90 lines
2.1 KiB
C++
90 lines
2.1 KiB
C++
// Animates white pixels to simulate flying through a star field
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#include <SPI.h>
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#include <TFT_eSPI.h>
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// Use hardware SPI
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TFT_eSPI tft = TFT_eSPI();
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// With 1024 stars the update rate is ~65 frames per second
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#define NSTARS 1024
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uint8_t sx[NSTARS] = {};
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uint8_t sy[NSTARS] = {};
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uint8_t sz[NSTARS] = {};
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uint8_t za, zb, zc, zx;
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// Fast 0-255 random number generator from http://eternityforest.com/Projects/rng.php:
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uint8_t __attribute__((always_inline)) rng()
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{
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zx++;
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za = (za^zc^zx);
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zb = (zb+za);
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zc = (zc+(zb>>1)^za);
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return zc;
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}
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void setup() {
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za = random(256);
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zb = random(256);
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zc = random(256);
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zx = random(256);
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Serial.begin(115200);
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tft.init();
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tft.setRotation(1);
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tft.fillScreen(TFT_BLACK);
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// fastSetup() must be used immediately before fastPixel() to prepare screen
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// It must be called after any other graphics drawing function call if fastPixel()
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// is to be called again
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//tft.fastSetup(); // Prepare plot window range for fast pixel plotting
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}
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void loop()
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{
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unsigned long t0 = micros();
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uint8_t spawnDepthVariation = 255;
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for(int i = 0; i < NSTARS; ++i)
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{
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if (sz[i] <= 1)
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{
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sx[i] = 160 - 120 + rng();
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sy[i] = rng();
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sz[i] = spawnDepthVariation--;
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}
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else
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{
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int old_screen_x = ((int)sx[i] - 160) * 256 / sz[i] + 160;
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int old_screen_y = ((int)sy[i] - 120) * 256 / sz[i] + 120;
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// This is a faster pixel drawing function for occassions where many single pixels must be drawn
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tft.drawPixel(old_screen_x, old_screen_y,TFT_BLACK);
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sz[i] -= 2;
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if (sz[i] > 1)
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{
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int screen_x = ((int)sx[i] - 160) * 256 / sz[i] + 160;
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int screen_y = ((int)sy[i] - 120) * 256 / sz[i] + 120;
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if (screen_x >= 0 && screen_y >= 0 && screen_x < 320 && screen_y < 240)
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{
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uint8_t r, g, b;
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r = g = b = 255 - sz[i];
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tft.drawPixel(screen_x, screen_y, tft.color565(r,g,b));
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}
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else
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sz[i] = 0; // Out of screen, die.
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}
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}
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}
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unsigned long t1 = micros();
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//static char timeMicros[8] = {};
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// Calcualte frames per second
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Serial.println(1.0/((t1 - t0)/1000000.0));
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}
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