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SGI Developer Toolbox 6.1
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SGI Developer Toolbox 6.1 - Disc 1.iso
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toolbox
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src
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demos
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OpenGL
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lorenz
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lorenz.c
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1996-11-11
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/*
* Lorenz Attractor Demo
*
* Adapted from code originally written for the 4D60GT by
* Aaron T. Ferrucci (aaronf@cse.ucsc.edu), 7/3/92.
*
* Description:
*
* This program shows some particles stuck in a Lorenz attractor (the parameters
* used are r=28, b=8/3, sigma=10). The eye is attracted to the red particle,
* with a force directly proportionate to distance. A command line
* puts the whole mess inside a box made of hexagons. I think this helps to
* maintain the illusion of 3 dimensions, but it can slow things down.
* Other options allow you to play with the redraw rate and the number of new
* lines per redraw. So you can customize it to the speed of your machine.
*
* For general info on Lorenz attractors I recommend "An Introduction to
* the Lorenz Equations", IEEE Transactions on Circuits and Systems, August '83.
*
* Bugs: hidden surface removal doesn't apply to hexagons, and
* works poorly on lines when they are too close together.
*
* Notes on OpenGL port:
*
* The timer functions do not exist in OpenGL, so the drawing occurs in a
* continuous loop, controlled by step, stop and go input from the keyboard.
* Perhaps system function could be called to control timing.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <math.h>
#include <time.h>
#include <getopt.h>
#include <GL/glut.h>
static GLuint asphere;
#define POINTMASK (unsigned long)511
#define G (0.002) /* eyept to red sphere gravity */
#define LG (0.3)
#define CUBESIDE (120.)
#define CUBESCALE (23.)
#define CUBEOFFX (-4.)
#define CUBEOFFY (0.)
#define CUBEOFFZ (57.)
#define FALSE 0
#define TRUE 1
/* globals */
float sigma = 10., r = 28., b = 8./3., dt = 0.003;
unsigned long rp = 0, bp = 0, gp = 0, yp = 0, mp = 0;
long xmax, ymax, zmax, zmin;
float rv[POINTMASK+1][3], /* red points */
bv[POINTMASK+1][3], /* blue points */
gv[POINTMASK+1][3], /* green points */
yv[POINTMASK+1][3], /* yellow points */
mv[POINTMASK+1][3]; /* magenta points */
int lpf; /* number of new lines per frame */
float eyex[3], /* eye location */
eyev[3], /* eye velocity */
eyel[3]; /* lookat point location */
GLint fovy = 600;
float dx, dy, dz;
GLUquadricObj *quadObj;
float cubeoffx = CUBEOFFX;
float cubeoffy = CUBEOFFY;
float cubeoffz = CUBEOFFZ;
float farplane = 80.;
int animate = 1;
/* option flags */
GLboolean hexflag, /* hexagons? */
sflag,
fflag,
wflag,
gflag,
debug;
/* option values */
short hexbright; /* brightness for hexagon color */
int speed, /* speed (number of new line segs per redraw) */
frame; /* frame rate (actually noise value for TIMER0) */
float a = 0,
da; /* hexagon rotational velocity (.1 degree/redraw) */
float gravity;
/* function declarations */
void init_3d(void);
void init_graphics(void);
void draw_hexcube(void);
void draw_hexplane(void);
void draw_hexagon(void);
void move_eye(void);
void redraw(void);
void next_line(float v[][3], unsigned long *p);
void parse_args(int argc, char **argv);
void print_usage(char*);
void print_info(void);
void sphdraw(float args[4]);
void setPerspective(int angle, float aspect, float zNear, float zFar);
static void Reshape(int width, int height)
{
glViewport(0,0,width,height);
glClear(GL_COLOR_BUFFER_BIT);
xmax = width;
ymax = height;
}
static void Key(unsigned char key, int x, int y)
{
switch (key) {
case 'g':
animate = 1;
glutPostRedisplay();
break;
case 's':
animate = 0;
glutPostRedisplay();
break;
case 27:
gluDeleteQuadric(quadObj);
exit(0);
}
}
static void Draw(void)
{
int i, j;
if (animate) {
i = speed;
while (i--) {
next_line(rv, &rp);
next_line(bv, &bp);
next_line(gv, &gp);
next_line(yv, &yp);
next_line(mv, &mp);
}
glPushMatrix();
move_eye();
redraw();
glPopMatrix();
}
}
void main(int argc, char **argv)
{
parse_args(argc, argv);
glutInitWindowSize(600, 600);
glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE);
glutCreateWindow("Lorenz Attractors");
init_3d();
init_graphics();
/* draw the first POINTMASK points in each color */
while(rp < POINTMASK) {
next_line(rv, &rp);
next_line(bv, &bp);
next_line(gv, &gp);
next_line(yv, &yp);
next_line(mv, &mp);
}
eyex[0] = eyex[1] = eyex[2] = 0.;
eyel[0] = rv[rp][0];
eyel[1] = rv[rp][1];
eyel[2] = rv[rp][2];
glPushMatrix();
move_eye();
redraw();
glPopMatrix();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutIdleFunc(Draw);
glutDisplayFunc(Draw);
glutMainLoop();
}
/* compute the next point on the path according to Lorenz' equations. */
void next_line(float v[][3], unsigned long *p)
{
dx = sigma * (v[*p][1] - v[*p][0]) * dt;
dy = (r*v[*p][0] - v[*p][1] + v[*p][0]*v[*p][2]) * dt;
dz = (v[*p][0] *v[*p][1] + b*v[*p][2]) * dt;
v[(*p + 1) & POINTMASK][0] = v[*p][0] + dx;
v[(*p + 1) & POINTMASK][1] = v[*p][1] + dy;
v[(*p + 1) & POINTMASK][2] = v[*p][2] - dz;
*p = (*p + 1) & POINTMASK;
}
void drawLines(unsigned long index, float array[POINTMASK][3])
{
unsigned long p;
int i;
#define LINE_STEP 4
p = (index+1)&POINTMASK;
i = LINE_STEP-(p % LINE_STEP);
if (i == LINE_STEP) i=0;
glBegin(GL_LINE_STRIP);
/* draw points in order from oldest to newest */
while(p != index) {
if (i == 0) {
glVertex3fv(array[p]);
i = LINE_STEP;
}
i--;
p = (p+1) & POINTMASK;
}
glVertex3fv(array[index]);
glEnd();
}
void redraw(void)
{
unsigned long p;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
if(hexflag)
draw_hexcube();
glColor3f(1.0, 0.0, 0.0);
drawLines(rp, rv);
sphdraw(rv[rp]);
glColor3f(0.0, 0.0, 1.0);
drawLines(bp, bv);
sphdraw(bv[bp]);
glColor3f(0.0, 1.0, 0.0);
drawLines(gp, gv);
sphdraw(gv[gp]);
glColor3f(1.0, 0.0, 1.0);
drawLines(yp, yv);
sphdraw(yv[yp]);
glColor3f(0.0, 1.0, 1.0);
drawLines(mp, mv);
sphdraw(mv[mp]);
glutSwapBuffers();
}
void move_eye(void)
{
/* first move the eye */
eyev[0] += gravity * (rv[rp][0] - eyex[0]);
eyev[1] += gravity * (rv[rp][1] - eyex[1]);
eyev[2] += gravity * (rv[rp][2] - eyex[2]);
/* adjust position using new velocity */
eyex[0] += eyev[0] * dt;
eyex[1] += eyev[1] * dt;
eyex[2] += eyev[2] * dt;
/* move the lookat point */
/* it catches up to the red point if it's moving slowly enough */
eyel[0] += LG * (rv[rp][0] - eyel[0]);
eyel[1] += LG * (rv[rp][1] - eyel[1]);
eyel[2] += LG * (rv[rp][2] - eyel[2]);
/* change view */
gluLookAt(eyex[0], eyex[1], eyex[2], eyel[0], eyel[1], eyel[2],
0, 1, 0);
}
void draw_hexcube(void)
{
a += da;
if(a >= 720.) /* depends on slowest rotation factor */
a = 0.;
/* draw hexplanes, without changing z-values */
glDepthMask(GL_FALSE);
glDisable(GL_DEPTH_TEST);
/* x-y plane */
glColor3f(0.2, 0.2, 0.6);
glPushMatrix();
glTranslatef(cubeoffx, cubeoffy, cubeoffz);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
/* x-y plane, translated */
glPushMatrix();
glTranslatef(cubeoffx, cubeoffy, cubeoffz - 2*CUBESIDE);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
glColor3f(0.6, 0.2, 0.2);
/* x-z plane, translate low */
glPushMatrix();
glRotatef(90, 1.0, 0.0, 0.0);
glTranslatef(cubeoffx, cubeoffz - CUBESIDE, -cubeoffy + CUBESIDE);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
/* x-z plane, translate high */
glPushMatrix();
glRotatef(90, 1.0, 0.0, 0.0);
glTranslatef(cubeoffx, cubeoffz - CUBESIDE, -cubeoffy - CUBESIDE);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
glColor3f(0.2, 0.6, 0.2);
/* y-z plane, translate low */
glPushMatrix();
glRotatef(90, 0.0, 1.0, 0.0);
glTranslatef(-cubeoffz + CUBESIDE, cubeoffy, cubeoffx + CUBESIDE);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
/* y-z plane, translate high */
glPushMatrix();
glRotatef (90, 0.0, 1.0, 0.0);
glTranslatef(-cubeoffz + CUBESIDE, cubeoffy, cubeoffx - CUBESIDE);
glScalef(CUBESCALE, CUBESCALE, CUBESCALE);
draw_hexplane();
glPopMatrix();
glFlush();
glDepthMask(GL_TRUE);
glEnable(GL_DEPTH_TEST);
}
float hex_data[8][3] = {
{0., 0., 0.},
{1.155, 0., 0.},
{0.577, 1., 0.},
{-0.577, 1., 0.},
{-1.155, 0., 0.},
{-0.577, -1., 0.},
{0.577, -1., 0.},
{1.155, 0., 0.},
};
/* draws a hexagon 2 units across, in the x-y plane, */
/* centered at <0, 0, 0> */
void draw_hexagon(void)
{
if(wflag) {
glPushMatrix();
glRotatef(a, 0.0, 0.0, 1.0);
}
glBegin(GL_TRIANGLE_FAN);
glVertex3fv(hex_data[0]);
glVertex3fv(hex_data[1]);
glVertex3fv(hex_data[2]);
glVertex3fv(hex_data[3]);
glVertex3fv(hex_data[4]);
glVertex3fv(hex_data[5]);
glVertex3fv(hex_data[6]);
glVertex3fv(hex_data[7]);
glEnd();
if(wflag)
glPopMatrix();
}
void tmp_draw_hexplane(void)
{
glRectf(-2.0, -2.0, 2.0, 2.0);
}
/* draw 7 hexagons */
void draw_hexplane(void)
{
if(wflag) {
glPushMatrix();
glRotatef(-0.5*a, 0.0, 0.0, 1.0);
}
/* center , <0, 0, 0> */
draw_hexagon();
/* 12 o'clock, <0, 4, 0> */
glTranslatef(0., 4., 0.);
draw_hexagon();
/* 10 o'clock, <-3.464, 2, 0> */
glTranslatef(-3.464, -2., 0.);
draw_hexagon();
/* 8 o'clock, <-3.464, -2, 0> */
glTranslatef(0., -4., 0.);
draw_hexagon();
/* 6 o'clock, <0, -4, 0> */
glTranslatef(3.464, -2., 0.);
draw_hexagon();
/* 4 o'clock, <3.464, -2, 0> */
glTranslatef(3.464, 2., 0.);
draw_hexagon();
/* 2 o'clock, <3.464, 2, 0> */
glTranslatef(0., 4., 0.);
draw_hexagon();
if(wflag)
glPopMatrix();
}
void sphdraw(float args[3])
{
glPushMatrix();
glTranslatef(args[0], args[1], args[2]);
glCallList(asphere);
glPopMatrix();
}
void setPerspective(int angle, float aspect, float zNear, float zFar)
{
glPushAttrib(GL_TRANSFORM_BIT);
glMatrixMode(GL_PROJECTION);
gluPerspective(angle * 0.1, aspect, zNear, zFar);
glPopAttrib();
}
/* initialize global 3-vectors */
void init_3d(void)
{
(void)srand48((long)time((time_t*)NULL));
/* initialize colored points */
rv[0][0] = (float)drand48() * 10.;
rv[0][1] = (float)drand48() * 10.;
rv[0][2] = (float)drand48() * 10. - 10.;
bv[0][0] = rv[0][0] + (float)drand48()*5.;
bv[0][1] = rv[0][1] + (float)drand48()*5.;
bv[0][0] = rv[0][2] + (float)drand48()*5.;
gv[0][0] = rv[0][0] + (float)drand48()*5.;
gv[0][1] = rv[0][1] + (float)drand48()*5.;
gv[0][0] = rv[0][2] + (float)drand48()*5.;
yv[0][0] = rv[0][0] + (float)drand48()*5.;
yv[0][1] = rv[0][1] + (float)drand48()*5.;
yv[0][0] = rv[0][2] + (float)drand48()*5.;
mv[0][0] = rv[0][0] + (float)drand48()*5.;
mv[0][1] = rv[0][1] + (float)drand48()*5.;
mv[0][0] = rv[0][2] + (float)drand48()*5.;
/* initialize eye velocity */
eyev[0] = eyev[1] = eyev[2] = 0.;
}
void init_graphics(void)
{
int width = 600;
int height = 600;
xmax = width;
ymax = height;
glDrawBuffer(GL_BACK);
glEnable(GL_DEPTH_TEST);
glClearColor(0.0, 0.0, 0.0, 0.0);
glClearDepth(1.0);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glViewport(0, 0, xmax, ymax);
setPerspective(fovy, (float)xmax/(float)ymax, 0.01, farplane);
quadObj = gluNewQuadric();
gluQuadricNormals(quadObj, GLU_NONE);
asphere = glGenLists(1);
glNewList(asphere, GL_COMPILE);
gluSphere(quadObj, 0.3, 12, 8);
glEndList();
}
extern char *optarg;
extern int optind, opterr;
#define USAGE "usage message: this space for rent\n"
void parse_args(int argc, char **argv)
{
int c;
hexflag = sflag = fflag = wflag = gflag = debug = FALSE;
opterr = 0;
while( (c = getopt(argc, argv, "Xhixs:f:w:g:")) != -1)
switch(c) {
case 'X':
debug = TRUE;
break;
case 'h':
print_usage(argv[0]);
exit(1);
case 'i':
print_info();
exit(1);
case 'x':
hexflag = TRUE;
farplane = 300.;
break;
case 's':
sflag = TRUE;
speed = atoi(optarg);
if(speed < 0) {
fprintf(stderr, "Use a small positive value for speed ('s').\n");
fprintf(stderr, "Try %s -h for help\n", argv[0]);
exit(1);
}
break;
case 'f':
fflag = TRUE;
frame = atoi(optarg);
if(frame < 0) {
fprintf(stderr, "Try a small positive value for \n");
fprintf(stderr, "'f'; this is the number of vertical ");
fprintf(stderr, "retraces per redraw\n");
fprintf(stderr, "Try %s -h for help\n", argv[0]);
exit(1);
}
break;
case 'w':
wflag = TRUE;
da = atof(optarg);
if(da > 10.) {
fprintf(stderr, "That's a large rotational velocity ('w')");
fprintf(stderr, " but you asked for it\n");
}
break;
case 'g':
gflag = TRUE;
gravity = atof(optarg);
if(gravity <= 0) {
fprintf(stderr, "Gravity ('g') should be positive\n");
fprintf(stderr, "Try %s -h for help\n", argv[0]);
}
break;
case '?':
fprintf(stderr, USAGE);
}
/* set up default values */
if(!sflag)
speed = 3;
if(!fflag)
frame = 2;
if(!wflag)
da = 0.;
if(!gflag)
gravity = G;
}
void print_usage(char *program)
{
printf("\nUsage: %s [-h] [-i] [-x] [-s speed]", program);
printf(" [-w rot_v] [-g gravity]\n\n");
printf("-h Print this message.\n");
printf("-i Print information about the demo.\n");
printf("-x Enclose the particles in a box made of hexagons.\n");
printf("-s speed Sets the number of new line segments per redraw \n");
printf(" interval per line. Default value: 3.\n");
/*** The X port does not currently include a timer, so this feature is disabled.
printf("-f framenoise Sets the number of vertical retraces per redraw\n");
printf(" interval. Example: -f 2 specifies one redraw per\n");
printf(" 2 vertical retraces, or 30 frames per second.\n");
printf(" Default value: 2.\n");
************/
printf("-w rot_v Spins the hexagons on their centers, and the sides\n");
printf(" of the box on their centers. Hexagons spin at the\n");
printf(" rate rot_v degrees per redraw, and box sides spin\n");
printf(" at -rot_v/2 degrees per redraw.\n");
printf("-g gravity Sets the strength of the attraction of the eye to\n");
printf(" the red particle. Actually, it's not gravity since\n");
printf(" the attraction is proportionate to distance.\n");
printf(" Default value: 0.002. Try large values!\n");
/* input added for GLX port */
printf(" Executions control: \n");
printf(" <spacebar> step through single frames\n");
printf(" g begin continuous frames\n");
printf(" s stop continuous frames\n");
}
void print_info(void)
{
printf("\nLORENZ ATTRACTOR DEMO\n\n");
printf("This program shows some particles stuck in a Lorenz attractor (the \n");
printf("parameters used are r=28, b=8/3, sigma=10). The eye is attracted to \n");
printf("the red particle, with a force directly proportional to distance. \n");
printf("A command line argument puts the particles inside a box made of hexagons, \n");
printf("helping to maintain the sense of 3 dimensions, but it can slow things down.\n");
printf("Other options allow you to play with the redraw rate and gravity.\n\n");
printf("Try lorenz -h for the usage message.\n");
}