FastLED 3D Circle with straight 100 LED Strip

/*
This code creates a spinning circle that is oriented in a horizontal plane like a bicycle wheel laying on its side.  A single LED appears to rotate around the circumference and there is one light in the middle.  It runs on an ordinary straight addressable LED light Strip.
It creates a very good 3D effect.  Derivative works can include multiple circles with different colors and directions, and even figure 8s.  Those are left to your imagination.*/

#include <FastLED.h>

#define LED_PIN     5
#define COLOR_ORDER BRG
#define CHIPSET     WS2811
#define NUM_LEDS    100




CRGB leds[NUM_LEDS];

void setup() {


//delay(3000); // sanity delay
FastLED.addLeds<CHIPSET, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
FastLED.setBrightness( BRIGHTNESS );

  circle(1);

}



/*****************************************************************
 **** circle - uses trig functions to drive a circular orbit ****
 * **************************************************************/
void circle(int reps)
{

int j,xpoint,quarter,color;
float testx,firstx,lastx,lasty,nextx,nexty,ledpos,lastledpos,brightpos;
float angle;
int bright, center;

center = 50; //positions the center of the circle
angle = .8; //set this to change the speed of rotation higher numbers are faster (it's degrees of rotation for
              //each show() command loop)
firstx=lastx= 50; //set this to change the diameter of the circle

lasty=0;  //can be changed but no good reason for it.



while(reps--)
{

  for (j=0;j<100;j++)leds[j].setRGB(0,0,0); //sets all the leds to off.
  FastLED.show();
while(1)
     { //endless loop - need to change this if used with other subroutines


      nextx=(lastx*cos(angle*PI/180)-lasty*sin(angle*PI/180));// These two lines calculate the next
                                                              // point on the circle from any other
                                                              // point on it.
      nexty=(lasty*cos(angle*PI/180)+lastx*sin(angle*PI/180));

      lastledpos = (lastx+NUM_LEDS)/2; // calculates the last led to be lit so that it can be turned off.

      ledpos=(nextx+NUM_LEDS)/2;




      brightpos=(nexty+NUM_LEDS)/2;

      bright = 85 * (brightpos-(center-(firstx/2)))/firstx;//want min brightness when lit led is at back of circle,
                                                           // max brightness when closest to front;

      if ((nextx>0)&&(nexty>0)) quarter = 1;
      if ((nextx<0)&&(nexty>0)) quarter = 2;
      if ((nextx<0)&&(nexty<0)) quarter = 3;
      if ((nextx>0)&&(nexty<0)) quarter = 4;

      //  figure out which quarter of the circle we're in

      color = bright*3;

      xpoint=int(ledpos);

      leds[int(lastledpos)].setRGB(0,0,0);
      leds[center].setRGB(0,150,0); //turns on a green dot in the middle of the string
      leds[xpoint].setRGB(0,color,color);

      if(((xpoint>(center-3))&&(xpoint<(center+4)))&&(quarter<3)) //dims dot when moving led passes in front
        {
           leds[center].setRGB(0,0,0);
        }


      if((quarter>2)&&(xpoint == center))leds[center].setRGB(0,150,0);

      lastx=nextx;
      lasty=nexty;

     FastLED.show();
    //delay(100);

     }
}}