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#include <stdint.h>
#include <inttypes.h>
#include <math.h>
#include <stdlib.h>
#include "til.h"
#include "til_fb.h"
/* Copyright (C) 2016 Vito Caputo <vcaputo@pengaru.com> */
/* Some defines for the fixed-point stuff in render(). */
#define FIXED_TRIG_LUT_SIZE 4096 /* size of the cos/sin look-up tables */
#define FIXED_BITS 11 /* fractional bits */
#define FIXED_EXP (1 << FIXED_BITS) /* 2^FIXED_BITS */
#define FIXED_MASK (FIXED_EXP - 1) /* fractional part mask */
#define FIXED_COS(_rad) costab[(_rad) % FIXED_TRIG_LUT_SIZE]
#define FIXED_SIN(_rad) sintab[(_rad) % FIXED_TRIG_LUT_SIZE]
#define FIXED_MULT(_a, _b) (((_a) * (_b)) >> FIXED_BITS)
#define FIXED_NEW(_i) ((_i) << FIXED_BITS)
#define FIXED_TO_INT(_f) ((_f) >> FIXED_BITS)
typedef struct color_t {
int r, g, b;
} color_t;
typedef struct roto_context_t {
unsigned r, rr;
} roto_context_t;
static int32_t costab[FIXED_TRIG_LUT_SIZE], sintab[FIXED_TRIG_LUT_SIZE];
static uint8_t texture[256][256];
static color_t palette[2];
static void * roto_create_context(unsigned ticks, unsigned n_cpus, til_setup_t *setup)
{
return calloc(1, sizeof(roto_context_t));
}
static void roto_destroy_context(void *context)
{
free(context);
}
/* linearly interpolate between two colors, alpha is fixed-point value 0-FIXED_EXP. */
static inline color_t lerp_color(color_t *a, color_t *b, int alpha)
{
/* TODO: This could be done without multiplies with a bit of effort,
* maybe a simple table mapping integer color deltas to shift values
* for shifting alpha which then gets simply added? A table may not even
* be necessary, use the order of the delta to derive how much to shift
* alpha?
*/
color_t c = {
.r = a->r + FIXED_MULT(alpha, b->r - a->r),
.g = a->g + FIXED_MULT(alpha, b->g - a->g),
.b = a->b + FIXED_MULT(alpha, b->b - a->b),
};
return c;
}
/* Return the bilinearly interpolated color palette[texture[ty][tx]] (Anti-Aliasing) */
/* tx, ty are fixed-point for fractions, palette colors are also in fixed-point format. */
static uint32_t bilerp_color(uint8_t texture[256][256], color_t *palette, int tx, int ty)
{
uint8_t itx = FIXED_TO_INT(tx), ity = FIXED_TO_INT(ty);
color_t n_color, s_color, color;
int x_alpha, y_alpha;
uint8_t nw, ne, sw, se;
/* We need the 4 texels constituting a 2x2 square pattern to interpolate.
* A point tx,ty can only intersect one texel; one corner of the 2x2 square.
* Where relative to the corner's center the intersection occurs determines which corner has been intersected,
* and the other corner texels may then be addressed relative to that corner.
* Alpha values must also be determined for both axis, these values describe the position between
* the 2x2 texel centers the intersection occurred, aka the weight or bias.
* Once the two alpha values are known, linear interpolation between the texel colors is trivial.
*/
if ((ty & FIXED_MASK) > (FIXED_EXP >> 1)) {
y_alpha = ty & (FIXED_MASK >> 1);
if ((tx & (FIXED_MASK)) > (FIXED_EXP >> 1)) {
nw = texture[ity][itx];
ne = texture[ity][(uint8_t)(itx + 1)];
sw = texture[(uint8_t)(ity + 1)][itx];
se = texture[(uint8_t)(ity + 1)][(uint8_t)(itx + 1)];
x_alpha = tx & (FIXED_MASK >> 1);
} else {
ne = texture[ity][itx];
nw = texture[ity][(uint8_t)(itx - 1)];
se = texture[(uint8_t)(ity + 1)][itx];
sw = texture[(uint8_t)(ity + 1)][(uint8_t)(itx - 1)];
x_alpha = (FIXED_EXP >> 1) + (tx & (FIXED_MASK >> 1));
}
} else {
y_alpha = (FIXED_EXP >> 1) + (ty & (FIXED_MASK >> 1));
if ((tx & (FIXED_MASK)) > (FIXED_EXP >> 1)) {
sw = texture[ity][itx];
se = texture[ity][(uint8_t)(itx + 1)];
nw = texture[(uint8_t)(ity - 1)][itx];
ne = texture[(uint8_t)(ity - 1)][(uint8_t)(itx + 1)];
x_alpha = tx & (FIXED_MASK >> 1);
} else {
se = texture[ity][itx];
sw = texture[ity][(uint8_t)(itx - 1)];
ne = texture[(uint8_t)(ity - 1)][itx];
nw = texture[(uint8_t)(ity - 1)][(uint8_t)(itx - 1)];
x_alpha = (FIXED_EXP >> 1) + (tx & (FIXED_MASK >> 1));
}
}
/* Skip interpolation of same colors, a substantial optimization with plain textures like the checker pattern */
if (nw == ne) {
if (ne == sw && sw == se) {
return (FIXED_TO_INT(palette[sw].r) << 16) | (FIXED_TO_INT(palette[sw].g) << 8) | FIXED_TO_INT(palette[sw].b);
}
n_color = palette[nw];
} else {
n_color = lerp_color(&palette[nw], &palette[ne], x_alpha);
}
if (sw == se) {
s_color = palette[sw];
} else {
s_color = lerp_color(&palette[sw], &palette[se], x_alpha);
}
color = lerp_color(&n_color, &s_color, y_alpha);
return (FIXED_TO_INT(color.r) << 16) | (FIXED_TO_INT(color.g) << 8) | FIXED_TO_INT(color.b);
}
static void init_roto(uint8_t texture[256][256], int32_t *costab, int32_t *sintab)
{
int x, y, i;
/* Generate simple checker pattern texture, nothing clever, feel free to play! */
/* If you modify texture on every frame instead of only @ initialization you can
* produce some neat output. These values are indexed into palette[] below. */
for (y = 0; y < 128; y++) {
for (x = 0; x < 128; x++)
texture[y][x] = 1;
for (; x < 256; x++)
texture[y][x] = 0;
}
for (; y < 256; y++) {
for (x = 0; x < 128; x++)
texture[y][x] = 0;
for (; x < 256; x++)
texture[y][x] = 1;
}
/* Generate fixed-point cos & sin LUTs. */
for (i = 0; i < FIXED_TRIG_LUT_SIZE; i++) {
costab[i] = ((cos((double)2*M_PI*i/FIXED_TRIG_LUT_SIZE))*FIXED_EXP);
sintab[i] = ((sin((double)2*M_PI*i/FIXED_TRIG_LUT_SIZE))*FIXED_EXP);
}
}
/* prepare a frame for concurrent rendering */
static void roto_prepare_frame(void *context, unsigned ticks, unsigned n_cpus, til_fb_fragment_t *fragment, til_fragmenter_t *res_fragmenter)
{
roto_context_t *ctxt = context;
static int initialized;
if (!initialized) {
initialized = 1;
init_roto(texture, costab, sintab);
}
*res_fragmenter = til_fragmenter_slice_per_cpu;
// This governs the rotation and color cycle.
ctxt->r += FIXED_TO_INT(FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(16)));
ctxt->rr += 2;
}
/* Draw a rotating checkered 256x256 texture into fragment. */
static void roto_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
{
roto_context_t *ctxt = context;
int y_cos_r, y_sin_r, x_cos_r, x_sin_r, x_cos_r_init, x_sin_r_init, cos_r, sin_r;
int x, y, frame_width = fragment->frame_width, frame_height = fragment->frame_height;
uint32_t *buf = fragment->buf;
/* This is all done using fixed-point in the hopes of being faster, and yes assumptions
* are being made WRT the overflow of tx/ty as well, only tested on x86_64. */
cos_r = FIXED_COS(ctxt->r);
sin_r = FIXED_SIN(ctxt->r);
/* Vary the colors, this is just a mashup of sinusoidal rgb values. */
palette[0].r = (FIXED_MULT(FIXED_COS(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
palette[0].g = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
palette[0].b = (FIXED_MULT(FIXED_COS(ctxt->rr / 3), FIXED_NEW(127)) + FIXED_NEW(128));
palette[1].r = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
palette[1].g = (FIXED_MULT(FIXED_COS(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
palette[1].b = (FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
/* The dimensions are cut in half and negated to center the rotation. */
/* The [xy]_{sin,cos}_r variables are accumulators to replace multiplication with addition. */
x_cos_r_init = FIXED_MULT(-FIXED_NEW(frame_width / 2) + FIXED_NEW(fragment->x), cos_r);
x_sin_r_init = FIXED_MULT(-FIXED_NEW(frame_width / 2) + FIXED_NEW(fragment->x), sin_r);
y_cos_r = FIXED_MULT(-FIXED_NEW(frame_height / 2) + FIXED_NEW(fragment->y), cos_r);
y_sin_r = FIXED_MULT(-FIXED_NEW(frame_height / 2) + FIXED_NEW(fragment->y), sin_r);
for (y = fragment->y; y < fragment->y + fragment->height; y++) {
x_cos_r = x_cos_r_init;
x_sin_r = x_sin_r_init;
for (x = fragment->x; x < fragment->x + fragment->width; x++, buf++) {
*buf = bilerp_color(texture, palette, x_sin_r - y_cos_r, y_sin_r + x_cos_r);
x_cos_r += cos_r;
x_sin_r += sin_r;
}
buf += fragment->stride;
y_cos_r += cos_r;
y_sin_r += sin_r;
}
}
til_module_t roto_module = {
.create_context = roto_create_context,
.destroy_context = roto_destroy_context,
.prepare_frame = roto_prepare_frame,
.render_fragment = roto_render_fragment,
.name = "roto",
.description = "Anti-aliased tiled texture rotation (threaded)",
.author = "Vito Caputo <vcaputo@pengaru.com>",
};
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