1 files changed, 111 insertions, 0 deletions
diff --git a/src/modules/sparkler/burst.c b/src/modules/sparkler/burst.c
new file mode 100644
index 0000000..828ca02
--- /dev/null
+++ b/src/modules/sparkler/burst.c
@@ -0,0 +1,111 @@
+#include <stdlib.h>
+
+#include "bsp.h"
+#include "container.h"
+#include "particle.h"
+#include "particles.h"
+
+
+/* a "burst" (shockwave) particle type */
+/* this doesn't draw anything, it just pushes neighbors away in an increasing radius */
+
+#define BURST_FORCE		0.01f
+#define BURST_MAX_LIFETIME	8
+
+typedef struct _burst_ctxt_t {
+	int	longevity;
+	int	lifetime;
+} burst_ctxt_t;
+
+
+static int burst_init(particles_t *particles, particle_t *p)
+{
+	burst_ctxt_t	*ctxt = p->ctxt;
+
+	ctxt->longevity = ctxt->lifetime = BURST_MAX_LIFETIME;
+	p->props->velocity = 0; /* burst should be stationary */
+	p->props->mass = 0; /* no mass prevents gravity's effects */
+
+	return 1;
+}
+
+
+static inline void thrust_part(particle_t *burst, particle_t *victim, float distance_sq)
+{
+	v3f_t	direction = v3f_sub(&victim->props->position, &burst->props->position);
+
+	/* TODO: normalize is expensive, see about removing these. */
+	direction = v3f_normalize(&direction);
+	victim->props->direction = v3f_add(&victim->props->direction, &direction);
+	victim->props->direction = v3f_normalize(&victim->props->direction);
+
+	victim->props->velocity += BURST_FORCE;
+}
+
+
+typedef struct burst_sphere_t {
+	particle_t	*center;
+	float		radius_min;
+	float		radius_max;
+} burst_sphere_t;
+
+
+static void burst_cb(bsp_t *bsp, list_head_t *occupants, void *_s)
+{
+	burst_sphere_t	*s = _s;
+	bsp_occupant_t	*o;
+	float		rmin_sq = s->radius_min * s->radius_min;
+	float		rmax_sq = s->radius_max * s->radius_max;
+
+	/* XXX: to avoid having a callback per-particle, bsp_occupant_t was
+	 * moved to the public particle, and the particle-specific
+	 * implementations directly perform bsp-accelerated searches.  Another
+	 * wart caused by this is particles_bsp().
+	 */
+	list_for_each_entry(o, occupants, occupants) {
+		particle_t	*p = container_of(o, particle_t, occupant);
+		float		d_sq;
+		
+		if (p == s->center) {
+			/* leave ourselves alone */
+			continue;
+		}
+
+		d_sq = v3f_distance_sq(&s->center->props->position, &p->props->position);
+
+		if (d_sq > rmin_sq && d_sq < rmax_sq) {
+			/* displace the part relative to the burst origin */
+			thrust_part(s->center, p, d_sq);
+		}
+
+	}
+}
+
+
+static particle_status_t burst_sim(particles_t *particles, particle_t *p)
+{
+	burst_ctxt_t	*ctxt = p->ctxt;
+	bsp_t		*bsp = particles_bsp(particles);	/* XXX see note above about bsp_occupant_t */
+	burst_sphere_t	s;
+
+	if (!ctxt->longevity || (ctxt->longevity--) <= 0) {
+		return PARTICLE_DEAD;
+	}
+
+	/* affect neighbors for the shock-wave */
+	s.radius_min = (1.0f - ((float)ctxt->longevity / ctxt->lifetime)) * 0.075f;
+	s.radius_max = s.radius_min + .01f;
+	s.center = p;
+	bsp_search_sphere(bsp, &p->props->position, s.radius_min, s.radius_max, burst_cb, &s);
+
+	return PARTICLE_ALIVE;
+}
+
+
+particle_ops_t	burst_ops = {
+			.context_size = sizeof(burst_ctxt_t),
+			.sim = burst_sim,
+			.init = burst_init,
+			.draw = NULL,
+			.cleanup = NULL,
+		};