Rather than just blindly copy and paste FastLED functions into sketches,

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Rather than just blindly copy and paste FastLED functions into sketches, I’m trying to break them down and understand them so that, hopefully, I can use what I learn to understand future functions (and, hopefully, bother you guys less).

I’ve been messing with fill-gradient and have figured out the following FastLED for Dummies explanation.

fill_gradient(leds,0,CHSV(0,255,255),100,CHSV(96,255,255),SHORTEST_HUES);

In the above example:

0 = the starting LED. LEDs are indexed to zero, so LED #1 is identified as 0, LED #2 is identified as 1, and so on.
CHSV(0,255,255) = the starting color of the gradient expressed in HSV values, in this case red.
100 = the ending LED. Like the starting LED, it can be any number.
CHSV(96,255,255) = the ending color for the gradient, in this case green.
SHORTEST_HUES = The hue is a value on a color wheel. There are always two directions you can go to get from one place on a wheel to another (one hue value to another hue value). FastLED lets you pick the direction you want to go. SHORTEST_HUES is the shortest distance between the two values (the most common choice), LONGEST_HUES is the longest way around. FORWARD_HUES always moves clockwise. BACKWARD_HUES always moves counter-clockwise.

My question is…

What does the ‘leds’ in the function (right after fill_gradient and before the zero) signify? Is it something that can be tweaked/altered/replaced – or does it just need to be there for some magical reason that only people far smarter than me understand?

I’ve also seen it in the fill-solids function, but sometimes it seems to be replaced by ‘struct CRGB * leds’ or ‘struct CHSV* targetArray’ or similar.

If it can be explained, I’d appreciate it. if it’s something you just have to keep hammering away at, I’m already on it! :slight_smile:

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In the beginning of your arduino sketch you defined a LED strip and gave it a name:

// Define the array of leds
CRGB leds[NUM_LEDS];

If you had more then one LED strip, you might have defined several at the top, something like:

// Define the array of leds
CRGB leds[NUM_LEDS];
CRGB leds_top[NUM_LEDS];
CRGB leds_helmet[NUM_LEDS_HELMET];

These names are used to specify which LED strip to operate on.

leds[0] = CRGB::Red; // set pixel 0 to red on strip leds.
leds_top[0] = CRGB::Green; // set pixel 0 to green on strip leds_top.
leds_helmet[0] = CRGB::Blue; // set pixel 0 to blue on strip leds_helmet.

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Now that you explain it I feel kind’a stupid! Thanks! It makes a lot more sense now.

I’m thinking there’s probably a way to use something similar to break a strip down into two or more ‘virtual’ strips? Time to go make some awesome mistakes!

Thanks again!

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Thanks AyTooZee, i am in a similar position and this input is invaluable.