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.

1 files changed, 157 insertions, 0 deletions

diff --git a/modules/sparkler/v3f.h b/modules/sparkler/v3f.h
new file mode 100644
index 0000000..8bf7e24
--- /dev/null
+++ b/modules/sparkler/v3f.h
@@ -0,0 +1,157 @@
+#ifndef _V3F_H
+#define _V3F_H
+
+#include <math.h>
+
+typedef struct v3f_t {
+	float	x, y, z;
+} v3f_t;
+
+#define v3f_set(_v3f, _x, _y, _z)	\
+	(_v3f)->x = _x;			\
+	(_v3f)->y = _y;			\
+	(_v3f)->z = _z;
+
+#define v3f_init(_x, _y, _z)		\
+	{				\
+		.x = _x,		\
+		.y = _y,		\
+		.z = _z,		\
+	}
+
+/* return if a and b are equal */
+static inline int v3f_equal(v3f_t *a, v3f_t *b)
+{
+	return (a->x == b->x && a->y == b->y && a->z == b->z);
+}
+
+
+/* return the result of (a + b) */
+static inline v3f_t v3f_add(v3f_t *a, v3f_t *b)
+{
+	v3f_t	res = v3f_init(a->x + b->x, a->y + b->y, a->z + b->z);
+
+	return res;
+}
+
+
+/* return the result of (a - b) */
+static inline v3f_t v3f_sub(v3f_t *a, v3f_t *b)
+{
+	v3f_t	res = v3f_init(a->x - b->x, a->y - b->y, a->z - b->z);
+
+	return res;
+}
+
+
+/* return the result of (-v) */
+static inline v3f_t v3f_negate(v3f_t *v)
+{
+	v3f_t	res = v3f_init(-v->x, -v->y, -v->z);
+
+	return res;
+}
+
+
+/* return the result of (a * b) */
+static inline v3f_t v3f_mult(v3f_t *a, v3f_t *b)
+{
+	v3f_t	res = v3f_init(a->x * b->x, a->y * b->y, a->z * b->z);
+
+	return res;
+}
+
+
+/* return the result of (v * scalar) */
+static inline v3f_t v3f_mult_scalar(v3f_t *v, float scalar)
+{
+	v3f_t	res = v3f_init( v->x * scalar, v->y * scalar, v->z * scalar);
+
+	return res;
+}
+
+
+/* return the result of (uv / scalar) */
+static inline v3f_t v3f_div_scalar(v3f_t *v, float scalar)
+{
+	v3f_t	res = v3f_init(v->x / scalar, v->y / scalar, v->z / scalar);
+
+	return res;
+}
+
+
+/* return the result of (a . b) */
+static inline float v3f_dot(v3f_t *a, v3f_t *b)
+{
+	return a->x * b->x + a->y * b->y + a->z * b->z;
+}
+
+
+/* return the length of the supplied vector */
+static inline float v3f_length(v3f_t *v)
+{
+	return sqrtf(v3f_dot(v, v));
+}
+
+
+/* return the normalized form of the supplied vector */
+static inline v3f_t v3f_normalize(v3f_t *v)
+{
+	v3f_t	nv;
+	float	f;
+
+	f = 1.0f / v3f_length(v);
+
+	v3f_set(&nv, f * v->x, f * v->y, f * v->z);
+
+	return nv;
+}
+
+
+/* return the distance squared between two arbitrary points */
+static inline float v3f_distance_sq(v3f_t *a, v3f_t *b)
+{
+	return powf(a->x - b->x, 2) + powf(a->y - b->y, 2) + powf(a->z - b->z, 2);
+}
+
+
+/* return the distance between two arbitrary points */
+/* (consider using v3f_distance_sq() instead if possible, sqrtf() is slow) */
+static inline float v3f_distance(v3f_t *a, v3f_t *b)
+{
+	return sqrtf(v3f_distance_sq(a, b));
+}
+
+
+/* return the cross product of two unit vectors */
+static inline v3f_t v3f_cross(v3f_t *a, v3f_t *b)
+{
+	v3f_t	product = v3f_init(a->y * b->z - a->z * b->y, a->z * b->x - a->x * b->z, a->x * b->y - a->y * b->x);
+
+	return product;
+}
+
+
+/* return the linearly interpolated vector between the two vectors at point alpha (0-1.0) */
+static inline v3f_t v3f_lerp(v3f_t *a, v3f_t *b, float alpha)
+{
+	v3f_t	lerp_a, lerp_b;
+
+	lerp_a = v3f_mult_scalar(a, 1.0f - alpha);
+	lerp_b = v3f_mult_scalar(b, alpha);
+
+	return v3f_add(&lerp_a, &lerp_b);
+}
+
+
+/* return the normalized linearly interpolated vector between the two vectors at point alpha (0-1.0) */
+static inline v3f_t v3f_nlerp(v3f_t *a, v3f_t *b, float alpha)
+{
+	v3f_t	lerp;
+
+	lerp = v3f_lerp(a, b, alpha);
+
+	return v3f_normalize(&lerp);
+}
+
+#endif