Das nehme ich doch beim Wort: Als nächstes würde ich gern den Schweif in einer beliebigen Richtung (0-360 Grad) berechnen.
Für 0, 45, 90, 135, ... Grad bekomme ich es hin. Aber wie könnte ich das verallgemeinern, dass es mit jedem Richtungsvektor/Winkel funktioniert?
Hier mal ein Beispielcode. Ein Punkt beschreibt eine Lissajousfigur. Die Funktion MoveAll() ganz am Ende erzeugt den Verwischeffekt nach unten. Ideen, wie man die modifizieren könnte?
/* 20 * 12 Matrix */
#include <FastLED.h>
// LED stuff
#define LED_PIN 23
#define COLOR_ORDER GRB
#define CHIPSET WS2811
#define BRIGHTNESS 255
// Matrix dimensions
const uint8_t WIDTH = 20;
const uint8_t HEIGHT = 12;
#define NUM_LEDS (WIDTH * HEIGHT)
CRGB leds[NUM_LEDS];
// Timer stuff
struct timer {unsigned long takt; unsigned long lastMillis; unsigned long count; int delta; byte up; byte down;};
timer multiTimer[3];
int timers = sizeof( multiTimer ) / sizeof( multiTimer[0] );
// Cos table
uint8_t const cos_wave[256]
{0,0,0,0,1,1,1,2,2,3,4,5,6,6,8,9,10,11,12,14,15,17,18,20,22,23,25,27,29,31,33,35,38,40,42,
45,47,49,52,54,57,60,62,65,68,71,73,76,79,82,85,88,91,94,97,100,103,106,109,113,116,119,
122,125,128,131,135,138,141,144,147,150,153,156,159,162,165,168,171,174,177,180,183,186,
189,191,194,197,199,202,204,207,209,212,214,216,218,221,223,225,227,229,231,232,234,236,
238,239,241,242,243,245,246,247,248,249,250,251,252,252,253,253,254,254,255,255,255,255,
255,255,255,255,254,254,253,253,252,252,251,250,249,248,247,246,245,243,242,241,239,238,
236,234,232,231,229,227,225,223,221,218,216,214,212,209,207,204,202,199,197,194,191,189,
186,183,180,177,174,171,168,165,162,159,156,153,150,147,144,141,138,135,131,128,125,122,
119,116,113,109,106,103,100,97,94,91,88,85,82,79,76,73,71,68,65,62,60,57,54,52,49,47,45,
42,40,38,35,33,31,29,27,25,23,22,20,18,17,15,14,12,11,10,9,8,6,6,5,4,3,2,2,1,1,1,0,0,0,0
};
void setup() {
FastLED.addLeds<CHIPSET, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
FastLED.setBrightness( BRIGHTNESS );
//Serial.begin(9600);
// set all counting directions positive for the beginning
for (int i = 0; i < timers; i++) multiTimer[i].delta = 1;
// set range (up/down), speed (takt=ms between steps) and starting point (count) of all variables
multiTimer[0].takt= 2; //x1
multiTimer[0].up = 255;
multiTimer[0].down = 0;
multiTimer[0].count = multiTimer[0].down;
multiTimer[1].takt= 5; //y1
multiTimer[1].up = 255;
multiTimer[1].down = 0;
multiTimer[1].count = multiTimer[1].down;
multiTimer[2].takt= 6; //color
multiTimer[2].up = 255;
multiTimer[2].down = 0;
multiTimer[2].count = multiTimer[2].down;
}
void loop()
{
UpdateTimers();
//DimmAll();
MoveAll();
// Lissajous point
leds[ XY(
cos_wave[ multiTimer[0].count ] * WIDTH / 255,
cos_wave[ multiTimer[1].count] * (HEIGHT-2) / 255) ]
+= CHSV( multiTimer[2].count, 255, 255);
FastLED.show();
}
uint16_t XY( uint8_t x, uint8_t y) { // translates from x, y into an index into the LED array
uint16_t i;
i = (y * WIDTH) + x;
return i;
}
void UpdateTimers() // counts all variables with different speeds linear up and down
{
unsigned long now=millis();
for (int i=0; i < timers; i++)
{
while (now-multiTimer[i].lastMillis >= multiTimer[i].takt)
{
multiTimer[i].lastMillis += multiTimer[i].takt;
multiTimer[i].count = multiTimer[i].count + multiTimer[i].delta;
if ((multiTimer[i].count == multiTimer[i].up) || (multiTimer[i].count == multiTimer[i].down))
{
multiTimer[i].delta = -multiTimer[i].delta;
}
}
}
}
void DimmAll() // the tail behind the dots
{
for(int i = 0; i < NUM_LEDS; i++)
{
leds[i].nscale8( 240 );
}
}
void MoveAll() // the tail downwards
{
for(int i = 0; i < NUM_LEDS - WIDTH; i++)
{
leds[i] += leds[i + WIDTH];
leds[i].nscale8( 120 );
}
}
Beste Grüße
Helmuth
edit: Ich muss das Problem wohl präziser beschreiben?! 
Habe im Hinterkopf die Frage, ob man den Bresenham-Algorithmus dafür missbrauchen könnte. Ich fürchte nur, das wird zu langsam, jeden Pixel als Linie der Länge 1 zu beschreiben...
