-/* mostly lifted from lament.c */
-static void
-rotate (float *pos, float *v, float *dv, float max_v)
-{
- double ppos = *pos;
-
- /* tick position */
- if (ppos < 0)
- ppos = -(ppos + *v);
- else
- ppos += *v;
-
- if (ppos > 360)
- ppos -= 360;
- else if (ppos < 0)
- ppos += 360;
-
- if (ppos < 0) abort();
- if (ppos > 360) abort();
- *pos = (*pos > 0 ? ppos : -ppos);
-
- /* accelerate */
- *v += *dv;
-
- /* clamp velocity */
- if (*v > max_v || *v < -max_v)
- {
- *dv = -*dv;
- }
- /* If it stops, start it going in the other direction. */
- else if (*v < 0)
- {
- if (random() % 4)
- {
- *v = 0;
-
- /* keep going in the same direction */
- if (random() % 2)
- *dv = 0;
- else if (*dv < 0)
- *dv = -*dv;
- }
- else
- {
- /* reverse gears */
- *v = -*v;
- *dv = -*dv;
- *pos = -*pos;
- }
- }
-
- /* Alter direction of rotational acceleration randomly. */
- if (! (random() % 120))
- *dv = -*dv;
-
- /* Change acceleration very occasionally. */
- if (! (random() % 200))
- {
- if (*dv == 0)
- *dv = 0.00001;
- else if (random() & 1)
- *dv *= 1.2;
- else
- *dv *= 0.8;
- }
-}
-
-
-static void
-bounce (float *pos, float *v, float *dv, float max_v)
-{
- *pos += *v;
-
- if (*pos > 1.0)
- *pos = 1.0, *v = -*v, *dv = -*dv;
- else if (*pos < 0)
- *pos = 0, *v = -*v, *dv = -*dv;
-
- if (*pos < 0.0) abort();
- if (*pos > 1.0) abort();
-
- /* accelerate */
- *v += *dv;
-
- /* clamp velocity */
- if (*v > max_v || *v < -max_v)
- {
- *dv = -*dv;
- }
-
- /* Alter direction of rotational acceleration randomly. */
- if (! (random() % 120))
- *dv = -*dv;
-
- /* Change acceleration very occasionally. */
- if (! (random() % 200))
- {
- if (*dv == 0)
- *dv = 0.00001;
- else if (random() & 1)
- *dv *= 1.2;
- else
- *dv *= 0.8;
- }
-}
-
-