Changing RGB LED brightness during show

Is there a command in the Fast LED library that can be called to instantly change the LED brightness during a show? Something to immediately brighten the LEDs to a specific level and then back to their normal level. I tried but couldn't get the "leds*.fadeLightBy( )" command to work correctly but I'm probably missing something.*
The full code was to long to post, but here is a snippet that sums up what I was hoping to do:
```
*#include<FastLED.h>
#define CLOCK_PIN 5
#define DATA_PIN 4
#define BRIGHTNESS  z1
#define LED_TYPE    APA102
#define COLOR_ORDER BGR

if( lastSecond != secondHand) {
   lastSecond = secondHand;
   if( secondHand ==  0)  { currentPalette = RainbowColors_p;         speed = 20; scale = 30; colorLoop = 1; }
   if( secondHand ==  5)  { SetupPurpleAndGreenPalette();             speed = 10; scale = 50; colorLoop = 1; }
    z1=10;                                                                   //sets the brightnes value
   if( secondHand == 7)  { SetupBlackAndWhiteStripedPalette();       speed = 20; scale = 30; colorLoop = 1; }
    z1=50;                                                                  //sets the brightnes value
    if( secondHand == 9)  { SetupBlackAndWhiteStripedPalette();       speed = 30; scale = 30; colorLoop = 1; }
    z1=10;*
```

#define BRIGHTNESS  z1 

z1=10

Do you know what #define does?
It changes the text before the program compiles so that every time the word BRIGHTNESS is see it replaces it with z1. As your code does not use the word BRIGHTNESS then it will do nothing.

This will not affect any previous use of the word BRIGHTNESS.

The full code was to long to post,

So post some complete code that can be compiled and run that illustrates your problem.

I did not know that. I changed it from "#define BRIGHTNESS" to float "BRIGHTNESS = z1;". I was hoping that I could just set z1=some value when I wanted to change the brightness but it didn't work.

#include<FastLED.h>
#define CLOCK_PIN 5
#define DATA_PIN 4

#define LED_TYPE    APA102
#define COLOR_ORDER BGR

const uint8_t kMatrixWidth  = 16;
const uint8_t kMatrixHeight = 16;
const bool    kMatrixSerpentineLayout = true;

float z1 = 20;                                              //sets the brightnes value
float BRIGHTNESS = z1;

#define NUM_LEDS (kMatrixWidth * kMatrixHeight)
#define MAX_DIMENSION ((kMatrixWidth>kMatrixHeight) ? kMatrixWidth : kMatrixHeight)

// The leds
CRGB leds[kMatrixWidth * kMatrixHeight];

// The 16 bit version of our coordinates
static uint16_t x;
static uint16_t y;
static uint16_t z;

// We're using the x/y dimensions to map to the x/y pixels on the matrix.  We'll
// use the z-axis for "time".  speed determines how fast time moves forward.  Try
// 1 for a very slow moving effect, or 60 for something that ends up looking like
// water.
uint16_t speed = 20; // speed is set dynamically once we've started up

// Scale determines how far apart the pixels in our noise matrix are.  Try
// changing these values around to see how it affects the motion of the display.  The
// higher the value of scale, the more "zoomed out" the noise iwll be.  A value
// of 1 will be so zoomed in, you'll mostly see solid colors.
uint16_t scale = 30; // scale is set dynamically once we've started up

// This is the array that we keep our computed noise values in
uint8_t noise[MAX_DIMENSION][MAX_DIMENSION];

CRGBPalette16 currentPalette( PartyColors_p );
uint8_t       colorLoop = 1;

void setup() {
  delay(3000);
  FastLED.addLeds<APA102, DATA_PIN, CLOCK_PIN, BGR>(leds, NUM_LEDS);
  LEDS.setBrightness(BRIGHTNESS);

  // Initialize our coordinates to some random values
  x = random16();
  y = random16();
  z = random16();
}

// Fill the x/y array of 8-bit noise values using the inoise8 function.
void fillnoise8() {
  // If we're runing at a low "speed", some 8-bit artifacts become visible
  // from frame-to-frame.  In order to reduce this, we can do some fast data-smoothing.
  // The amount of data smoothing we're doing depends on "speed".
  uint8_t dataSmoothing = 0;
  if ( speed < 50) {
    dataSmoothing = 200 - (speed * 4);
  }

  for (int i = 0; i < MAX_DIMENSION; i++) {
    int ioffset = scale * i;
    for (int j = 0; j < MAX_DIMENSION; j++) {
      int joffset = scale * j;

      uint8_t data = inoise8(x + ioffset, y + joffset, z);

      // The range of the inoise8 function is roughly 16-238.
      // These two operations expand those values out to roughly 0..255
      // You can comment them out if you want the raw noise data.
      data = qsub8(data, 16);
      data = qadd8(data, scale8(data, 39));

      if ( dataSmoothing ) {
        uint8_t olddata = noise[i][j];
        uint8_t newdata = scale8( olddata, dataSmoothing) + scale8( data, 256 - dataSmoothing);
        data = newdata;
      }

      noise[i][j] = data;
    }
  }

  z += speed;

  // apply slow drift to X and Y, just for visual variation.
  x += speed / 8;
  y -= speed / 16;
}

void mapNoiseToLEDsUsingPalette()
{
  static uint8_t ihue = 0;

  for (int i = 0; i < kMatrixWidth; i++) {
    for (int j = 0; j < kMatrixHeight; j++) {
      // We use the value at the (i,j) coordinate in the noise
      // array for our brightness, and the flipped value from (j,i)
      // for our pixel's index into the color palette.

      uint8_t index = noise[j][i];
      uint8_t bri =   noise[i][j];

      // if this palette is a 'loop', add a slowly-changing base value
      if ( colorLoop) {
        index += ihue;
      }

      // brighten up, as the color palette itself often contains the
      // light/dark dynamic range desired
      if ( bri > 127 ) {
        bri = 255;
      } else {
        bri = dim8_raw( bri * 2);
      }

      CRGB color = ColorFromPalette( currentPalette, index, bri);
      leds[XY(i, j)] = color;
    }
  }

  ihue += 1;
}

void loop() {
  // Periodically choose a new palette, speed, and scale
  ChangePaletteAndSettingsPeriodically();

  // generate noise data
  fillnoise8();

  // convert the noise data to colors in the LED array
  // using the current palette
  mapNoiseToLEDsUsingPalette();

  LEDS.show();
}

#define HOLD_PALETTES_X_TIMES_AS_LONG 1

void ChangePaletteAndSettingsPeriodically()
{
  uint8_t secondHand = ((millis() / 1000) / HOLD_PALETTES_X_TIMES_AS_LONG) % 60;
  static uint8_t lastSecond = 99;

  if ( lastSecond != secondHand) {
    lastSecond = secondHand;
    if ( secondHand ==  0)  {
      currentPalette = RainbowColors_p;
      speed = 20;
      scale = 30;
      colorLoop = 1;
    }
    if ( secondHand ==  5)  {
      SetupPurpleAndGreenPalette();
      speed = 10;
      scale = 50;
      colorLoop = 1;
    }
    z1 = 10;                                                                 //sets the brightnes value
    if ( secondHand == 7)  {
      SetupBlackAndWhiteStripedPalette();
      speed = 20;
      scale = 30;
      colorLoop = 1;
    }
    z1 = 50;                                                                //sets the brightnes value
    if ( secondHand == 9)  {
      SetupBlackAndWhiteStripedPalette();
      speed = 30;
      scale = 30;
      colorLoop = 1;
    }
    z1 = 10;                                                                //sets the brightnes value






    /* if( secondHand == 15)  { currentPalette = ForestColors_p;          speed =  8; scale =120; colorLoop = 0; }*/

    if ( secondHand == 12)  {
      currentPalette = CloudColors_p;
      speed =  5;
      scale = 30;
      colorLoop = 1;
    }

    /* if( secondHand == 25)  { currentPalette = LavaColors_p;            speed =  8; scale = 50; colorLoop = 0; }
     if( secondHand == 30)  { currentPalette = OceanColors_p;           speed = 20; scale = 90; colorLoop = 0; }
     if( secondHand == 35)  { currentPalette = PartyColors_p;           speed = 20; scale = 30; colorLoop = 1; }
     if( secondHand == 40)  { SetupRandomPalette();                     speed = 20; scale = 20; colorLoop = 1; }
     if( secondHand == 45)  { SetupRandomPalette();                     speed = 50; scale = 50; colorLoop = 1; }*/
    if ( secondHand == 50)  {
      SetupRandomPalette();
      speed = 90;
      scale = 90;
      colorLoop = 1;
    }
    if ( secondHand == 55)  {
      currentPalette = RainbowStripeColors_p;
      speed = 30;
      scale = 20;
      colorLoop = 1;
    }

  }
}

// This function generates a random palette that's a gradient
// between four different colors.  The first is a dim hue, the second is
// a bright hue, the third is a bright pastel, and the last is
// another bright hue.  This gives some visual bright/dark variation
// which is more interesting than just a gradient of different hues.
void SetupRandomPalette()
{
  currentPalette = CRGBPalette16(
                     CHSV( random8(), 255, 32),
                     CHSV( random8(), 255, 255),
                     CHSV( random8(), 128, 255),
                     CHSV( random8(), 255, 255));
}

// This function sets up a palette of black and white stripes,
// using code.  Since the palette is effectively an array of
// sixteen CRGB colors, the various fill_* functions can be used
// to set them up.
void SetupBlackAndWhiteStripedPalette()
{
  // 'black out' all 16 palette entries...
  fill_solid( currentPalette, 16, CRGB::Black);
  // and set every fourth one to white.
  currentPalette[0] = CRGB::White;
  currentPalette[4] = CRGB::White;
  currentPalette[8] = CRGB::White;
  currentPalette[12] = CRGB::White;
}

// This function sets up a palette of purple and green stripes.
void SetupPurpleAndGreenPalette()
{
  CRGB purple = CHSV( HUE_PURPLE, 255, 255);
  CRGB green  = CHSV( HUE_GREEN, 255, 255);
  CRGB black  = CRGB::Black;

  currentPalette = CRGBPalette16(
                     green,  green,  black,  black,
                     purple, purple, black,  black,
                     green,  green,  black,  black,
                     purple, purple, black,  black );
}


//
// Mark's xy coordinate mapping code.  See the XYMatrix for more information on it.
//
uint16_t XY( uint8_t x, uint8_t y)
{
  uint16_t i;
  if ( kMatrixSerpentineLayout == false) {
    i = (y * kMatrixWidth) + x;
  }
  if ( kMatrixSerpentineLayout == true) {
    if ( y & 0x01) {
      // Odd rows run backwards
      uint8_t reverseX = (kMatrixWidth - 1) - x;
      i = (y * kMatrixWidth) + reverseX;
    } else {
      // Even rows run forwards
      i = (y * kMatrixWidth) + x;
    }
  }
  return i;
}

LEDS.setBrightness Takes an integer with values from 0 to 255. Not a float.

Traditionally In C if something is in all upper case it denotes a constant.
Why have a variable called BRIGHTNESS which is just a copy of another variable? It makes no sense.