
 113
 114    glColor4f(1, 1, 1, 0.8);
 115    glEnable(GL_BLEND);
 116    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 117
 118    printf("Press 'p' to toggle polygon mode\n");
 119 }
 120
 121
 122 int
 123 main(int argc, char *argv[])
 124 {
 125    glutInit(&argc, argv);
 126    glutInitWindowPosition(0, 0);
 127    glutInitWindowSize(400, 400);
 128    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 129    Win = glutCreateWindow(argv[0]);
 130    glutReshapeFunc(Reshape);
 131    glutKeyboardFunc(Key);
 132    glutDisplayFunc(Draw);
 133    Init();
 134    glutMainLoop();
 135    return 0;
 136 }