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#include <stdlib.h>
#include "draw.h"
#include "fb.h"
#include "particle.h"
#include "particles.h"
/* a "spark" particle type, emitted from behind rockets */
#define SPARK_MAX_DECAY_RATE 20
#define SPARK_MIN_DECAY_RATE 2
#define SPARK_MAX_LIFETIME 150
#define SPARK_MIN_LIFETIME 1
typedef struct _spark_ctxt_t {
int decay_rate;
int longevity;
int lifetime;
} spark_ctxt_t;
static int spark_init(particles_t *particles, particle_t *p)
{
spark_ctxt_t *ctxt = p->ctxt;
p->props->drag = 20.0;
p->props->mass = 0.1;
ctxt->decay_rate = rand_within_range(SPARK_MIN_DECAY_RATE, SPARK_MAX_DECAY_RATE);
ctxt->lifetime = ctxt->longevity = rand_within_range(SPARK_MIN_LIFETIME, SPARK_MAX_LIFETIME);
return 1;
}
static particle_status_t spark_sim(particles_t *particles, particle_t *p)
{
spark_ctxt_t *ctxt = p->ctxt;
if (!ctxt->longevity || (ctxt->longevity -= ctxt->decay_rate) <= 0) {
ctxt->longevity = 0;
return PARTICLE_DEAD;
}
return PARTICLE_ALIVE;
}
static void spark_draw(particles_t *particles, particle_t *p, int x, int y, fb_fragment_t *f)
{
spark_ctxt_t *ctxt = p->ctxt;
if (!fb_fragment_contains(f, x, y)) {
/* offscreen */
ctxt->longevity = 0;
return;
}
draw_pixel(f, x, y, makergb(0xff, 0xa0, 0x20, ((float)ctxt->longevity / ctxt->lifetime)));
}
particle_ops_t spark_ops = {
.context_size = sizeof(spark_ctxt_t),
.sim = spark_sim,
.init = spark_init,
.draw = spark_draw,
.cleanup = NULL,
};
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