swab: add a perlin noise visualization

This maps a different Z-slice through the noise field to each color
channel.  The slices are moved up and down through the field over
time, and the size of the area each color samples is tweaked a bit
to make them less coherent with the noise field cells.

It could be improved, but I think the output is already neat enough
to be worth sharing.

7 files changed, 156 insertions, 2 deletions

diff --git a/README b/README
index b67b7b1..5f6ee69 100644
--- a/README
+++ b/README
@@ -10,6 +10,7 @@ rototiller is, rendered entirely in software:
 	pixbounce: a 2D bouncing pixmap demonstration
 	rtv: a "Rototiller TV" slideshow meta-module
 	snow: a "TV snow" / white noise effect
+	swab: a colorful perlin-noise visualization
 
 ---
 
diff --git a/configure.ac b/configure.ac
index 42db4fb..7a2f01e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,5 +52,6 @@ AC_CONFIG_FILES([
  src/modules/sparkler/Makefile
  src/modules/stars/Makefile
  src/modules/submit/Makefile
+ src/modules/swab/Makefile
 ])
 AC_OUTPUT
diff --git a/src/Makefile.am b/src/Makefile.am
index ad45024..48b0a4c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,4 +4,4 @@ rototiller_SOURCES = fb.c fb.h fps.c fps.h rototiller.c rototiller.h sdl_fb.c se
 if ENABLE_DRM
 rototiller_SOURCES += drm_fb.c
 endif
-rototiller_LDADD = modules/flui2d/libflui2d.a modules/julia/libjulia.a modules/pixbounce/libpixbounce.a modules/plasma/libplasma.a modules/ray/libray.a modules/roto/libroto.a modules/rtv/librtv.a modules/snow/libsnow.a modules/sparkler/libsparkler.a modules/stars/libstars.a modules/submit/libsubmit.a libs/grid/libgrid.a libs/ray/libray.a libs/txt/libtxt.a libs/ascii/libascii.a libs/din/libdin.a -lm
+rototiller_LDADD = modules/flui2d/libflui2d.a modules/julia/libjulia.a modules/pixbounce/libpixbounce.a modules/plasma/libplasma.a modules/ray/libray.a modules/roto/libroto.a modules/rtv/librtv.a modules/snow/libsnow.a modules/sparkler/libsparkler.a modules/stars/libstars.a modules/submit/libsubmit.a modules/swab/libswab.a libs/grid/libgrid.a libs/ray/libray.a libs/txt/libtxt.a libs/ascii/libascii.a libs/din/libdin.a -lm
diff --git a/src/modules/Makefile.am b/src/modules/Makefile.am
index fa913a0..0ab81b7 100644
--- a/src/modules/Makefile.am
+++ b/src/modules/Makefile.am
@@ -1 +1 @@
-SUBDIRS = flui2d julia pixbounce plasma ray roto rtv snow sparkler stars submit
+SUBDIRS = flui2d julia pixbounce plasma ray roto rtv snow sparkler stars submit swab
diff --git a/src/modules/swab/Makefile.am b/src/modules/swab/Makefile.am
new file mode 100644
index 0000000..4db914b
--- /dev/null
+++ b/src/modules/swab/Makefile.am
@@ -0,0 +1,3 @@
+noinst_LIBRARIES = libswab.a
+libswab_a_SOURCES = swab.c
+libswab_a_CPPFLAGS = -I@top_srcdir@/src -I@top_srcdir@/src/libs
diff --git a/src/modules/swab/swab.c b/src/modules/swab/swab.c
new file mode 100644
index 0000000..6528900
--- /dev/null
+++ b/src/modules/swab/swab.c
@@ -0,0 +1,147 @@
+/*
+ *  Copyright (C) 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/>.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "din/din.h"
+
+#include "fb.h"
+#include "rototiller.h"
+#include "util.h"
+
+
+typedef struct swab_context_t {
+	din_t		*din;
+	float		r;
+	unsigned	n_cpus;
+} swab_context_t;
+
+typedef struct color_t {
+	float	r,g,b;
+} color_t;
+
+
+/* convert a color into a packed, 32-bit rgb pixel value (taken from libs/ray/ray_color.h) */
+static inline uint32_t color_to_uint32(color_t color) {
+	uint32_t	pixel;
+
+	if (color.r > 1.0f) color.r = 1.0f;
+	if (color.g > 1.0f) color.g = 1.0f;
+	if (color.b > 1.0f) color.b = 1.0f;
+
+	if (color.r < .0f) color.r = .0f;
+	if (color.g < .0f) color.g = .0f;
+	if (color.b < .0f) color.b = .0f;
+
+	pixel = (uint32_t)(color.r * 255.0f);
+	pixel <<= 8;
+	pixel |= (uint32_t)(color.g * 255.0f);
+	pixel <<= 8;
+	pixel |= (uint32_t)(color.b * 255.0f);
+
+	return pixel;
+}
+
+
+static void * swab_create_context(void)
+{
+	swab_context_t	*ctxt;
+
+	ctxt = calloc(1, sizeof(swab_context_t));
+	if (!ctxt)
+		return NULL;
+
+	ctxt->din = din_new(12, 12, 100);
+	if (!ctxt->din) {
+		free(ctxt);
+		return NULL;
+	}
+
+	return ctxt;
+}
+
+
+static void swab_destroy_context(void *context)
+{
+	swab_context_t	*ctxt = context;
+
+	din_free(ctxt->din);
+	free(ctxt);
+}
+
+
+static int swab_fragmenter(void *context, const fb_fragment_t *fragment, unsigned num, fb_fragment_t *res_fragment)
+{
+	swab_context_t	*ctxt = context;
+
+	return fb_fragment_slice_single(fragment, ctxt->n_cpus, num, res_fragment);
+}
+
+
+static void swab_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_fragmenter_t *res_fragmenter)
+{
+	swab_context_t	*ctxt = context;
+
+	*res_fragmenter = swab_fragmenter;
+
+	ctxt->r += .0001f;
+	ctxt->n_cpus = n_cpus;
+}
+
+
+static void swab_render_fragment(void *context, fb_fragment_t *fragment)
+{
+	swab_context_t	*ctxt = context;
+	float		cos_r = cos(ctxt->r);
+	float		sin_r = sin(ctxt->r);
+	float		z1 = cos_r;
+	float		z2 = sin_r;
+	float		xscale = 1.f / (float)fragment->frame_width;
+	float		yscale = 1.f / (float)fragment->frame_height;
+
+	for (int y = fragment->y; y < fragment->y + fragment->height; y++) {
+		for (int x = fragment->x; x < fragment->x + fragment->width; x++) {
+			color_t		color;
+			uint32_t	pixel;
+			float		t;
+
+			t = din(ctxt->din, (v3f_t){ .x = (float)x * xscale * .5f, .y = (float)y * yscale * .5f, .z = -z2 }) * 33.f;
+
+			color.r = din(ctxt->din, (v3f_t){ .x = (float)x * xscale * .7f, .y = (float)y * yscale * .7f, .z = z1 }) * t;
+			color.g = din(ctxt->din, (v3f_t){ .x = (float)x * xscale * .93f, .y = (float)y * yscale * .93f, .z = -z1 }) * t;
+			color.b = din(ctxt->din, (v3f_t){ .x = (float)x * xscale * .81f, .y = (float)y * yscale * .81f, .z = z2 }) * t;
+
+			pixel = color_to_uint32(color);
+			fb_fragment_put_pixel_unchecked(fragment, x, y, pixel);
+		}
+	}
+}
+
+
+rototiller_module_t	swab_module = {
+	.create_context = swab_create_context,
+	.destroy_context = swab_destroy_context,
+	.prepare_frame = swab_prepare_frame,
+	.render_fragment = swab_render_fragment,
+	.name = "swab",
+	.description = "Colorful perlin-noise visualization (threaded)",
+	.author = "Vito Caputo <vcaputo@pengaru.com>",
+	.license = "GPLv3",
+};
diff --git a/src/rototiller.c b/src/rototiller.c
index 92f29fe..74ba006 100644
--- a/src/rototiller.c
+++ b/src/rototiller.c
@@ -43,6 +43,7 @@ extern rototiller_module_t	snow_module;
 extern rototiller_module_t	sparkler_module;
 extern rototiller_module_t	stars_module;
 extern rototiller_module_t	submit_module;
+extern rototiller_module_t	swab_module;
 
 static const rototiller_module_t	*modules[] = {
 	&flui2d_module,
@@ -56,6 +57,7 @@ static const rototiller_module_t	*modules[] = {
 	&sparkler_module,
 	&stars_module,
 	&submit_module,
+	&swab_module,
 };
 
 typedef struct rototiller_t {