progs/trivial/tri-point-line-clipped.c

   1 /**
   2  * Test frustum/user clipping w/ glPolygonMode LINE/POINT.
   3  *
   4  * The bottom/left and bottom/right verts are outside the frustum and clipped.
   5  * The top vertex is clipped by a user clipping plane.
   6  *
   7  * A filled gray reference triangle is shown underneath the points/lines.
   8  */
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <GL/glut.h>
  13
  14
  15 static int win;
  16
  17
  18 static void
  19 ColorTri(void)
  20 {
  21    glBegin(GL_TRIANGLES);
  22    glColor3f(1, 0, 0);   glVertex3f(-1.5, -0.8, 0.0);
  23    glColor3f(0, 1, 0);   glVertex3f( 1.5, -0.8, 0.0);
  24    glColor3f(0, 0, 1);   glVertex3f( 0.0,  0.9, 0.0);
  25    glEnd();
  26 }
  27
  28
  29 static void
  30 GrayTri(void)
  31 {
  32    glColor3f(0.3, 0.3, 0.3);
  33    glBegin(GL_TRIANGLES);
  34    glVertex3f(-1.5, -0.8, 0.0);
  35    glVertex3f( 1.5, -0.8, 0.0);
  36    glVertex3f( 0.0,  0.9, 0.0);
  37    glEnd();
  38 }
  39
  40
  41 static void
  42 Draw(void)
  43 {
  44    static const GLdouble plane[4] = { 0, -1.0, 0, 0.5 };
  45
  46    glClear(GL_COLOR_BUFFER_BIT);
  47
  48    glPointSize(13.0);
  49    glLineWidth(5.0);
  50
  51    glClipPlane(GL_CLIP_PLANE0, plane);
  52    glEnable(GL_CLIP_PLANE0);
  53
  54    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
  55    GrayTri();
  56
  57    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
  58    ColorTri();
  59
  60    glPolygonMode(GL_FRONT_AND_BACK, GL_POINT);
  61    ColorTri();
  62
  63    glutSwapBuffers();
  64 }
  65
  66
  67 static void Reshape(int width, int height)
  68 {
  69    glViewport(0, 0, (GLint)width, (GLint)height);
  70    glMatrixMode(GL_PROJECTION);
  71    glLoadIdentity();
  72    glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
  73    glMatrixMode(GL_MODELVIEW);
  74 }
  75
  76
  77 static void
  78 Key(unsigned char key, int x, int y)
  79 {
  80    if (key == 27) {
  81       glutDestroyWindow(win);
  82       exit(0);
  83    }
  84    else {
  85       glutPostRedisplay();
  86    }
  87 }
  88
  89
  90 static void
  91 Init(void)
  92 {
  93    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  94    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  95    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  96    fflush(stderr);
  97 }
  98
  99
 100 int
 101 main(int argc, char **argv)
 102 {
 103    glutInitWindowSize(300, 300);
 104    glutInit(&argc, argv);
 105    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH);
 106    win = glutCreateWindow(*argv);
 107    if (!win) {
 108       return 1;
 109    }
 110    Init();
 111    glutReshapeFunc(Reshape);
 112    glutKeyboardFunc(Key);
 113    glutDisplayFunc(Draw);
 114    glutMainLoop();
 115    return 0;
 116 }