spiro: spirograph emulator

This commit adds a module that emulates a spirograph

1 files changed, 155 insertions, 0 deletions

diff --git a/src/modules/spiro/spiro.c b/src/modules/spiro/spiro.c
new file mode 100644
index 0000000..f6aeddc
--- /dev/null
+++ b/src/modules/spiro/spiro.c
@@ -0,0 +1,155 @@
+#include <math.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "draw.h"
+#include "fb.h"
+#include "rototiller.h"
+
+/* Copyright (C) 2020 Philip J. Freeman <elektron@halo.nu> */
+
+/*
+
+Spirograph Emulator
+
+  refs:
+
+    - https://en.wikipedia.org/wiki/Spirograph#Mathematical_basis
+    - https://en.wikipedia.org/wiki/Unit_circle#Trigonometric_functions_on_the_unit_circle
+*/
+
+typedef struct spiro_context_t {
+	float r;
+	int r_dir;
+	float p;
+	int p_dir;
+} spiro_context_t;
+
+
+static void * spiro_create_context(unsigned num_cpus)
+{
+	spiro_context_t *ctxt;
+	float		z;
+
+	ctxt = malloc(sizeof(spiro_context_t));
+	if (!ctxt)
+		return NULL;
+
+	srand(time(NULL) + getpid());
+
+	ctxt->r=.25f+(rand()/(float)RAND_MAX)*.5f;
+	if(ctxt->r>.5f)
+		ctxt->r_dir=-1;
+	else
+		ctxt->r_dir=1;
+	ctxt->p=(rand()/(float)RAND_MAX)*ctxt->r;
+	ctxt->p_dir=ctxt->r_dir*-1;
+#ifdef DEBUG
+	printf("spiro: initial context: r=%f, dir=%i, p=%f, dir=%i\n", ctxt->r, ctxt->r_dir, ctxt->p, ctxt->p_dir);
+#endif
+	return ctxt;
+}
+
+static void spiro_destroy_context(void *context)
+{
+	spiro_context_t *ctxt = context;
+
+	free(context);
+}
+
+
+static void spiro_render_fragment(void *context, unsigned cpu, fb_fragment_t *fragment)
+{
+	spiro_context_t	*ctxt = context;
+
+	int		width = fragment->width, height = fragment->height;
+
+	int display_R, display_origin_x, display_origin_y;
+
+	/* Based on the fragment's dimensions, calculate the origin and radius of the fixed outer
+	circle, C0. */
+
+	if(width>=height) {			 // landscape or square aspect ratio
+		display_R=(height-1)*0.5f;
+		display_origin_x=((width-height)*.5f)+display_R;
+		display_origin_y=display_R;
+	} else {				// portrait
+		display_R=(width-1)*.5f;
+		display_origin_x=display_R;
+		display_origin_y=((height-width)*.5f)+display_R;
+	}
+
+	/* blank the fragment */
+	fb_fragment_zero(fragment);
+
+	/* plot one spirograph run */
+	float l=ctxt->p/ctxt->r;
+	float k=ctxt->r;
+	for(float t=0.f; t<128*2*M_PI; t+= M_PI/display_R) {
+		float my_x=((1.f-k)*cosf(t))+(l*k*cosf(((1.f-k)/k)*t));
+		float my_y=((1.f-k)*sinf(t))-(l*k*sinf(((1.f-k)/k)*t));
+		int pos_x=display_origin_x+(my_x*display_R);
+		int pos_y=display_origin_y+(my_y*display_R);
+		fb_fragment_put_pixel_unchecked(fragment, pos_x, pos_y,
+			makergb(sinf(M_1_PI*t)*127+128,
+				sinf(M_1_PI*t+(2*M_PI*.333333333333f))*127+128,
+				sinf(M_1_PI*t+(4*M_PI*.333333333333f))*127+128,
+				0.76));
+	}
+
+#ifdef DEBUG
+	/* plot the origin point */
+	fb_fragment_put_pixel_unchecked(fragment, display_origin_x, display_origin_y,
+		makergb(0xFF, 0xFF, 0x00, 1));
+
+	/* plot the fixed outer circle C0 */
+	for(float a=0.f; a<2*M_PI; a+= M_PI_2/display_R) {
+		int pos_x=display_origin_x+(cosf(a)*display_R);
+		int pos_y=display_origin_y+(sinf(a)*display_R);
+		fb_fragment_put_pixel_unchecked(fragment, pos_x, pos_y,
+			makergb(0xFF, 0xFF, 0x00, 1));
+	}
+
+	/* plot inner circle Ci */
+	fb_fragment_put_pixel_unchecked(fragment, display_origin_x+display_R-(ctxt->r*display_R),
+		display_origin_y, makergb(0xFF, 0xFF, 0x00, 1));
+
+	for(float a=0.f; a<2*M_PI; a+= M_PI_2/display_R) {
+		int pos_x=display_origin_x+display_R-(ctxt->r*display_R)+
+			(cosf(a)*ctxt->r*display_R);
+		int pos_y=display_origin_y+(sinf(a)*ctxt->r*display_R);
+		fb_fragment_put_pixel_unchecked(fragment, pos_x, pos_y,
+			makergb(0xFF, 0xFF, 0x00, 1));
+	}
+
+	/* plot p */
+	fb_fragment_put_pixel_unchecked(fragment, display_origin_x+display_R-(ctxt->r*display_R)+
+		(ctxt->p*display_R), display_origin_y, makergb(0xFF, 0xFF, 0x00, 1));
+#endif
+
+	/* check bounds and increment r & p */
+	float next_r=ctxt->r+(.00001f*ctxt->r_dir);
+	if(next_r >= 1.f || next_r <= 0.f || next_r <= ctxt->p)
+		ctxt->r_dir=ctxt->r_dir*-1;
+	else
+		ctxt->r=ctxt->r+(.00001f*ctxt->r_dir);
+
+	float next_p=ctxt->p+(.0003f*ctxt->p_dir);
+	if(next_p >= ctxt->r || next_p <= 0)
+		ctxt->p_dir=ctxt->p_dir*-1;
+	else
+		ctxt->p=ctxt->p+(.0003f*ctxt->p_dir);
+
+}
+
+rototiller_module_t	spiro_module = {
+	.create_context  = spiro_create_context,
+	.destroy_context = spiro_destroy_context,
+	.render_fragment = spiro_render_fragment,
+	.name = "spiro",
+	.description = "Spirograph Emulator",
+	.author = "Philip J Freeman <elektron@halo.nu>",
+	.license = "GPLv2",
+};