copy_and_offset_example.ino

Info posted for this post:
https://plus.google.com/101381095273549449891/posts/FqmG6S4rjpz


Another option (that uses a bit more memory) is to use a second array (let's call it leds_display) that
you copy your leds data to with the offset before displaying.  So it the top of your program you will
have two CRGB arrays:

CRGB leds[NUM_LEDS];  //working array
CRGB leds_display[NUM_LEDS];  //array that gets displayed


And in setup for your addLeds line use leds_show instead of leds:

  FastLED.addLeds<WS2812B, 11, RGB>(leds_show, NUM_LEDS);  //(using leds_show, not leds)


And create a function like this:

// function to copy leds to leds_display and offset pixel position
void offset_pixels() {
  for (uint16_t i=0; i<NUM_LEDS; i++) {
    leds_show[i] = leds[(i+400) % NUM_LEDS];  //offset by 400
  }
}


Then code way as normal...
And always call the copy and offset function right before you call show().
                                                                       
offset_pixels();  //always call right before show()
FastLED.show();  //display pixels