progs/trivial/point-param.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 <GL/glew.h>
  26 #include <math.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <stdlib.h>
  30 #include <GL/glut.h>
  31
  32
  33
  34 GLenum doubleBuffer;
  35
  36 static void Init(void)
  37 {
  38    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
  39    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
  40    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
  41    fflush(stderr);
  42
  43    glClearColor(0.0, 0.0, 1.0, 0.0);
  44 }
  45
  46 static void Reshape(int width, int height)
  47 {
  48     glViewport(0, 0, (GLint)width, (GLint)height);
  49
  50     glMatrixMode(GL_PROJECTION);
  51     glLoadIdentity();
  52     glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 100.0);
  53     glMatrixMode(GL_MODELVIEW);
  54 }
  55
  56 static void Key(unsigned char key, int x, int y)
  57 {
  58     switch (key) {
  59     case 27:
  60         exit(1);
  61     default:
  62         break;
  63     }
  64     glutPostRedisplay();
  65 }
  66
  67
  68 static float
  69 expected(float z, float size, const float atten[3])
  70 {
  71    float dist = fabs(z);
  72    const GLfloat q = atten[0] + dist * (atten[1] + dist * atten[2]);
  73    const GLfloat a = sqrt(1.0 / q);
  74    return size * a;
  75 }
  76
  77
  78 static void Draw(void)
  79 {
  80    static GLfloat atten[3] = { 0.0, 0.1, .01 };
  81    float size = 40.0;
  82    int i;
  83
  84    glClear(GL_COLOR_BUFFER_BIT);
  85
  86    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  87    glPointSize(size);
  88    glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, atten);
  89
  90    glColor3f(1,0,0);
  91
  92    printf("Expected point sizes:\n");
  93    glBegin(GL_POINTS);
  94    for (i = 0; i < 5; i++) {
  95       float x = -0.8 + i * 0.4;
  96       float z = -i * 20 - 10;
  97       glVertex3f( x, 0.0, z);
  98       printf(" %f\n", expected(z, size, atten));
  99    }
 100    glEnd();
 101
 102    glFlush();
 103
 104    if (doubleBuffer) {
 105       glutSwapBuffers();
 106    }
 107 }
 108
 109
 110 static GLenum Args(int argc, char **argv)
 111 {
 112     GLint i;
 113
 114     doubleBuffer = GL_FALSE;
 115
 116     for (i = 1; i < argc; i++) {
 117         if (strcmp(argv[i], "-sb") == 0) {
 118             doubleBuffer = GL_FALSE;
 119         } else if (strcmp(argv[i], "-db") == 0) {
 120             doubleBuffer = GL_TRUE;
 121         } else {
 122             fprintf(stderr, "%s (Bad option).\n", argv[i]);
 123             return GL_FALSE;
 124         }
 125     }
 126     return GL_TRUE;
 127 }
 128
 129
 130 int main(int argc, char **argv)
 131 {
 132     GLenum type;
 133
 134     glutInit(&argc, argv);
 135
 136     if (Args(argc, argv) == GL_FALSE) {
 137         exit(1);
 138     }
 139
 140     glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
 141
 142     type = GLUT_RGB | GLUT_ALPHA;
 143     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
 144     glutInitDisplayMode(type);
 145
 146     if (glutCreateWindow(argv[0]) == GL_FALSE) {
 147         exit(1);
 148     }
 149
 150     glewInit();
 151
 152     Init();
 153
 154     glutReshapeFunc(Reshape);
 155     glutKeyboardFunc(Key);
 156     glutDisplayFunc(Draw);
 157     glutMainLoop();
 158     return 0;
 159 }