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