100 lines
2.9 KiB
C
100 lines
2.9 KiB
C
#include <stdint.h>
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#include "../config.h"
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#include "../pixel.h"
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#include "../util.h"
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#include "../compat/pgmspace.h"
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#include "blackhole.h"
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// macro for simplifying flash memory access
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#define PGM(x) pgm_read_byte(&(x))
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/**
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* Integer variant of the sinus function which takes an integer based angle
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* (range from 0 to 63) where sin_i(64) corresponds to sin(2 * M_PI) * 64 and
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* sin_i(16) corresponds to sin(0.5 * M_PI) * 64 (each excluding the fractional
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* part). It uses a lookup table which models one quarter of a full sinus period
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* and calculates the rest of the function from that quarter.
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* @param angle angle based on an integer (range from 0 to 63)
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* @return result of the sinus function normalized to a range from -64 to 64
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*/
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static signed char sin_i(unsigned char angle) {
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// the aforementioned lookup table
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static signed char const sinus_table[] PROGMEM =
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{0, 6, 12, 19, 24, 30, 36, 41, 45, 49, 53, 56, 59, 61, 63, 64};
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// determine correct index for the lookup table depending on the given angle
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angle %= 64u;
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unsigned char index;
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if (angle < 16) {
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index = angle;
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} else if (angle < 32) {
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index = 31 - angle;
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} else if (angle < 48) {
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index = angle - 32;
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} else {
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index = 63 - angle;
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}
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return (signed char)(PGM(sinus_table[index])) * (angle < 32 ? 1 : -1);
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}
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/**
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* Integer variant of the cosinus function which takes an integer based angle
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* (range from 0 to 63) where cos_i(64) corresponds to cos(2 * M_PI) * 64 and
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* cos_i(16) corresponds to cos(0.5 * M_PI) * 64. It uses the sin_i function and
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* shifts the given angle by 16 (which corresponds to 90 degrees).
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* @param angle angle based on an integer (range from 0 to 63)
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* @return result of the cosinus function normalized to a range from -64 to 64
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*/
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static signed char cos_i(unsigned char const angle) {
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return sin_i(angle + 16);
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}
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#define NUM_CIRCLE 7
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/**
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* Draws a black hole like pattern (viewed from different perspectives).
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*/
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void blackhole(void) {
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pixel circlePoints[NUM_CIRCLE][8];
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unsigned char add = 0;
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signed char firstRadius = 80, helpRadius, angle = 0, x, y;
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// initialize data
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for (int k = 0; k < 800; k++) {
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if (k > 300)
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add = k / 16;
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helpRadius = firstRadius;
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for (unsigned char i = 0; i < NUM_CIRCLE; i++) {
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for (unsigned char j = 0; j < 8; j++) {
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if (j & 1) {
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circlePoints[i][j].x = 64
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+ (cos_i(angle + j * 8) * helpRadius) / 64;
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circlePoints[i][j].y = 64
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+ (sin_i(angle + add + j * 8) * helpRadius) / 64;
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} else {
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circlePoints[i][j].x = 64 +
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(cos_i(angle + j * 8 + 4) * helpRadius) / 64;
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circlePoints[i][j].y = 64 +
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(sin_i(angle + add + j * 8 + 4) * helpRadius) / 64;
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}
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x = circlePoints[i][j].x / 8;
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y = circlePoints[i][j].y / 8;
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if (x < 16 && y < 16)
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setpixel((pixel){x, y}, 3);
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}
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helpRadius = (helpRadius * 2) / 3;
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}
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wait(30);
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clear_screen(0);
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angle++;
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firstRadius += 2;
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if (firstRadius > 119)
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firstRadius = 80;
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}
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}
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