sparkler: parameterize particles

Having everything in fixed defines severely constrains the
diversity of particle behaviors and appearances.

This commit has been sitting around bitrotting since 2017, but
now that there's all this settings infra. and randomizing via
rtv, it seems worth landing, so I've rebased and am merging to
prevent a bitrot->rebase recurrence.

As-is, this commit ~minimally establishes a somewhat streamlined
parameterizing mechanism w/X-Macro patterns, while wiring up a
few of the obvious use cases surrounding xplode/burst, colorizing
the default sparkler explosions while at it.

It appears that when I first hacked this up I did some
experimentation with parameters as well, so there are some tweaks
to the behavior as opposed to a strict conversion of the fixed
defines to parameters.  They seem minor enough to just leave be.

Plus a few minor optimizations like converting divides to
multiplies were in there.

Future commits can now wire up settings to choose from parameter
presets for different sparklers...

1 files changed, 27 insertions, 11 deletions

diff --git a/src/modules/sparkler/burst.c b/src/modules/sparkler/burst.c
index cf35b31..ae74e26 100644
--- a/src/modules/sparkler/burst.c
+++ b/src/modules/sparkler/burst.c
@@ -1,6 +1,8 @@
+#include <stdarg.h>
 #include <stdlib.h>
 
 #include "bsp.h"
+#include "burst.h"
 #include "container.h"
 #include "particle.h"
 #include "particles.h"
@@ -9,21 +11,33 @@
 /* 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;
+#define PARAMS_DECLARE_STRUCT
+#include "burst_params.def"
+	int		age;
 } burst_ctxt_t;
 
 
-static int burst_init(particles_t *particles, const particles_conf_t *conf, particle_t *p)
+static int burst_init(particles_t *particles, const particles_conf_t *conf, particle_t *p, unsigned n_params, va_list params)
 {
 	burst_ctxt_t	*ctxt = p->ctxt;
 
-	ctxt->longevity = ctxt->lifetime = BURST_MAX_LIFETIME;
+#define PARAMS_ASSIGN_DEFAULTS
+#include "burst_params.def"
+
+	for (; n_params; n_params--) {
+		switch (va_arg(params, burst_param_t)) {
+#define PARAMS_IMPLEMENT_SWITCH
+#include "burst_params.def"
+		default:
+			return 0;
+		}
+	}
+
 	p->props->virtual = 1;
+	ctxt->age = ctxt->duration;
+	p->props->velocity = 0; /* burst should be stationary */
+	p->props->mass = 0; /* no mass prevents gravity's effects */
 
 	return 1;
 }
@@ -31,14 +45,15 @@ static int burst_init(particles_t *particles, const particles_conf_t *conf, part
 
 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);
+	burst_ctxt_t	*ctxt = burst->ctxt;
+	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;
+	victim->props->velocity += ctxt->force;
 }
 
 
@@ -100,12 +115,13 @@ static particle_status_t burst_sim(particles_t *particles, const particles_conf_
 	bsp_t		*bsp = particles_bsp(particles);	/* XXX see note above about bsp_occupant_t */
 	burst_sphere_t	s;
 
-	if (!ctxt->longevity || (ctxt->longevity--) <= 0) {
+	if (!ctxt->duration || (ctxt->duration--) <= 0) {
 		return PARTICLE_DEAD;
 	}
 
 	/* affect neighbors for the shock-wave */
-	s.radius_min = (1.0f - ((float)ctxt->longevity / ctxt->lifetime)) * 0.075f;
+	/* TODO: ctxt->radius should probably describe the max radius, and the min - .01f... FIXME later. */
+	s.radius_min = (1.0f - ((float)ctxt->duration / ctxt->age)) * ctxt->radius;
 	s.radius_max = s.radius_min + .01f;
 	s.center = s.last = p;
 	s.trace_matches = (conf->show_bsp_matches && !conf->show_bsp_matches_affected_only);