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/*
* 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 2 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/>.
*/
/* https://en.wikipedia.org/wiki/Metaballs */
#include <stdlib.h>
#include <unistd.h>
#include "til.h"
#include "til_fb.h"
#include "din/din.h"
#include "v2f.h"
#include "v3f.h"
#define META2D_NUM_BALLS 10
typedef struct meta2d_ball_t {
v2f_t position;
float radius;
v3f_t color;
} meta2d_ball_t;
typedef struct meta2d_context_t {
unsigned n;
din_t *din_a, *din_b;
float din_t;
meta2d_ball_t balls[META2D_NUM_BALLS];
} meta2d_context_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(v3f_t color) {
uint32_t pixel;
if (color.x > 1.0f) color.x = 1.0f;
if (color.y > 1.0f) color.y = 1.0f;
if (color.z > 1.0f) color.z = 1.0f;
if (color.x < .0f) color.x = .0f;
if (color.y < .0f) color.y = .0f;
if (color.z < .0f) color.z = .0f;
pixel = (uint32_t)(color.x * 255.0f);
pixel <<= 8;
pixel |= (uint32_t)(color.y * 255.0f);
pixel <<= 8;
pixel |= (uint32_t)(color.z * 255.0f);
return pixel;
}
static void * meta2d_create_context(unsigned ticks, unsigned n_cpus, til_setup_t *setup)
{
meta2d_context_t *ctxt;
ctxt = calloc(1, sizeof(meta2d_context_t));
/* perlin noise is used for some organic-ish random movement of the balls */
ctxt->din_a = din_new(10, 10, META2D_NUM_BALLS + 2);
ctxt->din_b = din_new(10, 10, META2D_NUM_BALLS + 2);
for (int i = 0; i < META2D_NUM_BALLS; i++) {
meta2d_ball_t *ball = &ctxt->balls[i];
v2f_rand(&ball->position, &(v2f_t){-.7f, -.7f}, &(v2f_t){.7f, .7f});
ball->radius = rand() / (float)RAND_MAX * .2f + .05f;
v3f_rand(&ball->color, &(v3f_t){0.f, 0.f, 0.f}, &(v3f_t){1.f, 1.f, 1.f});
}
return ctxt;
}
static void meta2d_destroy_context(void *context)
{
meta2d_context_t *ctxt = context;
din_free(ctxt->din_a);
din_free(ctxt->din_b);
free(ctxt);
}
static void meta2d_prepare_frame(void *context, unsigned ticks, unsigned n_cpus, til_fb_fragment_t *fragment, til_fragmenter_t *res_fragmenter)
{
meta2d_context_t *ctxt = context;
*res_fragmenter = til_fragmenter_slice_per_cpu;
/* move the balls around */
for (int i = 0; i < META2D_NUM_BALLS; i++) {
meta2d_ball_t *ball = &ctxt->balls[i];
float rad;
/* Perlin noise indexed by position for x,y and i for z
* is used just for moving the metaballs around.
*
* Two noise fields are used with their values interpolated,
* starting with the din_a being 100% of the movement,
* with every frame migrating closer to din_b being 100%.
*
* Once din_b contributes 100%, it becomes din_a, and the old
* din_a becomes din_b which gets randomized, and the % resets
* to 0.
*
* This allows an organic continuous evolution of the field
* over time, at double the sampling cost since we're sampling
* two noise fields and interpolating them. Since this is
* just per-ball every frame, it's probably OK. Not like it's
* every pixel.
*/
/* ad-hoc lerp of the two dins */
rad = din(ctxt->din_a, &(v3f_t){
.x = ball->position.x,
.y = ball->position.y,
.z = (float)i * (1.f / (float)META2D_NUM_BALLS)}
) * (1.f - ctxt->din_t);
rad += din(ctxt->din_b, &(v3f_t){
.x = ball->position.x,
.y = ball->position.y,
.z = (float)i * (1.f / (float)META2D_NUM_BALLS)}
) * ctxt->din_t;
/* Perlin noise doesn't produce anything close to a uniform random distribution
* of -1..+1, so it can't just be mapped directly to 2*PI with all angles getting
* roughly equal occurrences in the long-run. For now I just *10.f and it seems
* to be OK.
*/
rad *= 10.f * 2.f * M_PI;
v2f_add(&ball->position,
&ball->position,
&(v2f_t){
.x = cosf(rad) * .003f, /* small steps */
.y = sinf(rad) * .003f,
});
v2f_clamp(&ball->position,
&ball->position,
&(v2f_t){-.8f, -.8f}, /* keep the balls mostly on-screen */
&(v2f_t){.8f, .8f}
);
}
/* when din_t reaches 1 swap a<->b, reset din_t, randomize b */
ctxt->din_t += .01f;
if (ctxt->din_t >= 1.f) {
din_t *tmp;
tmp = ctxt->din_a;
ctxt->din_a = ctxt->din_b;
ctxt->din_b = tmp;
din_randomize(ctxt->din_b);
ctxt->din_t = 0.f;
}
}
static void meta2d_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
{
meta2d_context_t *ctxt = context;
float xf = 2.f / (float)fragment->frame_width;
float yf = 2.f / (float)fragment->frame_height;
v2f_t coord;
for (int y = fragment->y; y < fragment->y + fragment->height; y++) {
coord.y = yf * (float)y - 1.f;
for (int x = fragment->x; x < fragment->x + fragment->width; x++) {
v3f_t color = {};
uint32_t pixel;
float t = 0;
coord.x = xf * (float)x - 1.f;
for (int i = 0; i < META2D_NUM_BALLS; i++) {
meta2d_ball_t *ball = &ctxt->balls[i];
float f;
f = ball->radius * ball->radius / v2f_distance_sq(&coord, &ball->position);
v3f_add(&color, &color, v3f_mult_scalar(&(v3f_t){}, &ball->color, f));
t += f;
}
/* these thresholds define the thickness of the ribbon */
if (t < .7f || t > .8f)
color = (v3f_t){};
pixel = color_to_uint32(color);
til_fb_fragment_put_pixel_unchecked(fragment, x, y, pixel);
}
}
}
til_module_t meta2d_module = {
.create_context = meta2d_create_context,
.destroy_context = meta2d_destroy_context,
.prepare_frame = meta2d_prepare_frame,
.render_fragment = meta2d_render_fragment,
.name = "meta2d",
.description = "Classic 2D metaballs (threaded)",
.author = "Vito Caputo <vcaputo@pengaru.com>",
};
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