* 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
+ * software for any purpose. It is provided "as is" without express or
* implied warranty.
*
* Ported to X11 and xscreensaver by jwz, 27-Feb-2002.
* http://astronomy.swin.edu.au/~pbourke/modelling/fluid/
*/
+/* cjb notes
+ *
+ * Future ideas:
+ * Specifying a distribution in the ball sizes (with a gamma curve, possibly).
+ * Brownian motion, for that extra touch of realism.
+ */
+
#include <math.h>
#include "screenhack.h"
#include <stdio.h>
float *opx, *opy; /* previous ball positions */
float *r; /* ball radiuses */
+ float *m; /* ball mass, precalculated */
float e; /* coefficient of friction, I think? */
float max_radius; /* largest radius of any ball */
+ Bool random_sizes_p; /* Whether balls should be various sizes up to max. */
Bool shake_p; /* Whether to mess with gravity when things settle. */
float shake_threshold;
int time_since_shake;
state->max_radius = get_float_resource ("size", "Size") / 2;
if (state->max_radius < 1.0) state->max_radius = 1.0;
+ state->random_sizes_p = get_boolean_resource ("random", "Random");
+
state->accx = get_float_resource ("wind", "Wind");
if (state->accx < -1.0 || state->accx > 1.0) state->accx = 0;
state->font_baseline = font->descent;
}
+ state->m = (float *) malloc (sizeof (*state->m) * (state->count + 1));
state->r = (float *) malloc (sizeof (*state->r) * (state->count + 1));
state->vx = (float *) malloc (sizeof (*state->vx) * (state->count + 1));
state->vy = (float *) malloc (sizeof (*state->vy) * (state->count + 1));
{
state->px[i] = frand(extx) + state->xmin;
state->py[i] = frand(exty) + state->ymin;
- state->vx[i] = frand(0.2);
- state->vy[i] = frand(0.2);
+ state->vx[i] = frand(0.2) - 0.1;
+ state->vy[i] = frand(0.2) - 0.1;
- state->r[i] = state->max_radius;
+ state->r[i] = (state->random_sizes_p
+ ? ((0.2 + frand(0.8)) * state->max_radius)
+ : state->max_radius);
+ /*state->r[i] = pow(frand(1.0), state->sizegamma) * state->max_radius;*/
- /* not quite: */
- /* state->r[i] = 4 + (random() % (int) (state->max_radius - 4)); */
+ /* state->m[i] = pow(state->r[i],2) * M_PI; */
+ state->m[i] = pow(state->r[i],3) * M_PI * 1.3333;
}
return state;
y2b = (state->py[a] + state->r[a] - state->ymin);
/* if (x1a != x1b || y1a != y1b) -- leaves turds if we optimize this */
- {
+ {
gc = state->erase_gc;
XFillArc (state->dpy, state->window, gc,
x1a, y1a, x2a-x1a, y2a-y1a,
update_balls (b_state *state)
{
int a, b;
- float d, nx, ny, m, vxa, vya, vxb, vyb, dd, cdx, cdy, cosam;
- float dee2 = state->max_radius * state->max_radius * 4;
+ float d, vxa, vya, vxb, vyb, dd, cdx, cdy;
+ float ma, mb, vela, velb, vela1, velb1;
+ float dee2;
check_window_moved (state);
(state->px[a] - state->px[b]) +
(state->py[a] - state->py[b]) *
(state->py[a] - state->py[b]));
+ dee2 = (state->r[a] + state->r[b]) *
+ (state->r[a] + state->r[b]);
if (d < dee2)
{
state->collision_count++;
d = sqrt(d);
- vxa = state->vx[a];
- vya = state->vy[a];
- vxb = state->vx[b];
- vyb = state->vy[b];
- nx = state->px[b] - state->px[a];
- ny = state->py[b] - state->py[a];
- if (d < -0.0001 || d > 0.0001)
- {
- cdx = nx/d;
- cdy = ny/d;
- dd = state->r[a] + state->r[b] - d;
- state->px[a] -= dd*cdx; /* just move them apart */
- state->py[a] -= dd*cdy; /* no physical rationale, sorry */
- state->px[b] += dd*cdx;
- state->py[b] += dd*cdy;
- m = sqrt (state->vx[a] * state->vx[a] +
- state->vy[a] * state->vy[a]);
- if (m < -0.0001 || m > 0.0001) /* A's velocity > 0 ? */
- {
- cosam = ((cdx * state->vx[a] + cdy * state->vy[a]) *
- state->e);
- vxa -= cdx * cosam;
- vya -= cdy * cosam; /* conserve momentum */
- vxb += cdx * cosam;
- vyb += cdy * cosam;
- }
- m = sqrt (state->vx[b] *
- state->vx[b] +
- state->vy[b] *
- state->vy[b]);
- if (m < -0.0001 || m > 0.0001)
- {
- cosam = ((cdx * state->vx[b] + cdy * state->vy[b]) *
- state->e);
- vxa += cdx * cosam;
- vya += cdy * cosam;
- vxb -= cdx * cosam;
- vyb -= cdy * cosam;
- }
+ dd = state->r[a] + state->r[b] - d;
+ /* A pair of balls that have already collided in this
+ * current frame (and therefore touching each other)
+ * should not have another collision calculated, hence
+ * the fallthru if "dd ~= 0.0".
+ */
+ if ((dd < -0.01) || (dd > 0.01))
+ {
+ cdx = (state->px[b] - state->px[a]) / d;
+ cdy = (state->py[b] - state->py[a]) / d;
+
+ /* Move each ball apart from the other by half the
+ * 'collision' distance.
+ */
+ state->px[a] -= 0.5 * dd * cdx;
+ state->py[a] -= 0.5 * dd * cdy;
+ state->px[b] += 0.5 * dd * cdx;
+ state->py[b] += 0.5 * dd * cdy;
+
+ ma = state->m[a];
+ mb = state->m[b];
+ vxa = state->vx[a];
+ vya = state->vy[a];
+ vxb = state->vx[b];
+ vyb = state->vy[b];
+
+ vela = sqrt((vxa * vxa) + (vya * vya));
+ velb = sqrt((vxb * vxb) + (vyb * vyb));
+
+ vela1 = vela * ((ma - mb) / (ma + mb)) +
+ velb * ((2 * mb) / (ma + mb));
+ velb1 = vela * ((2 * ma) / (ma + mb)) +
+ velb * ((mb - ma) / (ma + mb));
+
+ vela1 *= state->e; /* "air resistance" */
+ velb1 *= state->e;
+#if 0
+ vela1 += (frand (50) - 25) / ma; /* brownian motion */
+ velb1 += (frand (50) - 25) / mb;
+#endif
+ state->vx[a] = -cdx * vela1;
+ state->vy[a] = -cdy * vela1;
+ state->vx[b] = cdx * velb1;
+ state->vy[b] = cdy * velb1;
}
- state->vx[a] = vxa;
- state->vy[a] = vya;
- state->vx[b] = vxb;
- state->vy[b] = vyb;
}
}
"*delay: 10000",
"*count: 300",
"*size: 25",
+ "*random: True",
"*gravity: 0.01",
"*wind: 0.00",
- "*friction: 0.97",
+ "*friction: 0.8",
"*timeScale: 1.0",
"*doFPS: False",
"*shake: True",
{ "-no-fps", ".doFPS", XrmoptionNoArg, "False" },
{ "-shake", ".shake", XrmoptionNoArg, "True" },
{ "-no-shake", ".shake", XrmoptionNoArg, "False" },
+ { "-random", ".random", XrmoptionNoArg, "True" },
+ { "-nonrandom", ".random", XrmoptionNoArg, "False" },
{ 0, 0, 0, 0 }
};
projects / xscreensaver / blobdiff