progs/trivial/quad-tex-alpha.c

   1 /*
   2  * Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
   3  *
   4  * Permission to use, copy, modify, distribute, and sell this software and
   5  * its documentation for any purpose is hereby granted without fee, provided
   6  * that (i) the above copyright notices and this permission notice appear in
   7  * all copies of the software and related documentation, and (ii) the name of
   8  * Silicon Graphics may not be used in any advertising or
   9  * publicity relating to the software without the specific, prior written
  10  * permission of Silicon Graphics.
  11  *
  12  * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
  13  * ANY KIND,
  14  * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
  15  * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
  16  *
  17  * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
  18  * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
  19  * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
  20  * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
  21  * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  22  * OF THIS SOFTWARE.
  23  */
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28 #include <GL/glut.h>
  29
  30
  31 #define CI_OFFSET_1 16
  32 #define CI_OFFSET_2 32
  33
  34
  35 GLenum doubleBuffer;
  36
  37 static void Init(void)
  38 {
  39    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  40    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  41    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  42    fflush(stderr);
  43
  44     glClearColor(0.0, 0.0, 1.0, 0.0);
  45
  46 #define SIZE 16
  47    {
  48       GLubyte tex2d[SIZE][SIZE][4];
  49       GLint s, t;
  50
  51       for (s = 0; s < SIZE; s++) {
  52          for (t = 0; t < SIZE; t++) {
  53             tex2d[t][s][0] = (s < SIZE/2) ? 0 : 255;
  54             tex2d[t][s][1] = (t < SIZE/2) ? 0 : 255;
  55             tex2d[t][s][2] = 0;
  56             tex2d[t][s][3] = ((t^s) & 3) * 63;
  57          }
  58       }
  59
  60       glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
  61       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_REPEAT);
  62       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  63       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  64
  65       glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
  66       glTexImage2D(GL_TEXTURE_2D, 0, 4, SIZE, SIZE, 0,
  67                    GL_RGBA, GL_UNSIGNED_BYTE, tex2d);
  68       glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
  69       glEnable(GL_TEXTURE_2D);
  70    }
  71 }
  72
  73 static void Reshape(int width, int height)
  74 {
  75
  76     glViewport(0, 0, (GLint)width, (GLint)height);
  77
  78     glMatrixMode(GL_PROJECTION);
  79     glLoadIdentity();
  80     glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
  81     glMatrixMode(GL_MODELVIEW);
  82 }
  83
  84 static void Key(unsigned char key, int x, int y)
  85 {
  86
  87     switch (key) {
  88       case 27:
  89         exit(1);
  90       default:
  91         break;
  92     }
  93
  94     glutPostRedisplay();
  95 }
  96
  97 static void Draw(void)
  98 {
  99    glClear(GL_COLOR_BUFFER_BIT);
 100
 101    glDisable(GL_DEPTH_TEST);
 102    glDisable(GL_STENCIL_TEST);
 103    glEnable(GL_ALPHA_TEST);
 104    glAlphaFunc(GL_GEQUAL, 0.5);
 105
 106    glBegin(GL_QUADS);
 107    glTexCoord2f(1,0);
 108    glVertex3f( 0.9, -0.9, -30.0);
 109    glTexCoord2f(1,1);
 110    glVertex3f( 0.9,  0.9, -30.0);
 111    glTexCoord2f(0,1);
 112    glVertex3f(-0.9,  0.9, -30.0);
 113    glTexCoord2f(0,0);
 114    glVertex3f(-0.9,  -0.9, -30.0);
 115    glEnd();
 116
 117
 118    glFlush();
 119
 120    if (doubleBuffer) {
 121       glutSwapBuffers();
 122    }
 123 }
 124
 125 static GLenum Args(int argc, char **argv)
 126 {
 127     GLint i;
 128
 129     doubleBuffer = GL_FALSE;
 130
 131     for (i = 1; i < argc; i++) {
 132         if (strcmp(argv[i], "-sb") == 0) {
 133             doubleBuffer = GL_FALSE;
 134         } else if (strcmp(argv[i], "-db") == 0) {
 135             doubleBuffer = GL_TRUE;
 136         } else {
 137             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 138             return GL_FALSE;
 139         }
 140     }
 141     return GL_TRUE;
 142 }
 143
 144 int main(int argc, char **argv)
 145 {
 146     GLenum type;
 147
 148     glutInit(&argc, argv);
 149
 150     if (Args(argc, argv) == GL_FALSE) {
 151         exit(1);
 152     }
 153
 154     glutInitWindowPosition(100, 0); glutInitWindowSize( 250, 250);
 155
 156     type = GLUT_RGB;
 157     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 158     glutInitDisplayMode(type);
 159
 160     if (glutCreateWindow(*argv) == GL_FALSE) {
 161         exit(1);
 162     }
 163
 164     Init();
 165
 166     glutReshapeFunc(Reshape);
 167     glutKeyboardFunc(Key);
 168     glutDisplayFunc(Draw);
 169     glutMainLoop();
 170         return 0;
 171 }