How do I change a variable slowly over time?  I am trying to change the color and the speed of random ellipses.   I'm very new at Processing so forgive my messy code.  Here's what I have so far:


int sphereCount = 50;
float [] sphereSize = new float [sphereCount];
float [] xPosition = new float [sphereCount];
float [] yPosition = new float [sphereCount];
float [] xSpeed = new float [sphereCount];
float [] ySpeed = new float [sphereCount];

// These variables are used to determine the color of the particles

int redValue = 255;
int blueValue = 255;
int greenValue = 255;

void setup(){
 
 size(900,300);


 for(int i=0; i<sphereCount; i++){
   sphereSize[i] = random(10,120);
   xPosition[i] = random(0,width);
   yPosition[i] = random(0, height);
   xSpeed [i] = random(-2,2);
   ySpeed [i] = random(-2,2);
   
       
  }
   
}
void draw(){
background(0);

 
for(int i=0; i<sphereCount; i++){
 xPosition[i] += xSpeed[i];
 yPosition[i] += ySpeed[i];
 
 if(xPosition[i]>width){
  xSpeed[i] *= -1;
}

if(xPosition[i]<0){
  xSpeed[i] *= -1;
}

if(yPosition[i]>height){
  ySpeed[i] *= -1;
}

if(yPosition[i]<0) {
  ySpeed[i] *= -1;
}

/* When the mouse button is pressed the particles increase in
speed and the color slowly changes red.  This represents heat being
applied to the gas and causing the particles to agitate at higher
velocities */

 if (mousePressed == true) {
     xSpeed [i] += 0.05;
     xSpeed [i] += 0.05;
   redValue += 1;
   blueValue -= 2;
   greenValue -= 2;
   //delay(500);
 }
   //else {
   // xSpeed [i] = i;
   // ySpeed [i] = i;
    fill(redValue,blueValue,greenValue,90);
   //}
  // fill(255,0,0,90);
 
   
 smooth();
 
 noStroke();
 ellipse(xPosition[i],yPosition[i],sphereSize[i],sphereSize[i]);
}
println(redValue);
}

Also, I wanted to make the ellipses into 3D spheres.  Would this be pretty difficult to do starting from the code I have so far.

Thanks!

Stephanie

how exactly should it change? just slowly turn to red and stay red? oder back to white again?

Hi Stephanie,

the revelation you're looking for is that the red, green and blue values passed to background(), fill(), and stroke() do not need to be integers.

Increment/decrement by fractional values to your heart's content!

If you have this problem for other programming tasks, remember that you can always use floats to keep track of progress and convert the float value to an int as and when you need it.

eg

Code:

myFloat += 0.01;
myIntFunction(int(myFloat)); 

-spxl