Christian Kroll
13 years ago
5 changed files with 117 additions and 0 deletions
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#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 = 32 - 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 = 64 - angle; |
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} |
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return (unsigned 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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} |
@ -0,0 +1,6 @@ |
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#ifndef BLACKHOLE_H_ |
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#define BLACKHOLE_H_ |
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void blackhole(void); |
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#endif /* BLACKHOLE_H_ */ |
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