modules/voronoi: voronoi diagram module

This adds a voronoi diagram module, which when used as an overlay
produces a mosaic effect.

Some settings:

 cells=N             number of voronoi cells
 randomize={on,off}  randomizes the cell locations every frame
 dirty={on,off}      uses a faster sloppy/dithery-looking method

Some TODO items:

- use a more space efficient representation of the distance
  buffer, maybe use uint16_t relative offsets into the cells
  rather than pointers - capping their quantity to 64KiB

- anti-alias edges between cells

6 files changed, 790 insertions, 2 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 20ef90f..10553fe 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,7 +3,7 @@ SUBDIRS = libs modules
 noinst_LTLIBRARIES = libtil.la
 libtil_la_SOURCES = til_args.c til_args.h til_fb.c til_fb.h til_knobs.h til.c til.h til_settings.h til_settings.c til_setup.c til_setup.h til_threads.c til_threads.h til_util.c til_util.h
 libtil_la_CPPFLAGS = -I@top_srcdir@/src
-libtil_la_LIBADD = modules/blinds/libblinds.la modules/checkers/libcheckers.la modules/compose/libcompose.la modules/drizzle/libdrizzle.la modules/flui2d/libflui2d.la modules/julia/libjulia.la modules/meta2d/libmeta2d.la modules/montage/libmontage.la modules/pixbounce/libpixbounce.la modules/plasma/libplasma.la modules/plato/libplato.la modules/ray/libray.la modules/roto/libroto.la modules/rtv/librtv.la modules/snow/libsnow.la modules/sparkler/libsparkler.la modules/spiro/libspiro.la modules/stars/libstars.la modules/submit/libsubmit.la modules/swab/libswab.la modules/swarm/libswarm.la libs/grid/libgrid.la libs/puddle/libpuddle.la libs/ray/libray.la libs/sig/libsig.la libs/txt/libtxt.la libs/ascii/libascii.la libs/din/libdin.la
+libtil_la_LIBADD = modules/blinds/libblinds.la modules/checkers/libcheckers.la modules/compose/libcompose.la modules/drizzle/libdrizzle.la modules/flui2d/libflui2d.la modules/julia/libjulia.la modules/meta2d/libmeta2d.la modules/montage/libmontage.la modules/pixbounce/libpixbounce.la modules/plasma/libplasma.la modules/plato/libplato.la modules/ray/libray.la modules/roto/libroto.la modules/rtv/librtv.la modules/snow/libsnow.la modules/sparkler/libsparkler.la modules/spiro/libspiro.la modules/stars/libstars.la modules/submit/libsubmit.la modules/swab/libswab.la modules/swarm/libswarm.la modules/voronoi/libvoronoi.la libs/grid/libgrid.la libs/puddle/libpuddle.la libs/ray/libray.la libs/sig/libsig.la libs/txt/libtxt.la libs/ascii/libascii.la libs/din/libdin.la
 
 if ENABLE_ROTOTILLER
 bin_PROGRAMS = rototiller
diff --git a/src/modules/Makefile.am b/src/modules/Makefile.am
index 92a4145..e5c9971 100644
--- a/src/modules/Makefile.am
+++ b/src/modules/Makefile.am
@@ -1 +1 @@
-SUBDIRS = blinds checkers compose drizzle flui2d julia meta2d montage pixbounce plasma plato ray roto rtv snow sparkler spiro stars submit swab swarm
+SUBDIRS = blinds checkers compose drizzle flui2d julia meta2d montage pixbounce plasma plato ray roto rtv snow sparkler spiro stars submit swab swarm voronoi
diff --git a/src/modules/voronoi/Makefile.am b/src/modules/voronoi/Makefile.am
new file mode 100644
index 0000000..f26a49b
--- /dev/null
+++ b/src/modules/voronoi/Makefile.am
@@ -0,0 +1,3 @@
+noinst_LTLIBRARIES = libvoronoi.la
+libvoronoi_la_SOURCES = voronoi.c v2f.h
+libvoronoi_la_CPPFLAGS = -I@top_srcdir@/src -I@top_srcdir@/src/libs
diff --git a/src/modules/voronoi/v2f.h b/src/modules/voronoi/v2f.h
new file mode 100644
index 0000000..8f51ee0
--- /dev/null
+++ b/src/modules/voronoi/v2f.h
@@ -0,0 +1,352 @@
+/*
+ *  Copyright (C) 2018-2019 - Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * 2D vector operations header
+ *
+ * Variants prefixed with _ return a result vector struct by value.
+ *
+ * Variants missing the _ prefix for vector result operations return a pointer
+ * and must be either supplied the result memory as the first "res" argument
+ * which is then returned after being populated with the result's value, or
+ * NULL to allocate space for the result and that pointer is returned after being
+ * populated with its value.  When supplying NULL result pointers the functions
+ * must allocate memory and thus may return NULL on OOM, so callers should
+ * check for NULL returns when supplying NULL for "res".
+ *
+ * Example:
+ *	v2f_t	foo, *foop;
+ *
+ *	foo = _v2f_mult(&(v2f_t){1.f,1.f}, &(v2f_t){2.f,2.f});
+ *
+ *	is equivalent to:
+ *
+ *	v2f_mult(&foo, &(v2f_t){1.f,1.f}, &(v2f_t){2.f,2.f});
+ *
+ *	or dynamically allocated:
+ *
+ *	foop = v2f_mult(NULL, &(v2f_t){1.f,1.f}, &(v2f_t){2.f,2.f});
+ *	free(foop);
+ *
+ *	is equivalent to:
+ *
+ *	foop = malloc(sizeof(v2f_t));
+ *	v2f_mult(foop, &(v2f_t){1.f,1.f}, &(v2f_t){2.f,2.f});
+ *	free(foop);
+ */
+
+#ifndef _V2F_H
+#define _V2F_H
+
+
+#include <math.h>
+#include <stdlib.h>
+
+
+typedef struct v2f_t {
+	float	x, y;
+} v2f_t;
+
+
+static inline v2f_t * _v2f_allocated(v2f_t **ptr)
+{
+	if (!*ptr)
+		*ptr = malloc(sizeof(v2f_t));
+
+	return *ptr;
+}
+
+
+static inline v2f_t _v2f_add(const v2f_t *a, const v2f_t *b)
+{
+	return (v2f_t){a->x + b->x, a->y + b->y};
+}
+
+
+static inline v2f_t * v2f_add(v2f_t *res, const v2f_t *a, const v2f_t *b)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_add(a, b);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_sub(const v2f_t *a, const v2f_t *b)
+{
+	return (v2f_t){a->x - b->x, a->y - b->y};
+}
+
+
+static inline v2f_t * v2f_sub(v2f_t *res, const v2f_t *a, const v2f_t *b)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_sub(a, b);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_mult(const v2f_t *a, const v2f_t *b)
+{
+	return (v2f_t){a->x * b->x, a->y * b->y};
+}
+
+
+static inline v2f_t * v2f_mult(v2f_t *res, const v2f_t *a, const v2f_t *b)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_mult(a, b);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_mult_scalar(const v2f_t *v, float scalar)
+{
+	return (v2f_t){ v->x * scalar, v->y * scalar };
+}
+
+
+static inline v2f_t * v2f_mult_scalar(v2f_t *res, const v2f_t *v, float scalar)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_mult_scalar(v, scalar);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_div_scalar(const v2f_t *v, float scalar)
+{
+	return _v2f_mult_scalar(v, 1.f / scalar);
+}
+
+
+static inline v2f_t * v2f_div_scalar(v2f_t *res, const v2f_t *v, float scalar)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_div_scalar(v, scalar);
+
+	return res;
+}
+
+
+static inline float v2f_dot(const v2f_t *a, const v2f_t *b)
+{
+	return a->x * b->x + a->y * b->y;
+}
+
+
+static inline float v2f_length(const v2f_t *v)
+{
+	return sqrtf(v2f_dot(v, v));
+}
+
+
+static inline float v2f_distance(const v2f_t *a, const v2f_t *b)
+{
+	return v2f_length(v2f_sub(&(v2f_t){}, a, b));
+}
+
+
+static inline float v2f_distance_sq(const v2f_t *a, const v2f_t *b)
+{
+	v2f_t	d = _v2f_sub(a, b);
+
+	return v2f_dot(&d, &d);
+}
+
+
+static inline v2f_t _v2f_normalize(const v2f_t *v)
+{
+	return _v2f_mult_scalar(v, 1.0f / v2f_length(v));
+}
+
+
+static inline v2f_t * v2f_normalize(v2f_t *res, const v2f_t *v)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_normalize(v);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_lerp(const v2f_t *a, const v2f_t *b, float t)
+{
+	v2f_t	lerp_a, lerp_b;
+
+	lerp_a = _v2f_mult_scalar(a, 1.0f - t);
+	lerp_b = _v2f_mult_scalar(b, t);
+
+	return _v2f_add(&lerp_a, &lerp_b);
+}
+
+
+static inline v2f_t * v2f_lerp(v2f_t *res, const v2f_t *a, const v2f_t *b, float t)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_lerp(a, b, t);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_nlerp(const v2f_t *a, const v2f_t *b, float t)
+{
+	v2f_t	lerp = _v2f_lerp(a, b, t);
+
+	return _v2f_normalize(&lerp);
+}
+
+
+static inline v2f_t * v2f_nlerp(v2f_t *res, const v2f_t *a, const v2f_t *b, float t)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_nlerp(a, b, t);
+
+	return res;
+}
+
+
+/*
+ *       1 ab-------bb
+ *       | |         |
+ *       | |         |
+ *       | |         |
+ *       0 aa-------ba
+ *  t_x:   0---------1
+ *       ^
+ *       t_y
+ */
+static inline v2f_t _v2f_bilerp(const v2f_t *aa, const v2f_t *ab, const v2f_t *ba, const v2f_t *bb, float t_x, float t_y)
+{
+	v2f_t	xa = _v2f_lerp(aa, ba, t_x);
+	v2f_t	xb = _v2f_lerp(ab, bb, t_x);
+
+	return _v2f_lerp(&xa, &xb, t_y);
+}
+
+
+static inline v2f_t * v2f_bilerp(v2f_t *res, const v2f_t *aa, const v2f_t *ab, const v2f_t *ba, const v2f_t *bb, float t_x, float t_y)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_bilerp(aa, ab, ba, bb, t_x, t_y);
+
+	return res;
+}
+
+
+/*
+ *     abb-------bbb
+ *     /|        /|
+ *   aba-------bba|
+ *    | |       | |
+ *    |aab------|bab
+ *    |/        |/
+ *   aaa-------baa
+ */
+static inline v2f_t _v2f_trilerp(const v2f_t *aaa, const v2f_t *aba, const v2f_t *aab, const v2f_t *abb, const v2f_t *baa, const v2f_t *bba, const v2f_t *bab, const v2f_t *bbb, float t_x, float t_y, float t_z)
+{
+	v2f_t	xya = _v2f_bilerp(aaa, aba, baa, bba, t_x, t_y);
+	v2f_t	xyb = _v2f_bilerp(aab, abb, bab, bbb, t_x, t_y);
+
+	return _v2f_lerp(&xya, &xyb, t_z);
+}
+
+
+static inline v2f_t * v2f_trilerp(v2f_t *res, const v2f_t *aaa, const v2f_t *aba, const v2f_t *aab, const v2f_t *abb, const v2f_t *baa, const v2f_t *bba, const v2f_t *bab, const v2f_t *bbb, float t_x, float t_y, float t_z)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_trilerp(aaa, aba, aab, abb, baa, bba, bab, bbb, t_x, t_y, t_z);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_rand(const v2f_t *min, const v2f_t *max)
+{
+	return (v2f_t){
+		.x = min->x + (float)rand() * (1.f/RAND_MAX) * (max->x - min->x),
+		.y = min->y + (float)rand() * (1.f/RAND_MAX) * (max->y - min->y),
+	};
+}
+
+
+static inline v2f_t * v2f_rand(v2f_t *res, const v2f_t *min, const v2f_t *max)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_rand(min, max);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_ceil(const v2f_t *v)
+{
+	return (v2f_t){
+		.x = ceilf(v->x),
+		.y = ceilf(v->y),
+	};
+}
+
+
+static inline v2f_t * v2f_ceil(v2f_t *res, const v2f_t *v)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_ceil(v);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_floor(const v2f_t *v)
+{
+	return (v2f_t){
+		.x = floorf(v->x),
+		.y = floorf(v->y),
+	};
+}
+
+
+static inline v2f_t * v2f_floor(v2f_t *res, const v2f_t *v)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_floor(v);
+
+	return res;
+}
+
+
+static inline v2f_t _v2f_clamp(const v2f_t *v, const v2f_t *min, const v2f_t *max)
+{
+	return (v2f_t){
+		.x = v->x < min->x ? min->x : v->x > max->x ? max->x : v->x,
+		.y = v->y < min->y ? min->y : v->y > max->y ? max->y : v->y,
+	};
+}
+
+
+static inline v2f_t * v2f_clamp(v2f_t *res, const v2f_t *v, const v2f_t *min, const v2f_t *max)
+{
+	if (_v2f_allocated(&res))
+		*res = _v2f_clamp(v, min, max);
+
+	return res;
+}
+
+#endif
diff --git a/src/modules/voronoi/voronoi.c b/src/modules/voronoi/voronoi.c
new file mode 100644
index 0000000..ea68136
--- /dev/null
+++ b/src/modules/voronoi/voronoi.c
@@ -0,0 +1,431 @@
+#include <errno.h>
+#include <float.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "til.h"
+#include "til_fb.h"
+#include "til_util.h"
+
+#include "v2f.h"
+
+/* Rudimentary Voronoi diagram module:
+ * https://en.wikipedia.org/wiki/Voronoi_diagram
+ *
+ * When used as an overlay, the output fragment's contents are sampled for
+ * coloring the cells producing a realtime mosaic style effect.
+ */
+
+/* Copyright (C) 2022 Vito Caputo <vcaputo@pengaru.com> */
+
+typedef struct voronoi_setup_t {
+	til_setup_t		til_setup;
+	size_t			n_cells;
+	unsigned		randomize:1;
+	unsigned		dirty:1;
+} voronoi_setup_t;
+
+typedef struct voronoi_cell_t {
+	v2f_t			origin;
+	uint32_t		color;
+} voronoi_cell_t;
+
+typedef struct voronoi_distance_t {
+	voronoi_cell_t		*cell;
+	float			distance_sq;
+} voronoi_distance_t;
+
+typedef struct voronoi_distances_t {
+	int			width, height;
+	size_t			size;
+	voronoi_distance_t	*buf;
+} voronoi_distances_t;
+
+typedef struct voronoi_context_t {
+	voronoi_setup_t		setup;
+	voronoi_distances_t	distances;
+	voronoi_cell_t		cells[];
+} voronoi_context_t;
+
+
+#define VORONOI_DEFAULT_N_CELLS		1024
+#define VORONOI_DEFAULT_DIRTY		0
+#define VORONOI_DEFAULT_RANDOMIZE	0
+
+
+static voronoi_setup_t voronoi_default_setup = {
+	.n_cells = VORONOI_DEFAULT_N_CELLS,
+	.dirty = VORONOI_DEFAULT_DIRTY,
+	.randomize = VORONOI_DEFAULT_RANDOMIZE,
+};
+
+
+static void voronoi_randomize(voronoi_context_t *ctxt)
+{
+	float	inv_rand_max= 1.f / (float)RAND_MAX;
+
+	for (size_t i = 0; i < ctxt->setup.n_cells; i++) {
+		voronoi_cell_t	*p = &ctxt->cells[i];
+
+		p->origin.x = ((float)rand() * inv_rand_max) * 2.f - 1.f;
+		p->origin.y = ((float)rand() * inv_rand_max) * 2.f - 1.f;
+
+		p->color = ((uint32_t)(rand() % 256)) << 16;
+		p->color |= ((uint32_t)(rand() % 256)) << 8;
+		p->color |= ((uint32_t)(rand() % 256));
+	}
+}
+
+
+static void * voronoi_create_context(unsigned ticks, unsigned num_cpus, til_setup_t *setup)
+{
+	voronoi_context_t	*ctxt;
+
+	if (!setup)
+		setup = &voronoi_default_setup.til_setup;
+
+	ctxt = calloc(1, sizeof(voronoi_context_t) + ((voronoi_setup_t *)setup)->n_cells * sizeof(voronoi_cell_t));
+	if (!ctxt)
+		return NULL;
+
+	ctxt->setup = *(voronoi_setup_t *)setup;
+
+	voronoi_randomize(ctxt);
+
+	return ctxt;
+}
+
+
+static void voronoi_destroy_context(void *context)
+{
+	voronoi_context_t	*ctxt = context;
+
+	free(ctxt->distances.buf);
+	free(ctxt);
+}
+
+
+static int voronoi_fragmenter(void *context, const til_fb_fragment_t *fragment, unsigned number, til_fb_fragment_t *res_fragment)
+{
+	voronoi_context_t	*ctxt = context;
+
+	return til_fb_fragment_tile_single(fragment, 64, number, res_fragment);
+}
+
+
+static inline size_t voronoi_cell_origin_to_distance_idx(const voronoi_context_t *ctxt, const voronoi_cell_t *cell)
+{
+	size_t	x, y;
+
+	x = (cell->origin.x * .5f + .5f) * (float)ctxt->distances.width;
+	y = (cell->origin.y * .5f + .5f) * (float)ctxt->distances.height;
+
+	return y * ctxt->distances.width + x;
+}
+
+
+static void voronoi_jumpfill_pass(voronoi_context_t *ctxt, v2f_t *ds, size_t step)
+{
+	voronoi_distance_t	*d = ctxt->distances.buf;
+	v2f_t			dp = {};
+
+	dp.y = -1.f;
+	for (int y = 0; y < ctxt->distances.height; y++, dp.y += ds->y) {
+
+		dp.x = -1.f;
+		for (int x = 0; x < ctxt->distances.width; x++, dp.x += ds->x, d++) {
+			voronoi_distance_t	*dq;
+
+			if (d->cell && d->distance_sq == 0)
+				continue;
+
+#define VORONOI_JUMPFILL																	\
+				if (dq->cell) {														\
+					float	dist_sq = v2f_distance_sq(&dq->cell->origin, &dp);							\
+																			\
+					if (!d->cell) { /* we're unassigned, just join dq's cell */							\
+						d->cell = dq->cell;											\
+						d->distance_sq = dist_sq;										\
+					} else if (dist_sq < d->distance_sq) { /* is dq's cell's origin closer than the present one?  then join it */	\
+						d->cell = dq->cell;											\
+						d->distance_sq = dist_sq;										\
+					}														\
+				}
+
+			if (x >= step) {
+				/* can sample to the left */
+				dq = d - step;
+
+				VORONOI_JUMPFILL;
+
+				if (y >= step) {
+					/* can sample above and to the left */
+					dq = d - step * ctxt->distances.width - step;
+
+					VORONOI_JUMPFILL;
+				}
+
+				if (ctxt->distances.height - y > step) {
+					/* can sample below and to the left */
+					dq = d + step * ctxt->distances.width - step;
+
+					VORONOI_JUMPFILL;
+				}
+
+			}
+
+			if (ctxt->distances.width - x > step) {
+				/* can sample to the right */
+				dq = d + step;
+
+				VORONOI_JUMPFILL;
+
+				if (y >= step) {
+					/* can sample above and to the right */
+					dq = d - step * ctxt->distances.width + step;
+
+					VORONOI_JUMPFILL;
+				}
+
+				if (ctxt->distances.height - y > step) {
+					/* can sample below */
+					dq = d + step * ctxt->distances.width + step;
+
+					VORONOI_JUMPFILL;
+				}
+			}
+
+			if (y >= step) {
+				/* can sample above */
+				dq = d - step * ctxt->distances.width;
+
+				VORONOI_JUMPFILL;
+			}
+
+			if (ctxt->distances.height - y > step) {
+				/* can sample below */
+				dq = d + step * ctxt->distances.width;
+
+				VORONOI_JUMPFILL;
+			}
+		}
+	}
+}
+
+
+static void voronoi_calculate_distances(voronoi_context_t *ctxt)
+{
+	v2f_t	ds = (v2f_t){
+			.x = 2.f / ctxt->distances.width,
+			.y = 2.f / ctxt->distances.height,
+		};
+
+	memset(ctxt->distances.buf, 0, ctxt->distances.size * sizeof(*ctxt->distances.buf));
+
+#if 0
+	/* naive inefficient brute-force but correct algorithm */
+	for (size_t i = 0; i < ctxt->setup.n_cells; i++) {
+		voronoi_distance_t	*d = ctxt->distances.buf;
+		v2f_t			dp = {};
+
+		dp.y = -1.f;
+		for (int y = 0; y < ctxt->distances.height; y++, dp.y += ds.y) {
+
+			dp.x = -1.f;
+			for (int x = 0; x < ctxt->distances.width; x++, dp.x += ds.x, d++) {
+				float	dist_sq;
+
+				dist_sq = v2f_distance_sq(&ctxt->cells[i].origin, &dp);
+				if (!d->cell || dist_sq < d->distance_sq) {
+					d->cell = &ctxt->cells[i];
+					d->distance_sq = dist_sq;
+				}
+			}
+		}
+	}
+#else
+	/* An attempt at implementing https://en.wikipedia.org/wiki/Jump_flooding_algorithm */
+
+	/* first assign the obvious zero-distance cell origins */
+	for (size_t i = 0; i < ctxt->setup.n_cells; i++) {
+		voronoi_cell_t		*c = &ctxt->cells[i];
+		size_t			idx;
+		voronoi_distance_t	*d;
+
+		idx = voronoi_cell_origin_to_distance_idx(ctxt, c);
+		d = &ctxt->distances.buf[idx];
+
+		d->cell = c;
+		d->distance_sq = 0.f;
+	}
+
+	/* now for every distance sample neighbors */
+	if (ctxt->setup.dirty) {
+		for (size_t step = 2; step <= MAX(ctxt->distances.width, ctxt->distances.height); step *= 2)
+			voronoi_jumpfill_pass(ctxt, &ds, step);
+	} else {
+		for (size_t step = MAX(ctxt->distances.width, ctxt->distances.height) / 2; step > 0; step >>= 1)
+			voronoi_jumpfill_pass(ctxt, &ds, step);
+	}
+#endif
+}
+
+
+static void voronoi_sample_colors(voronoi_context_t *ctxt, til_fb_fragment_t *fragment)
+{
+	for (size_t i = 0; i < ctxt->setup.n_cells; i++) {
+		voronoi_cell_t	*p = &ctxt->cells[i];
+		int		x, y;
+
+		x = (p->origin.x * .5f + .5f) * fragment->frame_width;
+		y = (p->origin.y * .5f + .5f) * fragment->frame_height;
+
+		p->color = fragment->buf[y * fragment->pitch + x];
+	}
+}
+
+
+static void voronoi_prepare_frame(void *context, unsigned ticks, unsigned n_cpus, til_fb_fragment_t *fragment, til_fragmenter_t *res_fragmenter)
+{
+	voronoi_context_t	*ctxt = context;
+
+	*res_fragmenter = voronoi_fragmenter;
+
+	if (!ctxt->distances.buf ||
+	    ctxt->distances.width != fragment->frame_width ||
+	    ctxt->distances.height != fragment->frame_height) {
+
+		free(ctxt->distances.buf);
+		ctxt->distances.width = fragment->frame_width;
+		ctxt->distances.height = fragment->frame_height;
+		ctxt->distances.size = fragment->frame_width * fragment->frame_height;
+		ctxt->distances.buf = malloc(sizeof(voronoi_distance_t) * ctxt->distances.size);
+
+		if (!ctxt->setup.randomize)
+			voronoi_calculate_distances(ctxt);
+	}
+
+	/* TODO: explore moving voronoi_calculate_distances() into render_fragment (threaded) */
+
+	if (ctxt->setup.randomize) {
+		voronoi_randomize(ctxt);
+		voronoi_calculate_distances(ctxt);
+	}
+
+	/* if the fragment comes in already cleared/initialized, use it for the colors, producing a mosaic */
+	if (fragment->cleared)
+		voronoi_sample_colors(ctxt, fragment);
+}
+
+
+static void voronoi_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
+{
+	voronoi_context_t	*ctxt = context;
+
+	for (int y = 0; y < fragment->height; y++) {
+		for (int x = 0; x < fragment->width; x++) {
+			fragment->buf[y * fragment->pitch + x] = ctxt->distances.buf[(y + fragment->y) * ctxt->distances.width + (fragment->x + x)].cell->color;
+		}
+	}
+}
+
+
+static int voronoi_setup(const til_settings_t *settings, til_setting_t **res_setting, const til_setting_desc_t **res_desc, til_setup_t **res_setup)
+{
+	const char	*n_cells;
+	const char	*n_cells_values[] = {
+				"512",
+				"1024",
+				"2048",
+				"4096",
+				"8192",
+				"16384",
+				"32768",
+				NULL
+			};
+	const char	*randomize;
+	const char	*bool_values[] = {
+				"off",
+				"on",
+				NULL
+			};
+	const char	*dirty;
+	int		r;
+
+	r = til_settings_get_and_describe_value(settings,
+						&(til_setting_desc_t){
+							.name = "Voronoi cells quantity",
+							.key = "cells",
+							.regex = "^[0-9]+",
+							.preferred = TIL_SETTINGS_STR(VORONOI_DEFAULT_N_CELLS),
+							.values = n_cells_values,
+							.annotations = NULL
+						},
+						&n_cells,
+						res_setting,
+						res_desc);
+	if (r)
+		return r;
+
+	r = til_settings_get_and_describe_value(settings,
+						&(til_setting_desc_t){
+							.name = "Constantly randomize cell placement",
+							.key = "randomize",
+							.regex = "^(on|off)",
+							.preferred = bool_values[VORONOI_DEFAULT_RANDOMIZE],
+							.values = bool_values,
+							.annotations = NULL
+						},
+						&randomize,
+						res_setting,
+						res_desc);
+	if (r)
+		return r;
+
+	r = til_settings_get_and_describe_value(settings,
+						&(til_setting_desc_t){
+							.name = "Use faster, imperfect method",
+							.key = "dirty",
+							.regex = "^(on|off)",
+							.preferred = bool_values[VORONOI_DEFAULT_DIRTY],
+							.values = bool_values,
+							.annotations = NULL
+						},
+						&dirty,
+						res_setting,
+						res_desc);
+	if (r)
+		return r;
+
+	if (res_setup) {
+		voronoi_setup_t	*setup;
+
+		setup = til_setup_new(sizeof(*setup), (void(*)(til_setup_t *))free);
+		if (!setup)
+			return -ENOMEM;
+
+		sscanf(n_cells, "%u", &setup->n_cells);
+
+		if (!strcasecmp(randomize, "on"))
+			setup->randomize = 1;
+
+		if (!strcasecmp(dirty, "on"))
+			setup->dirty = 1;
+
+		*res_setup = &setup->til_setup;
+	}
+	return 0;
+}
+
+
+til_module_t	voronoi_module = {
+	.create_context = voronoi_create_context,
+	.destroy_context = voronoi_destroy_context,
+	.prepare_frame = voronoi_prepare_frame,
+	.render_fragment = voronoi_render_fragment,
+	.setup = voronoi_setup,
+	.name = "voronoi",
+	.description = "Voronoi diagram",
+	.author = "Vito Caputo <vcaputo@pengaru.com>",
+	.flags = TIL_MODULE_OVERLAYABLE,
+};
diff --git a/src/til.c b/src/til.c
index d7281ee..5d375c3 100644
--- a/src/til.c
+++ b/src/til.c
@@ -44,6 +44,7 @@ extern til_module_t	stars_module;
 extern til_module_t	submit_module;
 extern til_module_t	swab_module;
 extern til_module_t	swarm_module;
+extern til_module_t	voronoi_module;
 
 static const til_module_t	*modules[] = {
 	&blinds_module,
@@ -67,6 +68,7 @@ static const til_module_t	*modules[] = {
 	&submit_module,
 	&swab_module,
 	&swarm_module,
+	&voronoi_module,
 };