stars: add starfield simulator from ph1l/stars

8 files changed, 260 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 13eef36..2e6c01b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,10 @@
 CFLAGS=-D_GNU_SOURCE -Wall -O3 -ffast-math -pthread $(shell pkg-config --cflags libdrm) -I.
 LDFLAGS=-lm -pthread $(shell pkg-config --libs libdrm)
-SRC=rototiller.c modules/ray/*.c modules/roto/roto.c modules/sparkler/*.c drmsetup.c fb.c fps.c util.c
+SRC=rototiller.c modules/ray/*.c modules/roto/roto.c modules/sparkler/*.c modules/stars/*.c drmsetup.c fb.c fps.c util.c
 
 all: rototiller
 
-rototiller: $(SRC) Makefile modules/ray/*.h modules/roto/roto.h modules/sparkler/*.h drmsetup.h fb.h fps.h util.h
+rototiller: $(SRC) Makefile modules/ray/*.h modules/roto/roto.h modules/sparkler/*.h modules/stars/stars.h drmsetup.h fb.h fps.h util.h
 	$(CC) -o $@ $(SRC) $(CFLAGS) $(LDFLAGS)
 
 clean:
diff --git a/README b/README
index 4f9dbb6..3f34c54 100644
--- a/README
+++ b/README
@@ -2,6 +2,7 @@ rototiller is, rendered entirely in software:
 	roto: a simple fixed-point tiled texture rotation
 	ray: a multi-threaded ray tracer
 	sparkler: a fireworks-like particle system with spatial interactions
+	stars: a starfield simulator
 
 ---
 
diff --git a/modules/stars/draw.h b/modules/stars/draw.h
new file mode 100644
index 0000000..58a4a36
--- /dev/null
+++ b/modules/stars/draw.h
@@ -0,0 +1,32 @@
+#ifndef _DRAW_H
+#define _DRAW_H
+
+#include <stdint.h>
+
+#include "fb.h"
+
+/* helper for scaling rgb colors and packing them into an pixel */
+static inline uint32_t makergb(uint32_t r, uint32_t g, uint32_t b, float intensity)
+{
+	r = (((float)intensity) * r);
+	g = (((float)intensity) * g);
+	b = (((float)intensity) * b);
+
+	return (((r & 0xff) << 16) | ((g & 0xff) << 8) | (b & 0xff));
+}
+
+static inline int draw_pixel(fb_fragment_t *f, int x, int y, uint32_t pixel)
+{
+	uint32_t	*pixels = f->buf;
+
+	if (y < 0 || y >= f->height || x < 0 || x >= f->width) {
+		return 0;
+	}
+
+	/* FIXME this assumes stride is aligned to 4 */
+	pixels[(y * f->width + (f->stride >> 2)) + x] = pixel;
+
+	return 1;
+}
+
+#endif
diff --git a/modules/stars/stars.c b/modules/stars/stars.c
new file mode 100644
index 0000000..e009714
--- /dev/null
+++ b/modules/stars/stars.c
@@ -0,0 +1,63 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+#include <time.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "draw.h"
+#include "fb.h"
+#include "rototiller.h"
+#include "starslib.h"
+
+/* Copyright (C) 2017 Philip J. Freeman <elektron@halo.nu> */
+
+static void stars(fb_fragment_t *fragment)
+{
+	static int	initialized, z;
+	static struct	universe* u;
+
+	struct		return_point rp;
+	int		x, y, width = fragment->width, height = fragment->height;
+
+	if (!initialized) {
+		z = 128;
+		srand(time(NULL) + getpid());
+
+		// Initialize the stars lib (and pre-add a bunch of stars)
+		new_universe(&u, width, height, z);
+		for(y=0; y<z; y++) {
+			while (process_point(u, &rp) != 0);
+			for(x=0; x<rand()%128; x++){
+				new_point(u);
+			}
+		}
+		initialized = 1;
+	}
+
+	// draw space (or blank the frame, if you prefer)
+	memset(fragment->buf, 0, ((fragment->width << 2) + fragment->stride) * fragment->height);
+
+	// draw stars
+	for (;;) {
+		int ret = process_point( u, &rp  );
+		if (ret==0) break;
+		if (ret==1) draw_pixel(fragment, rp.x+(width/2), rp.y+(height/2),
+				       makergb(0xFF, 0xFF, 0xFF, (float)rp.opacity/OPACITY_MAX)
+				      );
+	}
+
+	// add stars at horizon
+	for (x=0; x<rand()%128; x++) {
+		new_point(u);
+	}
+}
+
+rototiller_renderer_t	stars_renderer = {
+	.render = stars,
+	.name = "stars",
+	.description = "basic starfield",
+	.author = "Philip J Freeman <elektron@halo.nu>",
+	.license = "GPLv2",
+};
diff --git a/modules/stars/stars.h b/modules/stars/stars.h
new file mode 100644
index 0000000..70ef6f2
--- /dev/null
+++ b/modules/stars/stars.h
@@ -0,0 +1,8 @@
+#ifndef _STARS_H
+#define _STARS_H
+
+#include "fb.h"
+
+void stars(fb_fragment_t *fragment);
+
+#endif
diff --git a/modules/stars/starslib.c b/modules/stars/starslib.c
new file mode 100644
index 0000000..3c1905c
--- /dev/null
+++ b/modules/stars/starslib.c
@@ -0,0 +1,133 @@
+/*
+ * a starfield simulation library from: https://github.com/ph1l/stars
+ * Copyright 2014 Philip J. Freeman <elektron@halo.nu>
+ */
+
+#include <stdlib.h>
+#ifdef DEBUG
+#include <stdio.h>
+#endif
+#include "starslib.h"
+
+struct points
+{
+	int x, y, z;
+	struct points *next;
+};
+
+void new_universe( struct universe** u, int width, int height, int depth )
+{
+	*u = malloc(sizeof(struct universe));
+
+	(*u)->width  = width;
+	(*u)->height = height;
+	(*u)->depth  = depth;
+
+	(*u)->iterator  = NULL;
+	(*u)->points  = NULL;
+	#ifdef DEBUG
+	printf("NEW UNIVERSE: %lx: (%i,%i,%i)\n", (long unsigned int )(*u), (*u)->width, (*u)->height, (*u)->depth);
+	#endif
+
+	return;
+}
+
+void new_point( struct universe* u )
+{
+
+	struct points* p_ptr = malloc(sizeof(struct points));
+
+	p_ptr->x    = (rand()%u->width - (u->width/2)) * u->depth;
+	p_ptr->y    = (rand()%u->height - (u->height/2)) * u->depth;
+	p_ptr->z    = u->depth;
+
+	p_ptr->next = u->points;
+	u->points = p_ptr;
+	#ifdef DEBUG
+	printf("NEW POINT: %lx: (%i,%i,%i) next=%lx\n", (long unsigned int )p_ptr, p_ptr->x, p_ptr->y, p_ptr->z, (long unsigned int) p_ptr->next);
+	#endif
+
+	return;
+}
+
+void kill_point( struct universe* universe, struct points* to_kill )
+{
+
+	struct points *p_ptr, *last_ptr = NULL;
+
+
+	for ( p_ptr = universe->points; p_ptr != NULL; p_ptr = p_ptr->next)
+	{
+		if (p_ptr == to_kill)
+		{
+			#ifdef DEBUG
+			printf("KILL POINT: %lx: (%i,%i,%i).\n", (long unsigned int )p_ptr, p_ptr->x, p_ptr->y, p_ptr->z);
+			#endif
+			if (last_ptr == NULL)
+			{
+				universe->points = p_ptr->next;
+			} else {
+				last_ptr->next = p_ptr->next;
+			}
+			free(p_ptr);
+		} else {
+			last_ptr = p_ptr;
+		}
+	}
+	#ifdef DEBUG
+	printf("KILL POINT: %lx\n", (long unsigned int )p_ptr);
+	#endif
+	return;
+}
+
+int process_point( struct universe *u, struct return_point *rp )
+{
+
+	if ( u->iterator == NULL ) {
+		if (u->points == NULL){
+			return 0;
+		} else {
+			u->iterator = u->points;
+		}
+	}
+
+	if ( u->iterator->z == 0 ){
+		// Delete point that has reached us.
+		struct points *tmp = u->iterator;
+		u->iterator = u->iterator->next;
+		kill_point( u, tmp );
+		return(-1);
+	} else {
+		// Plot the point
+		int x, y;
+		x = u->iterator->x / u->iterator->z;
+		y = u->iterator->y / u->iterator->z;
+		if ( abs(x) >= u->width/2 || abs(y) >= u->height/2 ){
+			// Delete point that is off screen
+			struct points *tmp = u->iterator;
+			u->iterator = u->iterator->next;
+			kill_point( u, tmp );
+			if ( u->iterator == NULL ) {
+				return(0);
+			} else {
+				return(-1);
+			}
+		} else {
+			int m = OPACITY_MAX*((u->depth-u->iterator->z)*4)/u->depth;
+			if ( m>=OPACITY_MAX ){ m=OPACITY_MAX-1; }
+			u->iterator->z = u->iterator->z - 1;
+			#ifdef DEBUG
+			printf("RETURN POINT: %lx\n", (long unsigned int )u->iterator);
+			#endif
+			u->iterator = u->iterator->next;
+			rp->x = x;
+			rp->y = y;
+			rp->opacity = m;
+			if ( u->iterator == NULL ) {
+				return(0);
+			} else {
+				return(1);
+			}
+		}
+	}
+}
diff --git a/modules/stars/starslib.h b/modules/stars/starslib.h
new file mode 100644
index 0000000..0c125a3
--- /dev/null
+++ b/modules/stars/starslib.h
@@ -0,0 +1,19 @@
+struct universe
+{
+	int width, height, depth;
+	struct points* points;
+	struct points* iterator;
+};
+
+void new_universe( struct universe** u, int width, int height, int depth );
+void new_point( struct universe* universe );
+
+#define OPACITY_MAX 8
+struct return_point
+{
+	int x, y;
+	int opacity;
+};
+
+int process_point( struct universe *u, struct return_point *rp );
+
diff --git a/rototiller.c b/rototiller.c
index 17a8b52..3fa9395 100644
--- a/rototiller.c
+++ b/rototiller.c
@@ -28,12 +28,14 @@ extern rototiller_renderer_t	roto32_renderer;
 extern rototiller_renderer_t	roto64_renderer;
 extern rototiller_renderer_t	ray_renderer;
 extern rototiller_renderer_t	sparkler_renderer;
+extern rototiller_renderer_t	stars_renderer;
 
 static rototiller_renderer_t	*renderers[] = {
 	&roto32_renderer,
 	&roto64_renderer,
 	&ray_renderer,
 	&sparkler_renderer,
+	&stars_renderer,
 };