--- /dev/null
+/* xscreensaver, Copyright (c) 1992, 1995, 1996, 1997
+ * Jamie Zawinski <jwz@netscape.com>
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation. No representations are made about the suitability of this
+ * software for any purpose. It is provided "as is" without express or
+ * implied warranty.
+ */
+
+/* Simulation of a pair of quasi-gravitational fields, maybe sorta kinda
+ a little like the strong and weak electromagnetic forces. Derived from
+ a Lispm screensaver by John Pezaris <pz@mit.edu>. Mouse control and
+ viscosity added by "Philip Edward Cutone, III" <pc2d+@andrew.cmu.edu>.
+
+ John sez:
+
+ The simulation started out as a purely accurate gravitational simulation,
+ but, with constant simulation step size, I quickly realized the field being
+ simulated while grossly gravitational was, in fact, non-conservative. It
+ also had the rather annoying behavior of dealing very badly with colliding
+ orbs. Therefore, I implemented a negative-gravity region (with two
+ thresholds; as I read your code, you only implemented one) to prevent orbs
+ from every coming too close together, and added a viscosity factor if the
+ speed of any orb got too fast. This provides a nice stable system with
+ interesting behavior.
+
+ I had experimented with a number of fields including the van der Waals
+ force (very interesting orbiting behavior) and 1/r^3 gravity (not as
+ interesting as 1/r^2). An even normal viscosity (rather than the
+ thresholded version to bleed excess energy) is also not interesting.
+ The 1/r^2, -1/r^2, -10/r^2 thresholds proved not only robust but also
+ interesting -- the orbs never collided and the threshold viscosity fixed
+ the non-conservational problem.
+
+ Philip sez:
+ > An even normal viscosity (rather than the thresholded version to
+ > bleed excess energy) is also not interesting.
+
+ unless you make about 200 points.... set the viscosity to about .8
+ and drag the mouse through it. it makes a nice wave which travels
+ through the field.
+
+ And (always the troublemaker) Joe Keane <jgk@jgk.org> sez:
+
+ Despite what John sez, the field being simulated is always conservative.
+ The real problem is that it uses a simple hack, computing acceleration
+ *based only on the starting position*, instead of a real differential
+ equation solver. Thus you'll always have energy coming out of nowhere,
+ although it's most blatant when balls get close together. If it were
+ done right, you wouldn't need viscosity or artificial limits on how
+ close the balls can get.
+ */
+
+#include <stdio.h>
+#include <math.h>
+#include "screenhack.h"
+#include "spline.h"
+
+struct ball {
+ double x, y;
+ double vx, vy;
+ double dx, dy;
+ double mass;
+ int size;
+ int pixel_index;
+ int hue;
+};
+
+static struct ball *balls;
+static int npoints;
+static int threshold;
+static int delay;
+static int global_size;
+static int segments;
+static Bool glow_p;
+static Bool orbit_p;
+static XPoint *point_stack;
+static int point_stack_size, point_stack_fp;
+static XColor *colors;
+static int ncolors;
+static int fg_index;
+static int color_shift;
+
+/*flip mods for mouse interaction*/
+static Bool mouse_p;
+int mouse_x, mouse_y, mouse_mass, root_x, root_y;
+static double viscosity;
+
+static enum object_mode {
+ ball_mode, line_mode, polygon_mode, spline_mode, spline_filled_mode,
+ tail_mode
+} mode;
+
+static GC draw_gc, erase_gc;
+
+#define MAX_SIZE 16
+
+#define min(a,b) ((a)<(b)?(a):(b))
+#define max(a,b) ((a)>(b)?(a):(b))
+
+static void
+init_balls (Display *dpy, Window window)
+{
+ int i;
+ XWindowAttributes xgwa;
+ XGCValues gcv;
+ int xlim, ylim, midx, midy, r, vx, vy;
+ double th;
+ Colormap cmap;
+ char *mode_str;
+ XGetWindowAttributes (dpy, window, &xgwa);
+ xlim = xgwa.width;
+ ylim = xgwa.height;
+ cmap = xgwa.colormap;
+ midx = xlim/2;
+ midy = ylim/2;
+ r = get_integer_resource ("radius", "Integer");
+ if (r <= 0 || r > min (xlim/2, ylim/2))
+ r = min (xlim/2, ylim/2) - 50;
+ vx = get_integer_resource ("vx", "Integer");
+ vy = get_integer_resource ("vy", "Integer");
+ npoints = get_integer_resource ("points", "Integer");
+ if (npoints < 1)
+ npoints = 3 + (random () % 5);
+ balls = (struct ball *) malloc (npoints * sizeof (struct ball));
+ segments = get_integer_resource ("segments", "Integer");
+ if (segments < 0) segments = 1;
+ threshold = get_integer_resource ("threshold", "Integer");
+ if (threshold < 0) threshold = 0;
+ delay = get_integer_resource ("delay", "Integer");
+ if (delay < 0) delay = 0;
+ global_size = get_integer_resource ("size", "Integer");
+ if (global_size < 0) global_size = 0;
+ glow_p = get_boolean_resource ("glow", "Boolean");
+ orbit_p = get_boolean_resource ("orbit", "Boolean");
+ color_shift = get_integer_resource ("colorShift", "Integer");
+ if (color_shift <= 0) color_shift = 5;
+
+ /*flip mods for mouse interaction*/
+ mouse_p = get_boolean_resource ("mouse", "Boolean");
+ mouse_mass = get_integer_resource ("mouseSize", "Integer");
+ mouse_mass = mouse_mass * mouse_mass *10;
+
+ viscosity = get_float_resource ("viscosity", "Float");
+
+ mode_str = get_string_resource ("mode", "Mode");
+ if (! mode_str) mode = ball_mode;
+ else if (!strcmp (mode_str, "balls")) mode = ball_mode;
+ else if (!strcmp (mode_str, "lines")) mode = line_mode;
+ else if (!strcmp (mode_str, "polygons")) mode = polygon_mode;
+ else if (!strcmp (mode_str, "tails")) mode = tail_mode;
+ else if (!strcmp (mode_str, "splines")) mode = spline_mode;
+ else if (!strcmp (mode_str, "filled-splines")) mode = spline_filled_mode;
+ else {
+ fprintf (stderr,
+ "%s: mode must be balls, lines, tails, polygons, splines, or\n\
+ filled-splines, not \"%s\"\n",
+ progname, mode_str);
+ exit (1);
+ }
+
+ if (mode != ball_mode && mode != tail_mode) glow_p = False;
+
+ if (mode == polygon_mode && npoints < 3)
+ mode = line_mode;
+
+ ncolors = get_integer_resource ("colors", "Colors");
+ if (ncolors < 2) ncolors = 2;
+ if (ncolors <= 2) mono_p = True;
+ colors = 0;
+
+ if (!mono_p)
+ {
+ fg_index = 0;
+ switch (mode)
+ {
+ case ball_mode:
+ if (glow_p)
+ {
+ int H = random() % 360;
+ double S1 = 0.25;
+ double S2 = 1.00;
+ double V = frand(0.25) + 0.75;
+ colors = (XColor *) malloc(sizeof(*colors) * (ncolors+1));
+ make_color_ramp (dpy, cmap, H, S1, V, H, S2, V, colors, &ncolors,
+ False, True, False);
+ }
+ else
+ {
+ ncolors = npoints;
+ colors = (XColor *) malloc(sizeof(*colors) * (ncolors+1));
+ make_random_colormap (dpy, xgwa.visual, cmap, colors, &ncolors,
+ True, True, False, True);
+ }
+ break;
+ case line_mode:
+ case polygon_mode:
+ case spline_mode:
+ case spline_filled_mode:
+ case tail_mode:
+ colors = (XColor *) malloc(sizeof(*colors) * (ncolors+1));
+ make_smooth_colormap (dpy, xgwa.visual, cmap, colors, &ncolors,
+ True, False, True);
+ break;
+ default:
+ abort ();
+ }
+ }
+
+ if (!mono_p && ncolors <= 2)
+ {
+ if (colors) free (colors);
+ colors = 0;
+ mono_p = True;
+ }
+
+ if (mode != ball_mode)
+ {
+ int size = (segments ? segments : 1);
+ point_stack_size = size * (npoints + 1);
+ point_stack = (XPoint *) calloc (point_stack_size, sizeof (XPoint));
+ point_stack_fp = 0;
+ }
+
+ gcv.line_width = (mode == tail_mode
+ ? (global_size ? global_size : (MAX_SIZE * 2 / 3))
+ : 1);
+ gcv.cap_style = (mode == tail_mode ? CapRound : CapButt);
+
+ if (mono_p)
+ gcv.foreground = get_pixel_resource("foreground", "Foreground", dpy, cmap);
+ else
+ gcv.foreground = colors[fg_index].pixel;
+ draw_gc = XCreateGC (dpy, window, GCForeground|GCLineWidth|GCCapStyle, &gcv);
+
+ gcv.foreground = get_pixel_resource("background", "Background", dpy, cmap);
+ erase_gc = XCreateGC (dpy, window, GCForeground|GCLineWidth|GCCapStyle,&gcv);
+
+
+#define rand_size() min (MAX_SIZE, 8 + (random () % (MAX_SIZE - 9)))
+
+ if (orbit_p && !global_size)
+ /* To orbit, all objects must be the same mass, or the math gets
+ really hairy... */
+ global_size = rand_size ();
+
+ th = frand (M_PI+M_PI);
+ for (i = 0; i < npoints; i++)
+ {
+ int new_size = (global_size ? global_size : rand_size ());
+ balls [i].dx = 0;
+ balls [i].dy = 0;
+ balls [i].size = new_size;
+ balls [i].mass = (new_size * new_size * 10);
+ balls [i].x = midx + r * cos (i * ((M_PI+M_PI) / npoints) + th);
+ balls [i].y = midy + r * sin (i * ((M_PI+M_PI) / npoints) + th);
+ if (! orbit_p)
+ {
+ balls [i].vx = vx ? vx : ((6.0 - (random () % 11)) / 8.0);
+ balls [i].vy = vy ? vy : ((6.0 - (random () % 11)) / 8.0);
+ }
+ if (mono_p || mode != ball_mode)
+ balls [i].pixel_index = -1;
+ else if (glow_p)
+ balls [i].pixel_index = 0;
+ else
+ balls [i].pixel_index = random() % ncolors;
+ }
+
+ if (orbit_p)
+ {
+ double a = 0;
+ double v;
+ double v_mult = get_float_resource ("vMult", "Float");
+ if (v_mult == 0.0) v_mult = 1.0;
+
+ for (i = 1; i < npoints; i++)
+ {
+ double _2ipi_n = (2 * i * M_PI / npoints);
+ double x = r * cos (_2ipi_n);
+ double y = r * sin (_2ipi_n);
+ double distx = r - x;
+ double dist2 = (distx * distx) + (y * y);
+ double dist = sqrt (dist2);
+ double a1 = ((balls[i].mass / dist2) *
+ ((dist < threshold) ? -1.0 : 1.0) *
+ (distx / dist));
+ a += a1;
+ }
+ if (a < 0.0)
+ {
+ fprintf (stderr, "%s: domain error: forces on balls too great\n",
+ progname);
+ exit (-1);
+ }
+ v = sqrt (a * r) * v_mult;
+ for (i = 0; i < npoints; i++)
+ {
+ double k = ((2 * i * M_PI / npoints) + th);
+ balls [i].vx = -v * sin (k);
+ balls [i].vy = v * cos (k);
+ }
+ }
+
+ if (mono_p) glow_p = False;
+ XClearWindow (dpy, window);
+}
+
+static void
+compute_force (int i, double *dx_ret, double *dy_ret)
+{
+ int j;
+ double x_dist, y_dist, dist, dist2;
+ *dx_ret = 0;
+ *dy_ret = 0;
+ for (j = 0; j < npoints; j++)
+ {
+ if (i == j) continue;
+ x_dist = balls [j].x - balls [i].x;
+ y_dist = balls [j].y - balls [i].y;
+ dist2 = (x_dist * x_dist) + (y_dist * y_dist);
+ dist = sqrt (dist2);
+
+ if (dist > 0.1) /* the balls are not overlapping */
+ {
+ double new_acc = ((balls[j].mass / dist2) *
+ ((dist < threshold) ? -1.0 : 1.0));
+ double new_acc_dist = new_acc / dist;
+ *dx_ret += new_acc_dist * x_dist;
+ *dy_ret += new_acc_dist * y_dist;
+ }
+ else
+ { /* the balls are overlapping; move randomly */
+ *dx_ret += (frand (10.0) - 5.0);
+ *dy_ret += (frand (10.0) - 5.0);
+ }
+ }
+
+ if (mouse_p)
+ {
+ x_dist = mouse_x - balls [i].x;
+ y_dist = mouse_y - balls [i].y;
+ dist2 = (x_dist * x_dist) + (y_dist * y_dist);
+ dist = sqrt (dist2);
+
+ if (dist > 0.1) /* the balls are not overlapping */
+ {
+ double new_acc = ((mouse_mass / dist2) *
+ ((dist < threshold) ? -1.0 : 1.0));
+ double new_acc_dist = new_acc / dist;
+ *dx_ret += new_acc_dist * x_dist;
+ *dy_ret += new_acc_dist * y_dist;
+ }
+ else
+ { /* the balls are overlapping; move randomly */
+ *dx_ret += (frand (10.0) - 5.0);
+ *dy_ret += (frand (10.0) - 5.0);
+ }
+ }
+}
+
+static void
+run_balls (Display *dpy, Window window)
+{
+ int last_point_stack_fp = point_stack_fp;
+ static int tick = 500, xlim, ylim;
+ static Colormap cmap;
+ int i;
+
+ /*flip mods for mouse interaction*/
+ Window root1, child1;
+ unsigned int mask;
+ if (mouse_p)
+ {
+ XQueryPointer(dpy, window, &root1, &child1,
+ &root_x, &root_y, &mouse_x, &mouse_y, &mask);
+ }
+
+ if (tick++ == 500)
+ {
+ XWindowAttributes xgwa;
+ XGetWindowAttributes (dpy, window, &xgwa);
+ tick = 0;
+ xlim = xgwa.width;
+ ylim = xgwa.height;
+ cmap = xgwa.colormap;
+ }
+
+ /* compute the force of attraction/repulsion among all balls */
+ for (i = 0; i < npoints; i++)
+ compute_force (i, &balls[i].dx, &balls[i].dy);
+
+ /* move the balls according to the forces now in effect */
+ for (i = 0; i < npoints; i++)
+ {
+ double old_x = balls[i].x;
+ double old_y = balls[i].y;
+ double new_x, new_y;
+ int size = balls[i].size;
+ balls[i].vx += balls[i].dx;
+ balls[i].vy += balls[i].dy;
+
+ /* don't let them get too fast: impose a terminal velocity
+ (actually, make the medium have friction) */
+ if (balls[i].vx > 10)
+ {
+ balls[i].vx *= 0.9;
+ balls[i].dx = 0;
+ }
+ else if (viscosity != 1)
+ {
+ balls[i].vx *= viscosity;
+ }
+
+ if (balls[i].vy > 10)
+ {
+ balls[i].vy *= 0.9;
+ balls[i].dy = 0;
+ }
+ else if (viscosity != 1)
+ {
+ balls[i].vy *= viscosity;
+ }
+
+ balls[i].x += balls[i].vx;
+ balls[i].y += balls[i].vy;
+
+ /* bounce off the walls */
+ if (balls[i].x >= (xlim - balls[i].size))
+ {
+ balls[i].x = (xlim - balls[i].size - 1);
+ if (balls[i].vx > 0)
+ balls[i].vx = -balls[i].vx;
+ }
+ if (balls[i].y >= (ylim - balls[i].size))
+ {
+ balls[i].y = (ylim - balls[i].size - 1);
+ if (balls[i].vy > 0)
+ balls[i].vy = -balls[i].vy;
+ }
+ if (balls[i].x <= 0)
+ {
+ balls[i].x = 0;
+ if (balls[i].vx < 0)
+ balls[i].vx = -balls[i].vx;
+ }
+ if (balls[i].y <= 0)
+ {
+ balls[i].y = 0;
+ if (balls[i].vy < 0)
+ balls[i].vy = -balls[i].vy;
+ }
+
+ new_x = balls[i].x;
+ new_y = balls[i].y;
+
+ if (!mono_p)
+ {
+ if (mode == ball_mode)
+ {
+ if (glow_p)
+ {
+ /* make color saturation be related to particle
+ acceleration. */
+ double limit = 0.5;
+ double s, fraction;
+ double vx = balls [i].dx;
+ double vy = balls [i].dy;
+ if (vx < 0) vx = -vx;
+ if (vy < 0) vy = -vy;
+ fraction = vx + vy;
+ if (fraction > limit) fraction = limit;
+
+ s = 1 - (fraction / limit);
+ balls[i].pixel_index = (ncolors * s);
+ }
+ XSetForeground (dpy, draw_gc,
+ colors[balls[i].pixel_index].pixel);
+ }
+ }
+
+ if (mode == ball_mode)
+ {
+ XFillArc (dpy, window, erase_gc, (int) old_x, (int) old_y,
+ size, size, 0, 360*64);
+ XFillArc (dpy, window, draw_gc, (int) new_x, (int) new_y,
+ size, size, 0, 360*64);
+ }
+ else
+ {
+ point_stack [point_stack_fp].x = new_x;
+ point_stack [point_stack_fp].y = new_y;
+ point_stack_fp++;
+ }
+ }
+
+ /* draw the lines or polygons after computing all points */
+ if (mode != ball_mode)
+ {
+ point_stack [point_stack_fp].x = balls [0].x; /* close the polygon */
+ point_stack [point_stack_fp].y = balls [0].y;
+ point_stack_fp++;
+ if (point_stack_fp == point_stack_size)
+ point_stack_fp = 0;
+ else if (point_stack_fp > point_stack_size) /* better be aligned */
+ abort ();
+ if (!mono_p)
+ {
+ static int tick = 0;
+ if (tick++ == color_shift)
+ {
+ tick = 0;
+ fg_index = (fg_index + 1) % ncolors;
+ XSetForeground (dpy, draw_gc, colors[fg_index].pixel);
+ }
+ }
+ }
+
+ switch (mode)
+ {
+ case ball_mode:
+ break;
+ case line_mode:
+ if (segments > 0)
+ XDrawLines (dpy, window, erase_gc, point_stack + point_stack_fp,
+ npoints + 1, CoordModeOrigin);
+ XDrawLines (dpy, window, draw_gc, point_stack + last_point_stack_fp,
+ npoints + 1, CoordModeOrigin);
+ break;
+ case polygon_mode:
+ if (segments > 0)
+ XFillPolygon (dpy, window, erase_gc, point_stack + point_stack_fp,
+ npoints + 1, (npoints == 3 ? Convex : Complex),
+ CoordModeOrigin);
+ XFillPolygon (dpy, window, draw_gc, point_stack + last_point_stack_fp,
+ npoints + 1, (npoints == 3 ? Convex : Complex),
+ CoordModeOrigin);
+ break;
+ case tail_mode:
+ {
+ for (i = 0; i < npoints; i++)
+ {
+ int index = point_stack_fp + i;
+ int next_index = (index + (npoints + 1)) % point_stack_size;
+ XDrawLine (dpy, window, erase_gc,
+ point_stack [index].x,
+ point_stack [index].y,
+ point_stack [next_index].x,
+ point_stack [next_index].y);
+
+ index = last_point_stack_fp + i;
+ next_index = (index - (npoints + 1)) % point_stack_size;
+ if (next_index < 0) next_index += point_stack_size;
+ if (point_stack [next_index].x == 0 &&
+ point_stack [next_index].y == 0)
+ continue;
+ XDrawLine (dpy, window, draw_gc,
+ point_stack [index].x,
+ point_stack [index].y,
+ point_stack [next_index].x,
+ point_stack [next_index].y);
+ }
+ }
+ break;
+ case spline_mode:
+ case spline_filled_mode:
+ {
+ static spline *s = 0;
+ if (! s) s = make_spline (npoints);
+ if (segments > 0)
+ {
+ for (i = 0; i < npoints; i++)
+ {
+ s->control_x [i] = point_stack [point_stack_fp + i].x;
+ s->control_y [i] = point_stack [point_stack_fp + i].y;
+ }
+ compute_closed_spline (s);
+ if (mode == spline_filled_mode)
+ XFillPolygon (dpy, window, erase_gc, s->points, s->n_points,
+ (s->n_points == 3 ? Convex : Complex),
+ CoordModeOrigin);
+ else
+ XDrawLines (dpy, window, erase_gc, s->points, s->n_points,
+ CoordModeOrigin);
+ }
+ for (i = 0; i < npoints; i++)
+ {
+ s->control_x [i] = point_stack [last_point_stack_fp + i].x;
+ s->control_y [i] = point_stack [last_point_stack_fp + i].y;
+ }
+ compute_closed_spline (s);
+ if (mode == spline_filled_mode)
+ XFillPolygon (dpy, window, draw_gc, s->points, s->n_points,
+ (s->n_points == 3 ? Convex : Complex),
+ CoordModeOrigin);
+ else
+ XDrawLines (dpy, window, draw_gc, s->points, s->n_points,
+ CoordModeOrigin);
+ }
+ break;
+ default:
+ abort ();
+ }
+
+ XSync (dpy, True);
+}
+
+\f
+char *progclass = "Attraction";
+
+char *defaults [] = {
+ "Attraction.background: black", /* to placate SGI */
+ "Attraction.foreground: white",
+ "*mode: balls",
+ "*points: 0",
+ "*size: 0",
+ "*colors: 200",
+ "*threshold: 100",
+ "*delay: 10000",
+ "*glow: false",
+ "*mouseSize: 10",
+ "*mouse: false",
+ "*viscosity: 1",
+ "*orbit: false",
+ "*colorShift: 3",
+ "*segments: 500",
+ "*vMult: 0.9",
+ 0
+};
+
+XrmOptionDescRec options [] = {
+ { "-mode", ".mode", XrmoptionSepArg, 0 },
+ { "-colors", ".colors", XrmoptionSepArg, 0 },
+ { "-points", ".points", XrmoptionSepArg, 0 },
+ { "-color-shift", ".colorShift", XrmoptionSepArg, 0 },
+ { "-threshold", ".threshold", XrmoptionSepArg, 0 },
+ { "-segments", ".segments", XrmoptionSepArg, 0 },
+ { "-delay", ".delay", XrmoptionSepArg, 0 },
+ { "-size", ".size", XrmoptionSepArg, 0 },
+ { "-radius", ".radius", XrmoptionSepArg, 0 },
+ { "-vx", ".vx", XrmoptionSepArg, 0 },
+ { "-vy", ".vy", XrmoptionSepArg, 0 },
+ { "-vmult", ".vMult", XrmoptionSepArg, 0 },
+ { "-mouse-size", ".mouseSize", XrmoptionSepArg, 0 },
+ { "-mouse", ".mouse", XrmoptionNoArg, "true" },
+ { "-nomouse", ".mouse", XrmoptionNoArg, "false" },
+ { "-viscosity", ".viscosity", XrmoptionSepArg, 0 },
+ { "-glow", ".glow", XrmoptionNoArg, "true" },
+ { "-noglow", ".glow", XrmoptionNoArg, "false" },
+ { "-orbit", ".orbit", XrmoptionNoArg, "true" },
+ { 0, 0, 0, 0 }
+};
+
+void
+screenhack (Display *dpy, Window window)
+{
+ init_balls (dpy, window);
+ while (1)
+ {
+ run_balls (dpy, window);
+ if (delay) usleep (delay);
+ }
+}
projects / xscreensaver / blobdiff