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/*
* Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
*
* Permission to use, copy, modify, distribute, and sell this software and
* its documentation for any purpose is hereby granted without fee, provided
* that (i) the above copyright notices and this permission notice appear in
* all copies of the software and related documentation, and (ii) the name of
* Silicon Graphics may not be used in any advertising or
* publicity relating to the software without the specific, prior written
* permission of Silicon Graphics.
*
* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
* ANY KIND,
* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
*
* IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*/
#define GL_GLEXT_PROTOTYPES
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <GL/glut.h>
GLenum doubleBuffer;
static void Init(void)
{
fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR));
glClearColor(0.0, 0.0, 1.0, 0.0);
}
static void Reshape(int width, int height)
{
glViewport(0, 0, (GLint)width, (GLint)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 100.0);
glMatrixMode(GL_MODELVIEW);
}
static void Key(unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(1);
default:
return;
}
glutPostRedisplay();
}
static float
expected(float z, float size, const float atten[3])
{
float dist = fabs(z);
const GLfloat q = atten[0] + dist * (atten[1] + dist * atten[2]);
const GLfloat a = sqrt(1.0 / q);
return size * a;
}
static void Draw(void)
{
static GLfloat atten[3] = { 0.0, 0.1, .01 };
float size = 40.0;
int i;
glClear(GL_COLOR_BUFFER_BIT);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glPointSize(size);
glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, atten);
glColor3f(1,0,0);
printf("Expected point sizes:\n");
glBegin(GL_POINTS);
for (i = 0; i < 5; i++) {
float x = -0.8 + i * 0.4;
float z = -i * 20 - 10;
glVertex3f( x, 0.0, z);
printf(" %f\n", expected(z, size, atten));
}
glEnd();
glFlush();
if (doubleBuffer) {
glutSwapBuffers();
}
}
static GLenum Args(int argc, char **argv)
{
GLint i;
doubleBuffer = GL_FALSE;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-sb") == 0) {
doubleBuffer = GL_FALSE;
} else if (strcmp(argv[i], "-db") == 0) {
doubleBuffer = GL_TRUE;
} else {
fprintf(stderr, "%s (Bad option).\n", argv[i]);
return GL_FALSE;
}
}
return GL_TRUE;
}
int main(int argc, char **argv)
{
GLenum type;
glutInit(&argc, argv);
if (Args(argc, argv) == GL_FALSE) {
exit(1);
}
glutInitWindowPosition(0, 0); glutInitWindowSize( 250, 250);
type = GLUT_RGB | GLUT_ALPHA;
type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
glutInitDisplayMode(type);
if (glutCreateWindow(argv[0]) == GL_FALSE) {
exit(1);
}
Init();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
glutMainLoop();
return 0;
}
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