modules/swarm: add lines drawing style

Introduce drawing styles, adding a line style in addition to the
existing points.

Settings are style={points,lines}, default is now lines.

1 files changed, 197 insertions, 22 deletions

diff --git a/src/modules/swarm/swarm.c b/src/modules/swarm/swarm.c
index 7c8caeb..8ff4812 100644
--- a/src/modules/swarm/swarm.c
+++ b/src/modules/swarm/swarm.c
@@ -27,8 +27,10 @@
 #include "til.h"
 #include "til_fb.h"
 
-#define SWARM_SIZE	(32 * 1024)
-#define SWARM_ZCONST	4.f
+typedef enum swarm_draw_style_t {
+	SWARM_DRAW_STYLE_POINTS,	/* simple opaque pixel per particle */
+	SWARM_DRAW_STYLE_LINES,		/* simple opaque lines per particle, oriented and sized by direction and velocity */
+} swarm_draw_style_t;
 
 typedef struct v3f_t {
 	float	x, y, z;
@@ -50,6 +52,12 @@ typedef struct swarm_context_t {
 	boid_t		boids[];
 } swarm_context_t;
 
+#define SWARM_SIZE		(32 * 1024)
+#define SWARM_ZCONST		4.f
+#define SWARM_DEFAULT_STYLE	SWARM_DRAW_STYLE_LINES
+
+static swarm_draw_style_t swarm_draw_style = SWARM_DEFAULT_STYLE;
+
 
 static inline float randf(float min, float max)
 {
@@ -111,6 +119,16 @@ static inline void v3f_normalize(v3f_t *v)
 }
 
 
+static inline v3f_t v3f_invert(v3f_t v)
+{
+	return (v3f_t){
+		.x = -v.x,
+		.y = -v.y,
+		.z = -v.z,
+	};
+}
+
+
 static v3f_t v3f_lerp(v3f_t a, v3f_t b, float t)
 {
 	return (v3f_t){
@@ -184,10 +202,34 @@ static void swarm_update(swarm_context_t *ctxt, unsigned ticks)
 
 	{ /* [0] = leader */
 		float	r = M_PI * 2 * ((cosf((float)ticks * .001f) * .5f + .5f));
+		v3f_t	newpos = {
+				.x = cosf(r),
+				.y = sinf(r),
+				.z = cosf(r * 2.f),
+			};
+		boid_t	*b = &ctxt->boids[0];
+
+		if (newpos.x != b->position.x ||
+		    newpos.y != b->position.y ||
+		    newpos.z != b->position.z) {
+
+			/* XXX: this must be conditional on position changing otherwise
+			 * it could produce a zero direction vector, making normalize
+			 * spit out NaN, and things fall apart.
+			 */
+
+			b->direction = v3f_sub(b->position, newpos);
+			b->velocity = v3f_len(b->direction);
+			v3f_normalize(&b->direction);
+			b->position = newpos;
 
-		ctxt->boids[0].position.x = cosf(r);
-		ctxt->boids[0].position.y = sinf(r);
-		ctxt->boids[0].position.z = cosf(r * 2.f);
+		}
+#if 0
+		printf("pos={%f,%f,%f},dir={%f,%f,%f},v=%f\n",
+			b->position.x, b->position.y, b->position.z,
+			b->direction.x, b->direction.y, b->direction.z,
+			b->velocity);
+#endif
 	}
 
 	/* characterize the current swarm */
@@ -236,37 +278,169 @@ static void swarm_update(swarm_context_t *ctxt, unsigned ticks)
 }
 
 
-static void swarm_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
+static inline v2f_t swarm_project_point(swarm_context_t *ctxt, v3f_t *point)
 {
-	swarm_context_t	*ctxt = context;
+	return (v2f_t) {
+		.x = point->x / (point->z + SWARM_ZCONST + ctxt->ztweak),
+		.y = point->y / (point->z + SWARM_ZCONST + ctxt->ztweak),
+	};
+}
 
-	swarm_update(ctxt, ticks);
 
-	til_fb_fragment_zero(fragment);
+static inline v2f_t swarm_scale(v2f_t normcoord, v2f_t scale)
+{
+	return (v2f_t) {
+		.x = normcoord.x * scale.x + scale.x,
+		.y = normcoord.y * scale.y + scale.y,
+	};
+}
 
-	{
-		float		fw = fragment->frame_width, fh = fragment->frame_height;
-		uint32_t	color = color_to_uint32(ctxt->color);
 
-		fw *= .5f;
-		fh *= .5f;
+static inline v2f_t swarm_clip(v2f_t coord, til_fb_fragment_t *fragment)
+{
+//	printf("coord={%f,%f}\n", coord.x, coord.y);
 
-		for (unsigned i = 0; i < SWARM_SIZE; i++) {
-			boid_t	*b = &ctxt->boids[i];
-			v2f_t	nc;
+	return (v2f_t) {
+		.x = coord.x < 0.f ? 0.f : (coord.x > (fragment->frame_width - 1) ? (fragment->frame_width - 1) : coord.x),
+		.y = coord.y < 0.f ? 0.f : (coord.y > (fragment->frame_height - 1) ? (fragment->frame_height - 1) : coord.y),
+	};
+}
 
-			nc.x = b->position.x / (b->position.z + SWARM_ZCONST + ctxt->ztweak);
-			nc.y = b->position.y / (b->position.z + SWARM_ZCONST + ctxt->ztweak);
 
-			nc.x = nc.x * fw + fw;
-			nc.y = nc.y * fh + fh;
+static void swarm_draw_as_points(swarm_context_t *ctxt, til_fb_fragment_t *fragment)
+{
+	v2f_t		scale = (v2f_t){
+				.x = fragment->frame_width * .5f,
+				.y = fragment->frame_height * .5f,
+			};
+	uint32_t	color = color_to_uint32(ctxt->color);
 
-			til_fb_fragment_put_pixel_checked(fragment, nc.x, nc.y, color);
+	for (unsigned i = 0; i < SWARM_SIZE; i++) {
+		boid_t	*b = &ctxt->boids[i];
+		v2f_t	nc = swarm_scale(swarm_project_point(ctxt, &b->position), scale);
+
+		til_fb_fragment_put_pixel_checked(fragment, nc.x, nc.y, color);
+	}
+}
+
+
+static void draw_line_unchecked(til_fb_fragment_t *fragment, int x1, int y1, int x2, int y2, uint32_t color)
+{
+	int	x_delta = x2 - x1;
+	int	y_delta = y2 - y1;
+	int	sdx = x_delta < 0 ? -1 : 1;
+	int	sdy = y_delta < 0 ? -1 : 1;
+
+	x_delta = abs(x_delta);
+	y_delta = abs(y_delta);
+
+	if (x_delta >= y_delta) {
+		/* X-major */
+		for (int minor = 0, x = 0; x <= x_delta; x++, x1 += sdx, minor += y_delta) {
+			if (minor >= x_delta) {
+				y1 += sdy;
+				minor -= x_delta;
+			}
+
+			til_fb_fragment_put_pixel_unchecked(fragment, x1, y1, color);
 		}
+	} else {
+		/* Y-major */
+		for (int minor = 0, y = 0; y <= y_delta; y++, y1 += sdy, minor += x_delta) {
+			if (minor >= y_delta) {
+				x1 += sdx;
+				minor -= y_delta;
+			}
+
+			til_fb_fragment_put_pixel_unchecked(fragment, x1, y1, color);
+		}
+	}
+}
+
+
+static void swarm_draw_as_lines(swarm_context_t *ctxt, til_fb_fragment_t *fragment)
+{
+	v2f_t		scale = (v2f_t){
+				.x = fragment->frame_width * .5f,
+				.y = fragment->frame_height * .5f,
+			};
+	uint32_t	color = color_to_uint32(ctxt->color);
+
+	/* this is similar to draw_as_points(), but derives two 3D points per boid,
+	 * connecting them with a line in 2D.
+	 */
+	for (unsigned i = 0; i < SWARM_SIZE; i++) {
+		boid_t	*b = &ctxt->boids[i];
+		v3f_t	p1, p2;
+		v2f_t	nc1, nc2;
+
+		p1 = v3f_add(b->position, v3f_mult_scalar(b->direction, b->velocity));
+		p2 = v3f_add(b->position, v3f_mult_scalar(v3f_invert(b->direction), b->velocity));
+
+		/* don't bother drawing anything too close/behind the viewer, it
+		 * just produces diagonal lines across the entire frame.
+		 */
+		if (p1.z < -SWARM_ZCONST && p2.z < -SWARM_ZCONST)
+			continue;
+
+		nc1 = swarm_clip(swarm_scale(swarm_project_point(ctxt, &p1), scale), fragment);
+		nc2 = swarm_clip(swarm_scale(swarm_project_point(ctxt, &p2), scale), fragment);
+
+		draw_line_unchecked(fragment, nc1.x, nc1.y, nc2.x, nc2.y, color);
+	}
+}
+
+
+static void swarm_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
+{
+	swarm_context_t	*ctxt = context;
+
+	swarm_update(ctxt, ticks);
+
+	til_fb_fragment_zero(fragment);
+
+	switch (swarm_draw_style) {
+	case SWARM_DRAW_STYLE_POINTS:
+		return swarm_draw_as_points(ctxt, fragment);
+	case SWARM_DRAW_STYLE_LINES:
+		return swarm_draw_as_lines(ctxt, fragment);
 	}
 }
 
 
+static int swarm_setup(const til_settings_t *settings, til_setting_t **res_setting, const til_setting_desc_t **res_desc)
+{
+	const char	*styles[] = {
+				"points",
+				"lines",
+				NULL,
+			};
+	const char	*style;
+	int		r;
+
+	r = til_settings_get_and_describe_value(settings,
+						&(til_setting_desc_t){
+							.name = "Particle drawing style",
+							.key = "style",
+							.values = styles,
+							.preferred = styles[SWARM_DEFAULT_STYLE],
+							.annotations = NULL
+						},
+						&style,
+						res_setting,
+						res_desc);
+	if (r)
+		return r;
+
+	for (int i = 0; styles[i]; i++) {
+		if (!strcmp(styles[i], style))
+			swarm_draw_style = i;
+	}
+
+	return 0;
+}
+
+
 til_module_t	swarm_module = {
 	.create_context = swarm_create_context,
 	.destroy_context = swarm_destroy_context,
@@ -274,4 +448,5 @@ til_module_t	swarm_module = {
 	.name = "swarm",
 	.description = "\"Boids\"-inspired particle swarm in 3D",
 	.author = "Vito Caputo <vcaputo@pengaru.com>",
+	.setup = swarm_setup,
 };