progs/tests/persp_hint.c

   1 /*
   2  * Test the GL_PERSPECTIVE_CORRECTION_HINT setting and its effect on
   3  * color interpolation.
   4  *
   5  * Press 'i' to toggle between GL_NICEST/GL_FASTEST/GL_DONT_CARE.
   6  *
   7  * Depending on the driver, the hint may make a difference, or not.
   8  */
   9
  10
  11 #include <stdlib.h>
  12 #include <stdio.h>
  13 #include <GL/glut.h>
  14
  15
  16 static GLenum PerspHint = GL_DONT_CARE;
  17
  18
  19 static void
  20 init(void)
  21 {
  22    GLubyte image[256][256][4];
  23    GLuint i, j;
  24    for (i = 0; i < 256; i++) {
  25       for (j = 0; j < 256; j++) {
  26          image[i][j][0] = j;
  27          image[i][j][1] = j;
  28          image[i][j][2] = j;
  29          image[i][j][3] = 255;
  30       }
  31    }
  32    glTexImage2D(GL_TEXTURE_2D, 0, 4, 256, 256, 0,
  33                 GL_RGBA, GL_UNSIGNED_BYTE, image);
  34    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  35    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  36    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  37    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  38    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
  39
  40    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
  41 }
  42
  43
  44 static void
  45 display(void)
  46 {
  47    switch (PerspHint) {
  48    case GL_NICEST:
  49       printf("hint = GL_NICEST\n");
  50       break;
  51    case GL_FASTEST:
  52       printf("hint = GL_FASTEST\n");
  53       break;
  54    case GL_DONT_CARE:
  55       printf("hint = GL_DONT_CARE\n");
  56       break;
  57    default:
  58       ;
  59    }
  60
  61    glClear(GL_COLOR_BUFFER_BIT);
  62
  63 #if 1
  64    glBegin(GL_QUADS);
  65    /* exercise perspective interpolation */
  66    glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, -1.0, -1.0);
  67    glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, 1.0, -1.0);
  68    glColor3f(0.0, 1.0, 0.0); glVertex3f( 7.0, 1.0, -7.0);
  69    glColor3f(0.0, 1.0, 0.0); glVertex3f( 7.0, -1.0, -7.0);
  70
  71    /* stripe of linear interpolation */
  72    glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, -0.1, -1.001);
  73    glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0,  0.1, -1.001);
  74    glColor3f(0.0, 1.0, 0.0); glVertex3f( 1.0,  0.1, -1.001);
  75    glColor3f(0.0, 1.0, 0.0); glVertex3f( 1.0, -0.1, -1.001);
  76    glEnd();
  77 #else
  78    glEnable(GL_TEXTURE_2D);
  79    glBegin(GL_QUADS);
  80    glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, 0.0, -1.0);
  81    glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, -1.0);
  82    glTexCoord2f(1.0, 1.0); glVertex3f( 5.0, 1.0, -7.0);
  83    glTexCoord2f(1.0, 0.0); glVertex3f( 5.0, 0.0, -7.0);
  84
  85    glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, -1.001);
  86    glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 0.0, -1.001);
  87    glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, 0.0, -1.001);
  88    glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, -1.0, -1.001);
  89    glEnd();
  90 #endif
  91
  92    glFlush();
  93 }
  94
  95
  96 static void
  97 reshape(int w, int h)
  98 {
  99    glViewport(0, 0, w, h);
 100    glMatrixMode(GL_PROJECTION);
 101    glLoadIdentity();
 102    gluPerspective(90.0, (GLfloat) w / h, 1.0, 300.0);
 103    glMatrixMode(GL_MODELVIEW);
 104    glLoadIdentity();
 105 }
 106
 107
 108 static void
 109 key(unsigned char k, int x, int y)
 110 {
 111    switch (k) {
 112    case 27:  /* Escape */
 113       exit(0);
 114       break;
 115    case 'i':
 116       if (PerspHint == GL_FASTEST)
 117          PerspHint = GL_NICEST;
 118       else if (PerspHint == GL_NICEST)
 119          PerspHint = GL_DONT_CARE;
 120       else
 121          PerspHint = GL_FASTEST;
 122       glHint(GL_PERSPECTIVE_CORRECTION_HINT, PerspHint);
 123       break;
 124    default:
 125       return;
 126    }
 127    glutPostRedisplay();
 128 }
 129
 130
 131 int
 132 main(int argc, char** argv)
 133 {
 134     glutInit(&argc, argv);
 135     glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
 136     glutInitWindowSize (500, 500);
 137     glutCreateWindow (argv[0]);
 138     glutReshapeFunc (reshape);
 139     glutDisplayFunc(display);
 140     glutKeyboardFunc(key);
 141
 142     printf("Main quad: perspective projection\n");
 143     printf("Middle stripe: linear interpolation\n");
 144     printf("Press 'i' to toggle interpolation hint\n");
 145     init();
 146
 147     glutMainLoop();
 148     return 0;
 149 }