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#include <math.h>
#include <stdlib.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include "til.h"
#include "til_fb.h"
#include "draw.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 ticks, unsigned num_cpus)
{
spiro_context_t *ctxt;
float z;
ctxt = malloc(sizeof(spiro_context_t));
if (!ctxt)
return NULL;
srand(ticks + 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 ticks, unsigned cpu, til_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 */
til_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);
til_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 */
til_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);
til_fb_fragment_put_pixel_unchecked(fragment, pos_x, pos_y,
makergb(0xFF, 0xFF, 0x00, 1));
}
/* plot inner circle Ci */
til_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);
til_fb_fragment_put_pixel_unchecked(fragment, pos_x, pos_y,
makergb(0xFF, 0xFF, 0x00, 1));
}
/* plot p */
til_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);
}
til_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>",
};
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