From 8add1663d9a02db2bc65224cdceb480733a81379 Mon Sep 17 00:00:00 2001 From: Vito Caputo Date: Tue, 13 Dec 2016 07:51:23 -0800 Subject: sparkler: introduce a particle system A while ago I made this particle system on SDL, and had the beginnings of an octree implemented within it, but never finished actually using the octree to accelerate the proximity searches. This now has the octree completed and of course more particle interactions now that neighbors could be found more quickly. The simulation somewhat resembles a fireworks display. Every particle is drawn as a single pixel. The visual effect is dominated by spontaneously spawned rockets which explode into thousands of particles accompanied by bursts that thrust particles away from the explosion radially in an expanding sphere resembling a shock wave. When the shock wave happens to strike another rocket, it explodes, resulting in another shock wave. This can produce spectacular chain reactions, so it's worth running for some time and seeing what transpires. --- modules/sparkler/simple.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 modules/sparkler/simple.c (limited to 'modules/sparkler/simple.c') diff --git a/modules/sparkler/simple.c b/modules/sparkler/simple.c new file mode 100644 index 0000000..e453e46 --- /dev/null +++ b/modules/sparkler/simple.c @@ -0,0 +1,113 @@ +#include + +#include "draw.h" +#include "particle.h" +#include "particles.h" + + +/* a "simple" particle type */ +#define SIMPLE_MAX_DECAY_RATE 20 +#define SIMPLE_MIN_DECAY_RATE 2 +#define SIMPLE_MAX_LIFETIME 110 +#define SIMPLE_MIN_LIFETIME 30 +#define SIMPLE_MAX_SPAWN 15 +#define SIMPLE_MIN_SPAWN 2 + +extern particle_ops_t rocket_ops; + +typedef struct _simple_ctxt_t { + int decay_rate; + int longevity; + int lifetime; +} simple_ctxt_t; + + +static int simple_init(particles_t *particles, particle_t *p) +{ + simple_ctxt_t *ctxt = p->ctxt; + + ctxt->decay_rate = rand_within_range(SIMPLE_MIN_DECAY_RATE, SIMPLE_MAX_DECAY_RATE); + ctxt->lifetime = ctxt->longevity = rand_within_range(SIMPLE_MIN_LIFETIME, SIMPLE_MAX_LIFETIME); + + if (!p->props->of_use) { + /* everything starts from the bottom center */ + p->props->position.x = 0; + p->props->position.y = 0; + p->props->position.z = 0; + + /* TODO: direction random-ish within the range of a narrow upward facing cone */ + p->props->direction.x = (float)(rand_within_range(0, 6) - 3) * .1f; + p->props->direction.y = 1.0f + (float)(rand_within_range(0, 6) - 3) * .1f; + p->props->direction.z = (float)(rand_within_range(0, 6) - 3) * .1f; + p->props->direction = v3f_normalize(&p->props->direction); + + p->props->velocity = (float)rand_within_range(300, 800) / 100000.0; + + p->props->drag = 0.03; + p->props->mass = 0.3; + p->props->of_use = 1; + } /* else { we've been given properties, manipulate them or run with them? } */ + + return 1; +} + + +static particle_status_t simple_sim(particles_t *particles, particle_t *p) +{ + simple_ctxt_t *ctxt = p->ctxt; + + /* a particle is free to manipulate its children list when aging, but not itself or its siblings */ + /* return PARTICLE_DEAD to remove kill yourself, do not age children here, the age pass will recurse + * into children and age them independently _after_ their parents have been aged + */ + if (!ctxt->longevity || (ctxt->longevity -= ctxt->decay_rate) <= 0) { + ctxt->longevity = 0; + return PARTICLE_DEAD; + } + + /* create particles inheriting our type based on some silly conditions, with some tweaks to their direction */ + if (ctxt->longevity == 42 || (ctxt->longevity > 500 && !(ctxt->longevity % 50))) { + int i, num = rand_within_range(SIMPLE_MIN_SPAWN, SIMPLE_MAX_SPAWN); + + for (i = 0; i < num; i++) { + particle_props_t props = *p->props; + particle_ops_t *ops = INHERIT_OPS; + + if (i == (SIMPLE_MAX_SPAWN - 2)) { + ops = &rocket_ops; + props.velocity = (float)rand_within_range(60, 100) / 1000000.0; + } else { + props.velocity = (float)rand_within_range(30, 100) / 10000.0; + } + + props.direction.x += (float)(rand_within_range(0, 315 * 2) - 315) / 100.0; + props.direction.y += (float)(rand_within_range(0, 315 * 2) - 315) / 100.0; + props.direction.z += (float)(rand_within_range(0, 315 * 2) - 315) / 100.0; + props.direction = v3f_normalize(&props.direction); + + particles_spawn_particle(particles, p, &props, ops); // XXX + } + } + + return PARTICLE_ALIVE; +} + + +static void simple_draw(particles_t *particles, particle_t *p, int x, int y, fb_fragment_t *f) +{ + simple_ctxt_t *ctxt = p->ctxt; + + if (!draw_pixel(f, x, y, makergb(0xff, 0xff, 0xff, ((float)ctxt->longevity / ctxt->lifetime)))) { + /* immediately kill off stars that wander off screen */ + ctxt->longevity = 0; + } +} + + +particle_ops_t simple_ops = { + .context_size = sizeof(simple_ctxt_t), + .sim = simple_sim, + .init = simple_init, + .draw = simple_draw, + .cleanup = NULL, + }; -- cgit v1.2.1