Sine.

Sine.

Smoothly scaling size with the sin() function.

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float diameter; 
float angle = 0;

void setup() {
  size(640, 360);
  diameter = height - 10;
  noStroke();
  fill(255, 204, 0);
}

void draw() {
  
  background(0);

  float d1 = 10 + (sin(angle) * diameter/2) + diameter/2;
  float d2 = 10 + (sin(angle + PI/2) * diameter/2) + diameter/2;
  float d3 = 10 + (sin(angle + PI) * diameter/2) + diameter/2;
  
  ellipse(0, height/2, d1, d1);
  ellipse(width/2, height/2, d2, d2);
  ellipse(width, height/2, d3, d3);
  
  angle += 0.02;
}

Functions Used

fill()

Sets the color used to fill shapes

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size()

Defines the dimension of the display window width and height in units of pixels

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ellipse()

Draws an ellipse (oval) to the screen

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sin()

Calculates the sine of an angle

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setup()

The setup() function is run once, when the program starts

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draw()

Called directly after setup(), the draw() function continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called

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noStroke()

Disables drawing the stroke (outline)

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background()

The background() function sets the color used for the background of the Processing window

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